HEAVY MECHANICAL TRADES FOUNDATION / LEVEL 1 Line A Book 3 [3] 9780772669926

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HEAVY MECHANICAL TRADES

FOUNDATION / LEVEL 1

Line A: Common Occupational Skills Competencies A-14 to A-17

Ordering Crown Publications, Queen’s Printer PO Box 9452 Stn Prov Govt 563 Superior St. 3rd Flr Victoria, B.C. V8W 9V7 Phone: 1 800 663-6105 Fax: 250 387-1120 Email: [email protected] Web: www.crownpub.bc.ca

© 2013, 2016 by Industry Training Authority This publication may not be reproduced in any form without permission by the Industry Training Authority. Contact Director, Crown Publications, Queen’s Printer at 250 356-6876.

Acknowledgments

Open School BC

Heavy Mechanical Trades Project Working Group Writers: Lloyd Babcock, Bob Glover, Terry Lockhart, Roger Young Reviewers: Brian Haugen, Rene Tremblay, Paul Mottershead, Mark Scorah, Rick Cyr, Lloyd Babcock, Terry Lockhart Editor: Greg Aleknevicus

Project Manager: Solvig Norman, Christina Teskey (revisions) Production Technicians: Sharon Barker, Beverly Carstensen, Dennis Evans Art Coordination: Dennis Evans, Christine Ramkeesoon Art: Dennis Evans, Margaret Kernaghan, Max Licht

Image Acknowledgments The following suppliers have kindly provided copyright permission for selected product images: Acklands-Grainger Inc. Alcoa Fastening Systems, Industrial Products SKF USA Inc. Stemco LP an EnPro Industries Ray Vaughan Every effort has been made to secure copyright permission for the images used in this document.

ISBN 978-0-7726-6992-6

Please note that it is always the responsibility of any person using these materials to inform him/herself about the Occupational Health and Safety Regulation pertaining to his/her work. The references to WorkSafeBC safety regulations contained within these materials do not / may not reflect the most recent Occupational Health and Safety Regulation (the current Standards and Regulation in BC can be obtained on the following website: http://www.worksafebc.com). We want your feedback! Please go to the BC Trades Modules website (www.bctradesmodules.ca) to enter comments about specific sections that require correction or modification. All submissions will be reviewed and considered for inclusion in the next revision.

Disclaimer

The materials in these booklets are for use by students and instructional staff and have been compiled from sources believed to be reliable and to represent best current opinions on these subjects. These manuals are intended to serve as a starting point for good practices and may not specify all minimum legal standards. No warranty, guarantee, or representation is made by the Heavy Mechanical Articulation Committee of BC, the British Columbia Industry Training Authority or the Queen’s Printer of British Columbia as to the accuracy or sufficiency of the information contained in these publications. These manuals are intended to provide basic guidelines for heavy mechanical trades practices. Do not assume, therefore, that all necessary warnings and safety precautionary measures are contained in this booklet and that other or additional measures may not be required. Version 2, September 2016

Line A: Common Occupational Skills Competencies A-14 to A-17 Table of Contents Competency A-14: Use Cutting and Welding Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 1: Identify Regulations in Respect to Welding . . . . . . . . . . . . . . . . . Self Test 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task2: Identify Metals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 3: Identify Oxy-acetylene Components . . . . . . . . . . . . . . . . . . . . . Self Test 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 4: Correct Procedures to Assemble, Ignite, Shut Down, and Disassemble a Portable Oxy-acetylene Unit . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 5: Cut Mild Steel with Oxy-acetylene Equipment . . . . . . . . . . . . . . . Self Test 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 6: Weld Mild Steel with Oxy-acetylene Equipment . . . . . . . . . . . . . . Self Test 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 7: Braze Lap Joints with Oxy-acetylene Equipment . . . . . . . . . . . . . . Self Test 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 8: Solder Tubing and Sheet Metal . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 9: Describe the Shielded Metal Arc Welding (SMAW) Process . . . . . . . . Self Test 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 10: Identify Shielded Metal Arc Welding Equipment . . . . . . . . . . . . . Self Test 10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 11: Identify Mild Steel Electrodes for Shielded Metal Arc Welding . . . . . Self Test 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 12: Weld Mild Steel with Shielded Metal Arc Welding . . . . . . . . . . . . Self Test 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 13: Weld Mild Steel Using Wire-feed Processes . . . . . . . . . . . . . . . . Self Test 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 14: Describe Air Arc Gouging . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Competency A-15: Prepare Job Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251 Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 1: Describe the Procedures to Prepare a Job Action . Self Test 1 . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 2: Describe the Risks of Poor Job Action . . . . . . . . Self Test 2 . . . . . . . . . . . . . . . . . . . . . . . . .

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Competency A-16: Describe Diagnostic Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263 Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 1: Describe the Importance of Following a Diagnostic Process . Self Test 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 2: Describe General Diagnostic Procedures . . . . . . . . . . . . . Self Test 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . HEAVY MECHANICAL TRADES — FOUNDATION / LEVEL 1

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Learning Task 3: Describe the Importance of Following Manufacturer’s Diagnostic Procedures. Self Test 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 4: Describe the Importance of Failure Analysis . . . . . . . . . . . . . . . . . . . . . . Self Test 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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277 278 279 281

Competency A-17: Prepare for Employment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 Goals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 1: Describe the Areas and Types of Vehicles and Equipment Maintained and Repaired . . . . . . . . . . . . . . . . . . . . Self Test 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 2: Describe the Current Heavy Mechanical Trades . . . . . . . Self Test 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 3: Describe the Range of Working Conditions . . . . . . . . . Self Test 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 4: Describe Types of Businesses . . . . . . . . . . . . . . . . . . Self Test 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 5: Describe Labour Groups . . . . . . . . . . . . . . . . . . . . . Self Test 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 6: Describe Legislation Affecting Employment . . . . . . . . . Self Test 6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 7: Describe Positive Employee Attributes . . . . . . . . . . . . Self Test 7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 8: Describe Employer Responsibility . . . . . . . . . . . . . . . Learning Task 9: Prepare a Resume . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 10: Prepare a Cover Letter. . . . . . . . . . . . . . . . . . . . . . Self Test 10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 11: Identify Job Search Sources . . . . . . . . . . . . . . . . . . Self Test 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Learning Task 12: Prepare for an Interview . . . . . . . . . . . . . . . . . . . . Learning Task 13: Follow up on an Interview . . . . . . . . . . . . . . . . . . . Self Test 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Answer Key . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365

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HEAVY MECHANICAL TRADES — FOUNDATION / LEVEL 1

USE CUTTING AND WELDING EQUIPMENT

HEAVY MECHANICAL TRADES: LINE A—COMMON OCCUPATIONAL SKILLS

A-14 CUTTING/WELDING

COMPETENCY A-14

Goals • • •

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You must be able to identify WorkSafeBC regulations when cutting and welding. You must be able to quickly and accurately identify metals, the structural shapes they are available in, and the correct methods of storage. Oxy-fuel gases are used extensively in cutting and welding metals, so it’s important that you know the properties of these gases. It’s also important that you learn how to handle, store, and transport the various components of a welding outfit safely and correctly. You must understand the correct procedures and safety precautions when assembling, testing, lighting, adjusting, shutting-down, and disassembling a portable oxy-acetylene outfit. You must be able to perform fusion welding on corner joints, butt joints, lap joints, and tee joints. You must be able to describe the oxy-acetylene brazing process, describe the safe procedures for handling oxy-acetylene brazing, and perform oxy-acetylene brazewelding. You must be able to identify the tools, procedures, and protection used in soldering and perform soldering on tubing and sheet metal. You must be able to identify the tools, procedures, and protection used in shielded metal arc welding (SMAW) and perform SMAW on corner joints, butt joints, lap joints, and tee joints. You must be able to identify the tools, procedures, and protection used in wire-feed systems. You must be able to identify the tools, procedures, and protection used in air arc gouging.

HEAVY MECHANICAL TRADES— FOUNDATION / LEVEL 1

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A-14 CUTTING/WELDING

LEARNING TASK 1

LEARNING TASK 1

NOTES

Identify Regulations in Respect to Welding WorkSafeBC Safety Regulations WorkSafeBC administers the Workers’ Compensation Act (WCA) for the province of British Columbia. WorkSafeBC also consults with and educates employers and workers on safe work practices in the welding field. It also monitors workplaces within its jurisdiction to see that they follow the Occupational Health Standards (OHS) Regulation. In the event of welding work-related injury, disease, or death, WorkSafeBC works with those involved to provide return-to-work rehabilitation, health-care benefits, compensation, and a range of other services. The OHS Regulation sets the minimum safety standards that are legally required in all welding workplaces under the jurisdiction of WorkSafeBC. The OHS Regulation also defines the rights and responsibilities of employers and workers in ensuring a safe workplace environment. The OHS Regulation has 32 parts, each covering a particular topic related to safety in the workplace. Most welding-related information can be found in Parts 1 to 12. 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16.

OHS Regulation Parts Definitions 17. Transportation of Workers Application 18. Traffic Control Rights and Responsibilities 19. Electrical Safety General Conditions 20. Construction, Excavation Chemical and Biological Agents and Demolition Substance Specific Requirements 21. Blasting Operations Noise, Vibration, Radiation 22. Underground Workings and Temperature 23. Oil and Gas Personal Protective Clothing 24. Diving, Fishing and Other and Equipment Marine Operations Confined Spaces 25. Camps De-energization and Lockout 26. Forestry Operations and Fall Protection Similar Activities Tools, Machinery and Equipment 27. Wood Products Manufacturing Ladders, Scaffolds and 28. Agriculture Temporary Work Platforms 29. Aircraft Operations Cranes and Hoists 30. Laboratories Rigging 31. Firefighting Mobile Equipment 32. Evacuation and Rescue

You need to reference safety information from the OHS Regulation.

HEAVY MECHANICAL TRADES— FOUNDATION / LEVEL 1

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SELF TEST 1

A-14 CUTTING/WELDING

SELF TEST 1 1. Why does WorkSafeBC enforce the Occupational Health and Safety Regulation? a. to define the rights and responsibilities of employers b. to identify the safety standards that are legally required c. to make amendments to the Workers’ Compensation Act d. to protect every person in the workplace from work-related risks 2. What safety standard does the OHS Regulation provide? a. maximum legal standard b. minimum legal standard c. flexible standard, not legally binding d. general standard, not legally binding

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LEARNING TASK 2

LEARNING TASK 2

NOTES

Identify Metals Terminology The following terms are used to describe metals and their properties: Oxidize

To oxidize is to combine an element with oxygen or convert an element into an oxide. For example, when carbon burns, it combines with oxygen to form either carbon dioxide or carbon monoxide. Iron combines with the oxygen in the air to form an iron oxide commonly known as rust.

Tensile Strength

Tensile strength is the strength different materials display when placed under tension. In the imperial system, tensile strength is measured in pounds per square inch (psi). In the metric system, tensile strength is measured in kilopascals (kPa) or Newtons per square millimeter (N/mm2). The area referred to (in2 or mm2) is the crosssectional area of the material.

Ductility

Ductility is the ability of metal to be bent, molded, or formed without breaking.

Malleable

A malleable substance is one capable of being shaped or formed by hammering or by rolling. A malleable material may be bent without breaking.

Elasticity, Yield Point, Ultimate Tensile Strength Elasticity is the ability of a material to return to its original dimension after it has been strained or stretched. The yield point is where the elastic limit is reached and the material will not return to its original shape.

HEAVY MECHANICAL TRADES— FOUNDATION / LEVEL 1

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LEARNING TASK 2

NOTES

A-14 CUTTING/WELDING

Fatigue Strength

Fatigue strength is the ability of a metal to resist rapidly alternating stretching, twisting, and compressive stresses when the load is applied first from one direction and then from another. For example, a welded trailer axle or frame undergoes a complete reversal of stresses, from tensile to compressive. Metals will fail under a changing load at lower stresses than they will if the load is steady. Care must be used when welding metals that will be subjected to alternating stresses.

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Hardness

Hardness is the ability of a metal to resist indentation or penetration. Hardness is usually linked to other properties of the metal such as its tensile strength. Tests used to determine hardness can also be used as an indicator of tensile strength. The harder of two metals of similar composition will have higher tensile strength, lower ductility, and more resistance to abrasive wear. High hardness also indicates low impact strength. When properly treated, some steels have both high hardness and good impact strength.

Alloy

An alloy is a metal composed of two or more chemical elements, of which at least one is a metal.

Ferrous

The term ferrous is applied to metals or alloys that contain 5% or more of iron.

Pig Iron

Pig iron is the basic metal obtained from iron ore. Most ferrous metals begin as pig iron. It has a very high carbon content (2.5–4.5%) and is cast into bars called pigs.

Cast Iron

Cast iron is re-smelted pig iron and includes all of the iron and carbon alloys with more than 2% carbon and almost always some silicon. High carbon and silicon contents give cast iron a low melting temperature and high fluidity in its liquid stage. It is easy to pour cast iron into complex moulds. Cast iron is used for engine blocks, heads, and housing assemblies.

Iron

Soft malleable metals can be made by alloying pig iron and nickel. The resulting metal is known as nodular iron.

HEAVY MECHANICAL TRADES— FOUNDATION / LEVEL 1

A-14 CUTTING/WELDING

Standard Steel

Standard steel is an iron alloy containing manganese, carbon, or other alloying elements. Standard steel is stronger and harder than iron, yet it is softer than tool steel. The carbon content affects the properties of steel. About 0.2% carbon makes a structural steel such as would be used for a frame. Higher carbon content makes the steel harder. At 0.8% carbon, the steel is suitable for making drills and hammers.

Tool Steel

Steel with a high content of carbon is called tool steel. It is hard enough to cut standard steel and iron. The metal must be able to withstand high temperatures, high load, and abrasive conditions. Because of the many applications of tools, tool steels vary in their composition.

Alloy Steel

Steel is an alloy of iron and carbon. Nickel, chromium, molybdenum, tungsten, and vanadium may be added.

Stainless Steel

Stainless steel contains chromium and usually nickel, in amounts up to a total of 25%. Stainless steel has high tensile strength, ductility, and hardness, as well as being highly resistant to corrosion and oxidation.

Non-ferrous

Non-ferrous metals contain less than 5% iron and in most cases, no iron at all. Examples of non-ferrous metals are aluminum, copper, zinc, and lead. Included in this group of non-ferrous metals are alloys such as bronze and brass.

Aluminum

Aluminum is light-weight and resistant to corrosion. It has low electrical resistance, high heat conductivity, good ductility, and considerable strength. Used extensively in the aeronautical industry, aluminum is also used for industrial tanks, truck and bus frames, and equipment body parts.

Copper

Copper is fairly resistant to corrosion, has good tensile strength, and is an excellent conductor of electricity. Copper is highly resistant to many chemicals and to corrosion from air and seawater. It should not be used in contact with oxidizing acids.

LEARNING TASK 2

NOTES

Copper is malleable. As it is drawn or cold worked, it will increase in tensile strength and become less ductile. Copper is used for water supply lines, electrical wiring, and soft tubing.

HEAVY MECHANICAL TRADES— FOUNDATION / LEVEL 1

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LEARNING TASK 2

NOTES

A-14 CUTTING/WELDING

Brass

Brass is an alloy of copper and zinc. Brass is stronger than copper and is corrosive resistant, making it an ideal metal for ships’ fittings, locks, and condenser tubes. Standard brass, which contains 30–34% zinc.

Lead

Lead is a very dense, heavy metal. It has a low melting point of 327°C (620°F), making it easy to use in liquid form. Lead is also used in the construction of batteries and in solder.

Types of Steels and Their Classifications There are several ways steels can be grouped or classified: • • • • •

chemical composition mechanical properties heat treatment ease of machining specific usage

Steels usually fall into one of three categories, based on their chemical composition: • • •

carbon steel low-alloy steel alloy steel

Carbon Steel Plain carbon steels have carbon as the only alloying element. These steels are classified according to the percentage of carbon they contain and are called low-, medium-, and high-carbon steels. The chart in Figure 1 identifies the carbon content of the categories of carbon steel and describes common applications.

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HEAVY MECHANICAL TRADES— FOUNDATION / LEVEL 1

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LEARNING TASK 2

Carbon Content (%)

Typical Uses

Low-carbon steel (0.10–0.30%)

General-purpose steel for auto frames, wheels, welding electrodes, wire, sheet products, nails, tubing, structural steel shapes, plate and bar, forgings

Medium-carbon steel (0.30–0.60%)

Machine parts and tools, crankshafts, gears, axles

High-carbon steel (0.60–1.0%)

Railroad rails, dies, springs, cold chisels, hammers, wrenches, band saws, axes

Very-high-carbon steel (1.0–1.7%)

Twist drills, taps and dies, lathe tool files, razors, ball races

NOTES

Figure 1. Carbon Content for Different Uses

Low-carbon Steel Steel in this category is tough, ductile, and easily machined and formed. All the commercial welding processes can successfully weld it. Low- carbon steel can be cast or shaped by forging. Most types do not respond to heat-treatment, but they can be quenched and tempered to enhance their mechanical properties. Medium-carbon Steel Higher carbon content gives this steel high strength and hardness. It cannot be worked or welded as easily as low-carbon steel. Successful welding often requires special electrodes and care must be taken to prevent cracking in the weld area. Preheating and post-heating may also be necessary. The higher carbon content also means this steel can be successfully heat-treated. High- and Very-high-carbon Steel (Tool Steel) This steel becomes very difficult to weld as the carbon content increases. As a rule, steel up to 0.65% can be welded, provided special electrodes and heat treatments are used. With the high carbon content, this steel responds well to heat-treatment. It’s not usually practical or possible to successfully weld highcarbon steel beyond 0.65%.

HEAVY MECHANICAL TRADES— FOUNDATION / LEVEL 1

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LEARNING TASK 2

NOTES

A-14 CUTTING/WELDING

Low-alloy Steel and Alloy Steel In addition to carbon, these steels contain other elements that enhance specific properties of the steel. They can be added to improve strength and toughness, to increase or decrease hardenability, or to improve corrosion resistance. Although hardness is determined mainly by the carbon content, other properties such as ductility, machine-ability, or magnetic properties can be improved by adding other elements. Other than carbon, the main elements used in the lowalloy steel and alloy steel include: • • • • • • • • •

chromium cobalt copper manganese molybdenum nickel titanium tungsten vanadium

Chromium Chromium increases both the hardness and harden-ability of steel as well as its resistance to abrasion and corrosion. It also increases tensile strength. Chromium refines the grain structure of the steel, increasing its toughness. Chromium is used alone in carbon steel or in combination with other elements such as nickel, vanadium, molybdenum, or tungsten. Chromium is used in stainless steel and acid-resisting steels. Typical applications include tools, knives, instruments, and bearings. Cobalt Cobalt improves the high-temperature properties or the magnetic properties of steel. The most common applications are magnetic products and high-speed, high- temperature cutting tools. Copper Copper is used as an alloying element in steel to increase resistance to atmospheric corrosion. Copper-bearing steels are widely used for sheet roofing and siding. Manganese Manganese is one of the most basic alloying elements in steel. It is an effective deoxidizer. It improves the grain structure and surface appearance of steel. It enhances the harden-ability, toughness, strength, and ductility.

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A-14 CUTTING/WELDING

Molybdenum This element produces the greatest hardening effect of any element except carbon and checks enlargement of the grain structure. Molybdenum also increases shock resistance, high-temperature strength, and corrosion resistance. Molybdenum-bearing steels find use in tools, machining parts, ball bearings, aircraft, and steam plants.

LEARNING TASK 2

NOTES

Nickel Nickel improves the ductility of steel without sacrificing tensile strength. It also improves the low-temperature toughness of steel. Large quantities of nickel (25–35%) dramatically increase resistance to corrosion and shock. Nickel-bearing steel finds wide use in tools, pressure vessels, armour, stainless steels, drills, gears, and ball bearings. Titanium Titanium is used to increase the high-temperature strength of steel. It can also be used to stabilize the grain structure of the steel or to act as a deoxidizer. Tungsten Tungsten, when used as an alloying element in steel, improves the toughness, hardness, and wear resistance of the steel, notably at high temperatures. Tungsten in combination with cobalt gives steel red hardness. Tungsten (often combined with molybdenum and chromium) is used extensively in the highspeed, high-temperature steels from which tools are produced. Vanadium Vanadium is widely used in construction steel to produce a fine grain structure and to promote toughness and shock resistance. Vanadium-bearing steel is used in high-strength pressure pipe, steel springs, gears, shafts, and axles where fatigue and impact resistance are prime considerations.

Structural Shapes Metals can be formed into different shapes for use in a range of applications.

Sheet Metal Sheet metal is formed in a long continuous roll or is cut into individual sheets of various dimensions. The sheets are formed in a rolling mill where the almost white-hot slabs of steel are passed through a succession of rollers. Each pair of rollers is set slightly closer to each other than the previous pair. The metal is squeezed thinner as it passes through each pair of rollers. Rolling continues until the metal is the desired thickness.

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A gauge number designates the thickness of sheet metal. In this “gauge” system, the smaller the number, the thicker the sheet. Sheet metal may be made from many metals, including steel, aluminum, copper, or brass. It may be rolled hot or cold, depending on the properties desired. For cold-rolling, the metal is rolled hot at first, then cooled before the final rolling process. Cold-rolling increases the strength and hardness of the steel, as well as producing a more accurate thickness than hot-rolling. Sheet metal may be used for roof covering, heating and cooling ducts, door cladding, and work surfaces on work benches. Sheet metal is widely used in the manufacturing of simple items such as instrument panels, as well as more complex items such as automobile bodies and engine covers. When sheet steel requires protection from corrosion, it’s usually galvanized (coated with zinc).

Plate Metal is also available in a form known as plate. Plate is similar to sheet metal, but thicker. Sheets of metal are considered plate if they are at least 4.8 mm (3⁄16 in.) thick. Plate metal is available in flat sheets 150 mm (6 in.) or wider and in lengths up to 6 m (20 ft.). Plate undergoes the same rolling process as sheet metal. Hot-rolled steel plate has a dark blue, scaly surface; while cold-rolled steel plate is smoother and has a sheen. Plate is used in heavy industry such as equipment manufacturing, truck decks, and general fabrication.

Round and Flat Bar Steel is commonly used in solid round and flat bar shapes. Round bars in diameters of 20 mm (3⁄4 in.) and larger are available in lengths up to 6 m (20 ft.). Smaller diameter round bars may be coiled on spools for easier handling. Flat bar is similar to plate except it is never wider than 150 mm (6 in.). Flat bar is available either hot-rolled or cold-rolled. Hot-rolled steel is scaly and dark blue or black. Cold-rolled steel is smoother, has a bright finish, and is higher in tensile strength. Round and flat bar are used in a wide range of manufacturing and construction processes such as shafts and brackets.

Angle Angle shaped metal is available in many metals, including steel, aluminum, and wrought iron. The shape is used in manufacturing and fabricating and is more rigid than round or flat bar. Angle may be purchased in a variety of leg dimensions and in lengths up to 12 m (40 ft.).

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Channel Channel is available in many standard dimensions and materials and in lengths up to 12 m (40 ft.). Channel is used extensively in construction and manufacturing.

LEARNING TASK 2

NOTES

Tee The tee shape is a structural shape used mostly in large steel structures such as bridges or buildings. The shape provides rigidity in two directions while keeping weight to a minimum. Tees can be used for truck box dividers, mounts, and other applications.

Tubing Tubing is available in steel or aluminum in different wall thickness. It is normally used for such items as rollover protection devices. Other structural shapes include standard I-beam and wide flange I-beam.

Storage and Handling The purpose in storing any product is to: • • • • • • • •

provide easy access to materials provide easy identification of materials protect the products from physical damage protect personnel from injury by materials facilitate inventory of stock protect the finish of the product prevent theft prevent loss

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Structural metal shapes are extremely heavy and can cause serious injury. Always make sure that you wear the appropriate safety equipment including boots and head protection. Protect your hands by wearing gloves and always keep your hands out of areas where they could be pinched by shifting material. Never attempt to lift structural shapes by hand. Always use proper lifting devices and correct rigging practices:

NOTES

• • • • • • •

Place steel on organized racks. Place similar shapes together. Place the large pieces on the lower areas. Make sure the racks and steel are protected from water (rust). Use a forklift to lift and move the steel. Wear gloves, steel-toe shoes, and safety glasses when handling steel. Get help when handling long pieces.

Depending on the type and shape of metal, different storage practices must be followed to achieve the above goals.

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SELF TEST 2

SELF TEST 2 1. What is tensile strength of a material? a. ability to withstand forces pulling apart b. ability to withstand forces crush it c. ability to withstand forces bend it d. ability to withstand forces wearing on it 2. What 5% material is added to Ferrous metals? a. zinc b. lead c. iron d. carbon

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NOTES

Identify Oxy-acetylene Components Gases Oxy-fuel gas-cutting involves the mixing of two gases to complete the cutting process. One of these gases is always oxygen. The other gas is the fuel gas. The fuel gas can be acetylene, natural gas, propane, methylacetylene-propadiene (Mapp®), or propylene. It is useful to know something of the properties and application of these gases.

Oxygen (O2)

Oxygen is a colourless, odourless, and tasteless gas found in our atmosphere. It supports both life and combustion. Our atmosphere consists of about 21% oxygen, 78% nitrogen, and 1% other gases. The large nitrogen content in our air tends to slow down combustion or burning. Materials that burn in our normal atmosphere will burn much faster and more vigorously in pure oxygen. Other substances that do not burn in air (such as iron) burn very well in pure oxygen. It’s this property that makes oxygen effective in cutting iron and steel. It is also this property that makes oxygen extremely dangerous. Many substances that are not considered flammable will burn with explosive violence in pure oxygen. Oxygen will cause oil and grease to explode into flame. Keep oil and grease away from oxygen equipment. Never use oil on oxygen cylinder pressure regulators, cylinder valves, or torch valves.

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Acetylene (C2H2)

Acetylene is a compound formed by uniting two carbon atoms and two hydrogen atoms. It is colourless, but it has a strong, pungent odour. The average person can smell as little as 1% acetylene in the air. This odour makes acetylene leaks easy to detect. Acetylene is used in oxy-fuel gas-cutting because it burns at an extremely high temperature. When acetylene is mixed with oxygen, the resulting flame can reach 3480°C (6300°F). This is the highest flame temperature produced from the combustion of oxygen and any fuel gas. This high flame temperature makes acetylene the most preferred of the fuel gases. Acetylene is flammable and highly explosive. Even a small proportion of acetylene in the air can explode. It is important to treat any mixture of air or oxygen and acetylene as potentially explosive. Immediately extinguish all open flames and ventilate the room before even turning on a light switch. Test the acetylene equipment for leaks and repair them immediately. Acetylene is also a very unstable compound. The term “unstable” means that the material is likely to break down (decompose) or undergo a physical change because of slight variations in temperature or pressure. The point at which a material breaks down is called its “critical point.” The critical point of acetylene is 193 kPa (28 psi) pressure at 21°C (70°F). At this point, acetylene breaks down into carbon and hydrogen and explodes. If the temperature is higher, the pressure at which acetylene breaks down will be lower. To allow for temperature fluctuations in a work area, the maximum working pressure for free acetylene is set at 103 kPa (15 psi). Cylinders used for acetylene are packed with a porous filler such as asbestos, charcoal, or balsa wood. The cylinder is then filled with liquid acetone in which acetylene is dissolved. The filler absorbs the liquid acetone. Free acetylene is confined to small pockets of gas. In this way, there is a minimal amount of free acetylene in the cylinder. This means the pressure in the cylinders can be high, about 1.7 MPa (250 psi). Acetylene gas reacts with copper to form acetylide, a residue that is even more unstable than acetylene. The slightest jolt can cause an explosion. Fire will most certainly result. There could be injury or loss of life. Never use copper or red brass fittings or tubing on acetylene systems. Use only fittings of yellow brass, iron, or steel.

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Other Gases For several reasons, fuel gases other than acetylene are often used in oxy-fuel gas-cutting. It is extremely important to remember that all of these gases are potentially explosive and you must use extreme care when working with them. The more common fuel gases are: • • • •

NOTES

natural gas propane methylacetylene-propadiene (MPS or Mapp®) propylene

These fuel gases each need a different amount of oxygen in order to produce a neutral flame (a flame that burns the fuel gas completely) (Figure 1). The question of how much oxygen you need to completely burn the fuel gas is important in terms of cost, the convenience of working with the equipment, and the availability of oxygen. Specially designed cutting tips and, in some cases, mixing chambers are necessary with the liquid fuels, MPS gas, and propane, as the amount of oxygen required to burn them completely is considerably higher than with acetylene. Fuel Gas

Oxygen to Fuel Gas

Acetylene

1 to 1

Propane

4.5 to 1

Natural gas

2 to 1

MPS

2.5 to 1

Propylene

2.6 to 1

Figure 1. Volumes of Oxygen to Fuel Gas Required for a Neutral Flame

For some cutting operations, these fuel gases might be preferred over acetylene for reasons other than cost. Acetylene and oxygen generate the highest flame temperature, which permits fast starts when cutting. Although the other fuel gases have lower flame temperatures and slower starts, they produce cleaner cuts than acetylene, with little or no slag clinging to the bottom of the cut. Acetylene has a limited draw-off rate, so it cannot be used with large tips unless you also use a manifold system. Other fuel gases have higher draw-off rates, which means you can use large tips. This is especially critical when you are using large heating tips or cutting sections that are more than 125 mm (5 in.) thick.

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Natural Gas (CH4) Natural gas is often preferred in areas where it can be piped in because it eliminates the dangerous and time-consuming handling of fuel cylinders. Natural gas generates a flame temperature of 2540°C (4600°F), which is lower than that of acetylene or Mapp® gas. Although it takes longer to preheat the metal and cutting speeds are slower, natural gas is a common alternative to acetylene because it is inexpensive and convenient. It is delivered at such low pressure that special injector-type torches are needed. Propane Gas (C3H8) Propane gas is supplied in liquid form in low-pressure cylinders. It is widely used because it produces clean cuts and is relatively inexpensive. Propane has a high heat value but requires 4½ volumes of oxygen to 1 volume of propane to burn completely. The flame temperature is similar to natural gas, 2540°C (4600°F). Propane is stored in liquid form for convenient and safe handling. Methylacetylene-Propadiene Gas (C6H8) Rearranging the molecules in acetylene and propane to form a new compound, methylacetylene-propadiene (MPS), a stabilized gas is produced. It is sold in different configurations under such trade names as Mapp® gas and FG (Fuel Gas). This compound is much more stable and less explosive than acetylene, and it produces a flame almost as hot, 2900°C (5300°F). Like acetylene, it has a strong odour, so leaks are easy to detect. MPS gas is stored in a liquefied form under high pressure. One cylinder contains the same volume as five acetylene cylinders. The capability of using higher working pressures makes MPS gas effective for underwater cutting where acetylene would be ineffective. Because MPS gas is so stable, the cylinders are safe and easy to handle. The slightly lower flame temperature makes for slower cuts, but with its clear advantage in safety, MPS gas is an attractive alternative to acetylene. Propylene (C3H6) Propylene fuel gas is a byproduct of the crude oil refining process. It’s sold under trade names such as Apache®, B-Plus ®, H.P.G.®, T9®, UCON 96®, and Victorgas®. It’s available in its pure form or it might have other fuel gases added to it. One volume of propylene requires a minimum of 2.6 volumes of oxygen for a neutral flame. The combustion characteristics of the propylene flame are similar to those of methylacetylene-propadiene and therefore propylene uses much of the same equipment.

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Cylinders Most welders use oxygen and fuel gas from cylinders. Since these cylinders are an important part of your gas-cutting equipment, it’s important that you know about their construction and safety precautions when using them.

NOTES

Cylinders are not generally sold. Suppliers, who regularly pick up the empty cylinders and replace them with full ones, usually rent them. The supplier is also responsible for maintaining the cylinder in safe working condition. Any defects should be reported to the supplier immediately.

Oxygen Cylinders Oxygen is available either as a gas in high-pressure cylinders or as a liquid in relatively low-pressure “cryogenic” cylinders. High-pressure Oxygen Cylinders High-pressure oxygen cylinders are forged from a single piece of strong, highcarbon steel, with walls at least 6 mm (1⁄4 in.) thick. High-pressure oxygen cylinders have a threaded collar, compression-fitted to the top of the cylinder, for the removable protective cap to screw on to. They’re available in a variety of capacities, ranging from 0.5–9.35 m3 (20–335 ft.3) (Figure 2). Oxygen cylinders are made in various sizes ranging from 0.5–7 m3 (20–244 ft.3) capacity. The oxygen is compressed to 2200 psi (15 MPa) at 21°C (70°F). Removable protective cap

Safety device in valve

Wall thickness 6 mm (¼")

1422 mm (56")

230 mm (9") Figure 2. Typical 7 m3 Oxygen Cylinder

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It’s important to know that temperature affects the gas within the cylinder. Gases expand when heated and contract when cooled, so the pressure within the cylinder will vary with temperature changes. Since you might be working with welding equipment in a variety of climatic conditions, you need some idea of how temperature affects the pressure in a full K-type oxygen cylinder (Figure 3). Temperature

Approximate Pressure

°C (°F)

MPa (psi)

49 (120)

17.3 (2500)

38 (100)

16.4 (2380)

27 (80)

15.5 (2246)

21 (70)

15.2 (2200)

16 (60)

14.8 (2140)

10 (50)

14.3 (2080)

4 (40)

13.9 (2020)

–1 (30)

13.5 (1960)

–7 (20)

13.1 (1900)

–12 (10)

12.7 (1840)

–18 (0)

12.3 (1780)

–23 (–10)

11.9 (1720)

–29 (–20)

11.5 (1660)

Figure 3. Temperature Versus Pressure in a K-type Cylinder

It’s important to be aware of the amount of oxygen in the cylinder. You can find this by monitoring the flame and the working pressure. If the flame is no longer consistent or the working pressure becomes difficult to maintain, remove the cylinder from service. If you continue to cut with reduced oxygen levels, your cuts will be poor in quality. The likelihood of flashback also increases. High-pressure Oxygen Cylinder Valve The high-pressure oxygen cylinder valve is made of forged brass. The valve is specially designed to operate at high pressure. It comes with a screw-on protective cap that must be replaced when the cylinder is not being used. The cylinder valve is a double-seal construction to prevent oxygen from leaking around the stem (Figure 4). When the valve is closed, seal #1 shuts off the flow of oxygen from the cylinder. When the valve is opened all the way, seal #2 prevents any oxygen from travelling up the stem.

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The valve handle or handwheel at the top of the valve opens and closes the valve. Turn the valve wheel counter-clockwise to open and clockwise to close. Always open an oxygen valve slowly. This will prevent a quick release of highpressure gas that would put too much stress on the cylinder pressure regulator and gauges. In extreme cases, a pressure rush could blow up the cylinder pressure regulator. The resulting metal fragments could cause serious injury.

NOTES

Handwheel

Seal #2

Stem

Safety device Oxygen out

Threads to attach to regulator (right-hand thread) Seal #1 Rupture disk Threads to attach to cylinder Oxygen in Figure 4. Seals in an Oxygen Cylinder Valve

The oxygen pressure regulator attaches to an external threaded outlet fitting on the side of the valve. This fitting has right-hand threads. A fitting thread is considered to be a right-hand thread if the fitting tightens when turned in a clockwise direction. If the fitting tightens when turned in a counter-clockwise direction, it is a left-hand thread.

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High-pressure Oxygen Cylinder Valve Safety Device High-pressure oxygen cylinder valves also have a safety device. Outside the valve is a capped hexagonal nut that has small holes around the perimeter of the cap. Inside is a safety disk, made of a special material that will burst if the pressure inside the cylinder gets too high (Figure 5). If the cylinder temperature rises, the pressure increases, causing the safety disk to rupture and release the oxygen through the small holes in the hexagonal nut. Opposing vent holes allow the pressurized gas to be evenly diffused and prevent the blast effect of a single vent. The pressure at which the disk ruptures is 27 MPa (4000 psi). Vent holes

Oxygen from cylinder

Ruptured disk Figure 5. Oxygen Cylinder Safety Device

Never try to repair a damaged cylinder valve or ruptured safety disk. Tag the cylinder to indicate the fault, move it to an open area, and notify the supplier to pick it up immediately. Liquid Oxygen Cylinders When you need large volumes of oxygen, it is more economical to have liquid oxygen supplied in cryogenic containers. The term “cryogenic” means “low temperatures,” usually at or below –130°C (–200°F). Cryogenic containers are very much like large thermos bottles in that they have an inner and outer container arrangement. The boiling point of oxygen is –183°C (–297°F). This means that oxygen converts to a liquid when cooled below a temperature of –183°C (–297°F). Storing gases in their liquid state allows the container to hold much higher volumes of gas. Oxygen, for example, has a cryogenic liquid-to-gas expansion ratio of 1 to 861.

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Acetylene Gas Cylinders Acetylene gas cylinders are strong, welded-steel containers that are specially designed to store the highly unstable and explosive acetylene gas. The cylinder is completely filled with a porous material such as monolithic filler, asbestos, charcoal, or balsa wood. This filler material is then saturated with acetone, which has the ability to absorb twenty times its volume in acetylene gas. The inside of the cylinder resembles a very fine honeycomb. The honeycomb arrangement localizes the gas in small pockets, reducing the possibility of explosion. The acetone stabilizes the acetylene so that it can be contained at a higher pressure. The fine honeycomb prevents the mixture of acetylene and acetone from sloshing around, which would cause it to separate and possibly explode.

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NOTES

With this arrangement, acetylene cylinders can be charged (filled) beyond the normal critical zone of 103 kPa (15 psi). The cylinders can be charged to much higher pressures, around 1.7 MPa (250 psi), so they can hold much more acetylene. Acetylene cylinders must be kept upright when in use. If not, the liquid acetone could flow into the system. Acetone would damage the acetylene pressure regulator, hoses, and fittings. If it reaches the torch, acetone will contaminate the flame, resulting in poor-quality cuts. Acetylene cylinders are normally shorter and larger in diameter than oxygen cylinders. They are available in a variety of capacities from 0.28–10.8 m3 (10–380 ft.3). Acetylene cylinders come in two basic types. The more common type has a rounded top with a protective cap that fits over and protects the cylinder valve. The other type has a recessed top that by design protects the cylinder valve (Figure 6).

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Valve

NOTES

Fusible plugs

1075 mm (43")

Felt filter

Porous filler material Wall thickness 3 mm (1⁄8")

Fusible plugs

300 mm (12") Figure 6. Two Types of Acetylene Cylinders

Acetylene Cylinder Valves Acetylene cylinder valves are less complex in construction than the special double-seal design of the high-pressure oxygen cylinder valve. This is because the pressures are relatively low. The cylinder valve might have a handwheel for opening and closing, or it might have a square shank that you operate with a cylinder valve wrench (Figure 7). When the cylinder is in use, the cylinder valve wrench should remain in place on the cylinder valve in case you need to close the valve quickly.

Figure 7. Acetylene Cylinder Valve Wrench

Acetylene cylinders with a recessed top have a cylinder valve that is operated by a T-handle cylinder valve wrench (Figure 8). As with a cylinder valve wrench, the T-handle cylinder valve wrench should remain in place on the cylinder valve when the cylinder is in use in case the acetylene must be shut off quickly.

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NOTES

Figure 8. T-handle Cylinder Valve Wrench

The cylinder valve must always be opened slowly, 1 to 11⁄2 turns. Never open the cylinder valve more than 11⁄2 turns. This will allow you to close the cylinder valve quickly in case of an emergency. As with the oxygen cylinder, the acetylene valve is turned counter-clockwise to open and clockwise to close. The valve has a threaded fitting to accept an acetylene cylinder pressure regulator with left-hand threads. Acetylene Cylinder Safety Device The safety device for the acetylene cylinder is not built into the valve, but consists of fusible (easily melted) plugs threaded into the top and bottom of the cylinder (Figure 9). Heat causes these alloy plugs to melt and release the cylinder contents. The average range of melting temperatures for these plugs is 104– 115°C (220–240°F). Body

Fusible material

Threads Figure 9. Acetylene Cylinder Safety Device

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Acetylene cylinders should never be completely emptied. It is very important to monitor the acetylene level in order to prevent acetone from being drawn into the lines. Remove the cylinder from service when the flame is inconsistent and the working pressure cannot be maintained. There is a maximum rate at which acetylene can be withdrawn from the cylinder. Above this rate (the “draw limit”), liquid acetone will be drawn into the system. Acetone can damage the hoses and pressure regulators and contaminate the flame. Going past the draw limit is also dangerous because the drop in pressure could lead to flashback. You can detect acetone contamination by a purple colour in the flame. Too high a rate of withdrawal can occur when the cylinder is cold, because the cylinder pressure is reduced. It can also occur when you use a large tip, since they draw more acetylene from the cylinder. For operations that require large amounts of acetylene, you must connect two or more cylinders together with an approved manifold system.

Liquid Fuel Gas Cylinders Fuel gases such as propane and methylacetylene-propadiene (MPS) are liquids when stored under pressure in cylinders. When the cylinders are full, a space remains above the liquid. The gas vapour occupies that space. When the cylinder valve is opened, the gas flows out, reducing the pressure on the liquid. This pressure reduction allows more liquid to vaporize (become gas) and collect above the liquid (Figure 10). Cylinder valve

Protective shield Fuel gas vapour Liquid fuel gas

Figure 10. Liquid Fuel Gas Cylinder 34

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Since the cylinder contains a liquid fuel gas, it must be operated in an upright position. Cylinders filled with a liquid fuel gas contain a greater volume of gas than acetylene cylinders, which are filled with not only acetylene, but acetone and a porous filler material.

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NOTES

Since MPS gas is not so sensitive to shock, it can be stored and shipped in lighter containers. For example, an empty acetylene cylinder weighs 100 kg (220 lb.) and a comparable empty MPS cylinder weighs only 23 kg (50 lb.). Liquid fuel gas cylinders look alike and have similar valves. The safety device on liquid fuel gas cylinders is a pressure relief valve built into the cylinder valve. Liquid fuel gas cylinders are available in various sizes and also in bulk- size tanks for use with a manifold system.

Storage and Handling of Cylinders The flammable and explosive properties of the gases used in fuel gas-cutting and welding make it essential to follow safety procedures at all times. Not only must you know the correct way to store and handle full and empty gas cylinders, but you must make the practice of all safety precautions a habit. Storage • Oxygen and fuel gas cylinders should be stored separately in designated areas. If they are stored indoors, the area should be dry and wellventilated. If they are stored outdoors, cylinders should be protected from the weather and direct sunlight, which could cause a rise in temperature. Empty cylinders should also be stored separately or with the same type of gas cylinder. If empty and full cylinders are stored together, they should be separated into designated “FULL” and “EMPTY” areas (Figure 11).

Figure 11. Storage of Full and Empty Cylinders

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•

Cylinders must not be stored near radiators, stoves, or any other source of heat.

•

Cylinders should be stored in an upright position.

•

All cylinders must be secured to a stationary object such as a wall or to a portable cart. Store all cylinders where they will not be knocked over or struck by falling objects or passing vehicles.

Handling • Cylinders must always be handled very carefully. Never drop cylinders or allow them to bump together or against another object. This might generate a spark and there might be enough gas leakage to cause an explosion. •

Special cylinder carts must be used for moving cylinders and the cylinders must be secured to the cart.

•

Cylinders can be moved short distances by tilting and rolling them on their edge. Never drag or slide cylinders across a floor.

•

To lift a cylinder with a crane, always use a cradle or box that is certified and rigged by qualified personnel (Figure 12). Never lift a cylinder by its protective valve cap.

•

When moving cylinders, always remove the cylinder pressure regulators. Make sure that the cylinder valves are closed and the protective valve caps are in place.

Figure 12. Carriage for Lifting Cylinders

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Safety Precautions •

Keep cylinders away from live electrical wiring.

•

Keep oxygen and fuel gas cylinders as far as possible from any area where sparks or flame from welding or cutting could contact them.

•

Never cut or weld directly over cylinders.

•

To prevent an explosion, keep oily and greasy substances away from the oxygen cylinders, valves, hoses, fittings, and attachments. Take care to keep oil, paint, and grease cans far away from your oxy-fuel gas equipment. Wipe up oil spots immediately. Keep hoses and welding equipment off the floor. Never oil or grease cylinder valves, pressure regulators, torches, or other oxy-fuel gas equipment.

•

Do not use leaky fuel gas cylinders. A leaking fuel gas cylinder must be moved to an area where good ventilation exists (preferably outdoors) and warning signs must be displayed to prohibit sources of ignition. Always operate oxygen cylinder valves by hand. Never strike a cylinder valve with a wrench or hammer, as this could cause a spark. If a cylinder valve is clogged with snow or ice, use warm water to thaw it. Never use a flame.

•

Never tamper with or try to repair cylinder valves. If a cylinder valve does not function properly, notify the supplier.

•

Never tamper with cylinder safety devices.

•

When not in use, cylinder valves must be closed and the protective valve caps installed.

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NOTES

Pressure Regulators and Their Functions Oxygen and Fuel Pressure Regulators Oxygen and fuel gases are stored in cylinders at pressures much greater than the pressures required to perform cutting or welding tasks. For example, the pressure of a full K-type oxygen cylinder is 15 MPa (2200 psi), while the actual working pressure required at the cutting torch might only be 275 kPa (40 psi). Pressure regulators are installed on cylinders to control the flow of gas from the cylinder so that a lower working pressure can be maintained. Oxygen and acetylene cylinder pressure regulators have many features in common (Figure 13). They are usually made from a solid piece of brass or aluminum. Most of them have two calibrated gauges attached. The gauge with the higher numbers (calibrations) shows the pressure in the cylinder. The gauge with the lower calibrations shows the working pressure.

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The cylinder-pressure gauge is located on the same side as the cylinder connection. The working-pressure gauge is on the same side as the hose connection. To set working pressure, turn the working-pressure adjusting screw. Turn it clockwise to increase the working pressure or turn it counter-clockwise to reduce the working pressure. Both oxygen and acetylene cylinder-pressure regulators have a hex nut permanently attached to the cylinder connection. The connections for oxygen pressure regulators are always right-hand thread. The connections for fuel gas pressure regulators are always left-hand thread. This arrangement makes it impossible to connect a pressure regulator to the wrong cylinder. There are several important differences between oxygen and acetylene pressure regulators. The most obvious difference is the calibrations on the pressure gauges. On oxygen pressure regulators, the cylinder-pressure gauge is calibrated from 0–27 MPa (0–4000 psi). The working-pressure gauge is calibrated from 0–1.4 MPa (0–200 psi). On acetylene pressure regulators, these gauges have a much lower calibration range. The cylinder-pressure gauge is calibrated from 0–2.7 MPa (0–400 psi). The working-pressure gauge is calibrated from 0–200 kPa (0–30 psi). In addition, the acetylene working-pressure gauge has a red warning area that begins at 103 kPa (15 psi). Pressures in this zone are over the maximum safe working pressure.

Acetylene Pressure Regulator

Oxygen Pressure Regulator

Figure 13. Pressure Regulators

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Acetylene working pressure must be kept below 103 kPa (15 psi) to prevent the unstable acetylene gas from exploding.

NOTES

Pressure regulators are usually identified by the type of gas for which they are to be used. Oxygen pressure regulators have the word “oxygen” printed on the regulator body and one or both gauges. The word “acetylene” is printed on the body and one or both gauges of acetylene pressure regulators. The gas hose and cylinder connections are threaded differently. Oxygen pressure regulators have an internal right-hand thread connection. Acetylene pressure regulators, depending on the supplier, have either an internal or an external left-hand thread connection. In addition, the hex nut on an acetylene pressure regulator is grooved while the hex nut on an oxygen pressure regulator is plain. There are variations in the fitting connections on acetylene cylinders, but the fitting connections on the acetylene pressure regulator can be changed by the use of adapters to suit the different styles of cylinder valves.

Safe Use of Pressure Regulators •

Make sure the pressure-adjusting screw (Figure 14) has been backed out before you open the cylinder valve. If the full pressure of the cylinder gas surges into the pressure regulator, the regulator mechanism and gauges could be damaged. In an extreme case, especially if oil is present, they could burst and cause personal injury.

Figure 14. Pressure-adjusting Screw

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•

Watch for a “creeping” pressure regulator. This occurs when the gas hoses and torch are attached, the working pressure is set, and the torch valves are closed. The working-pressure gauge tends to “creep up” or increase. A faulty valve seat in the pressure regulator usually causes this. It should be repaired before you operate the equipment.

•

Never force connections. Tighten connections with a cylinder wrench. Never use pliers or a pipe wrench. Always check the pressure regulator before trying to connect it to the cylinder. Make sure you have the correct pressure regulator for the cylinder.

•

Never use oil or grease on the connections and never use pipe compound or Teflon tape on these connections. Pipe compounds contain oil. Teflon tape will get into the system and plug small orifices.

•

Never try to repair a pressure regulator. Only a trained technician should do this.

•

All pressure regulators are precision mechanisms. Treat them with care and never drop or misuse them. When regulators are removed from service or transported, turn in the working pressure-adjusting screw just far enough to take the pressure off the inlet valve seats. Store them in a box or suitable container with packing material to prevent damage. Clean them with a dry, clean rag. Never use oil, grease, cleaning fluids, or gasoline to clean them.

Oxy-fuel Gas Hose The hoses that carry fuel gases and oxygen are specifically designed for those purposes. The structure of the hose consists of two or three rubber layers, each separated by a layer of strong fabric for reinforcement (Figure 15). The outside layer of rubber can be plain or ribbed. The oxygen hose is coloured green or black, and the fuel gas hose (acetylene) is red. To prevent tangling, most oxy-fuel gas hoses are joined together by an outside layer of rubber. Red fuel gas hose Rubber outer casing Fabric reinforcement

Rubber inner casing Green or black oxygen hose Figure 15. Double Oxy-fuel Gas Hose

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Since a single hose is more prone to kinking and wear, it usually has two layers of reinforcement to make it tougher (Figure 16).

NOTES

Outer rubber layer Fabric reinforcement Rubber layer Fabric reinforcement Inner rubber layer

Figure 16. Single Oxy-fuel Gas Hose

Safe Handling of Oxy-fuel Gas Hoses To avoid serious explosions or fires, only use an oxy-fuel gas hose that is in good condition. A faulty or damaged hose should be repaired in an approved manner or replaced immediately. Do not try to repair the hose with tape. After working with the hose, always coil and tie it to avoid kinking. Never expose the hose to oil, grease, cleaning solvents, gasoline, paint, or contaminants of any kind. Keep the hose out of direct sunlight. New oxy-fuel gas hoses often contain talcum powder. These hoses should be blown out with compressed air. When using compressed air, be sure that the compressed air system is oil-less. This can be done by using a compressed air system that has an oil separator installed or by using an “oil-less” compressor. All oxy-fuel gas hoses must be purged before use. Purging flushes the hose with a small amount of the applicable gas by opening the pressure regulators for a brief period of time and then closing them. This assures that there is no dirt or foreign matter that can enter the small passages of the torch. These bits could plug a hole or orifice and possibly cause a flashback.

Oxy-fuel Gas Hose Fittings All fittings and connectors used to connect the oxy-fuel gas hose to the pressure regulators and torch body are made of a brass alloy. This prevents sparks if the fittings should accidentally come in violent contact with other metals or materials. Brass alloy fittings will not corrode or produce any dangerous byproducts if oxy-fuel gases come in contact with them.

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Oxy-fuel gas hose fittings have right-hand thread connections for oxygen and left-hand thread connections for the fuel gas (acetylene) so the hoses cannot be accidentally switched. A distinct groove is cut around the outside of the hex nuts on fuel gas fittings (Figure 17). Sleeve type ferrule

Figure 17. Oxy-fuel Gas Hose Connections

Oxygen and fuel gas connectors are made up of two pieces: a fitting with a machined seat and barbed gland and a nut (Figure 18). When the two pieces are assembled, the barbed gland fits tightly inside the hose. A metal ring (called a “ferrule”) is crimped over the end of the hose to secure the hose to the barbed gland. Band-type ferrule

Figure 18. Oxy-fuel Connectors

A special crimping tool is used to compress the ferrule on the hose (Figure 19). The connector must be firmly secured or the gas pressure will cause it to separate from the hose.

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Figure 19. Ferrule Crimping Tools

Hose couplings can be used to connect two lengths of oxy-fuel gas hose (Figure 20). These couplings or splicers can also be inserted in a hose where a damaged section of the hose has been removed.

Figure 20. Hose Splice Coupling

Never use copper or red brass for fittings or tubing on acetylene gas systems. Acetylene gas reacts with copper to form acetylide, a residue that is even more unstable than acetylene. The slightest jolt can cause an explosion. Fire will most certainly result, causing injury or death. Only fittings made of yellow brass, iron, or steel can be used on acetylene gas systems.

Oxy-fuel Gas-cutting Torches, Cutting Tips, and Heating Tips Basic Torch Features Although there are different types of oxy-fuel gas torches, all have certain elements in common (Figure 21). The most distinctive feature of a cutting torch is the cutting oxygen control lever. Depressing this lever fully releases a flow of cutting oxygen. Cutting torches also have two hose connections to supply the oxygen and fuel gas to the torch. The oxygen hose connection has right-hand threads and the fuel gas connection has left-hand threads.

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Cutting torches are all equipped with two needle valves that control the flow of preheat flame oxygen and fuel gas to the tip. Cutting torches all have a mixing chamber or head. Depending on the torch type, the mixing chamber can be either in the tip or in the torch body. They all use a cutting tip to concentrate and direct the preheat flame and cutting oxygen. Preheat flame oxygen valve Cutting oxygen control lever

Cutting tip

Preheat flame fuel gas valve Built-in flashback arrestors

Figure 21. Oxy-fuel Cutting Torch

In the oxy-fuel gas-cutting torch, oxygen and fuel gas are carried in separate tubes from the inlet control valves to the mixing chamber, where they are mixed for the preheat flame. There is a separate passageway for the flow of cutting oxygen (Figure 22).

Cutting oxygen control lever

Torch body oxygen control valve

Preheat flame oxygen valve Preheat flame fuel gas valve

Figure 22. Cutaway of a Two-piece Cutting Torch

Oxy-fuel Gas-cutting Torches Oxy-fuel gas-cutting torches are either injector or equal-pressure types. The choice of which to use depends on the fuel gas supply pressure. Injector-type Oxy-fuel Cutting Torches The injector-type oxy-fuel gas-cutting torch is used for fuel gases supplied at low pressure, usually natural gas or low-pressure acetylene generator systems. The fuel gas is mixed with the oxygen by means of an injector nozzle in the torch handle (Figure 23). As the high-pressure oxygen flows from the tip of the injector, it draws the low-pressure fuel gas into the mixing chamber (venturi effect). 44

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High-pressure oxygen Injector

Mixing chamber

NOTES

Low-pressure fuel gas

Figure 23. Injector Torch

Equal Pressure-type Oxy-fuel Gas-cutting Torch The equal pressure-type oxy-fuel gas-cutting torch is more common than the injector type. It is designed for use with fuel gases supplied at higher pressures. One-piece Oxy-fuel Gas-cutting Torch The one-piece oxy-fuel gas-cutting torch is designed to be used only for oxyfuel gas-cutting processes. Two-piece Oxy-fuel Gas Combination Cutting Torch The two-piece oxy-fuel gas combination torch consists of a torch handle designed with a cutting attachment, a heating tip, or a welding tip (Figure 24). The main difference between a one-piece and a two-piece oxy-fuel gas-cutting torch is that the two-piece torch has three control valves rather than two. When you cut with this torch, the oxygen control valve on the torch handle is opened all the way, so in effect the valve is bypassed. Bypassing this valve supplies oxygen directly to the preheat oxygen control valve on the cutting attachment and to the cutting lever control valve. The preheat flame is adjusted by using the fuel gas control valve on the torch handle and the oxygen control valve on the torch attachment. The combination torch is an exceptionally useful tool because it can also be used with welding and heating attachments.

Cutting Attachment

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NOTES

Torch Body Figure 24. Two-piece Combination Torch

Oxy-fuel Gas-cutting Tips Oxy-fuel gas-cutting tips are interchangeable with the same design of torch head. However, cutting tips made to one manufacturer’s design cannot be used with torches made to another manufacturer’s design. Oxy-fuel gas-cutting tips are precision tools that should never be subjected to abuse. The tip can become damaged by extreme temperature, by dropping the torch, or even by setting it down roughly on a workbench top. When tips are not attached to the cutting torch, they should be stored in their original containers or in a special storage rack. Oxy-fuel gas cutting tips have seats designed to match those in the head of the cutting torch (Figure 25). Before installing the cutting tip, you should visually inspect the seats, checking for dirt or damage to the seat surfaces. The tip nut should always be tightened snugly with a wrench to prevent gas leakage. All cutting tips have pre-heat flame orifices, usually arranged in an outer circle with a cutting oxygen orifice in the centre. Cutting tip nut Torch head

Cutting tip

Cutting jet oriface

Seats

Preheat flame holes

Figure 25. Injector Torch

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Cutting Tip Sizes Oxy-fuel gas cutting tips are available in several sizes based on the thickness of the metal to be cut. The diameters of the preheat flame and cutting oxygen orifices increase as the thickness of metal to be cut increases. As the diameters increase, so do the designated tip size numbers. The numbers and the brand name are normally stamped on the cutting tip for easy identification (Figure 26).

NOTES

Figure 26. Cutting Tip Labelling

The following table shows examples of cutting tip sizes and cutting pressures as they relate to the various metal thicknesses (Figure 27). Note that the pressure settings for oxygen and acetylene are listed. Tip size designations and pressure settings can vary with each equipment manufacturer. Metal

Tip size

thickness

Cutting pressures

number

Oxygen (min.–max. psi)

Acetylene (min.–max. psi)

3 mm (1⁄8")

000

20–25

3–5

6 mm (1⁄4")

00

20–25

3–5

10 mm (3⁄8")

0

25–30

3–5

13 mm (1⁄2")

0

30–35

3–5

19 mm (3⁄4")

1

30–35

3–5

25 mm (1")

2

35–40

3–6

38 mm (11⁄2")

2

40–45

3–7

51 mm (2")

3

40–45

4–9

64 mm (21⁄2")

3

45–50

4–10

76 mm (3")

4

40–50

5–10

102 mm (4")

5

45–55

5–12

127 mm (5")

5

50–55

5–13

152 mm (6")

6

45–55

7–13

203 mm (8")

6

55–65

7–14

254 mm (10")

7

55–65

10–15

305 mm (12")

8

60–70

10–15

Figure 27. Cutting Tip Size Chart

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Types of Oxy-fuel Cutting Tips There are many cutting tip designs available. Your choice will depend on the use of the cutting tip and the type of fuel gas. Each fuel gas, such as acetylene, methylacetylene-propadiene (Mapp®), propane, natural gas, or propylene, requires a specially designed tip for cutting. A cutting torch and tip assembly must never be used with a fuel gas for which it was not intended. Methylacetylene-propadiene (Mapp®), propane, and natural gas all require more oxygen than acetylene to produce a neutral flame. Therefore, the mixing chambers and preheat flame orifices must be adjusted to accommodate this increase in oxygen requirements. Cutting tips for fuel gases other than acetylene are often two-piece in construction to accommodate the large volume of oxygen and fuel gas burning characteristics. Cutting Tip Maintenance Cutting tips need to be cleaned frequently because the openings become clogged with oxide and slag from the cutting process. When the holes are clogged, the gas flow is reduced and the flame becomes distorted. Always use special tip-cleaning needles (Figure 28). These needles are designed with tiny file-like teeth to loosen and remove oxides and slag. Always select a cleaning needle that is one size smaller than the opening. When cleaning the preheat flame orifices, open the oxygen control valve slightly. The oxygen will blow any scrapings out of the tip.

Figure 28. Tip Cleaning Tools

Use only a straight up-and-down motion with the needle (Figure 29). If you bend or twist the needle, you could flare the opening, causing flame distortion.

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Figure 29. Cleaning a Cutting Tip

Most tip cleaners include a small, flat, file-like scraper that is used to remove any slag. If there are worn areas or the tip has become flared, you might have to recondition the tip using a flat file or tip dresser (tip nip). Using the flat file or tip nip, you can reshape the tip end by filing or reaming up to a point where there is no longer any flare—see the dashed line in Figure 30. After filing or reaming the tip, polish it with fine emery cloth. Then clean the orifices to remove any burrs and filings lodged inside. Some tip cleaner kits include a file and tip dresser for reconditioning tip ends.

Do not file past this point

Figure 30. Point at Which the Flare in the Orifice Ends

The efficient performance of torch handles, cutting attachments, and cutting tips depends on careful use and handling. Cutting torches are precision tools and can easily be damaged from misuse. Never use a cutting torch as a hammer or prying tool. When the handle and attachments are removed from service or transported, they should be placed in a box and stored in a clean, dry area. They must not be exposed to oil, grease, solvents, gasoline, or other contaminants.

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Special Purpose Tips In addition to tips for general cutting duties, there are tips designed for certain special purposes. Two of the most common are: • •

rivet-cutting tips gouging tips

When using rivet-cutting tips and gouging tips (Figure 31), you must make sure that your working pressures are correct and you do not exceed the acetylene draw limits. Exceeding draw limits will result in drawing acetone from the acetylene cylinder, which will affect the fuel gas flow and result in backfires and flashbacks. Rivet-cutting tips are used for cutting or washing heads off rivets and bolts. The flat part of the tip lies on the base metal, thus preventing the base metal from being burned as the rivet or nut is washed off.

Figure 31. Rivet-cutting Tip

Gouging tips are used for removing tack welds, weld defects, and casting defects (Figure 32).

Figure 32. Gouging Tip

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Heating Tips Another commonly used oxy-fuel gas tip is a heating tip attachment, often called a “rosebud” (Figure 33).

NOTES

Figure 33. Rosebud Heating Tip

Unlike a cutting tip, which has an oxygen cutting orifice as well as preheat flame holes, a heating tip has only preheat flame holes on its face. Like cutting tips, these heating tips are available for different fuel gases and must never be used with fuel gases for which they were not intended. Also like cutting tips, they are available in different sizes for various heating jobs. Heating tips can be used for preheating and post-heating weldments, and for straightening or forming structural shapes, pipe, plate, and sheet metal. They can also be used to flame-harden steel parts to resist wear. Remember, when using an oxy-acetylene rosebud, you must make sure that your working pressures are correct and you do not exceed the acetylene draw limits. Exceeding draw limits will result in drawing acetone from the acetylene cylinder. This will affect the fuel gas flow and result in a flashback. The resulting explosion will extend back to the cylinder pressure regulator, blowing your gas hoses apart. This is an expensive mistake that results in the destruction of equipment.

Oxy-fuel Gas Torchline Explosions: Causes and Prevention Torchline explosions and fires occur when a highly explosive mixture of fuel gas and oxygen backs up into the torch. The results can be disastrous. It’s important that you use your torch correctly in order to avoid torchline explosions. There are two types of explosions: backfire and flashback. Backfire During the oxy-fuel gas-cutting process, the torch flame could back up into the cutting tip and make a popping sound. Usually the flame re-establishes itself instantly. In some cases the flame might go out, but since both gases are still flowing, the flame is usually rekindled from the hot work. If the flame does not rekindle, immediately close the torch oxygen preheat flame valve, close the torch preheat flame fuel gas valve and check the equipment.

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There are several possible causes of backfire: • • • • •

obstruction of gas flow at the torch tip (carbon deposits, hot metal particles) touching the torch tip to the hot metal overheated torch tip a faulty connection between torch handle and cutting attachment working pressures that are too low

With working pressures that are too low, the flame disappears into the torch tip because the gas speed (the speed at which the mixed gases come out of the torch tip) is not great enough. The gas speed must always be greater than the speed of propagation (the speed at which the flame travels toward the torch tip). Backfire is momentary and is restricted to the torch tip. It occurs most often with beginners who touch the hot metal with the torch tip. If the backfires occur repeatedly, carefully inspect the equipment, clean the torch tip, purge the hoses, and relight. Flashback A flashback occurs when the backfire goes back beyond the torch tip and through the hose to the pressure regulators (Figure 34). The torch handle becomes hot, black smoke and sparks come out of the torch tip, a squealing or hissing noise is heard, and the fire burns through the hose. Aside from fire damage, a flashback could cause an explosion. Flashback area (through to cylinder pressure regulator)

Backfire area Figure 34. Areas of Backfire and Flashback

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The causes of a flashback are: • • •

• •

Incorrect working pressures. Incorrect adjustment of the torch oxygen and fuel gas control valves. Grossly unequal oxygen and fuel gas working pressures. The higherpressure gas can back up into the lower-pressure line and produce a flashback. A clogged tip, along with too high oxygen pressure. Igniting the torch before purging the hoses. A torch that has been sitting idle for a while might well have an explosive mixture present in one hose.

LEARNING TASK 3

NOTES

To help prevent backfires and flashbacks, make sure that the valves on the torch and pressure regulators are working properly. The tip should have clear, undamaged orifices. Flashback arrestors must be used. If you have a flashback, you must stop the flame immediately before an explosion occurs. Shut down the torch preheat flame gas control valves and the cylinder valves immediately. The torch preheat flame oxygen control valve must be shut off before the torch preheat flame fuel gas control valve. A flashback indicates that something is radically wrong with the setup. Before you reignite the torch, check all equipment to see if it is damaged. Replace any damaged equipment, purge each hose separately, and adjust working pressures. If a flashback occurs again, stop using the equipment and have it serviced by qualified personnel. Flashback Arrestors The best way to prevent flashbacks and explosions is to keep the oxygen and fuel gases separated. Close the torch gas control valves when you’re not using the torch. Bleed gas hoses properly when you’re finished using the equipment. You must regularly inspect the control valves on the torch and the cylinders, as well as the gauges on the pressure regulators. Remember, inspection cannot help you detect whether oxygen or fuel gases are flowing in reverse inside the torch or hoses. A device called a “flashback arrestor” (Figure 35) is designed to respond to the pressure of a flashback by immediately stopping the progress of the flame burning back into the hoses and stopping the reverse flow of gas. A flashback arrestor also serves as a reverse-flow check valve, automatically stopping the reverse flow of the gas the moment it starts. Reverse-flow check valves are available without flashback capability. These reverse-flow check valves are often installed in the connections between the torch and the gas hoses. But it is strongly recommended that a proper flashback arrestor be installed at this location. WorkSafeBC regulations require that flashback arrestors be properly installed between the torch control valves and the cylinder pressure regulators.

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They may be installed at either end of the hoses.

Figure 35. Flashback Arrestors

Flashback arrestors are specifically designed to be used for oxygen or fuel gas (oxygen has right-hand threads, fuel gas has left-hand threads). All flashback arrestors are marked with an arrow to indicate the direction of gas flow. This tells you whether they are designed to be installed at the torch or at the pressure regulators. Most new oxy-fuel cutting torches come equipped with built-in flashback arrestors. Those that don’t, might have reverse-flow check valves. If your torch does not have built-in flashback arrestors, WorkSafeBC requires you to install flashback arrestors at either end of the gas hoses between the torch and the pressure regulators. Since a torch is subjected to occasional banging or dropping, the flashback arrestor at the torch end of the hose might become faulty. The flashback arrestor at the pressure regulator end serves as a critical second line of defense. Even with a flashback arrestor at both ends of the hose, the devices should be checked weekly. Inspection can be as simple as blowing in the opposite direction of the arrow: if there is no bypass, the valve is good. Flashback arrestors are a different story: you will have to follow the manufacturer-specific procedures for inspection and replacement. Using flashback arrestors is an easy way to prevent personal injury, damage, and expense resulting from an explosion or fire.

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SELF TEST 3

SELF TEST 3 1. What material are the acetylene fittings are made of? a. copper or red brass b. steel, iron, or yellow brass c. red brass or steel d. iron, red brass, or yellow brass 2. What is the maximum safe working pressure for acetylene? a. 103 kPa (15 psi) b. 138 kPa (20 psi) c. 193 kPa (28 psi) d. 345 kPa (50 psi)

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LEARNING TASK 4

NOTES

Correct Procedures to Assemble, Ignite, Shut Down, and Disassemble a Portable Oxyacetylene Unit How to Assemble a Portable Oxy-acetylene Unit Although many shops have a manifold system, portable oxy-fuel equipment is commonly used in the welding trades. Portable units can be found in many job settings, especially on industrial maintenance and construction sites or in fabrication and repair shops, where portability is required. Portable oxy-fuel units can be used with a variety of fuel gases, as discussed earlier. Acetylene has some advantages over other fuel gases due to its higher flame temperature and lower consumption of oxygen. Therefore, it’s the most common fuel gas used with the portable oxy-fuel units. The assembly and operating procedures for oxy-fuel and oxy-acetylene equipment are basically the same. This Learning Task will only discuss portable oxy-acetylene equipment. The steps to follow when assembling, igniting, shutting down, and disassembling oxy-acetylene equipment must be done in the correct order. Not following these steps precisely can result in personal injury and explosion.

Steps to Assemble a Portable Oxy-Acetylene Unit When assembling a portable oxy-acetylene unit, you must follow these steps: 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12.

secure the cylinders remove the cylinder caps crack the cylinder valves attach the cylinder pressure regulators install the flashback arrestors connect the gas hoses open the cylinder valves purge the cylinder pressure regulators and gas hoses connect the cutting torch set the working pressure purge the closed system check the system for leaks

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1. Secure the Cylinders in an Upright Position A light chain is commonly used to secure oxy-fuel gas cylinders to a portable cart so they do not tip over or get jarred (Figure 1). The cylinder cart is designed to roll easily when tilted back on its wheels, yet be stable and secure when stationary.

Figure 1. Cylinders Mounted Upright

2. Remove the Caps Covering the Cylinder Valves Turn the cylinder cap counter-clockwise to remove it (Figure 2). Always replace the cylinder cap when transporting an oxy-fuel gas cylinder and when the cylinder is not in service. Cap over cylinder valve

Figure 2. Removing the Caps

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3. “Crack” the Oxygen and the Acetylene Cylinder Valves Slightly open and quickly close (“crack”) the valves (Figure 3). This procedure cleans any dust or foreign particles from the valve outlets. Stand to the side of the valve outlets and make sure they are not pointing toward you or anyone else. Any particles inside the valves are expelled with extreme force.

NOTES

Figure 3. “Crack” Cylinder Valve

Never crack a cylinder valve near sparks or open flames. 4. Attach the Oxygen and the Acetylene Cylinder Pressure Regulators First examine the outlet connection on the cylinder valve and the inlet connection on the cylinder pressure regulator to make sure the connections are clean and the threads are in good condition. Match the pressure regulator connections to the appropriate cylinder valve connection. Remember, oxygen fittings have right-hand threads; acetylene fittings have left-hand threads. While it is impossible to install the wrong regulator on a cylinder, you can damage the threads by trying. Start and turn the cylinder pressure regulator nut by hand until it is snug (it should turn easily) (Figure 4). Then tighten it with a cylinder wrench.

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NOTES

Figure 4. Attach Cylinder Regulator

Never lubricate fittings—oil or grease and pressurized oxygen can ignite and cause an explosion. Oxy-fuel gas fittings need no lubrication. 5. Install Flashback Arrestors Attach flashback arrestors to the cylinder pressure regulator outlet connections (Figure 5). Tighten them with a cylinder wrench. Make sure to use the flashback arrestor on the correct cylinder pressure regulator. Flashback arrestors have left- or right-hand threads to match the oxygen or acetylene fittings. Make sure the direction of flow arrow marking on the flashback arrestor is pointing in the direction of the gas flow.

Figure 5. Installing Flashback Arrestors

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6. Connect Hoses Attach the oxygen hose to the flashback arrestor with the right-hand threads and the acetylene hose to the flashback arrestor with left-hand threads. Avoid over-tightening the connections.

NOTES

7. Open Cylinder Valves and Pressure Regulators A. Turn the pressure-adjusting screws out (counter-clockwise) on the cylinder pressure regulators (Figure 6). This closes off the regulators so the working-pressure gauges are not permanently damaged when high-pressure cylinder gases are allowed to flow through the cylinder valves into the pressure regulator. Note that when you open the oxygen cylinder valve, the working-pressure gauge remains at “0.”

Figure 6. Turn Out Regulator Screw

B. Open the oxygen cylinder valve very slowly (to prevent damaging the pressure regulator) until maximum pressure is reached. Then open the valve completely to seal the double-sealing valve. C. Open the acetylene cylinder valve very slowly, watching the cylinder pressure gauge at the same time. When the pressure has reached its maximum (when the needle stops moving), open the valve 1 to 11⁄2 turns to maintain that pressure. By not fully opening the acetylene cylinder valve, you can quickly close it in an emergency. If you use a cylinder valve wrench, leave it on the valve. Note that when you open the acetylene cylinder valve, the working-pressure gauge remains at “0.” Always stand to the side of a cylinder pressure regulator when you open a cylinder valve in case the regulator fails (Figure 7).

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Figure 7. Stand to the Side

8. Purge the Cylinder Pressure Regulators and Gas Hoses Purge the cylinder pressure regulators and gas hoses to remove any dirt or debris before attaching the torch. Any debris in the system can block small orifices and is potentially flammable. Point the gas hoses away from you and open each pressure regulating adjusting screw by turning it clockwise. This will allow the gas to flow, blowing out any dirt or debris from the hose. Then close the adjusting screw by turning it counterclockwise to shut off the gas flow (Figure 8).

Figure 8. Purge Hoses and Regulators

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9. Connect the Cutting Torch Install the flashback arrestors on the torch handle (if required). Follow the same procedure you used to attach flashback arrestors to the cylinder pressure regulators. Remember to match the direction of flow arrow on the flashback arrestor with the gas flow. Attach the hoses to the flashback arrestors. Connect the oxygen hose to the right-hand threaded flashback arrestors and the acetylene hose to the left-hand threaded flashback arrestors (Figure 9).

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NOTES

Figure 9. Attach Flashback Arrestors to Torch Handle, Then to Hoses

Using a cylinder wrench, tighten the hose connections. The oxy-acetylene outfit is now completely assembled. Now you need to set the working pressures. Before setting the working pressure, make sure that the cylinder valves are open and the cylinder pressure regulator working pressure-adjusting screws are turned all the way out. On a one-piece torch, make sure that the cutting torch’s preheat flame oxygen and fuel gas valves are closed. On a two-piece combination torch, make sure that the preheat flame oxygen valve on the cutting attachment is closed and the oxygen valve on the torch handle is fully open (Figure 10). The torch handle preheat flame fuel gas valve should remain closed.

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Open oxygen valve fully

NOTES

Close oxygen preheat valve Close acetylene valve Figure 10. Two-piece Torch

10. Set the Working Pressure Turn in the pressure-adjusting screw until the working-pressure gauge reads the selected working pressure. Repeat this process for both the oxygen and the acetylene (Figure 11).

How to Set Working Pressure Select and install the appropriate cutting tip. Be sure the cutting tip is clean. Insert the tip into the cutting torch head and tighten it. Use just enough pressure to make sure that the tip is tight. The cutting tip might already be installed, but you still need to know its size so that you can find the correct working-pressure settings on the equipment manufacturer’s cutting tip chart. Remember, the working pressure depends on the tip size, and the basis for selecting a tip size is the thickness of the metal being cut.

Figure 11. Set the Working Pressure

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11. Purge the Closed System Open the torch handle fuel gas valve until you are sure only fuel gas is coming out of the cutting tip (approximately 5 seconds). Close the fuel gas valve and follow the same procedure for the oxygen. The cutting lever valve may be used instead of the oxygen preheat flame valve. Purging the closed system will ensure that the system only has fuel gas in the fuel gas side of the system and only oxygen in the oxygen side of the system. If there is mixed gas in either side of the system it could result in a torchline explosion.

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The cutting torch is now ready to use, but before attempting any cutting, you must test the entire outfit for leaks. 12. Check the System for Leaks Before you start to use the cutting torch, you should always check the system for leaks, whether the equipment is being assembled for the first time or the setup is being used continuously. The system should also be tested after any new cylinders or components have been installed. To detect leaks, first set the working pressure, then close the cylinder valve. After you have closed the cylinder valve, watch the cylinder pressure gauge. If the gauge shows a pressure drop, you have a leak. This is a good practice that can be done every time you take a break for coffee or lunch. Just leave the system pressurized, close the cylinder valve and go for your break. When you return, watch the cylinder pressure gauge as you open the cylinder valve. If the gauge “jumps” up, you have a leak in the system. The easiest and most efficient way to locate the leak is by sound and smell. You might be able to hear the leak or, in the case of the fuel gas, you can smell it. If this fails, then you should use a commercially prepared leak check solution (Figure 12). If commercially prepared leaks check solution is not available, you can use a non-detergent soap solution. Be very careful not to use a hydrocarbon-based cleaning product. Commercially prepared leak check solutions are recommended, as they are safe, economical, and readily available.

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NOTES

Figure 12. Use a Leak Check Solution

You should apply leak check solution to the following areas of an oxy-acetylene system: • • • • • • • •

oxygen cylinder valve acetylene cylinder valve oxygen cylinder pressure regulator inlet connection acetylene cylinder pressure regulator inlet connection hose and flashback arrestor connections at the cylinder pressure regulators and cutting torch oxygen and acetylene torch valves cutting oxygen lever valve preheat flame oxygen valve (two-piece torch only)

If you find a leak, repair it immediately. Retighten the connection with a cylinder wrench and test the connection again. If the connection continues to leak, shut off the gas pressure, open the connection, and examine the threads and seat for dirt or damage. A leaking oxygen or acetylene cylinder valve is a very serious problem. Since they pose an extreme explosion or fire hazard, they should be removed from service and placed outside. The supplier should be notified.

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How to Ignite and Adjust the Preheat Flame The flint lighter, also known as a “spark lighter” or “striker,” is the only approved means of lighting an oxy-fuel gas torch. The steel cup on the flint lighter traps the fuel gas, and when the flint contacts the file segment, it produces a spark that ignites the gas. The two models shown in Figure 13 are the most common type.

NOTES

Figure 13. Flint Torch Lighters or Strikers

Never use matches, cigarette lighters (especially pressurized lighters), another torch, or hot metal to ignite your torch. Never keep pressurized lighters or matches in your pocket while you weld as they could ignite or explode and cause severe burns or personal injury. Wear fire-retardant coveralls, leather welding gloves, CSA-approved boots, welding cap, and CSA-approved safety goggles. Be careful where you point the torch flame and where you let the sparks and slag fall once you begin to cut. Take a few minutes to familiarize yourself with the feel of the cutting torch and the striker with your gloves on. Practice using the striker; hold it about 25 mm (1 in.) from the end of the cutting tip (Figure 14).

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NOTES

Figure 14. Lighting the Torch

Igniting the Torch To ignite the torch, open the preheat flame acetylene valve on the torch handle no more than 1⁄2 turn and ignite the fuel gas at the tip. The flame will look long and yellow. Continue to open the acetylene valve slowly until the flame becomes turbulent and stops giving off black smoke (Figure 15A).

Add Oxygen to the Flame Slowly open the cutting torch preheat flame oxygen valve. On a two-piece combination torch, use the cutting torch attachment preheat flame valve to adjust the amount of oxygen. As preheat flame oxygen is fed into the flame, the colour changes from yellow-red to blue and a fuzzy inner cone forms. As more oxygen is added, the inner cone becomes white, round, and smooth. Each of the preheat holes has such a cone. This is called a “neutral flame.” A neutral flame means that the oxygen and acetylene are mixed in the right proportions to burn the acetylene completely (Figure 15B).

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A. Acetylene only

NOTES

Long yellow-orange flame B. Neutral flame Blue envelope

Rounded white inner cones C. Oxidizing flame–excessive oxygen Light blue envelope

Sharp white inner cones D. Carburizing flame–excessive acetylene

Blue envelope

Light blue feather

Rounded white inner cones Figure 15. Types of Flames

If the inner cone is pointed and the flame hisses, too much oxygen has been added. This is an oxidizing flame (Figure 15C). It will cause the metal being heated to burn or oxidize. A carburizing flame has too much acetylene and results in adding carbon to the metal. The carburizing flame is blue with a dark-blue, feathered inner cone (Figure 15D). Since any one of these flames can be used in a given application, it is important that you know how to make the necessary adjustments. Now press down on the cutting oxygen control lever and adjust the oxygen to maintain a neutral flame.

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How to Shut Down an Oxy-acetylene Outfit It’s very important to know how to correctly shut down an oxy-acetylene outfit once the cutting is completed or when you leave the work area. A mistake could result in personal injury to you or others, so you must make sure that you follow, in the correct order, the steps listed below: 1. Close the cutting torch preheat flame acetylene valve. The flame immediately goes out and only oxygen gas flows from the tip. 2. Close the cutting torch preheat oxygen valve. On a two-piece combination torch, first close the cutting torch attachment preheat flame oxygen valve, and then close the torch handle oxygen valve. Gas is no longer leaving the cutting tip, but the system is still pressurized. In this state, you can leave the torch unmanned for only a short time. Anytime you stop work for a longer period, you must bleed off the pressurized oxygen and acetylene from the torch, hose, and regulators. 3. Bleed the system. “Bleeding the lines” means releasing the gas pressure still in the system. First close the acetylene cylinder valve, then close the oxygen cylinder valve. Next, open the torch acetylene valve. The pressure reading on both acetylene pressure regulator gauges will drop to “0” and you will hear any acetylene gas left in the system being released from the cutting tip (Figure 16).

Figure 16. Open Torch Acetylene Valve

Turn the acetylene pressure regulator working pressure-adjusting screw all the way out (counter-clockwise) to close the regulator. Then close the torch acetylene valve.

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Open the torch oxygen valve. The pressure reading on both oxygen pressure regulator gauges will drop to “0” and you will hear any oxygen gas left in the system being released from the cutting tip (Figure 17).

NOTES

Figure 17. Open Torch Oxygen Valve

Turn the oxygen pressure regulator working pressure-adjusting screw all the way out (counter-clockwise) to close the regulator. Close the torch oxygen valve. Put your equipment away. Store the hose and torch off the floor and away from objects that might damage them. Make sure the hose is free of kinks.

How to Disassemble the Oxy-acetylene Outfit Before you disassemble oxy-acetylene equipment, make sure the pressure regulator gauges read “0,” the system has been bled, and the cylinder valves are tightly closed. 1. Disconnect the hose from the flashback arrestors on the torch handle. Flashback arrestors can stay on the torch handle unless they need service or replacement. If you are disassembling a two-piece cutting torch, disconnect the cutting attachment from the torch handle and store it in a container that is free of oil and grease. 2. Disconnect the hose from the flashback arrestors on the cylinder pressure regulators. Flashback arrestors can stay on the pressure regulators. Coil the hose and store it in a well-ventilated place that is free of dust, oil, grease, and direct heat.

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3. Disconnect the pressure regulators from the cylinder valves. Carefully place each regulator in a separate container. 4. Place the protective cylinder caps over the cylinder valves and hand-tighten them. You must install the cylinder caps even if the cylinders are empty. Use soapstone or blackboard chalk to label empty cylinders with the letters “MT.” Store them separately from full cylinders (Figure 18).

Figure 18. Store Oxygen and Acetylene Separately

Although an instructor will demonstrate the procedures for assembling, testing, igniting, adjusting, shutting down, and disassembling the oxy-fuel gas outfit, carefully read and understand the sequences before entering the shop. After the demonstration, be prepared to answer questions and perform the steps as outlined. Do not take shortcuts, and never take safety for granted; otherwise you and others might become victims of your negligence.

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SELF TEST 4

SELF TEST 4 1. What is the first step in putting out a fire in the hoses of an oxy-acetylene outfit? a. use a fire extinguisher on the hoses b. close only the acetylene cylinder valve c. close only the oxygen cylinder valve d. close both the oxygen and acetylene cylinder valves 2. What must you do before you attach the pressure regulators to the cylinders? a. replace cylinder caps on the cylinder b. install flashback arrestors c. crack the cylinder valves d. seal the double-sealing valve 3. What flame has too much acetylene? a. oxidizing b. acetylide c. carburizing d. neutral

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LEARNING TASK 5

Cut Mild Steel with Oxy-acetylene Equipment Set-up Settings of Preheat Flames Adjustment of preheat flames affects the quality of a cut. If the preheat flames are too small, preheating is too slow. The cut will have the same problems that occur when the speed of travel is too slow. When preheat flames are too long, the cut is too fast, with too much slag and an irregular top edge.

Position of Cutting Torch Tip The inner cone of the preheat flame should be held 1.5–3 mm (1⁄6–1⁄8 in.) from the surface of the base metal. If the tip is allowed to touch the base metal, it could cause a backfire or the tip to overheat. Also, scale or slag from the surface of the base metal can get into the cutting orifice, which will result in a poor cut. The position of the preheat holes is another factor to consider. Cutting tips come with different numbers of preheat holes, depending on the tip size and design. For a straight, square cut, the preheat holes should be positioned so that two preheat holes follow each other along the line of cut (Figure 1). Otherwise, preheating is slower, and the cut displays a characteristic rounded top edge and irregular kerf (width of the cut).

Figure 1. Cutting Tip Pre-heat Hole Alignment

When cutting a bevel, you must change the position of the preheat holes in the tip (Figure 1). Setting the preheat holes in this position gives better preheat to the metal.

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This positioning is especially important for cutting tips with only two or four preheat holes. For cutting tips with more than four preheat holes, the exact positioning becomes less of a consideration.

Free Hand Travel Speed of Travel The speed at which you move the torch across the work is one of the most important factors affecting cut quality. Cutting with too fast of a travel speed will result in a poor quality cut (Figure 2). The draglines angle back away from the direction of travel and excessive slag clings to the bottom edge. Heavy slag buildup is undesirable because it takes time to remove, which adds to the cost of the cut. If the travel speed is excessively fast, the cut will be “lost.” The cutting stream will not completely penetrate the metal and the kerf will no longer be a clean opening or may be lost completely. Top edge square

Bottom edge slag

Curved drag lines

Figure 2. Cutting Speed Too Fast

Cutting with a travel speed that’s too slow also produces an inferior cut (Figure 3). The draglines are very pronounced and irregular, the bottom edge is very uneven, and the top edge is rounded rather than square.

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Top edge round

Bottom edge uneven

Irregular drag lines

Figure 3. Cutting Speed Too Slow

Operator Comfort When cutting, you should stand in a comfortable position so that you can clearly see the cut as you make it. The torch should move away from you, so that you have a good view into the kerf. With practice, you will develop a smooth, even torch movement that will enable you to produce smooth, high-quality cuts. Make sure that you keep the oxy-fuel gas hoses well out of the way (preferably behind you). Do not use your body or arms to support them. Take any twist out of the oxy-fuel gas hoses and place the hoses out of the range of falling slag and sparks from the cutting process.

Starting the Cut There are several methods you can use to start a cut. The most common way is to place the tip halfway over the edge of the plate, with the ends of the preheat flame cones about 3 mm (1⁄8 in.) above the base metal surface (Figure 4). When the edge reaches a cherry red colour, slowly depress the cutting oxygen lever to start the cutting process.

Figure 4. Starting a Cut

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Factors Affecting Cut Quality The main factors affecting cut quality are: • • • • • • • • •

surface condition of the base metal thickness of the base metal cutting tip size oxygen and fuel gas working pressures setting of the preheat flames position of the cutting torch tip not fully depressing the cutting oxygen lever speed of travel operator comfort and position

Surface Condition Before you cut a piece of steel, make sure the surfaces are clean. Any dirt, rust, grease, or slag will slow the cutting speed and result in a rough and irregular kerf. Thickness of Base Metal The base metal thickness has an important bearing on the quality of the cut. It’s the thickness that determines the correct cutting tip size, oxygen and fuel gas working pressures, speed of travel, and the angle at which you hold the torch. When cutting steel plate, normally you hold the cutting tip perpendicular (90°) to the base metal (Figure 5A), especially when profile cutting. However, on material 13 mm (1⁄2 in.) and thinner, it is better to use a slight push angle (70–90° off the base metal) when possible (Figure 5B). Using a push angle will preheat the base metal ahead of the cut as you work. Also, the slight angle allows the heat to deflect off the base metal and away from the tip. This helps to prevent the tip from overheating. When cutting steel sheet, hold the cutting tip with an extreme push angle (10– 20° off the base metal). This low angle makes for faster, straighter, and cleaner cuts with less slag attaching itself to the base metal (Figure 5C).

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A

B

C

Figure 5. Angle of Cutting Torch Depends on Thickness of Metal

Cutting Tip Size You should always check the equipment manufacturer’s cutting chart for the cutting torch that you are using. The cutting chart will tell you the recommended tip size for the thickness of metal you are cutting, along with the correct working pressures. Note that there is no standard tip size numbering system that equipment manufacturers follow. Each manufacturer develops and uses their own system. Also, gas consumption can vary from manufacturer to manufacturer. This means that tips from different manufacturers might use different volumes and pressures to cut the same thickness of metal. For safety and economic reasons, it’s important to check the equipment manufacturer’s cutting charts. If you use a cutting tip that’s too large for the material being cut, you waste oxygen and end up with an unsatisfactory, bell-shaped kerf. If you use a cutting tip that’s too small for the material being cut, the cut proceeds much too slowly, causing the same effects as a slow cutting speed. As well as selecting the correct size, you must make sure to keep your cutting tip clean and free of debris. Dirt, scale, or slag on the tip or in the cutting orifice will deflect the stream of cutting oxygen and cause the cut to be of poor quality (Figure 6). There might be too much bottom-edge slag, a rough-cut surface and a concave cut surface.

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Rough cut face Bottom edge slag

Irregular drag lines

Figure 6. Dirty Tip Used

Cutting Oxygen Pressure Since the cutting oxygen jet actually does the cutting, you must make sure that oxygen delivery is steady. When the oxygen pressure is too low, you’ll get a cut similar to that produced by a slow travel speed, with a characteristic rounded top edge. When the oxygen pressure is too high, the kerf becomes bell-shaped (Figure 7). High pressures are also uneconomical, since more oxygen than necessary is consumed in the process.

Slag Figure 7. Effects of Too Much Cutting Oxygen

Guided Cuts Sometimes you’ll need greater precision in oxy-fuel gas cutting than is possible with unguided manual cutting. For oxy-fuel gas cutting, there are a number of cutting accessories and machines that improve the quality and speed of the cutting process.

Manual Oxy-fuel Gas-cutting Guides Cutting guides are used to help control the position of the cutting torch. They do not, however, control the speed or preheat flame-to-work distance of the cutting torch. You must be skilled or rough cuts will result.

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Straight Line Cutting Guide A piece of flat bar (or angle) can be used as a straight-line cutting guide (Figure 8). The cutting tip is held against the cutting guide to produce a straight cut.

NOTES

Figure 8. Straight-line Cutting Guide

Circle Cutting Guide Circle cutting guides are used to cut circles and arcs. A typical circle-cutter attachment consists of an adjustable rod with a centre pivoting point, an adjustable wheel to set the pre-heat flame-to-work distance, and a rotating mechanism for attaching to the cutting tip (Figure 9).

Figure 9. Typical Circle Cutting Guide

Templates Templates serve as a master pattern for cutting irregular shapes. Once you have measured and cut one accurate pattern piece (allowing for the kerf ), you can then use that pattern piece as your template for all the identical pieces required. The use of templates saves time and ensures accuracy and consistency.

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Hole Piercing Steps for piercing holes: 1. Preheat the marked area to a red colour, keeping the preheat flames about 3 mm (1⁄8 in.) above the surface of the plate. 2. Lift the tip until the preheat flames are about 13 mm (1⁄2 in.) above the plate and slowly depress the cutting control lever on the torch. You’ll see the metal start to burn and slag will blow away from the preheated area. 3. Lower the tip back to 3 mm (1⁄8 in.) above the plate and maintain a circular motion over the area of the hole until the cutting oxygen jet has passed through the steel. 4. When you’re finished, there should be a clean hole with no slag on the cutting tip.

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SELF TEST 5

SELF TEST 5 1. What are the vertical lines called created by the cutting action on the metal? a. bowlines b. draglines c. kerfs d. stress ridges 2. How can a cut made too slowly be identified? a. curved draglines b. too much slag c. a rounded top edge d. no bowlines

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LEARNING TASK 6

Weld Mild Steel with Oxy-acetylene Equipment Fusion-welding Process and its Applications Fusion-welding is a process used for joining similar metals by melting and joining. There are many fusion-welding processes. These differ in their heat source and other factors. Fusion-welding that uses oxy-acetylene is called “oxyacetylene fusion-welding” and is abbreviated “OAW.” Fusion-welding that uses oxygen with gases other than acetylene is called “oxy-fuel gas-welding” and is abbreviated “OFW.” OFW also includes acetylene, but OAW is limited to acetylene.

Principles of Fusion-welding In the fusion-welding process, the facing edges of two pieces of metal are melted and the molten metal flows together and then solidifies into a single piece of metal. In oxy-acetylene fusion-welding, a concentrated flame is applied to the base metal with a welding torch. As the edges melt, they create a weld puddle or pool made up of metal from both edges of the base metal and from the filler rod (if used). Fusion takes place when there is complete blending of the base metal and filler metal in this weld pool. This is called the “weld metal.” As the weld metal cools, it forms a strong bond between the two pieces of metal (Figure 1). The area of fusion between the metals is called the “weld bead.” Weld bead

Weld pool

Base metal

Filler metal rod

Torch tip

Figure 1. Oxy-acetylene Fusion Weld

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In a fusion-welded joint, the weld bead should be slightly convex (Figure 2). The weld should penetrate to the bottom of the joint. Most often in the fit-up of weld joints, a root opening (gap or space) is left between the two pieces of metal in order to ensure full penetration. Convex bead

Fusion

Root opening

Root penetration

Figure 2. Cross-section of a Fusion-welded Single-vee Butt Joint

Filler Metal A welding rod (filler metal) is almost always used in fusion-welding. Filler metal is not always necessary in some joint designs, especially the closed corner and flange joints, because these joints often have enough extra base metals to make a strong bond. For most joints though, filler metal is necessary. Filler metal provides the extra metal required for reinforcement that will ensure that the welded joint has the required strength and the correct bead shape and depth. For fusion-welding, the base metal and the filler metal rod usually have the same composition. Filler metal rods are made with a wide range of metal alloys to meet most welding needs. They range in size from 1.6–5 mm (1⁄16– 3⁄16 in.) in diameter.

Applications of Fusion-welding Various arc-welding processes have largely replaced OAW and OFW. Electrical welding processes now account for over 90% of all welding work. For many welding jobs, OAW and OFW are too slow and are not cost-effective. Metals like aluminum, stainless steel, and thicker metals are more easily welded with arcwelding equipment.

Maintenance and Repair Work OFW is still used in some types of repair work because it’s a low-cost, portable means of welding. It’s also very versatile since it can be used to repair most ferrous metals as well as aluminum, magnesium, nickel alloys, titanium, copper, brass, cast iron, stainless steel, and almost any other metal. For specialized maintenance and repair work, the OAW and OFW processes will likely remain widely used.

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Fluxes for Fusion-welding Flux is a chemical compound that’s applied to weld joint surfaces before welding or brazing to help the bonding process. A flux is required for all braze-welding and brazing procedures. Fusion-welding of cast iron, stainless steel, and some non-ferrous metals also requires a flux. Flux is not usually needed for fusionwelding low-carbon steel. The high temperature required produces enough heat to melt any iron oxides already present or that have formed during the welding process. These oxides float to the surface of the weld pool and do not interfere with the fusion process.

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When fusion-welding cast iron, stainless steel, aluminum, or magnesium, you’ll need a flux. The oxides of these metals have a higher melting temperature than the parent metal. This is the same phenomenon that makes the metals difficult to cut with an oxy-fuel gas-cutting torch. The oxides remain solid at the temperature that melts the parent metal and interfere with the fusion process. The flux serves to increases the fluidity of the molten metal, dissolve oxides, and float off impurities to the surface of the weld pool. The flux you choose depends on the metal being welded, there’s no one universal flux. When choosing a flux for fusion-welding, be sure to read the manufacturer’s label carefully to see if the flux is suitable for the metal you’re welding.

Purpose of Flux Flux is always necessary for braze-welding and brazing processes to create a good bond. Flux serves three purposes: •

It chemically cleans the surface of the base metal, removing oxides that might not have been removed during pre-cleaning. Since braze-welding and brazing bonds require surface adhesion, it’s extremely important that the base metal surface be clean and free of oxides.

•

It prevents the formation of oxides during the braze-welding and brazing processes. The heating of the base metal accelerates the formation of oxides. The flux coats the weld joint and acts as a protective coating over the base metal.

•

It allows the filler metal to flow easily on the base metal.

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Oxy-fuel Gas Torches and Torch Tips for Fusion-welding The oxy-fuel gas welding torch is often called a “blow pipe.” The torch comes in various sizes and styles. Oxy-fuel gas is used for fusion-welding, braze-welding, and brazing. Heavy-duty industrial torches are used to heat large sections and to weld metals thicker than 50 mm (2 in.). Oxy-fuel gas Welders’ most commonly use a medium-duty torch to weld metals from 0.8–16 mm (1⁄32– 5⁄8 in.) thick.

How Oxy-fuel Gas-welding Torches Work There are two major types of oxy-fuel gas torch: the equal-pressure or balancedpressure torch, and the injector torch. In both, oxygen and the fuel gas are delivered from their respective hoses to separate tubes within the torch handle. Oxygen and fuel gas valves in the torch handle control the gas flow. These valves are usually located at the inlet points on the torch handle (Figure 3). Welding tip

Torch handle

Torch handle oxygen valve

Torch handle fuel gas valve

Figure 3. Oxy-fuel Gas-welding Torch

The torch types differ in how the gases are mixed. On the balanced- or equalpressure torch (Figure 4), the gases are delivered at about equal pressures to the mixing chamber, where they are thoroughly mixed and then emitted through the tip orifice. Union nut Welding tip attachment

Torch handle

Mixing chamber

Mixed gases Oxygen Acetylene

Tip orifice Figure 4. Cutaway View of the Equal-pressure Torch

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In injector-type torches, the oxygen gas flows at a higher pressure than the fuel gas (Figure 5). The oxygen flows through a venturi into the mixing chamber. As the oxygen passes through the venturi, the venturi effect allows the higher oxygen pressure to draw in the fuel gas through small openings so that the fuel gas is injected into the oxygen stream.

NOTES

High-pressure oxygen Injector

Mixing chamber

Low-pressure fuel gas

Figure 5. Cutaway View of the Injection Type Torch

The injector torch is used mainly with fuel gases that have very low delivery pressures. One drawback to the injector torch is the need for different mixers for different fuel gases. Before using an injector torch, you must check the torch carefully to make sure that the correct mixer attachment is installed. Equal-pressure torches are much more versatile. You only need to select the correct tip for the fuel gas, since the mixing chamber is always correct.

Oxy-fuel Gas-welding Tips Modern welding torches have separate, detachable welding tips that attach into the end of the torch handle. These tips are made of copper alloy, which is easily bent or dented, and they must be handled carefully and stored away from oil, grease, and paint. Choosing the Correct Oxy-fuel Gas-welding Tip The correct choice of welding tip size depends mainly on three factors: • • •

type of metal thickness of the metal type of welding process

The weld tip size is measured by the diameter of the tip’s flame orifice. A large tip has a large flame orifice and is able to deliver greater volumes of heat. Note that all welding tips, regardless of size, produce the same flame temperature at the tip. The difference is in the volume of heat delivered.

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The numbering system for oxy-fuel gas-welding tip sizes is similar to that of oxyfuel gas-cutting tips. The system is not standardized, so you should follow the manufacturer’s recommendations. Figure 6 shows how metal thickness determines the welding tip size used, and how tip size affects working-pressure settings on an oxy-fuel gas-welding torch. These listings vary with the type of welding tip, the type of torch, and the manufacturer. Welding Pressures Metal Thickness

Tip Size Number

Oxygen

Acetylene

0.8 mm (1⁄32 in.)

0–1

7–14 kPa (1–2 psi)

7–14 kPa (1–2) psi

1.6 mm (1⁄16 in.)

1–2

14–21 kPa (2–3 psi)

14–21 kPa (2–3) psi

2.4 mm (3⁄32 in.)

1–3

14–28 kPa (2–4 psi)

14–28 kPa (2–4) psi

3.2 mm (1⁄8 in.)

3–4

21–34 kPa (3–5 psi)

21–34 kPa (3–5) psi

4.8 mm (3⁄16 in.)

4–5

28–41 kPa (4–6 psi)

28–41 kPa (4–6) psi

6.4 mm (1⁄4 in.)

5–6

34–41 kPa (5–6 psi)

34–41 kPa (5–6) psi

9.5 mm (3⁄8 in.)

6–8

41–55 kPa (6–8 psi)

41–55 kPa (6–8) psi

Figure 6. Typical OAW Tip Chart for Steel Plate

Figure 7. Tip Size Stamped in Tip

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The type of welding process also affects the size of the welding tip you will require. Braze-welding and brazing requires less heat than fusion-welding, and usually a smaller tip size is used for metals of comparable thicknesses.

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The type of material also affects your choice of the welding tip size. When you are welding aluminum, copper, and other non-ferrous metals, the heat dissipates so quickly that you will need a larger tip size than you would for welding steel of the same thickness. It’s important that you use the correct tip size. If you use a tip that is too large, the metal will heat very quickly and it can burn through. This can be disastrous during low-temperature braze-welding or brazing, where you don’t want the base metal melting at all. If you fusion-weld using a tip that’s too small, it will take a long time for the base metal to melt. In braze-welding and brazing; a tip that’s too small will cause the base metal to take too long to get to the correct temperature to melt the filler rod. If it’s taking too long to reach the desired temperature, do not increase the gas pressure. Change to a larger size tip instead. Trying to increase the gas pressure will generally produce a very noisy, turbulent flame that disturbs the weld pool and creates poor welds. Choosing the correct welding tip for all circumstances requires experience. Always check the manufacturer’s welding tip specification chart for the correct tip size for the thickness of base metal you’re welding. It’s important to connect only welding tips and attachments that are specifically designed to mate with the torch handle. After choosing the correct tip size, insert the tip attachment into the torch handle. Examine the threads, seals, and seats before attaching the tip to the torch. If there’s a damaged seal or seat, the resulting leak can cause a fire or explosion. Tighten the union nut by hand only. Never use a wrench. Welding Tip Maintenance The welding tip will need to be cleaned from time to time. It can become clogged with small particles from the welding process and this can greatly affect the performance of the torch. The cleaning process is similar to cleaning an oxy-fuel gas-cutting tip. Use a flattip file to smooth off and remove any carbon or metal particles from the end of the tip (Figure 8).

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Figure 8. Use a Flat File to Remove Deposits from the Tip

Use a cleaning needle that is smaller than the diameter of the tip orifice and clean the inside of the tip orifice. Use a straight up-and-down motion only, taking care not to twist or bend the cleaning needle (Figure 9).

Figure 9. Clean Tip Orifice with Cleaning Needle

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Main Factors in Oxy-acetylene Fusion-welding

NOTES

Correct Cutting Tip Sizes Different torch tip sizes are manufactured to correspond to the heat requirements of various thicknesses of base metal. Since the numbering systems from the various tip manufacturers are not standardized, you must always follow the manufacturer’s tip specification chart. If you use a tip that’s too small, not enough volume of heat is present to melt the base metal. On the other hand, a tip that is too large produces too great a volume of heat, which can affect your work. The welding tip must also be clean. A clogged tip orifice interferes with the gas flow, causing a distorted flame. Be sure to set the working pressure of the oxygen and the acetylene at the pressures given in the tip specification chart. If you set the pressures too high, the turbulent flow of the gases will disturb the weld pool. This affects fusion and produces poor appearance. The correct pressures for the welding tip used will produce a flame that is quiet and a weld pool that is calm.

Correct Flame Setting The correct flame setting for oxy-acetylene fusion-welding of low-carbon steel is a neutral flame, the same as for oxy-fuel gas-cutting (Figure 10). It’s important to avoid using an oxidizing flame. An oxidizing flame causes oxides to form in the weld metal. Oxides will make the weld metal very brittle. You should use a very slightly carburizing flame to prevent an oxidizing flame from being formed if the gas pressures fluctuate. You should learn to recognize the sharp hissing sound and appearance of an oxidizing flame. A. Neutral flame

Blue envelope

Rounded white inner cone B. Oxidizing flame–excessive oxygen Light blue envelope

Sharp white inner cone C. Carburizing flame–excessive acetylene Blue envelope

Light blue feather

Rounded white inner cone Figure 10. Three Types of Flames

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Flame to Work Distance The tip of the inner cone of the flame should be about 1.6–3.2 mm (1⁄16–1⁄8 in.) above the base metal (Figure 11). This is the hottest part of the oxyacetylene flame. You want the metal to reach its molten state as quickly as possible and to maintain the weld pool during the welding process.

Direction of travel 30–45º 1.6–3.2 mm

Figure 11. Optimal Flame-to-work Distance

Types of Welding Techniques There are two basic techniques used in oxy-acetylene welding: forehand welding and backhand welding. In the forehand technique, the direction of travel is the direction the tip is pointing (Figure 12). In effect, the torch is “pushing” the weld pool and the welding flame is preheating the weld joint just ahead of the torch. The fillermetal rod is held in front of the weld pool and is fed in as required. In the backhand technique, the torch tip is tilted so that it points away from the direction of travel (Figure 12). In effect, the torch is “dragging” the weld pool and the tip points back toward the weld pool. The filler-metal rod is held in front of the weld pool and follows the movement of the torch. 90º–120º

30–45º

Direction of travel

Forehand

45º–90º

30–45º

45–75º

Direction of travel

Backhand Figure 12. Welding Techniques

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Forehand welding is the most popular technique. It’s used in all positions for welding light-gauge sheet up to 3 mm (1⁄8 in.) thick. Typically this technique requires a wider filler metal rod to torch-included angle (Figure 13). This gives good control and good weld appearance. Thin material 3 mm (1⁄8 in.) or less—wide angle

NOTES

Thick material greater than 3 mm (1⁄8 in.)—narrow angle Filler metal rod 45–90º

Filler metal rod

Torch tip 90–120º Torch tip Forehand travel direction

Backhand travel direction

Figure 13. Torch Tip to Filler Metal Rod Angle

The backhand technique is best for welding material that is more than 3 mm (1⁄8 in.) thick. Typically this technique requires a narrower filler metal rod to torchincluded angle (Figure 13). This helps to get good penetration at the weld root. The welding tip should be at least one size larger than what would be used on the same material with the forehand method. This is necessary because there is some heat loss. The forehand and backhand techniques have their own applications and you will need to learn both.

Torch Angle The welding torch angle includes two angles: the work angle and the travel angle (Figure 14). Both angles are taken from the surface of the base metal at the weld pool. The work angle is taken across the weld joint (or more precisely, in a transverse plane from the weld axis). The travel angle is taken along the length of the weld joint (or, in a longitudinal plane from the weld axis). A torch travel angle of 45–75° is typical for backhand welding. A torch travel angle of 30–45° is typical for forehand welding. Through experience, you will learn to vary the angles of the torch and the filler-metal rod to suit the job you are doing.

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Work angle

Travel angle

45–75º

90º

Backhand travel direction Front view

End view

30º 90º Front view

End view

Forehand travel direction Figure 14. Torch Tip Angle and Work Angle

Speed of Travel Speed of travel (rate of travel) is a very important factor in producing good fusion welds. The speed of travel depends on the base metal thickness, the welding joint design, and the volume of heat produced by the welding torch. If your speed of travel is too fast, the weld bead becomes too narrow and the bead ripples become pointed. The heat has not penetrated and lack of fusion is the result (Figure 15).

Figure 15. Weld Bead Formed When Speed of Travel Was Too Fast

If your speed of travel is too slow, it will result in too much penetration and a scaly appearance on the weld bead (Figure 16).

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Figure 16. Weld Bead Formed When Speed of Travel Was Too Slow

If you allow too much heat to build up, the molten weld pool will collapse through to the bottom of the plate and leave holes (Figure 17). The underside of the weld might have molten metal that has solidified, forming icicle-like structures.

Figure 17. Weld Bead Formed with Too Much Heat

If you complete your weld properly, it will have uniform bead ripples, even bead width and a shiny surface appearance (Figure 18).

Figure 18. Weld Bead Formed Correctly

The movement of the torch is also extremely important. As soon as there is a small weld pool (pool of molten weld metal), start to move the torch forward with a side-to-side or circular motion. At the same time, insert the end of the filler rod into the weld pool, dipping the rod into and out of the weld pool. The filler rod should be withdrawn just enough to remove it from the weld pool, but not entirely from the flame, since it should not be allowed to oxidize or cool.

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Coordinating the motion of the filler rod and the motion of the welding torch is an important factor in producing a quality weld. You will become better at this with continued practice.

Welder Comfort and Position When welding, you should always position yourself so you can clearly see the weld pool, and you should (whenever possible) be in a firm, steady position. Bracing your body against something stationary can help. Place the elbow of your filler-rod arm on something solid or rest your hip against the edge of your workbench to improve your ability to hold steady. Using both your elbow and your hip is best. Do not brace your torch hand. If you weld standing upright with no part of your body touching a steady point, you’ll find that you will have difficulty steadying yourself. Find a way to hold the torch comfortably so that you have good control over the movement of the tip. Support or arrange the gas hoses so there is no interference with torch movement. The important thing is to be comfortable and have good control over the torch. If you’re right-handed, welding with the forehand technique, the direction of travel is normally from right to left. If you’re left-handed, the direction of travel would normally be from left to right.

Weld Faults in the Oxy-acetylene Welding Process There are several common weld defects you should be aware of and learn to avoid. The faults presented here are the ones you’re most likely to experience when oxy-acetylene welding. These defects are called “structural discontinuities.” They include: • • •

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Incomplete Penetration Incomplete penetration occurs when the weld pool and the base metal have not fused at the bottom, or root, of the weld joint (Figure 19).

Complete penetration

Complete penetration

Incomplete penetration

Incomplete penetration

A

Figure 19. Penetration

NOTES

B

This is one of the most serious welding defects. In welding joints such as a butt joint (left image in Figure 19), the joint can be turned over and inspected for complete penetration. However, in other joints such as lap (right image in Figure 19) and tee joints, incomplete penetration is impossible to detect. Incomplete penetration is usually the result of inadequate welding heat. It occurs most often if the welding tip is too small, the speed of travel is too fast or the flame is held too far away from the base metal. Poor weld joint design or fit can also contribute to incomplete penetration.

Incomplete Fusion Incomplete fusion is a very serious problem that is also hard to detect. This fault differs from incomplete penetration in that the weld joint might be full, but the weld deposit has not fully joined with the base metal. In other words, fusion has not taken place. The filler metal has been deposited, but the weld deposit has not fused with the base metal. Incomplete fusion can occur anywhere in a weld. Incomplete fusion at the edge or toe of the weld is called “overlap” or “cold lap.” Overlap is most often a sign of poor fusion throughout the weld deposit (Figure 20).

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Overlap (Cold lap)

NOTES

Figure 20. Overlap or Cold Lap Faults

There are several causes of incomplete fusion. The most common is failure to preheat the base metal to the filler rod’s melting point before melting the filler rod into the weld joint. On some metals, not using the proper flux can also cause poor fusion and overlap.

Undercut Undercut is a cutting away of the plate surfaces at the edge of the weld (Figure 21). A sharp recess forms in the plate where the next layer or bead must fuse with the base metal. The plate is thinner at this point, so the joint is weaker. Joint failure is especially likely when the undercut occurs at the toe of the weld.

Figure 21. Undercut

Too much heat, improper torch work angle, or too slow a travel speed are the most common causes of undercut.

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Reinforcement on Grooved Welds In addition to these serious structural faults, there are weld faults that affect the dimension of the finished weld. If the dimension of the finished weld does not meet specification, it’s called a “dimensional defect.”

NOTES

Metal deposited above the surface of the plate is called “reinforcement.” In a groove weld, there should be sufficient weld deposit to build up the weld profile above the surface of the base metal (Figure 22). This reinforcement, however, should not be higher than 3.2 mm (1⁄8 in.). Adequate reinforcement

Insufficient reinforcement

Figure 22. Reinforcement

Correct Weld Profile Fillet welds are used on lap, tee, and corner joints (Figure 23). A fillet weld is roughly triangular in shape. The most preferred fillet weld is flat to slightly convex in order to provide the necessary strength to the welded joint. Concave weld profiles can be specified for certain welds, but generally, they should be avoided.

Concave

Convex

Size

Size

Size

Flat

45º Size

C

Figure 23. Fillet Weld Profiles

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Basic Joint Designs and Welding Positions for Fillet Welds Five Basic Joints There are five basic joint designs used in welding (Figure 24). Of these joint designs, the corner, lap, and tee are the type you will weld with a fillet weld. The edge joint is used mainly on light-gauge sheet metal and normally does not require additional filler metal.

Lap joint

Tee joint

Butt joint

Corner joint

Edge joint Figure 24. Five Basic Joints

Corner Joint The corner joint joins two pieces of metal at right angles (90°) to each other (Figure 25).

Slight gap Tack welds

90º

Figure 25. Corner Joint

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When forming a corner joint, position the two pieces to form an angle close to 90°. Make sure that the edges of the weld joint meet from end to end and do not overlap.

NOTES

Incomplete penetration is a relatively common defect in corner joints. It can result from a fit that’s too tight. Therefore, it’s necessary to leave a slight gap between the plates in order to ensure complete penetration. Incomplete penetration can also be caused by a speed of travel that’s too fast. In this case, the weld pool becomes too small to melt through to the bottom edges of the plates. A welding flame that does not supply enough volume of heat to penetrate to the bottom edges of the plates can also cause incomplete penetration. Lap Joint A lap joint is used to join two pieces of metal that overlap (Figure 26). It’s a useful way of joining two plates where a “tight” joint is necessary, but great strength isn’t required. This joint is not practical for many applications. Some base metal is wasted in the overlap, the plates are offset (which might not be desirable) and the joint itself is not as strong as a butt joint.

Tack welds 19 mm (¾")

t

Tack welds Figure 26. Lap Joint

A good lap joint weld is slightly convex in shape (Figure 27A). If not enough filler metal is added, a concave profile will result (Figure 27B).

A. Good weld bead contour

B. Bad weld bead contour

Figure 27. Cross-section of Lap Joint Bead Contours

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Other faults that are common with lap joint welds are incomplete fusion (cold lap) and incomplete penetration (Figure 28). Incomplete fusion most often comes in the form of cold lap, which results from insufficient heat input to the lower plate. Incomplete penetration occurs at the root of the weld bead so that a gap is left between the bottom of the bead and the inside corner of the weld joint. Cold lap

Gap under bead Cold lap

Incomplete penetration Figure 28. Weld Defects on Lap Joints

Tee Joint For a tee joint, the plates are set up so that the edge of one plate is butted to the face of another to form a 90° angle (Figure 29). Once welded, it forms a strong joint that’s even stronger when welded on both sides. Tee joints are especially prone to distortion. You can minimize this distortion by tack welding the joint at both ends and on both sides.

90º

Tack welds

Figure 29. Tee Joint

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A cross-section of the weld profile should show the bead to be flat or slightly convex, with penetration through to the inside corner of the weld joint (Figure 30). The legs of the tee joint weld bead should be equal in length, which means the completed weld should be evenly distributed between the vertical and horizontal members of the joint.

NOTES

Figure 30. Tee Joint Weld Bead Contour

A fault that’s common to tee joints is undercut on the vertical plate (Figure 31A). Using an extreme weaving motion of the torch usually causes this. Another common problem is a weak, concave weld bead (Figure 31B), which occurs when not enough filler metal is added to the weld pool.

A

B

Undercut Concave

Figure 31. Common Faults on Tee Joints

The tee joint is a difficult weld to master. When you have become proficient, the weld bead will be flat or slightly convex and have good fusion, consistent width, a clean appearance, equal legs, and no undercut.

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Butt Joints Square Butt Joints The square butt joint requires no edge preparation. For the oxy-acetylene welding process, the square butt joint is suitable only for thin material, 3.2 mm (1⁄8 in.) thick or less. When fitting a square butt joint, you must leave a small gap between the members about the thickness of the plate. If the filler rod is the same thickness as the base metal, it becomes a handy scale with which to measure the gap (Figure 32).

Figure 32. Square Butt Joint Spaced with a Filler Rod

Single-vee Butt Joint The single-vee butt joint is normally used on thicker material, up to 19 mm (3⁄4 in.). The single-vee butt joint has several significant dimensions, including the root opening (root gap), the root face (land), the included angle, and the bevel angle (Figure 33). These surfaces can be prepared with an oxy-fuel gas-cutting torch or with a grinder.

Included angle

Bevel angle

Thickness (T) Root face

Root opening Figure 33. Single-vee Butt Joint

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Often, you will need to make more than one pass to fill a weld joint between a thick plate or pipe. The first pass, called a “root pass,” is the most important. If there is incomplete fusion, penetration, or reinforcement, the weld will be flawed. In a two-pass weld, the second pass, called a “cap” pass, fills up the weld joint and provides reinforcement at the top (cap) of the weld deposit. The joint should be filled until it forms a slightly convex bead (Figure 34).

NOTES

Cap and fill pass

Root opening

Root pass

Cap pass Fill passes Root face

Root opening

Root pass

Figure 34. Butt Joint in Multiple Passes

Getting complete penetration is difficult when welding butt joints. In order for the weld to have full strength, the heat must penetrate completely through to the bottom of the joint. As with the corner joint, you need to make sure that there is a “keyhole” at the leading edge of the weld (Figure 35). The keyhole indicates that the weld pool is melted through to the bottom edge of the base metal.

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Weld pool

NOTES

Keyhole Figure 35. Keyhole at the Leading Edge of the Weld

Four Basic Lap, Tee, and Corner Joint Welding Positions There are four basic welding positions: • • • •

flat horizontal vertical overhead

These positions are common to all welding processes. You will see these names in qualification tests, specifications, and instruction manuals. Flat Positions In the flat position, the work piece is positioned so that the weld joint is parallel to the floor (Figure 36). The torch usually points downward and the weld metal is deposited on top of the base metal. For corner joints with equal-sized plates, the two joint members can simply be placed on the workbench and welded. Lap joints and tee joints must be supported in an angled position in order to get a true flat position.

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Figure 36. Flat Positions

Horizontal Position In the horizontal position, the work piece is also positioned so that the weld joint is parallel to the floor so the surfaces of the plates are vertical (Figure 37). For butt joints, the two plates are supported in the vertical position. The other four joints are positioned so that one edge surface of the weld joint is parallel to the floor and the weld is on top of the plate. With horizontal welds, the main difficulty is that gravity causes the weld pool to flow toward the lower side of the weld joint.

Figure 37. Horizontal Positions

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Vertical In the vertical position, the plate to be welded is positioned vertically and the weld itself is vertical. The direction of travel can be uphill (vertical-up) or downhill (vertical-down), but the majority of vertical welding is done uphill (from bottom to top) (Figure 38).

Figure 38. Vertical Positions

Overhead The overhead position is the same as the flat position rotated 180°. This is considered to be the “true” overhead position. The overhead position is also the same as the horizontal position rotated 180° (Figure 39). The work piece is positioned so that the torch and filler rod point upward. Overhead welding is considered the most difficult to master. The force of gravity causes the weld pool to drip. When these drips solidify, they are called “grapes” or “icicles.”

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Figure 39. Overhead Positions

Four Basic Butt Welding Positions Butt joints can be welded in all four positions (Figure 40).

Flat

Overhead

Vertical

Horizontal Figure 40. Welding Positions for Butt Joints

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SELF TEST 6 1. What is the name for the area of fusion where two pieces of metal have been joined? a. slag b. kerf c. weld bead d. filler deposit 2. What is the main purpose of filler metal in fusion welding? a. to cool the weld pool b. to create a bond c. to add metal d. to slow the progress of the weld 3. What thickness of metal is the single-vee butt joint used on? a. 3 mm to 10 mm (1⁄8" to 3⁄8") b. 6 mm to 19 mm (¼" to ¾") c. 19 mm to 25 mm (¾" to 1") d. 25 mm to 38 mm (1" to 1½")

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Braze Lap Joints with Oxy-acetylene Equipment Braze-welding Process and its Applications Braze-welding is carried out in much the same way as fusion-welding. However, the filler metal is non-ferrous and always has a melting point below that of the base metal. The base metal is never melted, so the filler metal and base metal do not actually fuse together. The strength of the joint comes from the cohesion or bond of the filler metal to the base metal. This is done by raising the temperature of the base metal above 427°C (800°F) until the melted filler rod “tins” or forms a thin, even film on the surface of the joint. Additional filler metal is added to complete the joining process to create a strong bond. Although there is no fusion, there is actually a very narrow line (observable only at high magnification) where the atoms of the base metal and the filler metal have mixed. Many metals can be brazed; such as cast iron, malleable iron, aluminum alloys, stainless steels, tungsten, copper, and nickel. Dissimilar metals can be joined; such as cast iron to steel, copper to steel, or alloy steel to cast iron. In general, the joints are not as strong as fusion-welded joints and they start to lose strength at temperatures above 260°C (500°F). There is less heat required and less distortion to the base metal. In addition, brazing is usually faster than fusion-welding and the filler material is resistant to corrosion (Figure 1). Molten bronze will flow easily and evenly over the surface of a solid metal, which has been mechanically or chemically cleaned and properly heated. If the base metal is not clean or properly heated, the braze-weld filler metal will not flow or “tin” properly. All dirt, grease, scale, and rust should be completely removed from the base metal by grinding, filing, or using an emery cloth before applying heat. Even after thorough mechanical cleaning, certain oxides may be present on the base metal surfaces. These are chemically removed by means of a suitable flux, usually a mixture of borax and boric acid. When heated to a liquid state, the flux dissolves any surface oxides and prevents the formation of any new oxides. In most cases, the welding rod is coated with an even distribution of flux.

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Flux is also available in powder form and a plain filler rod is dipped into the flux during brazing. Coated rod is usually preferred as it eliminates the need to constantly interrupt the brazing procedure. When heated, the flux melts and forms a liquid film. The film dissolves surface oxides or prevents them from forming and generally cleans the metal where the pieces are to be joined. The flux floats to the top of the puddle and, once solidified, can be easily chipped off. Weld bead

Weld pool

Base metal

Brazing filler metal rod

Torch tip

Figure 1. Braze-welding

Filler Metal The filler rod used for most brazing is a non-ferrous alloy, containing roughly 60% copper, 40% zinc, and small amounts of tin, iron, manganese, and silicon. There are many other alloy combinations, such as silver solder, available for various base metals. The rod is manufactured and coded the same way as steel filler rod, with standard classification codes and manufacturers’ trade names. The size of the rod is measured by the diameter of the filler rod, not including the flux coating (Figure 2).

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Figure 2. Filler Rod

Applications In many cases, it’s easier and faster to braze-weld than to fusion-weld because the base metal does not have to be melted. Braze-welding has a wide variety of applications, especially in factory maintenance and repair work. A common application is the building up of surfaces on damaged or worn parts.

Light-gauge Metals On light-gauge metals, the base metal does not have to be melted, so the temperature is lower, which means less distortion. This process is especially useful on galvanized steel, because the lower temperature does not adversely affect the heat-sensitive zinc coating.

Dissimilar Metals Braze-welding can bond almost any type of metal to another type of metal. Steel tubing, for example, can be braze-welded to cast iron, copper can be joined to steel, and brass can be joined to cast iron. This versatility makes braze-welding very valuable for maintenance and repair.

Grey Cast Iron Braze-welding is often better for cast iron than fusion-welding. Since the base metal does not have to be melted, braze-welding is faster and, in some ways, easier. There’s less need for preheating, and in some cases, may not be needed at all. For instance, a cracked cast-iron pump housing can be repaired with brazewelding.

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Non-ferrous Metal Braze-welding can also be used on many non-ferrous metals. It is widely used for welding copper, brass, and aluminum.

Brazing Process and its Application Brazing is another process for joining metals using oxy-fuel gas as a heat source. It is another torch-brazing process and, like braze-welding, it’s identified by the process abbreviation “TB.”

Principles of Brazing In some ways, brazing is similar to braze-welding. In both processes, the base metal is heated but not melted, and both use brazing filler metals. However, joints prepared for brazing must be very tight fitting. Once the filler metal melts, it is instantly drawn into the tiny space between the joint members by a force called “capillary action” (Figure 3). This action is the same force that pulls water up in a small tube when one end of the tube is placed into a container of water.

Concentrate heat here

Brazing filler-metal rod

Exaggerated gap Filler metal flow Figure 3. Capillary Action

The bond that brazing produces is similar to that of braze-welding, in that surface adhesion between the filler metal and base metal creates the bond. In brazing, however, once this adhesion occurs, the joint is complete. In brazewelding, more filler metal is deposited to fill the weld joint.

Filler Metal Brazing filler metals (brazing rods or wires) are made of non-ferrous metals such as silver alloys or brass. They are available in a wide range of sizes, shapes, temperature ranges, and composition to match the requirements of the job and the base metal.

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All brazing filler metals have melting temperatures above 450°C (840°F). The melting point of the base metals they’re used on is higher. The temperature 450°C (840°F) is the division between filler metals classified as brazing and those classified as soldering. Filler metals with melting temperatures below 450°C (840°F) are called “solder” and, generally, they are softer and weaker than brazing filler metals.

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Applications Brazing is widely used in production and maintenance work. It has the same versatility as braze-welding in that it can be used on a wide variety of ferrous and non-ferrous metals. It’s especially effective on complex shapes because of the way the filler metal is “drawn in” to the joint by capillary action. Welded joints made by this process are strong and corrosion resistant. Like braze-welding, brazing can be used to join both ferrous and non-ferrous metals and to join dissimilar metals. If the correct filler rod is used, almost any metal can be brazed. As in braze-welding, the base metal is not melted, so brazing is especially effective on light-gauge metals that would be distorted by the high temperatures used in fusion-welding. Because silver conducts electricity very well, silver alloy brazing is used to fabricate and repair electrical connections. For the same reason, it’s also used in the fabrication and repair of refrigeration and air-conditioning equipment.

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SELF TEST 7 1. What type of filler rod is used for braze welding joints? a. 60% copper 40% zinc b. 60% tin 40% led c. 40% copper 60% zinc d. 40% tin 60% lead 2. What draws the filler metal into the joint of the brazing process? a. flux b. heat c. capillary action d. filler rod 3. What is the minimum temperature of the base metal required when brazing? a. 323°C (613°F) b. 427°C (800°F) c. 537°C (1000°F) d. 648°C (1200°F) 4. What does the filler rod for brazing contain? a. 70% lead, 30% brass b. 50% brass, 50% copper c. 60% copper, 40% zinc d. 70% brass, 30% zinc

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Solder Tubing and Sheet Metal Describe the Soldering Process Soldering is the process of joining two pieces of heated metal by using a metal alloy that has a melting point lower than the metals being joined. The metal alloy used is called solder.

Heat Source Although electric soldering irons may be used to solder small sheet metal projects, the usual heat source for soldering copper tubing or sheet metal is a gas torch. The torch fuel may be propane, butane, or oxy-acetylene. The size of the flame is adjusted to suit the job. The torch may be attached directly to the tank, as shown in Figure 1, or connected to the tank with a hose. Figure 1. Small Propane Torch

Preparation Soldering is only effective if the surfaces to be joined are clean. All oxidization must be removed from the surface of the metal with fine sandpaper, steel wool, or a wire brush. The sandpaper used is generally cloth-backed emery. Small wire brushes are used to clean the inside surfaces of smaller fittings. To improve the flow of the molten solder and to further clean the metals by chemical action, a flux is applied to the surfaces to be soldered. Flux also serves to prevent the surfaces from being oxidized when they become heated. It’s available in paste or liquid form for use on copper tubing or sheet metal. Some flux, especially the liquid variety, is quite corrosive. Handle flux carefully.

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Solder Two main classes of solder are hard solder and soft solder. Hard solder is an alloy of copper and zinc, while soft solder is made of tin and lead. Soft solder is generally used for joining copper tubing or sheet metal. Soft solder is available in varying compositions such as 30/70, 50/50, or 60/40. The first number indicates the tin content, so solder with a 30/70 composition will be 30% tin and 70% lead. Pure tin has a melting point of about 232°C (450°F) while pure lead melts at about 327°C (620°F). A solder consisting of equal parts of tin and lead melts at about 212°C (415°F). The higher the tin content, the stronger the solder joint. Solder containing a high content of lead is weak, but those containing a high content of tin are brittle. Combining the two in the right proportions produces a solder that is strong but not brittle. Lead-free solder is available as a replacement for lead-type solders. Solder is available in bar or wire form. The wire form is available in varying diameters and may be either solid wire or have a hollow centre filled with rosintype or acid-type flux. Popular diameters for wire core solder are 1⁄16 in., 3⁄32 in., and 1⁄8 in. The amount of solder to be used at each joint usually dictates the diameter of wire to use. Wiring connections are to be soldered with rosin core solder only.

Describe the Procedures for Soldering Successful soldering of copper tubing with soft solder requires that you follow these steps: 1. Select a suitable solder. Of the many varieties you can choose from, one that contains more tin than lead will provide a strong joint provided that it’s not subjected to flexing. In general, most copper tube can be soldered with a soft solder with a 50/50 composition. 2. Use steel wool or emery cloth to clean all surfaces to be joined. Use a small wire brush to clean the interiors of copper socket fittings that have small diameters. Large diameter fittings may have their sockets cleaned with a small section of steel wool or emery cloth. Blow off residue from the cleaning process. Do not touch the cleaned surfaces with your bare hands, as this will contaminate the surfaces.

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3. Apply flux to all surfaces to be joined. Handle corrosive flux very carefully. Flux should be applied as soon as possible to the areas that have been cleaned. Any lengthy delay in the application of flux permits oxides to form on the surface of the metal. Cover the entire joining surfaces with a thin layer of flux.

NOTES

4. Fit the two joining surfaces and secure them so that no movement between them is possible. Be sure that the fitting is fully seated on the tube. 5. Apply heat gradually to the parts to be joined. Too much heat applied in one spot may burn the copper and make it brittle or cause cast copper fittings to crack. Ply the torch back and forth, starting at the top and working downward. Continue applying heat until the metal is hot enough to melt the solder. 6. Now apply solder to the joint. The solder should melt the moment it makes contact with the heated copper, as illustrated in Figure 2. Remove the heat source from the joint and continue to add solder until the joint does not draw in any more solder. You should end up with a slight bead of solder showing at the shoulder of the fitting. Never touch the solder wire with the heat source.

Figure 2. Soldering a Joint

7. Give the joint a quick wipe with a dry rag to remove any excess melted solder or flux. Allow the joint to cool naturally for a minute or two, giving the solder a chance to solidify. If you cool the joint too quickly, you risk warping or cracking the fitting.

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When the joint has cooled, wipe the entire joint area with a wet rag or shop towel to cool it down. Wash the entire area of the joint, making sure no flux remains on the surfaces of the tubing or fitting. The procedure for soldering sheet metal with soft solder is as follows: 1. Select a suitable solder. As with copper tubing, if you require a strong joint that will not need to flex, choose a solder that has a high tin content. Sheet metal can be soldered using soft solder with a 50/50 composition; however 60/40 is more popular because it will form a stronger joint. 2. Use steel wool or emery cloth to clean all surfaces. 3. Apply flux as soon as possible to the areas that have been cleaned. Flux penetrates and removes oxide formations on the surface of the metals. Some of the paint-on acid-based fluxes suitable for use on metal sheet are very corrosive. Handle them carefully. 4. Fit the two joining surfaces and secure them so that no movement between them is possible. 5. Apply heat gradually to the metal. Too much heat applied in one spot may cause the metal to warp. Move the torch back and forth over the entire area of the joint. Continue applying heat until the metal is hot enough to melt the solder. Do not touch the flame to the solder wire. The solder must be melted by the hot metal, not by the torch. 6. Apply solder to the joint (Figure 3). The solder should melt the moment it makes contact with the heated metal. Remove the heat from the joint and continue to add solder until the joint does not draw in any more solder. Solder flows toward the heat. If two surfaces are hot enough to melt the solder, but one is hotter than the other, the solder will flow toward the hotter surface. You should end up with a slight bead of solder showing at the shoulder or edge of the metal.

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Figure 3. Soldering Sheet Metal

7. Allow the joint to cool naturally for a few minutes. Wipe the entire joint area with a wet rag or shop towel to cool it down. Wash the entire area of the joint making sure no flux remains on the surface. Residue flux invites corrosion.

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SELF TEST 8 1. What does 40/60 solder mean? a. 40% to 60% lead b. 40% lead and 60% tin c. 40% zinc and 60% lead d. 40% tin and 60% lead 2. What type of solder is used on wire connections? a. acid core solder b. rosin core solder c. solid core solder d. 50/50 solder

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Describe the Shielded Metal Arc Welding (SMAW) Process SMAW Process and its Applications Principles of SMAW Shielded metal arc welding (SMAW) is commonly called “stick welding” or “electric arc welding.” An electric arc is the bridge of light and heat that develops when an electric current is forced to leap across a small gap in an electrical circuit. In the SMAW process, the welding equipment is designed to maintain this arc. The intense heat of the arc and metal transfer fuses the metals. Electricity flows through an electrical circuit because there is electrical “pressure” created by a generator at the power source. This electrical pressure is called “voltage” and is measured in volts (V). The flow of electricity is called “current” and is measured in amperes (A). In order to work, an electrical current must flow through the conductors in a closed electrical circuit. If for some reason this circuit is broken (or “opened”), the flow of electricity will stop. Electrical pressure (voltage) will continue to exist while the generator runs. As soon as the circuit is completed (“closed”), current will resume flow.

The Arc Welding Circuit An arc welding circuit is an electrical circuit that you can close or open by touching the electrode to the work piece or pulling it away (Figure 1). The SMAW welding circuit consists of: • • • • •

a welding power source a work piece lead (cable) and ground clamp an electrode lead (cable) a welding electrode and electrode holder the work piece

When you touch the electrode to the work piece and immediately withdraw it a short distance, the arc is struck and the electrical circuit is completed. The current flows through the electrode, across the arc, through the work piece, through the ground clamp and work piece lead, and back to the power source (Figure 1). The metal table may or may not be part of the welding circuit, depending on the location of the ground clamp.

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Electrode holder

NOTES +

Welding power source Ground clamp

–

Electrode Workpiece

Workpiece lead Metal work table Electrode lead Figure 1. Arc Welding Circuit

The SMAW Process When the power source for a welding circuit is turned on, but before the arc has been struck, the circuit is “open.” At this point the voltage or the potential in the circuit is at its maximum and is called the “open circuit voltage.” The moment you strike the arc, the circuit is “closed,” the voltage drops to what is called the “arc voltage,” and the current flows through the welding circuit. As this current crosses the arc from the electrode to the work piece, tremendous heat is generated, anywhere from 5500–6600°C (9900–11 900°F). The heat melts the end of the electrode and the base metal in the work piece directly beneath the arc, forming a pool of molten metal. As the electrode melts, small particles of molten metal are carried across the arc stream and deposited in the molten pool on the base metal, forming the weld deposit. This weld deposit is actually a mixture of the melted electrode and the melted base metal. At the same time, the force of the arc digs into the work piece and provides the necessary depth of penetration for the weld.

Electrodes The electrodes used in the SMAW process are coated with a flux. Most electrodes have a core that consists of a solid metal wire. For some applications, the core is a tube containing metal powders or other particles. The metal core conducts the electrical current to the arc and also provides the filler metal for the weld joint. This filler metal is deposited as the electrode is gradually consumed and as the Welder moves the arc over the work piece at the correct arc length and travel speed.

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The coating of the electrode helps keep the arc stable and concentrated on a precise point on the weld. The chemicals in the electrode coating provide the shielding required protecting the molten metal from contamination by the atmosphere. This is where the name “shielded metal arc welding” comes from.

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Welding Power Source The welding machine that provides the power for arc welding is an important part of the process. Its proper name is “welding power source.” Welding power sources for SMAW might supply either direct current (DC) or alternating current (AC). Controls on the welding power source enable you to vary the current as required for different welding tasks, materials, and positions.

Applications of SMAW The SMAW process can meet almost any requirement for welding carbon, stainless and alloy steels, and cast iron. Its uses include manufacture, construction, maintenance, and repair in: • • • • • • • •

shipbuilding commercial transport and automotive industrial and agricultural equipment engineering applications boiler and pressure vessels piping and pipelines bridge-building building construction and structural applications

The Arc Welding Station Many arc welding tasks, both in training and on the job, take place at a welding station (Figure 2). The main parts of the station are: • • • • • • • •

welding power source metal work table electrode lead (cable) and terminals electrode holder welding booth or welding screens work lead (cable) and terminals ventilation system ground clamp or work piece connection

Localized fume extraction is becoming more common.

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NOTES To exhaust fan

Non-flammable curtains on all open sides

Welding power source

Metal work table

Concrete floor Figure 2. Welding Station

Welding Station Inspection The welding station provides a safe work environment and protection for fellow workers. To maintain the efficiency and safety of the station, it’s important that you get into the habit of completing a thorough inspection before starting any work. When inspecting an arc welding station, the following points must be considered:

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•

Make sure that the welding power source is turned off before proceeding further.

•

Inspect all cables to make sure that they’re free from damage.

•

Use channel iron to cover all cables that have to run across aisles. Wheeled machines such as lift trucks and pallet movers easily damage cables.

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•

Check the electrode holder assembly carefully to make sure that: § The cable is fastened securely in the holder. § The holder insulation is in good condition. § The holder jaws are clean to ensure good electrical contact with the electrode.

•

Check that the connection between the work piece lead and the work piece or work table is secure to ensure that the ground clamp makes good electrical contact.

•

Check that the welding booth or temporary screens have no holes that could expose people to the dangers of arc flash.

•

Check that the ventilation system is working, and that the ventilation pickup duct is placed so that fumes are removed before they reach the Welder’s breathing zone. This is very important if a fume extraction arm is used instead of a canopy (Figure 2).

•

Make sure that there is an insulated hook to hang the electrode holder on when it is not in use.

•

Make sure that there is an electrode stub receptacle.

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Safety Requirements During all welding processes, you must protect yourself from the sparks, heat, light, and fumes given off. Each welding process also has its own special safety requirements. With oxy-fuel gas-welding and cutting processes, you must take extreme caution with the gases to prevent an explosion. With SMAW and other electrical welding processes such as GMAW, FCAW, and GTAW, you must take great care to protect against arc radiation and electric shock. Potential hazards and protective measures with SMAW are: • • • • • •

personal protective equipment (PPE) arc burn electric shock fire and explosion prevention safety requirements for operating electric welding equipment toxic fumes/ventilation

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Personal Protective Equipment Eye Protection for the Electrical Welding Processes When you weld using an electrical process such as SMAW, you must take extreme care to protect your eyes. The infrared and ultraviolet rays that arc welding produces can cause serious and sometimes permanent injury to your eyes. Exposing inadequately protected eyes to the welding arc can cause a burn called “arc flash.” Even a one-second exposure at a distance of 0.5 m (20 in.) is enough to burn the eyes. WorkSafeBC recommends a minimum distance of 12 m (40 ft.) between the welding area and unprotected viewers. Never look at an arc with the naked eye. If you receive an arc flash, immediately report it to your instructor. Keep a minimum distance of 12 m (40 ft.) between an arc and the naked eye. Welding Helmets To protect your eyes, face, and neck during arc welding, you must wear a welding helmet equipped with a dark filter lens. These filter lenses come in a range of different shades (Figure 3), each with a different number. Your choice of filter lens depends on the level of current you are using, since this determines the intensity of the arc. Figure 3 lists filter lens shade numbers recommended for different current settings. These are suggestions only. If your eyes are sensitive, you might need a darker lens. Filter lens shades recommended for level of current Below 30 A

No. 6

30–70 A

No. 9

70–200 A

No. 10

200–300 A

No. 11

300–400 A

No. 12

Over 400 A

No. 13

Figure 3. Filter Lens Shades Recommended for Current Level

If your eyesight requires it, use a clear magnifying lens—also known as a “cheater lens.” These special lenses fit behind your filter lens and take the place of reading glasses. They are available from welding supply companies. Always check the filter lens in your face shield or helmet before you start to weld to make sure it’s not cracked or broken. If it is cracked or chipped, replace it immediately.

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If you are in a work area where arc welding is being done, always wear approved safety glasses with side shields as protection from arc flash and flying debris.

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The shade numbers for auto-darkening helmets are equivalent to those in Figure 3. Check the manufacturer’s literature to confirm the correct adjustment of your helmet.

Arc Burn The infrared and ultraviolet radiation that arc welding produces can damage improperly protected eyes and severely burn your skin. For this reason, you must wear the proper protective clothing and equipment during SMAW and other electrical welding processes. The amount of protective clothing you require will depend on how much welding you’re doing, and on the welding positions you use. When welding, all parts of your body must be covered. Depending on the welding position and type of welding, you’ll need either full or partial flame-resistant clothing. This could include jackets, sleeves, aprons, leggings, and anklets. Do not wear synthetics such as Nylon or Dacron, as they will melt and cling to your skin as they burn. Your standard protective clothing for arc welding must also include a peaked cap, leather gloves, and safety boots. If you’re burned while arc welding, get medical attention immediately.

Electric Shock The electrical currents used in SMAW are very high. If you become part of the electrical circuit at any point, you could receive an electric shock severe enough to kill you. Even a small shock that is not immediately fatal could be sufficient to cause you to jerk and fall, leading to a serious injury. One of the main factors contributing to electric shock (fatal or otherwise) is dampness. Any dampness between your body and an energized part of the equipment provides a ground conductor that could carry the current to your body. The best way to prevent being grounded in this way is to make sure that your hands and clothing are dry. Do not weld if conditions require you to stand in water or on a wet surface. Instead, find a dry board or rubber mat to stand on.

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Initial Electrical Isolation of Shock Victims If one of your fellow workers receives an electric shock, it’s essential to remove the victim from contact with the power source as soon as possible. Do not touch the victim if he or she is still in contact with the live source of electrical power. To do so, or even to come close to the victim, could put you in danger of electrical shock and leave you powerless to help. If you know that the power switch is nearby, disconnect the circuit. If you do not know where the power switch is or if it is not close by, send someone else to disconnect the power, and at the same time, send for emergency medical aid. In the meantime, find some non-conductive material such as a length of dry wood, some rope, or a blanket and try to pull or pry the conductor from the victim. For more detailed instructions in the procedures to use in cases of electrical shock, refer to WorkSafeBC’s website, www.worksafebc.com, and click on OHS Regulation under the “Quick Links.”

Fire Prevention Electrical welding (such as SMAW) poses as great a fire hazard as oxy-fuel welding. Follow these safety points: • •

• •

Make sure that your workplace is as free as possible of combustible materials before you begin to weld. If flammable materials cannot be removed from the work area, be sure they are protected adequately from sparks and slag before you start to weld. Assigning a fire watcher is highly recommended. Do not weld anywhere near containers of flammable liquids. Know the locations and types of fire extinguishers in your immediate work area and how to use them.

Safety Requirements for Operating Electrical Welding Equipment The greatest electrical hazard for Welders is from their electric welding power sources. For this reason, every time you work with these machines, you must follow all the standard safety precautions. In addition, all switches must be clearly marked, all electrical tools and equipment must be properly grounded, and metal ladders must be kept away from any source of electrical power.

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WorkSafeBC publishes a useful guide called Working Safely Around Electricity. It’s also available on the Web at:

NOTES

http://www.worksafebc.com/publications/health_and_safety/by_ topic/assets/pdf/electricity.pdf Maintenance and Equipment The Welder who is about to use a welding power source is responsible for making sure that the machine is in a safe operating condition. The wiring, switches, controls, and cables must all be thoroughly checked before use. Preventive maintenance (such as internal cleaning and lubrication) must be carried out at regular intervals. In most welding shops, the electrical power for arc welding equipment is 230 V, 460 V, or 575 V. These are high voltages that can easily deliver severe or fatal shocks. When performing any internal preventive maintenance work on electrical welding equipment, observe the following rules: •

•

All troubleshooting and maintenance of welding power sources must be done only on open circuits. Make sure that the main power supply disconnect switch is open and locked out (Figure 4). Do not work on main power lines, junction boxes, or fuses. Only an electrician qualified in accordance with the requirements of the Canadian Electrical Code can do this. The Welder’s maintenance responsibilities end with the welding power source.

Figure 4. Lockout

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When you connect an electrical welding power source to its main power supply, it’s extremely important to make sure that the main power circuit is properly grounded. Without proper grounding, any stray current that develops could give you or another worker a severe or even fatal shock. If you have one hand on an inadequately grounded power supply in which a current is flowing and you accidentally touch a grounded metal object such as a switch box, you become part of the electrical circuit. The resulting electric shock could be fatal. Without proper grounding, stray current can also damage cranes, motors, and controls as well as computerized equipment. Welding Cables Check the cables on a welding power source every time you use it. Never use electrical current that is more than the rated capacity of the welding cables on your power source. Not only is this uneconomical but, more importantly, it causes overheating and rapid deterioration of the insulation. Faulty insulation is a hazard. If exposed sections of cable come in contact with any grounded metal object in the welding circuit, they could create an arc, which could in turn ignite any flammable materials in the area. Make inspection of the cables a standard part of your inspection of welding equipment. If the cables are in good condition, you can use them. If they are not, take these steps: • • •

Make sure the main power source is disconnected or locked out. If there are surface cracks in the insulation, repair them with electrical tape before starting the machine. If there are breaks in the insulation that expose any wire, do not try to repair it. Replace the cable with one that’s in good condition.

Electrode Holders Your SMAW electrode and electrode holder are a part of the welding circuit. When the welding power source is on but you are not welding, always be extremely careful to remove the electrode from the holder so that the live electrode will not accidentally make contact with the surrounding metal and cause arc strikes. Arc strikes could result in damage to your work or cause fire or personal injury. Your welding booth should have an insulated hook on which to hang the electrode holder. Always use the hook to prevent a hazardous situation from arising.

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Electrode Stubs Electrodes should be used down to a stub length of 50 mm (2 in.) or less. Dispose of these stubs in fireproof metal containers. If you throw them on the floor they create a slipping hazard. Not containing electrode stubs is against WorkSafeBC regulations.

NOTES

Electrode stubs are a work site contaminant that cause flat tires on equipment, damage to machinery, and electrical short circuits. Slag The coating that forms on the top of an arc weld is called “slag.” When it’s first deposited, it’s very hot. It has to be removed after it has cooled and solidified. As you chip off slag, make sure that fragments do not hit you or anyone else. Always wear approved eye protection while removing slag. Ventilation When welding in a booth, make sure that it’s equipped to extract fumes at an adequate rate. The air movement must be no less than 2.8 m3/min (100 ft.3/min). The ventilation pickup duct must be located so that the hazardous fumes are removed before they reach your face (Figure 5). With SMAW, you might work with materials that can produce toxic fumes. Among the materials you might encounter that produce fumes in harmful concentrations are lead, zinc, cadmium, beryllium, chromium, and Teflon.

To exhaust fan

Figure 5. Fume Removal

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Always be sure you know the metallic and chemical composition of the materials and electrodes you’re welding with. You must always be fully aware of the possibilities of toxic gas fumes in any location. Many toxic fumes cannot be easily identified by smell, and they can accumulate undetected in areas where you’re welding. You might need to use special detection equipment to determine whether harmful concentrations exist. Operate engine-driven welding power sources in open and wellventilated outside areas or vent the exhaust and heat to the outdoors. Engine exhaust is harmful to health and a risk to life.

Summary As you prepare to weld, remember these safety points: • • • • • • •

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Always turn off your welding power source when not in use. Wear gloves when handling arc welding equipment. Keep all equipment dry and do not work in damp or wet conditions. Make sure that the work piece or work table is properly grounded. Do not overload the welding cables. Remove the electrode from the electrode holder before putting the holder down. Switch the welding power source off when you’re finished working.

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SELF TEST 9

SELF TEST 9 1. When is the electrical circuit closed, in the SMAW process? a. the power supply is turned on b. the electrode is inserted in the hold c. the arc is struck d. the parent metal begins to melt 2. What helmet filter lens should be selected for 70 to 200 Amps of current? a. #12 lens b. #11 lens c. #10 lens d. #9 lens 3. What is arc burn? a. skin burns from sparks b. skin burns from welding radiation c. skin burns from contacting the metal d. skin burns from the electrodes 4. What filter lens shade is recommended when SMAW at 100A? a. 6 b. 9 c. 10 d. 13

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Identify Shielded Metal Arc Welding Equipment Types of Current and Their Applications Electrical current is the flow of electrons through a conductor. This electron flow is from the negative pole to the positive pole. The current can be either alternating current (AC) or direct current (DC). Each type has different characteristics and is suitable for different welding applications. Welding power sources can be designed to produce both types of current, making them more versatile. SMAW electrodes are designed for use with either AC or DC current, and some types can be used with both. The type of welding current will affect your choice of electrode. To develop good welding techniques, it’s essential to know the differences between the two types of current. In SMAW, the type of welding current can affect: • • • • •

polarity of the work piece and the electrode heat that is distributed to the work piece and the electrode rate at which the electrode is deposited in the weld pool depth of penetration of the weld deposit occurrence of arc blow

Alternating Current The flow of alternating current reverses direction 120 times per second. A complete direction change from zero to maximum volts at one pole, then back to zero volts and up to maximum voltage at the other pole, is called a “cycle.” Most electrical utility companies distribute alternating current at 60 cycles per second. This means that 60 times a second, the voltage reaches a maximum in one direction and 60 times per second it reaches a maximum in the other direction. The current is said to be operating at 60 hertz (cycles per second). The symbol for alternating current (AC) is “~.” Some of the characteristics of alternating current can be represented in the form of a sine wave diagram (Figure 1).

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NOTES

One cycle

+

Volts

Current

Time

–

1⁄120 sec

1⁄120 sec 1⁄60 sec

Figure 1. Alternating Current Sine Wave

Alternating current can be single-phase AC (Figure 2) or three-phase AC (Figure 3).

Figure 2. Single-phase

Figure 3. Three-phase

Single-phase Alternating Current Single-phase AC power is useful for most domestic and light industrial operations. But during each cycle there is a considerable period of time when less than maximum power is being delivered (Figure 2). This makes single-phase power inefficient for heavy industrial welding applications.

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Three-phase Alternating Current Three-phase AC power is more often used in industry. In three-phase AC power, there are three single-phase currents. These are timed to start at regular intervals from each other (Figure 3). The advantage of three-phase power is that even though one phase may be delivering only minimum power, one of the other two phases will be delivering nearly maximum power. Welding power sources that use three-phase power produce a smoother arc than single-phase equipment.

NOTES

Direct Current With direct current (Figure 4), the electrons in a circuit flow steadily in one direction only, from the negative pole to the positive pole. DC generators produce this type of current, with batteries or by rectifying AC current.

Volts

Current

Time Figure 4. Direct Current

Polarity Electron flow in an electrical circuit is always from the negative pole to the positive pole. The practical effects of this for welding are important with DC welding current (Figure 5).

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Current flow reverse polarity half of AC cycle

NOTES

+

Current flow

–

DCEP Heat concentrated at the workpiece

–

Current flow

+

DCEN Heat concentrated at the electrode

Current flow straight polarity half of AC cycle

+

–

–

+

AC

Figure 5. Effects of Polarity in Welding

In direct current, the electron flow is in one direction only. Depending on how you connect the circuit, the current flow can be made to affect the heat of the electrode or of the work piece. An additional influence is the type of gas that makes up the arc plasma and the material that is moving along this path. For SMAW, the polarity of a DC welding circuit can be used in two ways: •

Direct current electrode negative (DCEN) connects the welding circuit so that the electrode is attached to the negative terminal of the power source (Figure 6). In SMAW, when using DCEN, the heat generated by the arc is concentrated at the electrode. In SMAW using coated electrodes, DCEN generally allows for faster welding speeds and higher filler metal deposition. It provides a medium depth of penetration.

•

Direct current electrode positive (DCEP) connects the welding circuit so that the electrode is attached to the positive terminal of the power source (Figure 6). In SMAW, when using DCEP, the heat generated by the arc is concentrated at the work piece. In SMAW using coated electrodes, DCEP generally allows for deeper penetration of the weld, but the welding speed is slower.

Note that the concentration of heat generated by the arc will depend on the process being used. For example, in gas tungsten arc welding (GTAW), where the tungsten electrode is not consumed and the shielding gas is inert, the heat will be concentrated at the positive side of the arc. This is opposite to SMAW. The difference is due to the ionization of molten metal and flux particles across the arc as compared to ionized shielding gas.

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NOTES – +

DCEP

– +

DCEN

Figure 6. Polarity Arrangements

The polarity you choose will depend on: • • •

the type of coating material on the electrode the type of material to be welded the welding position

AC and DC Welding Power Sources Welding power sources for SMAW produce AC welding current, DC welding current, or both. Transformer-type welding power sources convert or transform the existing main line electricity to a form usable in the welding process. Generator- or alternator-type welding power sources generate their own current.

Transformer-type Welding Power Sources A transformer welding power source takes the main alternating current supplied to the welding shop (line supply) and transforms it into welding current. Some transformer welding power sources produce only AC current. The line supply AC is stepped down to produce the lower voltage and higher current levels demanded by arc welding. Adding a rectifier system enables a transformer to produce direct current (DC) from an AC welding power source. On some power sources, the rectifier circuit can be switched in or out of the main transformer circuit. These power sources can supply either AC or DC welding current. AC Transformers The AC transformers used as welding power sources are known as “step- down transformers” (Figure 7). They take the line voltage from the main electrical supply and bring it down to a suitable voltage level for welding.

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The line supply is usually single-phase at 115 V or 220 V, or three-phase at 115 V, 208 V, 480 V, or 575 V. The transformer converts these line voltages to open circuit welding voltages in the range of 60–80 V. Current values can be as high as 1500 A, depending on the line supply and the type of welding power source.

Figure 7. AC Transformer Power Source

Transformer/Rectifiers The purpose of a transformer/rectifier welding power source is to produce the DC that is required for certain welding operations. The machine consists of an AC transformer and rectifier circuit (Figure 8). The rectifiers act like one-way valves and allow current to flow in one direction only. The transformer part of the welding power source transforms the AC line supply to suitable AC welding voltage and current. This transformed current is then fed into the rectifier circuit, which converts it to DC. Rectifying a single-phase line supply does not always provide the steady DC needed for welding. Some transformer/rectifier welding power sources use capacitors to help provide more consistent levels of current. Heavy industrial welding power sources use a three-phase AC line supply.

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Figure 8. Transformer/Rectifier Welding Power Source

DC Transformer/Rectifier Control The current control on a transformer/rectifier is the same as that on an AC transformer welding power source. Generally, there are coarse current adjustments in low, medium, and high ranges. There are also finer adjustments to match the current to variables such as electrode type and size, metal thickness, and welding position. Some transformer/rectifiers also have a switch that controls the polarity of the circuit. This allows you to choose an electrode negative or electrode positive circuit to match the job requirements without having to change the leads on the machine. Avoid changing welding current range control settings or polarity switches under load. Most fine-adjust dial controls can be adjusted while welding. AC/DC Transformer/Rectifiers Some transformer/rectifiers can provide both transformed AC current and rectified DC current. These welding power sources have a switch that allows the transformed current to bypass the rectifier circuit when you need AC current. Machines with this capability are called “AC/DC welding power sources.”

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Advantages of transformer/rectifier-type welding power sources: • • •

relatively quiet operation AC and/or DC welding current available available for singe-phase or three-phase line supply

Disadvantages of transformer/rectifier-type welding power sources: • • • •

not considered portable for field work sensitive to line supply fluctuations limited adjustability of volt-amp curve DC welding current subject to arc blow

Engine-driven Welding Power Sources The generator or alternator of an engine-driven welding power source will be powered by a diesel, gasoline, propane, or natural gas-fuelled internal combustion engine. This type of welding power source can be used in fieldwork where there is no access to electrical supply lines (Figure 9). It’s generally called a “portable electrical welding power source.” It often has auxiliary outlets to power additional equipment such as lights or grinders. The engine has a governor that responds to the demands from the generator or alternator. The governor automatically reduces the speed of the engine when you are not welding. The engine speed increases when the generator demands more power.

Figure 9. Engine-driven DC Generator Welding Power Source

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Engine-driven DC Generator Welding Power Source Most engine-driven DC generators for SMAW have controls for both current and voltage levels. These allow you to change the slope of the volt-amp curve. In this way, you can adjust the characteristics of the arc to suit the requirements of a particular welding task. Use the fine-adjustment controls to get the exact setting you need for the metal thickness, electrode size and type, and welding position for a given job. These fine controls can be adjusted under load.

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NOTES

Engine-driven AC and AC/DC Alternator Welding Power Sources An engine can also drive an alternator to produce AC welding current. This AC welding current can be changed to DC through the use of rectifiers and/or inverter technology. The controls on these welding power sources are much the same as those described for the DC generators. Advantages of engine-driven welding power sources: • • • • • •

They’re not susceptible to fluctuations in line voltage. They’re ideal for field work. Greater adjustability of volt-amp curve. The alternator type are more reliable and need less maintenance. The alternator type provide AC and/or DC welding current. The alternator type allow for use of AC power tools.

Disadvantages of engine-driven welding power sources: • • • •

They’re noisy. They produce engine exhaust, which must be controlled. They’re expensive to operate because of fuel costs compared to line power from a utility. Engine and rotating components are expensive to maintain and need regular servicing.

Inverters Inverter welding power sources use the frequency converter principle to produce DC current (Figure 10). Inverters are also called “rectifier- converters” or “converters.” They work in the following way: 1. 1take in AC line power 2. rectify it to DC 3. convert it electronically to high-frequency (3–50 kilohertz) AC 4. transform it to welding voltage 5. convert it back to DC

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At the heart of the inverter is a high-frequency transformer. Remember that 1 hertz is one single cycle in one second. Domestic AC power operates at 60 hertz. A conventional transformer operating at 60 hertz would weigh 19.5 kg (42 lb.). It would operate at 90% efficiency and produce a heat loss of 10%. An equivalent inverter operating at 200 000 hertz would weigh 1.5 kg (31⁄3 lb.). It would operate at 98% efficiency and produce a heat loss of only 2%. Inverter welding power sources operate in the region of 20 000 hertz. But their electrical efficiency is still remarkable when compared to old technology. Inverters can operate on either single-phase or three-phase power. The use of high-frequency current in the conversion means that all of the components are electronic. This reduces size and weight and increases electrical efficiency. A standard transformer/rectifier can lose as much as 55% of the incoming power, while the energy loss with an inverter can be as low as 15%. A traditional 300 A transformer/rectifier weighs approximately 360 kg (800 lb.). An inverter version weighs less than 40 kg (85 lb.).

1 2 3 4 5 6 7

input line voltage 60 cycles per second (Hz) rectifier: DC ripple current filter: smooth DC current inverter: high-frequency AC current 20 000 Hz transformer: low-voltage high-frequency AC current rectifier: ripple DC low-voltage current filter: smooth low-voltage welding current

Figure 10. Process Steps in an Inverter Power Source

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Advantages of inverter-type welding power sources: • • • • • •

• • •

Energy-efficient. Loss is minimal and energy is only used when there is an arc. The cooling fan is thermostatically controlled. Their light weight means they can be moved between work sites. Small size saves floor space. Built-in programs allow a limitless number of custom welding currents. Many can be connected to a laptop computer and be reprogrammed for any new welding process developed. Arc blow is minimized. Many can adapt to any input current from single-phase to higher voltage three-phase without any adjustment. They compensate for slight variations in voltage from the utility.

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NOTES

Duty Cycle The duty cycle is a way of rating a welding power source. The duty cycle is the length of time a welding power source can be used continuously at its rated capacity during any 10-minute period. The length of time is expressed as a percentage of the 10-minute period. For example, if you need a welding power source that can be used at its maximum rated capacity for 10 minutes out of every 10 minutes, then you require a 100% duty cycle. Most manual arc welding power sources are rated at a current output of 200 A, 300 A, or 400 A and a duty cycle of 60%. This means that they can be used at their rated current output for 6 minutes out of every 10. When you’re welding, you’ll also have to spend time on other tasks such as preparing the work piece, changing electrodes, and cleaning and inspecting the finished weld. This means that operating with less than 100% duty cycle is quite acceptable. Smaller power sources, such as those used for light industrial or home use, are normally in the range of 150 A output with a 20–30% duty cycle. The duty cycle rating tells you the percentage of time you can use the power source at its maximum rated current output. This means that at lower settings, the power source can be used for a longer continuous period. Manufacturers usually supply a graph that shows the length of time you can use the power source at a given current setting (Figure 11).

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The graph shows that, at a rated output of 250 A, the duty cycle is 30%. At 200 A it is 40%, and at 150 A it is 75%. At the bottom end, the graph shows that at 140 A, the power source has a 100% duty cycle. However, no welding power source should be used continuously unless it has an official 100% duty cycle. Exceeding the duty cycle guidelines for a power source will cause overheating of the internal components and permanent damage. 300 250

Welding amperes

200

150

100 80 15

20

30

40

50

60 70 80 90

% Duty cycle Figure 11. Duty Cycle Graph

Under normal operation with SMAW, the time spent welding (including the time spent chipping, cleaning, inspecting, and changing electrodes) will not exceed a 60% duty cycle.

General Maintenance of Welding Power Sources Follow these maintenance tips: • • •

•

150

See the manufacturer’s operating manual for correct information. Maintain a regular preventive maintenance schedule. At least twice a year, electrically lock out or disconnect the power source and clean as recommended by the manufacturer. If you use compressed air, blow with low velocity and use personal protective equipment. Watch out for rodent nests—Hantavirus is a risk.

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• • • • • • •

LEARNING TASK 10

When you’re not using your welding power source, follow a storage procedure that protects it from weather and secondary damage. Operate away from grinding dust in cool, clean air to make sure that proper internal cooling can take place. Locate away from weld spatter and sparks. Inspect cable connections daily and repair as necessary to reduce welding circuit resistance. Check daily that ventilation openings are not blocked by dust or dirt. Check engine-driven equipment daily for coolant and oil levels as well as air filters as required in the operating manual. Have a shop copy of the equipment manufacturer’s operating manual attached to or nearby the welding power source. Most manufacturers supply their product manuals online. Some manuals are available dating back to the 1940s.

NOTES

Electrode Holders, Ground Clamps, and Welding Cables Electrode Holder The electrode holder or “stinger” carries the welding current to the welding electrode (Figure 12). It’s also the means by which you hold the electrode while welding. The two most common types of electrode holder are the twist head type (left) and the jaw type (right). The jaw type grips the electrode between two jaws activated by a powerful spring. The twist head type secures the electrode in place through the screw action of the head.

Figure 12. Electrode Holders

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The handle of any type of electrode holder is extremely well-insulated to protect you against electric shock and heat. Because it’s the part of the welding circuit that you hold, the electrode holder must be kept clean and in good condition to minimize any risk of shock. Replace any insulation that is damaged and clean the grooves of the jaw to remove any weld spatter that has collected. The connection between the welding cable and the electrode holder is a vulnerable point in the welding circuit because it is constantly being flexed during welding operations. This connection is usually a mechanical one. You must inspect the connection every time you weld. Make sure that the connection is tight. Loose connections increase electrical resistance and cause additional heat. If your electrode holder becomes hot, it means that you need to check the connection. Inspect for broken strands of cable, burned insulation, or loose clamping screws. If there is damage, cut off the end and make a new connection, either mechanically or by soldering/brazing before you start any welding.

Ground Clamps At the other end of the welding circuit is the ground clamp that makes the work piece connection. The ground clamp is needed to make the welding circuit complete. Excessive heat buildup at the clamp indicates welding cable connection problems similar to those mentioned for electrode holders. Without a good cable connection, there can be a loss of power through increased resistance, a risk of fire from sparking, and increased danger of electric shock. The work piece connection can be attached to a welding table or bench that has a permanently bolted or tack-welded lug. The work table might have an insulated terminal instead. If you are not welding on a welding bench, you can connect the work lead to the work piece with a ground clamp. There are different types of ground clamps. The most common are the springloaded clamp and C-clamp. Spring-loaded Clamp One common type of ground clamp is the spring-loaded type (Figure 13). The advantage of the spring-loaded clamp is that you can easily change the location of the work piece connection. You might need to do this when trying to reduce the effects of arc blow.

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NOTES

Figure 13. Spring-loaded Ground Clamp

C-clamp The C-clamp is useful because it allows for a secure connection, preventing arcing on the base metal and ensuring a solid electrical connection.

Figure 14. C-clamp

Cables Current is conducted from the welding power source to the electrode holder and work piece clamp by cables called “welding leads.” These cables are normally made of insulated copper wire. A typical welding cable consists of thousands of hair-like wires braided into strands (Figure 15). These strands are braided to form the conductor and are enclosed in a durable paper wrapping that allows the conductor to move easily inside the insulation when it is bent. Outside the paper is a layer of rubber insulation surrounded by a layer of woven fabric reinforcement to provide additional wear resistance. The outer layer is a special composition rubber with a smooth finish, highly resistant to wear.

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Woven fabric Paper

Rubber

Rubber insulation

Wires Figure 15. Typical Welding Cable

Cable Size There may be times when you’ll have to change to a different size of cable. The size you choose depends on two factors: the welding current and the length of the welding leads. The resistance in any conductor and the current flow combined with the length of the leads reduce the voltage available from the welding power source. As you learned earlier, this reduction in voltage due to resistance in the welding leads is called “voltage drop.” Voltage drop in welding leads cannot be eliminated. But choosing cable with the appropriate diameter can control it. Figure 16 gives AWG wire gauge numbers (diameters) that match certain cable lengths and welding current levels. The voltage drop for each size of cable is about 4 V over the given length (as long as no resistance comes from poor connections). Choosing the right cable size will increase efficiency and welding productivity.

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Current capacity

Length of cable

100 A 150 A 200 A 250 A 300 A 350 A 400 A 450 A 500 A 15 m/50 ft.

2

2

2

2

1

1/0

1/0

2/0

2/0

23 m/75 ft.

2

2

1

1/0

2/0

2/0

3/0

3/0

4/0

30 m/100 ft.

2

1

1/0

2/0

3/0

4/0

4/0

38 m/125 ft.

2

1/0

2/0

3/0

4/0

45 m/150 ft.

1

2/0

3/0

4/0

53 m/175 ft.

1/0

3/0

4/0

60 m/200 ft.

1/0

3/0

4/0

75 m/250 ft.

2/0

4/0

90 m/300 ft.

3/0

105 m/350 ft.

3/0

120 m/400 ft.

4/0

Figure 16. Recommended Copper Cable AWG Sizes for Arc Welding

Maintenance Maintenance and care of welding leads is important. Follow these guidelines: • • • •

Protect the leads against hot sparks and weld spatter from your work or that of nearby coworkers. Protect the leads from falling objects and cover them properly if vehicles will be driving over them. Prevent the leads from rubbing against sharp corners that could damage the insulation and create a fire or shock hazard. Use electrical tape to repair minor surface breaks in the welding leads. Replace any lead that appears to have serious damage.

Cable Connections Welding leads have four possible connections: • • • •

cable to electrode holder cable to work piece or ground clamp cable to cable cable to welding power source terminals

No matter which type of terminal or type of attachment method you use, always make sure that all connections in the welding circuit are tight and clean before you start welding. If the connection requires protection by insulation, make sure this insulation is in good condition. Cable to Electrode Holder The connection of the welding cable to the electrode holder is usually a mechanical one (Figure 17). The bared end of the cable is wrapped with copper or brass shim stock. It is then fitted into the brass socket end of the electrode holder and secured with a set-screw. This connection will always be insulated, and usually the electrode holder handle provides this insulation.

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Figure 17. Welding Cable to Electrode Holder Connection

Cable to Work Lead Clamp (Ground Clamp) The connection to the work lead clamp is a mechanical connection (Figure 18). It can be very similar to the connection to the electrode holder but can also be bolted to the clamp with an un-insulated lug.

Figure 18. Cable to Work Lead Clamp Connection

Lugs are normally attached to the cable by crimping, soldering, or brazing. If they are soldered or brazed, great care must be taken to make sure that the filler metal bridges the entire area of electrical current flow. This means that cable end and lug socket are tinned properly and you must fill the entire socket with filler metal. A joint with insufficient fill will overheat, melt, and come apart. Cable to Cable Cable-to-cable connections are used to extend the length of your leads when you’re required to work at a greater distance from the welding power source. It’s also common for Welders to use a “whip.” This is a short length of smaller diameter cable connected to an electrode holder, and is used to increase flexibility and reduce fatigue. Twist-lock quick connectors are a convenient and practical cable-to-cable connection (Figure 19). To connect, simply push the two connectors together and twist. To separate: twist, then pull apart. These usually attach to the cable ends with a mechanical socket and setscrew similar to the electrode holder connection. 156

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NOTES

Figure 19. Cable-to-cable Connections

Commercially produced permanent connectors are a convenient way of connecting welding leads to each other. The bared ends of the cables are inserted into the connector socket ends and either setscrews or crimping makes the connection. These connections must always be insulated. Another way of making a cable-to-cable connection is by attaching a lug to each cable end, then bolting the two lugs together. This is a non-preferred method. You must always properly insulate these connections. Cable to Welding Source Terminals There are two main types of connectors that are used between the welding cables and the terminals of the welding power source: •

•

The welding power source often has terminal connections requiring an un-insulated lug. These lugs are the same as the ones used for the cable to work lead clamp connection. Another common and convenient terminal connection is the built-in quick connector (Figure 20). The welding power source has a female quick connect receptacle, allowing it to receive any compatible male quick connect cable end. The quick connects may or may not be twist locks.

Figure 20. Welding Power Source Cable Connections

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SELF TEST 10 1. What does a transformer welding machine produce, without a rectifier? a. AC current only b. DC current only c. both AC and DC current d. high frequency AC current 2. What is the electrical term that identifies an AC signal that is 1⁄60 of a second? a. frequency b. three phase c. one cycle d. 60 hertz 3. What polarity is the welding electrode with an AC signal? a. electrode .5 cycle negative, .5 cycle positive b. electrode negative c. electrode positive d. electrode positive and negative 4. The duty cycle is a way of rating a welding power source. What time period is the duty cycle rated at? a. 5 minutes b. 10 minutes c. 15 minutes d. 20 minutes

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NOTES

Identify Mild Steel Electrodes for Shielded Metal Arc Welding Operation of Common Electrodes for SMAW The basic function of the welding electrode in the arc welding circuit is to carry the current that generates the arc. This means that an electrode must be a good conductor of electricity. In the SMAW process, the electrode must also melt and fuse with the base metal in order to create an effective weld (Figure 1). For this reason, electrodes are manufactured with a variety of different cores that are compatible with different base metals. In the SMAW process, electrodes have another important function: to help control the following aspects of the welding process: • • • • • • • •

rate of melting amount of deposition creation of slag stability and direction of the arc depth of penetration rate at which the molten weld metal solidifies (weld pool freezes) addition of alloys to the weld metal provision of gases to protect or shield the molten weld pool

To fulfill these functions, the composition of arc welding electrodes are more complex than the filler rods used in oxy-fuel and gas tungsten arc welding.

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Direction of travel

NOTES

Flux coating Arc stream

Electrode core wire

Gaseous shield Molten weld metal Slag

Crater

Penetration

Weld deposit

Base metal Figure 1. Action of a Coated Arc Electrode

Bare Electrodes Early arc welding used a non-consumable carbon electrode with a separate filler rod. Later, bare-wire electrodes were developed that eliminated the need for the separate filler material. Although bare-metal electrodes are still used today, they’re rare. Uncoated manganese electrodes are an example.

Coated and Shielded Electrodes The typical welding electrode (also called a “stick electrode”) consists of an inner wire core surrounded by a flux coating (Figure 2). The wire core carries the current and supplies most of the filler metal, while the coating contains the chemicals that are specially chosen to help control aspects of the welding process. Flux coating Core wire CSA

E491

8 AW

S E7

018

Figure 2. Welding Electrode

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Functions of Flux Coatings The flux coating on the electrode performs six functions: • • • • • •

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It forms a gaseous shield to keep oxygen and nitrogen away from the weld pool. It aids and controls the nature of the electric arc stream of plasma and metal particles. It cleans the weld pool by floating out impurities and scavenging for trace amounts of oxygen. It adds alloying elements and in some cases, filler material to the weld metal. It forms a cover that shapes the cooling weld metal and protects it from oxidation. It forms a cover of slag over the cooling weld bead to reduce the cooling rate.

Size of the Electrodes Sizes of SMAW electrodes are measured as the diameter of the inner core wire, excluding the flux coating. Following are standard SMAW electrode sizes: • • • • • • • • •

1.6 mm (1⁄16 in.) 2.0 mm (5⁄64 in.) 2.5 mm (3⁄32 in.) 3.2 mm (1⁄8 in.) 4.0 mm (5⁄32 in.) 5.0 mm (3⁄16 in.) 5.6 mm (7⁄32 in.) 6.4 mm (1⁄4 in.) 8.0 mm (5⁄16 in.)

Lengths range from 225–1000 mm (9–36 in.). The most common length is 350 mm (14 in.). The coatings are designated as light, medium, or heavy.

Types of Electrodes SMAW electrodes come in several types, depending on the composition of their coatings. The ingredients in the electrode coating control four important features: • • • •

the amount of filler metal produced the speed at which filler metal is deposited the speed with which the molten weld metal solidifies (weld pool freezes) the inclusion of hydrogen in the weld deposit

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Fast-fill Fast-fill electrodes deposit substantial amounts of filler metal at a fast rate. Electrodes used for production work frequently have this characteristic. They’re usually heavy-coated and often contain substantial amounts of iron powder to add filler metal. Fast-freeze Fast-freeze electrodes deposit a weld bead with the ability to solidify or freeze quickly. They generally operate with an arc that penetrates deeply but produces little slag. These characteristics make them suitable for welding in the vertical and overhead positions where the effects of gravity need to be counteracted. Fill-freeze Fill-freeze or fast-follow electrodes allow for higher travel speeds with consistent bead formation. They deposit thin, narrow stringer beads with shallow penetration. Their main use is for welds that require little filler material, as on light-gauge sheet metal. As the name suggests, fill-freeze electrodes combine both fast-fill and fast-freeze characteristics. Low-hydrogen Another special group of electrodes is the low-hydrogen, or basic, electrodes. Hydrogen can be harmful to the metallic properties of weld metal, especially to welds on high-strength low-alloy, medium-carbon, high-carbon, and highsulphur steels. The transfer of hydrogen from the electrode to the weld deposit can lead to hydrogen being trapped in the weld metal. This can lead to cracking, which often occurs many hours after the weld is completed. Submersing weldments in glycerin shortly after the welds are completed shows that hydrogen can be trapped in the weld metal (Figure 3). The image on the left shows the surface of a weld bead, while the image on the right shows a weld cut on the diagonal. In both pictures, the hydrogen trapped in the weld metal can be seen leaving the weld bead.

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Figure 3. Weldments Submerged in Glycerin

These pictures clearly show that hydrogen has been trapped in the weld metal. Hydrogen trapped in weld metal can create internal stresses that can lead to underbead cracking, even in low-carbon steels. Hydrogen is a serious concern when welding high-strength low-alloy, medium-carbon, high-carbon, and highsulphur steels. To protect sensitive base metals from the presence of hydrogen, low-hydrogen electrodes are manufactured with electrode coatings that do not have organic substances containing hydrogen.

Composition of SMAW Electrode Coatings SMAW electrode coatings can contain many different chemicals, minerals, and ores. Different combinations of these materials serve specific purposes. This generally restricts each electrode type to a particular situation, such as welding position, welding current, or current setting.

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The main chemical ingredients used in different combinations to produce electrodes of different types are: • • • • • • • •

cellulose rutile china clay, silica, and mica potassium ferro-manganese iron oxide (magnetite, hematite) iron powder sodium silicate

Cellulose Cellulose is made from wood pulp. It helps form the inverted cup-type shield at the electrode tip that gives direction to the shielding gases and to the arc stream. Cellulose also produces the shielding gases. As the cellulose is consumed, it forms a gaseous envelope of carbon dioxide and water vapour that excludes oxygen and nitrogen. Sodium or potassium is added to these coatings to stabilize the arc. Rutile “Rutile” is another term for titanium dioxide. It makes the arc smooth and stable and forms a hard, black slag that gives a smooth finish to the weld. Like cellulose, rutile is frequently combined with sodium or potassium. China Clay, Silica, and Mica China clay, silica, and mica are generally used in electrode coatings to provide slag volume. In varying quantities, they’re also important in controlling the viscosity and the surface tension of the slag as well as the rate at which the slag freezes. Potassium In electrode coatings, potassium is used as an arc stabilizer and as an ionizer. As an ionizer, it alters the electrical characteristics of the arc and helps ease and stabilize the flow of current. In addition to its use in compounds with cellulose and rutile, potassium is combined with feldspar or with titanium. It’s commonly used in AC electrodes to promote a stable arc. Ferro-manganese Ferro-manganese is an alloy containing about 80% manganese. When used in electrode coatings, it helps remove oxygen from the arc by combining with the oxygen to form an oxide. The oxide then forms part of the slag.

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Iron Oxide (Magnetite, Hematite) Magnetite and hematite are ores that produce a heavy slag. Their particular property is that they can dissolve large quantities of oxides that might be formed during the welding operation. Although the resulting weld is lower in tensile strength, the appearance of the weld is smooth.

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NOTES

Iron Powder Iron powder can make up 10–60% of an electrode coating. It creates a heavier coating that adds to the filler material produced by the electrode wire. It also allows for the use of higher welding current. This increases the rate of deposition of the weld. Iron powder also improves the appearance of the finished weld, makes the weld more ductile, and makes slag removal easier. Using iron powder in the electrode also helps reduce arc instability during AC welding. Sodium Silicate Sodium silicate, more commonly known as “water glass,” is a heavy liquid, quite viscous and sticky. It is used to bind together the various ingredients of electrode coatings so that they can coat the core wire.

Metal Transfer with SMAW Electrodes In the SMAW process, the heat of the arc melts the core wire of the coated electrode and this metal is transferred across the arc gap to the base metal. At the same time, the heat of the arc melts the base metal. The molten metal from the electrode combines with the molten base metal in the weld pool (or puddle) to form the weld metal. There are a number of theories to explain how the molten metal in the electrode is carried across the arc gap to the work piece. None of these explanations gives a complete picture. What is clear is that this metal transfer always takes place, whether electrode positive or electrode negative. It also occurs in opposition to the force of gravity when you weld in the overhead position. Gravity Gravity is clearly a factor in metal transfer from electrode to weld pool. When you’re welding in the flat position, gravity helps metal transfer. But when you’re welding in the overhead, vertical, or horizontal positions, gravity has an adverse effect. Using smaller diameter electrodes helps minimize this by reducing the loss of weld metal.

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At the same time, you should keep the arc length as short as possible to reduce the distance molten electrode metal has to travel. A short arc also decreases the risk that molten metal will fall and burn you. Gas Expansion The rapid expansion of gases at the tip of the melting electrode is another factor in metal transfer. These gases form as the electrode coating burns and breaks down, and as the electrode wire melts and produces carbon monoxide. The gases will force metal and slag particles across the arc gap. Electromagnetic Force The magnetic field associated with the arc has a pinching effect on the melting electrode (Figure 4). This frees globules of molten metal, and the electromagnetic force carries them across the arc gap. Flux coating

Core wire

Pinch effect Figure 4. Pinching Effect of Magnetic Field on Electrode

Electromotive Force The circuit voltage produces an electromotive force that pushes the globules of molten metal along, regardless of the position in which you’re welding. Surface Tension Surface tension on the work piece attracts the globules of filler metal and slag from the electrode as they approach the molten weld pool. Once they are part of the weld pool, surface tension helps keep the metal in place even in the overhead position.

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Classifications of Low-carbon Steel Electrodes

NOTES

Standards of Coated Electrode Manufacture Advances in welding technology have resulted in the development of a wide variety of electrodes to meet different welding requirements. This has made it necessary to have a method of electrode classification that ensures uniformity of manufacture and performance. The systems developed use a letter and number code to indicate the content and performance specifications of an electrode. Manufacturers must print the appropriate code number on the coating of every electrode (Figure 5). In North America, three basic classification systems are used. These are the ASME, CSA, and AWS systems.

CSA E4918 AWS E7018

CSA E4310 AWS E6010 Figure 5. Electrode with Code Marking

The most general classification system is that developed by the American Society of Mechanical Engineers (ASME). It uses F numbers to group electrodes according to their filler metal and coating type. This system is important in the complete definition of the specifications of any electrode, but it is not the system that Welders normally use to identify individual electrodes. The classification systems Welders commonly use, are those developed by the Canadian Standards Association (CSA) in conjunction with the Canadian Welding Bureau (CWB) and the American Welding Society (AWS). These two systems both use a letter/number code to convey similar information. The main difference between the systems is that the CSA system uses metric measurement while the AWS system uses imperial measurement. All low-carbon steel electrodes manufactured or used in Canada must meet the standards published by the CSA in its Bulletin W48-06 and certified by the CWB. These standards are almost identical to those published by the AWS in its Bulletin A5.1.

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CSA and AWS Designations There are over 150 different electrodes available in the area of low-carbon, low-alloy, stainless, and specialty steels. To choose the most appropriate electrode for a particular job, you must understand the identification information given by the code numbers in both the CSA and the AWS systems. The code number provides the following information: • • • • •

if the filler metal rod is to be used for electric arc welding or gas welding the tensile strength of the welds produced with that filler metal rod the welding position recommended for use with that filler metal rod the kind of current supply and circuit setup to be used the composition of the filler metal rod coating

Under the CSA system that’s used in Canada, an identification number consists of a letter or letters followed by four digits (Figures 6–8). E

43

1

0

designates electric welding

designates tensile strength in tens of megapascals (MPa)

designates welding position

designates composition of coating and current requirements

Figure 6. E4310 Electrode

2nd to last digit

Position

1

all positions except vertical down*

2

flat and horizontal fillet

3

flat position only**

4

vertical down

* Vertical down restrictions may vary between certifying authorities. ** Not a CSA or AWS designation. Figure 7. Weld Positions Indicated by the Second Last Digit

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Last Digit

Coatings

Current

0

Cellulose, sodium

DCEP

1

Cellulose, potassium

AC or DCEP

2

Titania, sodium

AC or DCEN

3

Titania, potassium

AC or DC

4

Titania, iron powder

AC or DC

5

Basic, sodium-calcium

DCEP

6

Basic, potassium

AC or DCEP

7

Iron oxide, high iron powder

AC or DCEN

8

Basic, iron powder

AC or DCEP

NOTES

Figure 8. Coating Ingredients and Current Characteristics Indicated by the Last Digit

The CSA and AWS specifications designate the characteristics of electrodes in similar ways. Both electrode standards meet the same basic performance requirements, with minor variations. The code numbers are the same in both systems except for the indication of tensile strength (Figure 9). AWS code numbers indicate tensile strength using the imperial system, in thousands of pounds per square inch, rather than in megapascals. CSA (MPa x 10)

AWS (psi x 1000)

E43XX

E60XX

E49XX

E70XX

E55XX

E80XX

E62XX

E90XX

E69XX

E100XX

E76XX

E110XX

E83XX

E120XX

Figure 9. Equivalent CSA and AWS Minimum Tensile Strength Ratings of Weld Deposits

For example, the E4310 electrode can be designated in the AWS system as E6010 (Figure 10).

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CSA System (Metric)

NOTES

AWS System (Imperial)

Example: E4310 where E = Electrode

Example: E6010 where E = Electrode

43 = minimum tensile strength in megapascals (MPa) x 10

60 = minimum tensile strength (psi) x 1000

1 = usability position

1 = usability position

0 = type of coating, current, polarity

0 = type of coating, current, polarity

Figure 10. AWS and CSA Comparison

Many manufacturers use their own trade names and numbers for their electrodes. On the job, you’re just as likely to know electrodes by these names as by their CSA identification number. For instance, the E4924 (AWS: E7024) electrode may be known as Rocket 24®, Easyarc 12®, or L.A. 7024®, but each one will meet the CSA W48.1-06 and the AWS A5.1 standards. You might come across electrodes that do not have certification numbers. These electrodes do not meet standards required by the CSA or AWS codes. If an electrode does not have a certifying number, it does not meet code requirements.

Select Common Electrodes for SMAW Principles of Electrode Selection To be effective, the electrode you choose for any given job should provide the following characteristics: • • • • • • •

good arc stability swift deposition of filler metal maximum weld strength good weld appearance minimum weld spatter easy slag removal good handling in the given weld position

To help make sure that you achieve these conditions, there are seven factors you should consider in choosing an electrode for a given job. These are: • • • • • • •

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the properties of the base metal base metal dimensions joint design and fit-up welding position and thickness of weld deposit welding current service conditions production factors

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Properties of the Base Metal The weld you make must be as strong as the base metal you’re welding. To achieve this, the electrode must provide the same mechanical properties as the base metal and have a metallurgical composition compatible with the base metal. This means that you need to know both the composition and the strength of the base metal you’re about to weld. This information will determine the composition of the core wire, what alloying elements should be in the electrode coating, and whether the electrode needs to be of the low-hydrogen variety.

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Base Metal Dimensions Generally, thin material will require a small-diameter electrode, thicker material, a larger diameter electrode. Joint Design and Fit-up Some electrodes are particularly suited for work on specific types of joint design. The CSA designation numbers do not include this information, but when you’re choosing an electrode, you should consider the joint type. In addition, electrodes vary with respect to the amount of penetration they provide. When the edges of the base metal have not been beveled and when the fit is tight rather than open, choose an electrode that provides deeper penetration. Welding Position and Thickness of Weld Deposit Your choice of electrode diameter will depend in part on welding position. CSA electrode designation numbers indicate the welding positions for which each electrode is particularly suited. For example, those with high deposition rates are appropriate for flat and horizontal position welding. Fast-freeze type electrodes are designed to perform effectively in the vertical and overhead positions. Thicker electrodes are generally unsuitable for vertical and overhead positions where gravity is a negative factor. The thickness of the required weld deposit will also determine your choice of electrode. In multi-pass groove welds, the narrower dimensions at the bottom of the joint will generally call for a smaller diameter electrode, while the fill passes will require a larger diameter electrode. Welding Current The current that welding power sources produce can be AC, DC, or both. Many electrodes perform equally well with either AC or DC. Some electrodes (as their numbers indicate) can be used only with AC, others only with DCEN, and still others only with DCEP.

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Service Conditions On many jobs, the actual specifications for welds are given and will generally dictate the electrode you will use. When you do not receive the specifications, you must assess the conditions that the weld will encounter when in use and choose the appropriate electrode. Conditions such as shock loading or extreme temperature will require a particular electrode choice. Production Factors Your choice of electrode could depend on production requirements. For example, fast-fill electrodes that have high deposition rates might be a desirable choice because of the increased productivity they provide.

Common Low-carbon Steel Electrodes The guidelines above provide a sound basis for choosing electrodes in almost all circumstances. In practice, you’ll quickly become familiar with a range of electrodes, their characteristics, and the conditions for their use. The following is an introduction to some of the more common SMAW electrodes you will use when welding low-carbon steel. To help you become familiar with both the CSA (metric) and the AWS (imperial) systems, the AWS designation is given in parentheses after the CSA number. E4310 (E6010) E4310 (E6010) E electric

43 minimum tensile strength 430 MPa (60 000 psi)

1 all positions except vertical downhill*

0 cellulose and sodium—DCEP only

* Vertical down restrictions might vary between certifying authorities.

• • • • • • • • •

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all positions except vertical downhill (vertical downhill restrictions might vary between certifying authorities) DCEP only classified as a fast-freeze electrode because of its quick solidification deep-penetrating arc often chosen for vertical and overhead welds cellulose flux creates good shielding gas production thin and easily removed slag excellent choice for X-ray quality specifications common in shipbuilding, pressure vessels, and storage tank construction

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E4311 (E6011)

NOTES

E4311 (E6011) E electric

43 minimum tensile strength 430 MPa (60 000 psi)

1 all positions except vertical downhill*

1 cellulose and potassium—AC or DCEP

* Vertical down restrictions might vary between certifying authorities.

• • • • • • • •

all positions except vertical downhill (vertical downhill restrictions might vary between certifying authorities) AC, DCEP classified as a fast-freeze electrode [AC version of E4310 (E6010)] deep-penetrating arc cellulose flux provides good shielding gas production thin and easily removed slag excellent choice for X-ray quality specifications common in shipbuilding, pressure vessels, and storage tank construction

E4313 (E6013) E4313 (E6013) E electric

• • • • • •

43 minimum tensile strength 430 MPa (60 000 psi)

1 all positions

3 titania (rutile) potassium—AC or DC

all-position electrode AC, DC (either polarity, DCEN preferred) classified as fill-freeze (fast-follow) medium penetration rutile electrode coating medium slag coating that gives a good weld appearance and flakes off easily popular for vertical down on light gauge and for use on simple AC power sources

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E4914 (E7014) E4914 (E7014) E electric

• • • • • • • •

49 minimum tensile strength 490 MPa (70 000 psi)

1 all positions except vertical downhill

4 titania (rutile) iron powder—AC or DC

all-position electrode AC, DC (either polarity) medium to low penetration thick slag gives a smooth bead appearance slag flakes off easily thick flux coating contains iron powder, which adds to the filler metal high deposition rate increases productivity fill-freeze

E4924 (E7024) E4924 (E7024) E electric

• • • • • • •

174

49 minimum tensile strength 490 MPa (70 000 psi)

2 flat and horizontal positions

4 titania (rutile) iron powder—AC or DC

flat and horizontal positions AC, DC (either polarity) low penetration heavy slag, easily removed iron powder version of E4914 with up to 50% iron powder known as a contact electrode since the thick flux allows you to drag the tip of the electrode along the base metal very clean and smooth weld fast-fill

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E4918 (E7018)

NOTES

E4918 (E7018) E electric

• • • • • •

49 minimum tensile strength 490 MPa (70 000 psi)

1 all positions except vertical downhill

8 low hydrogen, potassium, iron powder—AC or DCEP

all positions except vertical downhill low hydrogen (basic coating) designed for low-alloy steels and unknown alloys that are prone to underbead cracking from hydrogen entrapment 25–40% iron powder in flux arc length must be kept short to prevent porosity designator after the number indicates the maximum level of hydrogen (e.g., H2, H4, H16)

Electrodes for Hardfacing Electrodes for hardfacing are applied to surfaces that require a hard skin. The hardness of the skin depends on the alloys in the electrode. There’s no exact standard for hardfacing welding electrodes. Each manufacturer produces different formulations and supplies data on the weld beads produced and their expected hardness and toughness. The various products create surfaces that range from very soft, all the way up to glass hard. When you apply a hardfacing weld, it’s important to understand the application. If the weld is too hard and brittle, it will fracture and break away from the surface (spalling). If it’s too soft, it will be quickly worn away. Hardfacing welding electrodes are based on several alloys made from carbon, cobalt, nickel, chromium, tungsten, and manganese. They can be loosely categorized as: • • • • • • •

tungsten carbides chromium carbides semi-austenitic steels austenitic manganese steels austenitic stainless steels martenisitic stainless steels carbon steel alloys

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You should consult the supplier as to the correct alloy to choose. The purpose of hardfacing is to extend the life of the machinery being welded by controlling wear. The wrong choice can be a waste of time and material but can also shorten the life of the equipment. In a large mining operation, the correct choice can save millions of dollars per year.

Shielded Metal Arc Cutting Electrodes The shielded metal arc cutting (SMAC) process uses electrodes specially developed for cutting. These are not the same as the electrodes for shielded metal arc welding (SMAW). Manufacturers have developed special electrodes for cutting, piercing, and beveling stainless steel, copper, aluminum, bronze, nickel, cast iron, manganese, steel, and alloy steels. The special feature of these cutting electrodes is the high-velocity gas and particle stream they develop that cuts through the metal. The special slowburning ingredients in the electrode coating and the deep cavity in the electrode end are the features that help develop this cutting action (Figure 11).

Steel core Coating

– Deeply recessed electrode

+ Kerf

Plate

Arc stream and gas jet from electrode covering and wire Figure 11. Shielded Metal Arc Cutting Electrodes

SMAC electrodes are available in standard lengths. The most common length is 350 mm (14 in.). SMAC electrodes are available in diameters of 2.5 mm (3⁄32 in.), 3.2 mm (1⁄8 in.), 4.0 mm (5⁄32 in.), 5.0 mm (3⁄16 in.), and 6.0 mm (1⁄4 in.). These electrodes are used with a constant current machine producing either AC or DC. Your choice of electrode sizes and current settings for cutting depends on the thickness of the metal being cut.

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Techniques used for cutting include the use of a very short arc. The electrode can be dragged across the metal without any danger of it shorting out because of the heavy coating and the recessed electrode wire.

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Cutting with Standard SMAW Electrodes Regular shielded metal arc welding electrodes can also be used for cutting lowcarbon steel. However, this will require a higher current than a SMAC electrode would. SMAW electrodes used for cutting will last a little longer if they are soaked in water for a few minutes before use. The absorbed moisture slows down the vapourizing of the coating and helps produce a deeper cup at the end of the electrode. This increased cavity creates a more forceful jet action. Never use a water-soaked electrode for welding. The absorbed moisture will cause hydrogen to be trapped in the weld.

Correct Handling and Storage of Common SMAW Electrodes SMAW electrodes are both fragile and expensive. You must handle electrodes carefully at all times.

Handling of Electrodes Before and After Use Electrodes must be handled with great care to avoid breaking or cracking the coating. An electrode with a damaged coating will usually perform poorly. If pieces of the coating are actually missing, the result will be poor weld appearance and porosity in the weld. Because electrodes with very different properties can look the same, correct handling of electrodes also includes marking them accurately after the package has been opened. It’s equally important to collect and clearly mark unused electrodes that are being returned to storage. Do not risk producing a weld that does not meet specifications just because you used the wrong electrode. An electrode that is not clearly identified should be considered unusable.

Storage of Electrodes The main requirement for storing electrodes is to keep them dry. Not only are electrode coatings fragile, but their composition allows them to pick up moisture from the air.

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Prolonged exposure to moisture can cause the coating to disintegrate. Even if the disintegration is not obvious, the heat of the arc will actually blow away portions of the coating. In either case, the electrode becomes useless and must be discarded. Any moisture that an electrode absorbs contains hydrogen. During welding, some of this hydrogen is transferred to the weld metal. This can lead to a number of problems with the weld. Depending on the composition of the base metal, these problems can include embrittlement, porosity, cracking of the weld, and a rough weld appearance. In addition, welding with a moist electrode increases the arc voltage, increases weld spatter, and makes slag removal difficult. Some electrodes (such as mineral-coated ones) are more prone to absorbing moisture than others. The length of time electrodes can be exposed to the atmosphere varies from 30 minutes to four hours or longer, depending on the relative humidity of the atmosphere. For example, the maximum exposure time for low-hydrogen electrodes is between two and four hours, depending on the relative humidity. A perfectly dry, low-hydrogen electrode is essential to produce a satisfactory weld. Low-hydrogen electrodes must be thrown away if they have been directly exposed to water. With all electrodes, it’s impossible to tell simply by looking at them whether they have absorbed dangerous amounts of moisture. To protect electrodes from moisture, manufacturers ship them in airtight containers. On the job site, electrodes are stored in sealed portable electrode containers.

Electrode Ovens Some electrodes can be safely stored at normal room conditions if the temperature and relative humidity do not go above certain normal tolerances. For other types of electrodes, electrode ovens are used to guarantee a humiditycontrolled environment for storage. Ovens are essential for the more sensitive low-hydrogen and hardfacing electrodes and for special-alloy electrodes such as stainless steel, brass, bronze, aluminum, Inconel, and Monel. Welding shops often have large electrode ovens that are capable of holding several hundred kilograms of electrodes. There are also smaller field ovens that can be connected to an auxiliary power supply. Ovens can sometimes be used to re-bake electrodes that have been exposed to moisture in order to make the usable. Electrode manufacturers and suppliers provide information on storage and re-baking conditions for their electrodes and, if available, these recommendations should be followed (Figure 12).

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CSA #

AWS #

Normal room

Holding ovens

E4310

E6010

25ºC ± 10ºC

E4311

E6011

(80ºF ± 20ºF)

Consult supplier for storage and re-bake conditions.

(50–70% relative humidity) E4313

E6013

25ºC ± 10ºC (80ºF ± 20ºF)

E4914

E7014

E4924

E7024

E4918

E7018

10ºC to 20ºC (20ºF to 40ºF)

Re-bake

NOTES

135ºC ± 15ºC

above ambient temperature

50% max. relative humidity

1 hr. at temp.

25ºC to 140ºC (50ºF to 250ºF) above ambient temperature

350ºC ± 25ºC

Stainless steel

103ºC to 127ºC

179ºC to 315ºC

Hardfacing

(215ºF to 260ºF)

(350ºF to 600ºF)

(650ºF ± 50ºF) for 1 hr.

check manufacturer for detailed procedure

High-strength alloy

Figure 12. Electrode Storage Conditions

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SELF TEST 11 1. What force is responsible for transferring molten particles of metal across the arc, by means of a pinching effect? a. gravity b. electromagnetism c. gas expansion d. surface tension 2. What does the electrode code E4918 (E7018) stand for? a. 49000 psi/flat and horizontal position/ cellulose and potassium b. 70000 psi/ all positions/ cellulose and potassium c. 70000 psi/ all positions/ low hydrogen d. 49000 psi/ all positions/ low hydrogen 3. What does the number “8” refer to when using an E7018 welding rod? a. tensile strength b. position c. composition of coating and current requirements d. heat range

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Weld Mild Steel with Shielded Metal Arc Welding Set-up Procedures Set-up procedures will vary depending on the location of the weld and equipment. You may be working on a bench in a shop environment or on a machine on a job site. Each of these requires different set-up and safety concerns.

Shop Environment Most shops will have a welding area close to the repair shop, but some shops will use the repair shop area for both welding and repairs. There are several aspects of any welding area that deserve your attention: • • • • • • •

proper fume ventilation screens for visual protection against flashes noise protection when welding, grinding, and air-arcing air particle contamination fire hazards fire safety equipment proper egress

Once you’ve met all the concerns, you can move your cables and prepare for the weld. You’ll set-up the machine and perform a test pass before welding the project. You should always be aware of your environment and remember that other people may be working in the same area.

Job Site Environment When at a job site, you will often need to work outdoors. This presents a different set of concerns: • • • • • • • •

brush and grass fire fire safety equipment screens for visual protection against flashes noise protection when welding, grinding, and air-arcing ambient temperature for a proper weld ambient temperature for the Welder (personal safety) rain water for welding material damage rain water for electric shock

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• • • •

insect protection for the Welder machine electrical wire heat damage machine computer damage machine anti-friction bearing damage

Welding Ground Placement You must be very careful about the location of the welding ground clamp. Current must flow between the stinger and the ground clamp to perform the weld. Current will pass through components on the machine if the ground clamp is not properly located. You should always locate the ground on the same material that you’re welding. This will prevent current from passing through other components on the machine.

Bearing Damage Anti-friction bearings utilize an inner and outer race and rolling elements between the races. Any current that passes through the rolling elements will burn a mark on the races and rolling elements. This will cause premature bearing failure. It’s common to find final drive bearings damaged because of improper ground connection while re-grousering a track machine. This is a very expensive failure.

Electronic Component Damage Electronic components may be damaged from welding current passing through them, or current created by the magnetic fields from the welding process. Welding currents can be over 300 A and this can damage wiring or computers. Computers have wires capable of carrying only 20–30 Ma and so cannot handle the heavier current. Machine service manuals are very specific about how to protect their wiring and computers. Some require the batteries be disconnected and the computer cables disconnected. Some require that the computers be removed from the machine. You must follow the specific manufacturer’s instructions. Some machines may have four computers onboard. Damaging them will result in a very expensive repair.

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Weld Joint Design There are five basic joint designs used in welding (Figure 1). Each of these has many variations. Your choice of which joint or variation to use will depend on four important factors: • • • •

NOTES

the load applied to the weld (e.g., compression, torsion, bending, or fatigue) the way the load is applied (e.g., sudden, variable, or steady) the thickness of the base metal the cost of the joint preparation and welding time

Lap Joint The lap joint joins two pieces of metal that overlap for the weld.

Tee Joint The tee joint joins two pieces of metal at right angles (90°) to each other.

Corner Joint The corner joint also joins two pieces of metal at right angles, but the joint is formed at the ends of both pieces in an L shape.

Butt Joint The butt joint joins two pieces of metal lying in the same plane.

Edge Joint The edge joint joins two pieces of metal that are turned up at the edges. It is also called a “flange joint.”

Lap joint

Tee joint

Butt joint

Corner joint

Edge joint Figure 1. Five Basic Weld Joints

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Variations in Weld Joint Design On thicker material, the edges must be prepared to get additional weld penetration. There are several ways of preparing the edges of a weld joint. Lap Joints Lap joints need little or no edge preparation. On thicker material, a single bevel is all that is usually required, although such preparations are extremely rare. Lap joints are often used for welds joining two materials of different thickness. If a weld does not need great strength, a single lap joint might be enough to provide a “tight” joint. Do not use a single lap joint when the weld will be subjected to fluctuating, bending, or twisting loads. For these types of loads, weld the joint from both sides, or use a double lap joint (Figure 2).

Single lap joint

Double lap joint

Figure 2. Variations of Lap Joints

Lap joints have two significant drawbacks. As with tee joints, the material requirements are high. That means you can only get maximum tensile strength when the overlap is five times the thickness of the thinner member. Also, the joint tends to lose its strength under stress loading. Tee Joints The square tee joint requires no edge preparation. It’s widely used because it’s relatively inexpensive and easy to fit. On thicker material, the edges might be prepared with a single bevel, double bevel, single J, or double J (Figure 3).

Single bevel

Double bevel

Single J

Double J

Figure 3. Edge Preparation for Tee Joint

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Tee joints that are welded on one side are only satisfactory for light static loads. For heavy or fluctuating loads, tee joints need to be welded on both sides to increase their strength.

NOTES

Tee joints are relatively easy to design and they provide maximum access for welding. However, the chance of them being distorted is high. They are also expensive because they need more filler weld material, especially on larger tee joints and on joints that need to be welded from both sides. Corner Joints There are two types of corner joints: the open corner and the closed corner (Figure 4).

Open

Closed Figure 4. Types of Corner Joints

Welders use the open corner joint more often than the closed corner joint because penetration is usually excellent, resulting in a full-strength weld. With the closed corner, penetration is impossible on all but light-gauge sheet metal. On thicker material, you must prepare the edges (Figure 5). A small root opening can be left between the two pieces in order to ensure full penetration.

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NOTES

Single bevel

Single V

Double bevel

Single J

Single U

Double J

Figure 5. Variations of Corner Joints

Square corner joints are relatively easy to prepare and assemble, but the bevel, the V, the J, and the U preparations require more skill and time to accurately fit the joint. Corner joints are not satisfactory for heavy stress loading if they’re only welded from one side. For heavy stress loading applications, corner joints are welded from the inside before gouging the outside to sound metal and welding. Although this increases the cost of the weld, it produces joints capable of withstanding heavy stress loading. Edge Joints Edge or flange joints are most commonly used on light-gauge material such as sheet metal. The edges of the sheet metal are turned up with a piece of metalforming equipment called a “brake.” The turned-up edges reduce the danger of burn-through on thin metal and at the same time help to prevent distortion. On thin metal, no additional filler metal is required. With plate, the edges must be prepared in order to ensure sufficient penetration (Figure 6).

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NOTES

Single bevel

Single J

Single V

Single U

Figure 6. Edge Joint Preparation

Butt Joints Butt joints are the most widely used of the five designs. Like tee joints, butt joints provide the most access for welding. They use the least weld material. Butt joints allow 100% penetration, so they are effective for all types of stresses. Butt joints are the preferred joint for resisting fatigue stresses if complete penetration is assured. A correctly prepared and welded butt joint is nearly as strong as the base metal. On thin metal, complete penetration and full strength can be achieved using a square butt joint without extensive edge preparation. The thicker the metal, the more edge preparation you need to do. There are two basic designs: the bevel and the J. These basic butt joint designs have a number of variations (Figure 7).

Square

Single bevel

Single V

Single J

Single U

Double bevel

Double V

Double J

Double U

Figure 7. Edge Preparation for Butt Joints

Joints that are prepared and welded from both sides are called “double joints.” Joints that are welded from only one side are called “single joints.” To ensure complete penetration on single joints, you will often need to add a backing strip or plate. The main drawback of the butt joint is the higher skill and accuracy needed to fit and weld the joint. Of the five joints, the butt joint is the most difficult to master. It takes considerable experience to become proficient in preparing and welding butt joints.

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Bevel Angles The common bevel angles used in preparing the edge of materials are: • •

30° 37.5°

•

45°

most common bevel for plate; provides a 60° included angle a common bevel angle on pipe ends used in butt joints; gives a 75° included angle a wider than usual bevel angle for V butt joints; gives a 90° included angle

The 90° opening requires a greater amount of weld. Narrower angles are used unless there is a need for more access to the bottom of the weld joint, as with cast iron and aluminum. Single-bevel joints are commonly 30–45°.

Welding Positions Basic Weld Positions There are four basic welding positions: flat, horizontal, vertical, and overhead. Welding techniques for the four positions vary according to the ease of depositing the weld metal. Welding in the flat position is generally faster and less tiring than in the other three positions. Whenever possible, you should try to place your work piece in the flat position. The term “welding out of position” means welding in any position other than flat. There are four positions that are used for plate and two that are for pipe (Figure 8).

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Position Flat 1

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Groove—Plate 1G

Groove—Pipe 1G

Fillet

NOTES

1F 15º 15º

Pipe horizontal and rotated, weld flat ± 15º

Horizontal 2 2G

2G

2F

Pipe vertical and not welding, weld horizontal (± 15º)

15º 15º

Vertical 3

3G

N/A

3F

Overhead 4

4G

N/A

4F

Pipe 5

N/A

5G

5F 15º 15º

at vertical, overhead ± 15º

Pipe 6

N/A

6G

N/A V

45º ± 5º

H

Figure 8. Welding Positions

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Flat Position (Downhand) In the flat position, the work piece is positioned so that the weld joint is parallel to the floor. The electrode will generally point downward. For butt joints on plate, the two pieces are simply placed on a flat surface. For lap and tee joints, the two pieces of plate must be supported in an angled position so that the actual joint is parallel to the floor (Figure 9). With corner joints, the ends of the plate are positioned on a flat surface so that the two pieces meet at the top to form a small tent.

Figure 9. Joints in the Flat Position

Horizontal Position Welds in the horizontal position are also parallel to the floor, but they are done along a vertical surface. Weld metal is deposited from the upper side of the weld joint. For butt joints, the electrode is held horizontally (parallel to the floor), but for the other four weld joints, it is usually either slightly higher or lower than horizontal, depending on the technique used. For butt joints, the two plates are supported in the vertical position, but the lap, tee, and edge joints can be set up and welded on a flat surface. With horizontal welds, the main difficulty is that gravity causes the molten pool to flow toward the lower side of the weld. Vertical Position In the vertical position, the plate to be welded is positioned vertically and the weld joint itself is vertical. The direction of travel can be uphill or downhill, but the majority of vertical welding is usually done uphill, from bottom to top. The electrode points slightly upward. As with horizontal welding, gravity causes the molten metal to pull away from the edges of the bead and, unless the weld pool is correctly controlled, molten metal will drip. Overhead Position The overhead position is the reverse of the flat position: the weld is done from the underside of the plate with the electrode pointing upward rather than downward. Overhead welding is considered difficult to master. In the overhead position, the force of gravity typically pulls the molten metal from the toe of the weld bead to the centre of the bead, where it can drip. These frozen drips of metal hanging from the weld bead are commonly called “grapes.”

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Abbreviations for Weld Positions In the welding trade, abbreviations can be used to indicate the type of weld and the welding position. Letter abbreviations are used to indicate weld type, as follows: • •

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NOTES

F: fillet weld G: groove weld

Each weld position is designated with a number, as follows: • • • • • •

1: flat position (pipe rolled) 2: horizontal position 3: vertical position 4: overhead position 5: pipe—axis of pipe fixed at the horizontal 6: pipe—axis of pipe fixed at a 45° incline

The position number and the letter abbreviation are used together. For example: • • • •

1G is a groove weld in the flat position. 3F is a fillet weld in the vertical position. 4G is a groove weld in the overhead position. 5G is a groove weld in a pipe with the axis of the pipe fixed at the horizontal.

A common weld joint design is a single-bevel butt joint with a specified root opening and a backing bar. This is called a “GF weld,” meaning that it is a combined groove and fillet weld. The welding sequence requires a fillet weld to join the backing bar to the square edge of the joint. The fillet weld and the bevelled edge then form a vee-groove joint. If this joint was to be done in the vertical position on plate, it would be called a “3GF position.” The single-bevel butt joint with backing is commonly used as a welding qualification test as it tests your ability to weld a groove weld and a fillet weld all in one exercise. You should expect to regularly face similar qualification tests for CWB qualification and Welder certification.

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Weld Types, Their Sizes, and Profiles Types of Welds There are five main types of welds: • • • • •

surfacing welds tack welds fillet welds groove welds plug and slot welds

Surfacing weld

Tack weld

Fillet weld

Groove weld

Plug weld

Figure 10. Weld Types

Surfacing Welds Surfacing welds are deposits of weld materials used to build up the surface of metal or to replace metal on worn surfaces. The following terms are used to more exactly describe surfacing welds: • • • •

“Buildup” is intended to change dimensions such as thickness. “Buttering” means that the buildup is intended to provide a base (transition) for another surface weld. “Hardfacing” is the application of surfacing welds intended to create a hard or tough surface to control wear. “Cladding” is the application of surface welds that create a corrosionresistant or heat-resistant layer.

Tack Welds Tack welds are a series of short welds used to hold the joint assembly in place during the fit-up procedure (Figure 11). Each tack weld is a short (sometimes temporary) weld about 13 mm (1⁄2 in.) long. Tack welds are usually deposited at both ends of the weld joint and at roughly equal intervals along the length of the joint.

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Figure 11. Tack Welds

Tack welds should be used on the opposite side of the weld joint whenever possible. Joints that require welds on both sides should be tack welded on the side opposite to the first side to be welded. On tee joints, tack welds are used along the opposite side of the weld to prevent the upright plate from leaning toward the weld (Figure 12).

Tack weld

Figure 12. Tee Joints with and without Tack Welds

Fillet Welds Fillet welds are used extensively on lap, tee, and corner joints, where they join two pieces of metal that are usually at right angles (90°) to each other. A fillet weld consists of one or more beads or passes that are roughly triangular in crosssection. There are a number of terms for describing various aspects of a fillet weld (Figure 13).

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Depth of fusion or bond

NOTES

Leg Face Leg

Toe

Throat Root Root penetration Figure 13. Fillet Weld

The ideal fillet weld is characterized by: • • • •

joint faces at right angles (90°) face that is flat or slightly convex toes that merge smoothly with the surface of the joint members legs of equal length

In many cases, fillet welds are more economical than groove welds because they’re easier to assemble and require less edge preparation. On the other hand, they usually use more weld filler metal, and are less able to withstand stress loads. Fillet welds are not considered capable of carrying stress loads unless their length is at least four times the leg length of the weld. For material up to 25 mm (1 in.) thick, stress-carrying fillet welds should not have a leg length of less than 10 mm (3⁄8 in.).

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Size

Size

Size

NOTES

45º Flat

Concave

Convex

Figure 14. Fillet Weld Profiles

The most preferred profile is flat to slightly convex (Figure 14). The choice of profile depends on several factors, including: • • • •

welding position type of electrode type of joint stress requirements of the joint

Size of the Fillet Welds The size of a fillet weld is often designated as the length of its shorter leg (the distance from the root of the weld joint to the toe of the weld) (Figure 15). This designation is accurate for flat and convex fillet welds. But there is a more correct description of fillet weld size. First, imagine that you draw the largest equal-leg triangle that you can inside the cross-section of the weld. The size of the weld will be the length of each of the triangle’s legs. For concave fillet welds, the size is not the leg length. The size of a concave weld is its throat thickness (“T”) multiplied by 1.4.

Long leg

Leg Leg

T

Effective size

Short Leg

T

Size = short leg

Leg Leg

T

Effective size

Figure 15. Fillet Weld Dimensions

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Acceptable Fillet Weld Profiles The three basic weld profiles are flat, concave, and convex. However, every weld will be slightly different. You need to check each weld to make sure its profile is acceptable (Figure 16).

Concave Size

Size

Flat

45º

Convexity (C) must not exceed 0.07 × face width + 1.5 mm (1⁄16")

Size

Size

Convex

Size

Size

C

C

Acceptable fillet weld profiles

Insufficient throat

Size

Excessive undercut

Size

Excessive convexity

Size

Overlap

Size

Insufficient leg

Size

Unacceptable fillet weld profiles Figure 16. Acceptable and Unacceptable Fillet Weld Profiles

On flat or concave fillet welds, the effective or theoretical throat is usually the same as the actual throat thickness. On convex fillet welds, the actual throat dimension is more than the effective throat, but this extra weld filler metal does not increase the strength of the weld. For this reason, excessively convex fillet welds are undesirable.

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For similar reasons, excessively concave fillet welds are also undesirable. The longer leg length requires additional weld material that does not contribute to the strength of the weld. A flat or convex fillet weld with the same effective throat (strength) uses less weld material and is a more economical weld.

NOTES

Note on the flat profile (Figure 16) the toes of the weld must be at a 45° angle to the face of the weld. With convex profiles, the convexity (C) must not exceed 0.07 x face width + 1.5 mm (1⁄16 in.). Of the three profiles, convex fillet welds are much less susceptible to shrinkage cracking than concave and flat fillet welds. Concave and flat fillet welds are much more likely to crack, especially on heat-sensitive metals such as high-carbon steels. There are also fewer problems with undercutting on convex fillets than on concave or flat fillets. Concave fillet welds have two major advantages over the other two profiles: • •

They provide a smoother contour at the toe of the weld. They provide a greater surface area for the distribution of stress loads.

Concave fillet welds are preferred for joints that are subjected to fatigue stresses. Concave fillet welds are also used in such applications as inside grain feed chutes, where free flow is desired. Groove Welds Groove welds fill in the gap or groove between two pieces of metal. Groove welds are most commonly used on butt joints. The weld on an open corner joint or on specially prepared lap and tee joints can sometimes be considered a groove weld. Groove welds consist of a root bead, fill passes, and a cap (Figure 17). The number of passes will vary depending on the thickness of the metal. On thinner metal, the fill pass and cap can be combined into one pass. In some cases, a single pass is adequate for the entire weld. Cap pass Fill passes Root face

Root opening

Root pass

Figure 17. Multi-pass Groove Weld

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The significant dimensions of groove welds include the root opening, the root face, the included angle, the thickness, and the throat (Figure 18). On bevelled joints, the bevel angle is important. On groove joints with a J preparation, the root radius is significant.

Included angle

Bevel angle

Thickness (T) Root face

Root opening

Throat

Groove or included angle

Thickness (T) Root face

Root radius Root opening Figure 18. Groove Weld Dimensions

The size of the root opening, the root face, the included angle, and the root radius all affect the amount of weld material required and the depth of penetration. For example, too large a root opening, root face, or included angle will result in excessive penetration and the deposition of unnecessary weld metal. On the other hand, dimensions that are too narrow will make full penetration extremely difficult, if not impossible. If the root radius on a U-joint is too great, you will deposit too much weld material, and the possibility of uncontrollable distortion increases. These dimensions will depend on the material thickness, the electrode size, and the welding process.

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Groove Weld Size and Profile The size of a groove weld is the depth that the weld penetrates into the groove, or the gap between the two pieces. In Figure 19, the weld size of A (where penetration is complete) is the same as the thickness of the plate.

NOTES

Where penetration is incomplete, as in B, the weld size is the depth of the penetration. In C (where the plates differ in thickness and there is complete penetration), the weld size is the thickness of the thinner plate.

Size

Size A. Complete penetration

Size

B. Incomplete penetration

C. Complete penetration

Figure 19. Groove Weld Sizes

Metal deposited above the surface of the plate is called “reinforcement.” Profiles of groove welds show the amount of reinforcement at the centre of the weld (Figure 20). This reinforcement must not be more than 3 mm (1⁄8 in.) because excessive reinforcement is uneconomical and contributes nothing to the strength of the weld. It decreases the working strength of the weld joint because stresses concentrate at the toe of the weld.

R

Reinforcement (R) must not exceed 3 mm (1⁄8")

R Correct groove weld profile

Insufficient throat

Excessive convexity

Excessive undercut

Overlap

Figure 20. Groove Weld Profiles

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Gouging or grinding can remove excessive reinforcement. There must be no valley or groove along the edge or in the centre of the weld. The width of a groove weld should not extend more than 3 mm (1⁄8 in.) beyond the shoulder or edge of the joint on either side. Extra deposit beyond this is uneconomical, because there is no corresponding increase in joint strength. It also can negatively affect the heat-affected zone next to the weld bead. Plug and Slot Welds These welds are used mainly for lap joints. They are sometimes used for tee joints where a fillet weld is not adequate or where the joint is not accessible for a fillet weld. When a slot is made rather than a circular hole, the weld is called a “slot weld” (Figure 21).

Weld

Weld

Figure 21. Plug and Slot Welds

To prepare the weld joint for a plug or slot weld; punch, drill, or flame cut the hole or slot in the overlaying plate. Position the plates, and then make the weld through the opening to the underlying plate. The hole or slot may or may not be entirely filled in with weld metal and, on relatively thin metal, the hole or slot might not be necessary. Continuous and Intermittent Welds Continuous weld joints extend without a break throughout the length of the joint. Continuous welds are used on joints that require maximum strength and tightness. Intermittent welds are a series of short welds spaced along the length of the weld joint (Figure 22). The size and spacing of the welds depends on plate thickness, type of joint, welding process, and strength requirements of the weld.

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NOTES

Figure 22. Intermittent Welds

Intermittent welds should not be used on weld joints that must be sealed (airtight or watertight) or require maximum strength. Where permitted, intermittent welding reduces the cost of labour and materials. Intermittent welds are most commonly used on lap and tee joints. They are sometimes used on square butt joints.

Striking the Arc Striking an arc is an important part of the set-up and start. The machine should be set for AC or DC, straight polarity or reverse polarity. The current should be set for the size and type of rod and the thickness of plate. Using the correct striking method will minimize damage to the base metal to be welded and may prevent damage to other parts in the area. • •

Procedure 1A: Strike an arc using the scratch method Procedure 1B: Strike an arc using the tap method

To strike an arc, you simply touch the electrode to the base metal. You must then immediately lift the electrode. The arc forms as soon as the electrode is lifted from the base metal. If you allow the electrode to remain in contact with the base metal, the two will fuse. If you lift the electrode too far from the base metal, the arc will go out. The tap method is the main method used to strike an arc. It reduces the chance of arc strikes on the surrounding material.

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Tap Method 1. Hold the electrode about 25 mm (1 in.) above the base metal (Figure 23A). It should be perpendicular to the base metal and inclined 10–20° in the direction of travel. 2. Lower your welding helmet and strike an arc by moving the electrode straight down until it touches the base metal (Figure 23B). 3. When the burst of light occurs, bring the electrode up 6 mm (1⁄4 in.) from the base metal (Figure 23C). 4. Hold this length for a second or two, and then lower the electrode until it is 3 mm (1⁄8 in.) away from the plate (Figure 23D). Maintain the arc for three or four seconds then break the arc by pulling the electrode away from the base metal.

25 mm (1")

touch base metal

B. Touch base metal

A. Start position

6 mm (¼")

C. Raise electrode 6 mm (¼")

3 mm (1⁄8")

D. Lower to 3 mm (1⁄8") to start welding Figure 23. Tap Method

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Scratch Method Hold the electrode about 25 mm (1 in.) above the base metal. It should be perpendicular to the base metal and inclined 10–20° in the direction of travel. Lower your welding helmet and strike an arc by quickly and gently dragging the electrode across the base metal, using a wrist movement only (Figure 24). If you strike the arc correctly, a burst of light (an arc) will occur.

NOTES

Scratch electrode across base metal with wrist movement only Figure 24. Scratch Method

Lift the electrode about 6 mm (1⁄4 in.). Hold this distance for a second or two. Then lower the electrode until it is 3 mm (1⁄8 in.) away from the base metal. The purpose of holding a long arc for that second or two is to allow the tip to heat up, making the arc more stable. Maintain the arc for three or four seconds. Then pull the electrode away from the steel plate until the arc is broken.

Basic Weld Faults and Their Causes There are three categories of weld defects: •

• •

Dimensional faults where the weld deposit does not meet the specifications and requirements of the weld, including incorrect weld sizes and profiles. Structural discontinuities including such defects as porosity, undercut, incomplete penetration, and lack of fusion. Defects in the mechanical properties of the weld metal, including reduced tensile strength, ductility, hardness, or corrosion resistance.

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You have limited control over defects in mechanical properties of the weld metal. Mechanical properties can be affected by electrode selection, heat input, cooling rate, and welding technique.

Dimensional Defects Incorrect Weld Size Any variation from the specified weld size affects the distribution of stress in the weld. This will affect the strength of the weld. Undersized welds usually have insufficient throat (Figure 25). This condition is also called “underfill.” This reduces the strength of the weld. Stresses concentrate at the centre of the weld, increasing the likelihood the joint will fail. Undersized welds are usually the result of a fast rate of travel. Oversized fillet welds are too convex (Figure 26). Oversized groove welds have too much reinforcement. These defects tend to produce notches at the toe of the weld, where stresses will concentrate. The weld metal also will trap slag and gases, creating a condition called “porosity.” Porosity weakens the weld. Oversized welds can also mean poor fusion of the weld and base metal.

Figure 25. Undersized Weld

Figure 26. Oversized Weld

Overlap “Overlap” is a condition in which too much weld metal is deposited at the toe of the weld (Figure 27). Overlap is most often a sign of poor fusion between the weld metal and base metal. This condition is extremely serious because stresses concentrate in notches that form at the toes of the weld. In fillet welds, overlap will also reduce the effective weld size.

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Dimensional defects also include the distortion and warping that occur as a result of stresses from the heating and cooling of the weld deposit and base metal during welding.

NOTES

Figure 27. Weld Overlap

Structural Discontinuities in the Weld Structural discontinuities include a broad range of weld defects such as: • • • • • • •

undercut incomplete penetration underfill incomplete fusion porosity slag inclusion cracking

These defects often appear with size and profile problems. They can also occur in welds that meet size and profile specifications. Undercut “Undercut” means a cutting away of the plate surfaces at the edge of the weld (Figure 28). A sharp recess forms in the plate where the next layer or bead must fuse with the base metal. The plate is thinner at this point, so the joint is weaker. Joint failure is especially likely when the undercut occurs at the toe of the weld. Undercut is usually caused by improper electrode manipulation. Other causes are too much current, too long an arc, or slow travel. On joints that are not very accessible, undercut can be very hard to avoid.

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Figure 28. Undercut

Undercut can be corrected. When it occurs at the sidewall of the weld between layers, you can deposit extra weld passes in the groove before depositing the next layer. At the surface of the weld where you can see the defect, you can make extra passes until you reach 3 mm (1⁄8 in.) above the base metal surface, normally the maximum permitted. Incomplete Penetration Incomplete penetration is the failure of the weld pool and the base metal to fuse together at the root of the joint. On groove and fillet welds, this defect occurs when the areas above the root reach fusion temperatures before the root does. The molten weld metal forms a bridge across the joint and prevents the arc from reaching the root. The main cause of incomplete penetration is a joint design that is not suitable for the welding process being used. For single groove welds, there are several conditions that can cause this discontinuity (Figure 29).

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Root opening too small

Included angle too small

Root face too large Figure 29. Incomplete Penetration

Even when the joint is correctly designed, incorrect welding procedures can cause incomplete penetration. If the current is too low, the weld metal is not able to reach the root of the joint and/or the arc is not hot enough to melt the base metal at the root. If the rate of travel is too fast, the weld metal is deposited only on the surfaces above the root. Electrode size is also an important factor, especially for the root bead. If the electrode is too large, it will not fit into the narrow root opening. Underfill “Underfill” means there is not enough weld metal in the weld joint to bring the face of the weld level with or above the surface of the base metal (Figure 30).

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Figure 30. Underfill

Incomplete Fusion “Incomplete fusion” means that the layers of weld metal or the weld metal and base metal did not fuse together completely (Figure 31). This failure can occur at any point in groove and fillet welds. Overlap at the toe of the weld is often a sign of inadequate fusion.

Figure 31. Incomplete Fusion

The usual causes of incomplete fusion are: •

•

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Not heating the base metal or the previously deposited weld metal to the melting point. This usually happens if the electrode is too small, the travel is too fast, or the current is too low. Electrode flux does not dissolve the oxides or other foreign material.

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Porosity “Porosity” means that there are gas pockets in the weld metal (Figure 32). Porosity can be spread evenly in the weld metal or be grouped in clusters.

NOTES

Figure 32. Porosity

Although too much porosity has a serious effect on the mechanical properties of the joint, some welding codes allow a specified maximum amount of porosity. When the porosity is concentrated at the root, it is often called “wormholes” or “piping.” This condition is regarded as a special case of incomplete penetration. The gases that cause porosity form during chemical reactions in the weld pool as the weld metal is heated and cooled. Porosity is usually the result of one of the following factors: • • • • • • • •

overheating or underheating the weld metal too much sulphur or moisture in the base metal or electrode welding current too high or too low incorrect electrode manipulation oil or other contaminants on the weld joint defective or unsuitable electrodes too long an arc length arc blow

Slag Inclusion “Slag” is the metallic oxides and other solid compounds that chemical reactions produce during the welding process. Sometimes slag can become trapped in the weld metal. Like gas, it creates porosity in the weld metal (Figure 33).

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Figure 33. Slag Inclusions

In SMAW, slag can form when flux is trapped in the weld pool. The stirring action of the arc can force the slag into the molten metal. Slag can also be pushed ahead of the arc and then be covered over by the weld pool. Because it’s less dense than molten metal, slag tends to rise to the surface of the pool, where it can be chipped away when the weld is cooled. Several factors can prevent the release of slag from the weld pool: • • • • •

high viscosity of the weld metal rapid cooling too low a welding amperage incorrect manipulation of the electrode undercut on previous passes

You can prevent slag inclusions by doing the following: • • •

prepare the weld joint correctly before depositing each weld bead make sure to maintain the correct weld bead contour for each layer so that the arc can access the weld joint completely make sure you clean all slag from the surface of the previous weld bead

You can also help to promote the release of slag by making sure that the weld pool becomes hot enough to reduce its viscosity (thickness) and by pre- and post-heating to slow down the cooling process. Cracking Cracks are the most dangerous weld defects. They happen when stresses are greater than the ultimate strength of the base metal. Cracking that occurs shortly after the weld metal has been deposited and is just beginning to solidify is called “hot cracking.” Hot cracking is more likely with certain metals, especially the high-alloy steels and high-temperature alloys. Cracking that occurs later, as the metal is approaching room temperature or after the weld has cooled completely, is called “cold cracking.” Cold cracking is much less common than hot cracking.

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External Cracks Cracking that’s visible or external usually occurs in the weld metal (Figure 34). External cracks might run across the face of the weld metal and sometimes extend into the base metal. These are called “transverse cracks.”

NOTES

“Longitudinal cracks” run lengthways along the weld, usually down the centre of the weld deposit. “Crater cracks” form in the centre of the crater and can become a starting point for longitudinal cracking. Crater cracks are usually the result of interruptions in the welding procedure.

Crater cracks

Longitudinal cracks

Transverse cracks

Figure 34. External Cracks

There are several causes of external cracks: • • • •

too much strain on the weld joint too rapid cooling (particularly on hardenable and brittle metals) too little deposit on weld passes incorrect choice of electrode

Less-common causes of external cracks are defects such as: • • • •

porosity lack of penetration slag inclusion incomplete fusion

You can avoid most cracking by doing the following: • • •

increase the thickness of the weld deposit on the first bead decrease the speed of travel to allow more weld metal to build up use correct pre- and post-heat treatments

Internal Cracks Internal cracks usually occur within the heat-affected zone of the base metal (Figure 35). Underbead cracking (a type of internal crack) occurs almost exclusively in steel. It is often related to the use of low-hydrogen electrodes. Hairline cracks at the toe of the weld are caused by hot cracking in or near the fusion zone of weld and base metal.

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Internal cracks happen mostly in metals that have been hardened and that are less ductile. They often occur with other weld faults such as undercutting, lack of fusion, incomplete penetration, and slag inclusions. You can prevent internal cracking by doing the following: • • •

use low-hydrogen electrodes follow correct pre- and post-heating procedures pay careful attention to correct fit-up and welding procedures

Toe cracks

Underbead cracks Figure 35. Internal Cracks

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SELF TEST 12

SELF TEST 12 1. Where is the best place to locate the ground clamp? a. at least 1 meter (3 feet) from the electrode b. as far as possible from the electrode c. on the same material to be welded d. as close as possible without touching the material to be welded 2. What joint uses the plug welds? a. lap joint b. tee joint c. but joint d. corner joint 3. What is the main method to strike an arc? a. scratch method b. tap method c. touch method d. drag method 4. What type of weld joint has one piece of metal laying over a second piece of metal? a. corner b. edge c. butt d. lap 5. What is the type of weld that has two metals overlapping each other and welded through a hole or slot? a. basic b. plug c. bottoming d. penetrating

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Weld Mild Steel Using Wire-feed Processes GMAW, GMAW-P, FCAW, and MCAW Gas metal arc welding (GMAW) was patented in the 1940s. Since then, GMAW and the related flux cored arc welding (FCAW) processes have become major processes used in the welding industry. Their single most important advantage over other welding processes is the continuous filler metal wire-feed mechanism.

Gas Metal Arc Welding (GMAW) GMAW is extremely versatile and is suitable for welding almost all commercial metal thickness (from light sheet to heavy plate) and structural shapes. The introduction of pulsed gas metal arc welding (GMAW-P), a variation of GMAW, has made the process even more versatile. GMAW can be used to join many metals: carbon steels, high-strength low-alloy steels, stainless steels, aluminum alloys, magnesium alloys, copper alloys, and nickel alloys. GMAW was originally developed for production welding. Small, low-cost power sources, wire-feeders, and guns have been developed for use in plants and for maintenance welding. GMAW is used in the auto body repair industry and is popular with hobbyists. Principles of Operation In the gas metal arc welding process, an electric arc is drawn between a filler metal electrode and the base metal (Figure 1). The heat from the arc melts the end of the electrode wire and an area of the base metal. A flow of shielding gas protects the arc and the molten weld pool from atmospheric contamination.

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NOTES Shielding gas nozzle

Shielding gas Solidified weld deposit

Contact tip

Weld pool

Welding arc

Base metal

Figure 1. GMAW Process

The main components of the basic GMAW system are: • • • • •

DC power source to supply the current required for melting the filler metal and base metal welding gun complete with hose and cables to direct the filler metal, electrical current, and shielding gas to the work feed mechanism complete with contactor and controls to deliver filler metal wire at the required speed shielding gas system, including hose and flowmeter, to protect the arc and molten metal from atmospheric contamination continuous bare electrode filler metal wire fed through the wire-feeder and electrode gun

GMAW normally uses direct current, electrode positive (DCEP). The wire-feed unit and the power source are normally coupled to provide automatic self-regulation of the arc length. In this setup, the power source is a constant voltage machine and the wire-feed unit is the constant speed type. Although all GMAW setups have the components shown in Figure 2, there are many variations. In some setups, for example, the power source and the wire-feeder are combined in a single unit. In smaller units, a spool of filler metal wire might be included in the welding gun. For high-production setups, however, the wirefeeder is often a separate unit from the power source.

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Welding power source

Flow meter Pressure regulator

+ – Electrode lead

Shielding gas cylinder

Welding gun

Wire-feed unit

Ground clamp

NOTES

Work lead

Spool of filler metal wire

Figure 2. Basic GMAW Set-up

Flux Cored Arc Welding (FCAW) FCAW is a GMAW process that uses a tubular electrode wire with powdered flux inside (Figure 3). This process is especially well-suited to welding low-carbon structural steels and low-alloy and stainless steels. It’s also widely used for hardfacing applications. Contact tip Nozzle

Molten slag

Flux-cored electrode

Solidified slag

Shielding gas envelope Weld metal

Arc

Molten metal Figure 3. FCAW Process

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The flux in the centre of the electrode contains elements similar to the coating on an SMAW electrode. These elements act as deoxidizers, slag formers, and arc stabilizers. In some cases, they can enhance the properties of the weld metal. Advantages and Disadvantages of FCAW The main advantages of FCAW (other than continuous feeding, which it shares with GMAW) are deeper penetration, higher deposition rates, and high deposition efficiency. The deeper penetration means that heavier stock can be welded in fewer passes. Deep penetration also reduces the need for edge preparation with FCAW. On larger thicknesses that require beveling, the bevel and included angles are reduced compared to those prepared for SMAW. Narrow openings mean that you need less filler weld metal to fill the joint, saving both filler metal and welding time. The main disadvantage of FCAW is its limited application. It can be used only on ferrous metals, including low- and medium-carbon steels, some low-alloy steels, and a limited number of stainless steels. This is because filler metals have not been developed for other materials. Another disadvantage is the initial cost of the equipment. The equipment and electrodes are more expensive than those for SMAW, but faster welding speeds mean that this expense can be recovered. When compared to GMAW, post-weld cleanup to remove the slag is an additional expense.

Metal Cored Arc Welding (MCAW) Like FCAW, metal cored arc welding (MCAW) is a continuous wire-feed process that uses a tubular filler metal wire. The difference is that the metal cored wire has no fluxing ingredients inside. Instead, the wire is filled with powdered metal. Usually, the powdered metal is iron powder with alloying elements. MCAW wires are designed to run best using argon-rich shielding gases. Advantages and Disadvantages of MCAW The main advantages of MCAW are: • • • • • • •

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low smoke and fume levels high deposition efficiency a broad range of alloy choices no slag minimal spatter good penetration good bead appearance

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As with FCAW filler metal, the manufacturer can easily customize MCAW filler metal by changing the ingredients of the core material.

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Because MCAW has no flux, the fume levels are lower than for FCAW. Having no flux and little spatter also contributes to a high deposition efficiency of 92–96%. By adding small percentages of other metals such as molybdenum, manganese, chromium, and so on to the metal powder inside the tubular wire, welding filler metals have been designed to achieve a wide range of metallurgical characteristics. The addition of deoxidizers such as silicon helps reduce the chance of porosity and improves weld pool fluidity. Spray transfer is recommended for MCAW, therefore weld spatter is minimal. There is more weld spatter when using short-circuit or globular transfer. One of the main advantages of MCAW is excellent penetration with a good depth-to-width ratio. Lack of fusion or cold lap is rare. Compared to MCAW, GMAW is a better choice for welding thinner material such as gauge metal and thin wall structural shapes and FCAW is a better choice if the base metal is very rusty or dirty.

Safety Requirements for Semi-automatic Welding Processes Electric Shock As with all arc welding processes, you must take great care to protect yourself from receiving an electric shock. The electric currents used in GMAW are very high. If you become part of the electric circuit at any point, you could receive an electric shock severe enough to kill you. Even a small shock that’s not immediately fatal could be sufficient to cause you to jerk or fall, leading to a serious injury. Protect yourself from dangerous electrical shock by following these rules: •

• •

The electrode and work (or ground) circuits are electrically “hot” when the power source is on. Never permit contact between “hot” parts of the circuits and bare skin or wet clothing. Wear dry, hole-free gloves to insulate your hands. Always insulate yourself from the welding circuit by using some form of dry electrical insulation. Welding in damp locations, on metal floors, gratings, and scaffolds, or in positions such as sitting or laying down increase the possibility of electrical shock. Make certain that the electrical insulation you’re using is large enough to cover your full area of physical contact with the work piece and the work area.

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•

•

•

•

Always be sure the work lead ground clamp makes a good electrical connection with the work piece. The connection should also be positioned as close as possible to the welding arc as practical. As a precaution, it’s a good idea to ground your work piece, or the structure you are welding on, with a secondary ground to earth. This earth ground is meant to be a safety precaution similar to a lightning rod and is not meant to be a part of the welding circuit. Maintain the filler metal wire-feed system, ground clamp, welding lead cables, and welding power source in good, safe operating condition. When working above floor level, use personal fall protection equipment to protect yourself in the event that you get a shock and fall.

Safe Handling of Shielding Gas Cylinders and Pressure Regulators Always handle compressed gas cylinders carefully. When you’re using them, make sure they’re properly secured. Knocks, falls, or rough handling can damage the cylinders, valves, or safety devices and cause leakage or an accident. Cylinder valve protective caps should be hand tightened and kept in place until the cylinder is secured and put into service. Follow these rules when setting up and using cylinders of shielding gas: • •

•

Properly secure the cylinder. Before you connect a cylinder pressure regulator to the cylinder valve, crack open and immediately close the valve to clear it of dust or dirt that otherwise might enter the regulator. When opening a cylinder valve, you should stand to one side of the valve, never in front of it. Release the working pressure adjusting screw on the cylinder pressure regulator by turning it counter-clockwise. The flowmeter adjusting valve should be set to closed. Then open the cylinder valve slowly to prevent a rapid surge of high-pressure gas into the cylinder pressure regulator. Again, stand to one side of the valve as you open it. Always shut off the source of the shielding gas supply to the pressure regulator if it will be left unattended.

Toxic Gases The main toxic gases associated with GMAW are ozone, nitrogen dioxide, and carbon monoxide. Dangerous gas could also be present as a result of thermal or ultraviolet decomposition of cleaning agents located in the vicinity of welding operations.

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Degreasing or other cleaning operations should be done in a place where vapours from these operations cannot reach radiation from the welding arc.

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Ozone The ultraviolet light emitted by the GMAW arc acts on the oxygen in the surrounding atmosphere to produce ozone. The amount of ozone produced depends on the intensity and wavelength of the ultraviolet energy, the humidity, and the amount of screening provided by any welding fumes. The ozone concentration will increase as the welding current increases, with the use of argon as the shielding gas and when welding highly reflective metals such as stainless steel and aluminum. If the ozone cannot be reduced to a safe level by ventilation or changing the process, supply fresh air to the Welder with an airsupplied respirator or by other means. Nitrogen Dioxide Some test results show that high concentrations of nitrogen dioxide are found only within 150 mm (6 in.) of the welding arc. With normal natural ventilation, these concentrations are quickly reduced to safe levels in your breathing zone, as long as your head stays out of the plume of fumes (and thus out of the plume of welding-generated gases). Carbon Monoxide The heat of the welding arc in the GMAW process breaks down the carbon dioxide shielding to form carbon monoxide. The welding process creates only a small amount of carbon monoxide, but the plume of fumes temporarily contains relatively high concentrations of fumes. However, the hot carbon monoxide oxidizes to carbon dioxide so that the concentrations of carbon monoxide become insignificant at distances of more than 75–100 mm (3–4 in.) from the welding plume. Under normal welding conditions there should be no hazard from carbon monoxide. But you will need adequate ventilation to deflect the plume or to remove the fumes and gases if you’re working in a confined space or if you must work with your head over the welding arc where natural ventilation moves the plume of fumes toward your breathing zone. Toxic Metal Fumes The welding fumes generated by GMAW and FCAW can be controlled by general ventilation, by local exhaust ventilation, or by respiratory protective equipment.

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The method of ventilation required to keep the level of toxic substances within your breathing zone at acceptable concentrations depends directly on a number of factors. Among these are the material being welded, the size of the work area, and the degree of confinement or obstruction to normal air movement where the welding is being done. Each operation should be evaluated separately in order to determine what type of ventilation is required. Good ventilation is especially important when you’re using self-shielded wires in the FCAW process. These filler metals distill fumes high in metal particles and fluoride oxides. You should take extra precautions (such as CSA-approved respiratory protective equipment) to avoid inhaling them. Shielding Gases Shielding gases used in GMAW and FCAW can displace oxygen and cause lung damage or death from suffocation. Always ensure that there is sufficient ventilation. Take special care and attention in confined spaces.

Protection Against Radiation The total radiation (radiant energy) produced by the GMAW process can be higher than that produced by the SMAW process. This is due to the significantly lower amounts of welding fumes and the more exposed welding arc. Generally, the highest ultraviolet radiant energy intensities are produced when using an argon shielding gas and when welding on aluminum. Refer to WorkSafeBC’s website, www.worksafebc.com, and click on OHS Regulation under the “Quick Links.” The minimum suggested filter lens shades for GMAW and FCAW range from 10–12, depending on the welding current level. Non-reflective, fire-retardant clothing is recommended for GMAW. Reflection of ultraviolet radiation can cause ultraviolet burns to the face and neck underneath the helmet. The greater intensity of the ultraviolet radiation will cause rapid disintegration of untreated cotton clothing. CSA-approved safety eyewear must always be worn. Protect other people in the work area from ultraviolet radiation with suitable non-flammable, non-reflective welding screens.

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Equipment for Semi-automatic and Automatic Filler Metal Wire-feed Systems

NOTES

The GMAW system requires light, flexible, and durable equipment that can feed a small-diameter filler metal wire electrode at a constant rate. The feeder should also keep the filler metal wire clean and snag-free and provide controls for starting, stopping, and adjusting wire-feed speed. Constant voltage welding power sources need a constant speed wire-feed, so the wire-feed speed must be adjustable for different welding currents. There are many kinds of wire-feed units, but they generally all consist of a spool or coil of filler metal electrode wire, a set of drive feed rolls for the wire and an adjustable, constant speed motor to turn the drive rolls. There are three types of wire-feeders for handling different types of electrode wire: the push-type, the pull-type and the push-pull type (Figure 4). The difference between them is in the way the drive rolls feed the electrode wire to the welding gun. The push-type pushes the wire, the pull-type pulls the wire, and the push-pull combines both a pushing and pulling mechanism.

Push 4.5 m (15')

Pull 4.5 m (15')

Pull

Push 9 m (30')

Figure 4. Feed Mechanics

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Push-type Wire-feed The most common wire-feed system is the push-type. It consists of a support assembly that holds the spool of filler metal wire, an adjustable constant speed motor and drive roll assembly to pull the filler metal wire from the spool and push it through the cable assembly to the welding gun, and a wire-feed speed control unit. The wire-feed assembly is usually a one-piece unit. The filler metal wire spool support, wire-feed drive motor, and drive rolls are attached to an all-welded frame that is mounted on the welding power source (Figure 5).

Figure 5. Push-type Wire-feed Unit

In some cases, the filler metal wire-feeder is mounted on an overhead crane to allow you to easily access a larger work area. The wire-feeder and controls can also be combined with the welding power source in a single unit. In another variation, used mainly for maintenance and field welding, the wire-feeder is small and portable and can be located a great distance from the welding power source. The drive rolls clamp the filler metal wire securely to provide the necessary friction to push the wire through the conduit to the welding gun. The upper drive rolls, or pressure rolls, are adjustable up and down by means of a springloaded thumbscrew. This screw controls the pressure of the drive rolls on the wire, which is extremely important. You should apply only enough pressure to drive the wire without slippage. Too much pressure will flatten solid wire or crush flux-cored wire. Damaged wire will not feed through the conduit and welding gun properly.

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The upper and lower drive rolls must also be correctly aligned with each other for the wire to feed smoothly (Figure 6). To adjust the alignment, the lower drive rolls can be moved in or out. This feature also makes it easier for you to align the wire in the groove of the feed roll.

NOTES

Pressure adjustment

Knurled portion

Pressure roll

Drive roll

In-out adjustment

Wheels adjusted rolls in alignment with sufficient pressure

Rolls misaligned adjust drive roll

Insufficient pressure on wire adjust pressure

Figure 6. Feed Roller Alignment

The alignment between the filer metal wire guides and the drive rolls is also important. Although the wire guides are properly aligned when the unit is manufactured, over time they might need readjustment. The wire guides are mounted on the drive housing, which might move up or down, causing the guides to become misaligned (Figure 7). To realign, you need to loosen the drive housing mounting bolts and adjust the housing until the rolls and guides come into alignment. The inner end of each wire guide should be as close as possible to the drive rolls, without touching them.

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Drive roll Wire guide

Housing bolts

Drive housing

Drive rolls and wire guides properly aligned

Wire bent down housing and wire guides too high, lower drive housing

Wire bent up housing and wire guides too low, raise drive housing

Figure 7. Correct and Incorrect Alignment of Wire Guides

Filler metal wire-feed systems are available with two or four drive rolls (Figure 8). The four-roll system offers more uniform feed roll pressure, more precise control of the wire-feed speed, and more positive non-slip wirefeeding.

Figure 8. Drive Roller Assembly

To be effective in a push-type wire-feeder, the filler metal electrode wire must be strong enough to be pushed through the conduit without kinking. Low-carbon steel and stainless steel (the “hard” wires) can be readily pushed distances up to 6 m (20 ft.). The “soft” wires (such as aluminum) and very fine diameter steel wires are much more difficult to push and kinking or buckling become problems as the distance approaches 3 m (10 ft.). These problems with soft wires have been solved with pull-type feeders with the feed rolls in the welding gun and pushpull systems with feed motors in both the wire-feeder unit and the welding gun.

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Pull-type Wire-feed In pull-type wire-feed systems, a smaller but higher speed motor is located in the welding gun to pull the filler metal wire through the conduit. This system makes it possible to increase the distance between the filler metal wire spool and the welding gun for soft wires such as aluminum.

NOTES

There are disadvantages to the pull-type wire-feed system, however. The welding gun is heavier and more difficult to use and rethreading the filler metal wire is more time consuming. Because the motor is smaller with higher speeds, its operating life tends to be shorter.

Push-pull Wire-feed The push-pull wire-feed system uses synchronized feed motors and drive roll assemblies located at both ends of the filler metal electrode wire conduit. A wirefeed motor and drive roll assembly located in the welding gun pulls the wire through the feed conduit, while a drive motor and drive roll assembly located in the control unit pushes the wire through the conduit to the welding gun. This system extends the possible distance between the wire-feeder unit and welding gun to about 9 m (30 ft.). Compared to the pull-type system, the push-pull type system has many advantages. Distances are extended, feeding is much faster, and the reduced load on the motor in the welding gun means its operating life is longer. The main disadvantages of this system are its complexity and cost. Some welding guns have both the filler metal wire-feeder and wire spool housed in the welding gun (Figure 9). These spool-type, welding guns (commonly called “spool guns”) are used mostly for welding aluminum.

Figure 9. Spool-type Welding Gun

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Filler Metal Wire-feed Drive Rolls There are several designs of wire-feed drive rolls. Your choice of which to use depends on the type and diameter of the filler metal wire (Figure 10). You should follow the directions of the filler metal wire manufacturer.

Filler metal wire diameter mm

Filler metal wire types

in.

Hard Wire

Hard Wire

Hard and Tubular Wire

Soft Wire

Hard and Tubular Wire

Tubular Wire

0.024

YES

YES

—

YES

—

—

0.75

0.030

YES

YES

—

YES

—

—

0.9

0.035

YES

YES

—

YES

—

—

1.1

0.045

YES

YES

—

—

—

—

—

—

—

YES

—

—

YES

YES

—

YES

—

YES

1.2

3⁄64

1.3

(0.047)

0.052

1.6

1⁄16

(0.063)

—

—

YES

YES

YES

YES

2.0

5⁄64

(0.078)

—

—

YES

YES

YES

YES

2.4

3⁄32

(0.094)

—

—

YES

YES

YES

YES

2.8

7⁄64

(0.109)

—

—

YES

YES

YES

YES

3.2

1⁄ 8

(0.125)

—

—

YES

YES

YES

YES

4.0

5⁄32

(0.156)

—

—

—

—

YES

YES

4.8

3⁄16

(0.188)

—

—

—

—

YES

YES

5.6

7⁄32

(0.129)

—

—

—

—

YES

YES

6.4

1⁄ 4

(0.250)

—

—

—

—

YES

YES

Smooth V

Smooth V

Smooth V

Smooth V

Knurled

Knurled

Flat smooth Flat knurled Smooth V

Smooth V

Smooth V

Knurled

Wire feed drive roll selection

Figure 10. Typical Wire-feed Drive Roller Surfaces

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Wire-feed Drive Speed Controls Depending on the design, the wire-feed drive speed control can be located on the feeder unit or on the welding gun. On many push-type systems, the controls and wire-feed motor are combined in one integrated unit. This unit provides controls for the wire-feed drive speed, shielding gas, water flow (on water-cooled systems), and welding power (contactor switch). All of these functions (along with starting the wire-feed) are started and stopped by squeezing and releasing the gun trigger.

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Solenoids (which control gas and water flow) are regulated to coincide with the weld start and stop. Most wire-feed units have a wire-feed inch control and a shielding gas purge control. These controls may be a switch type or a button type. The inch control causes the wire-feed drive motor to feed the wire through the electrode conduit to the welding gun. When you are setting-up, use the inch switch to feed the filler metal wire through to the contact tip and the shielding gas purge control to set the flow rate of shielding gas. When using these controls, the filler metal wire is not energized with welding current as it would be if the welding gun trigger was used to perform these operations. Some filler metal wire-feeders have a feed or retract control that is used to reverse the direction of the wire-feed. They might also have a shielding gas purge control to clear the system of contaminating air or moisture before you begin welding. On some, there are controls for automatic pre-flow and post-flow of shielding gas.

Constant Speed and Variable Speed Metal Wire-feeders Constant-speed wire-feeders are used with constant voltage power sources. For heavy industrial work, these wire-feeders are usually independent of the welding power source. For lighter commercial work, the wire-feeders are often built right into the welding power source. The arc voltage remains steady where set and the wire-feed speed determines the welding amperage. Variable-speed wire-feeders are used with constant current welding power sources (Figure 11). These units are independent of the welding power source. Amperage is set at the power source and remains steady, and the arc voltage determines the wire-feed speed. A voltage-sensing clamp is attached to the work piece, and the arc voltage is relayed back to the wire-feed drive motor, which speeds up or slows down to maintain the arc length required.

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NOTES

Figure 11. Variable Speed Wire-feed

Welding Gun Assemblies for Semi-automatic Processes The welding gun directs the filler metal wire and shielding gas into the weld zone and conducts electrical power to the filler metal wire electrode. Different types of welding guns have been designed to provide maximum efficiency for all types of applications. Welding gun types range from heavy-duty guns for highcurrent, high-production work to lightweight guns for low-current or out-ofposition welding. Welding guns can be further categorized as curved head (gooseneck) or pistol grip and as air-cooled or water-cooled. For FCAW, the guns are also classified as self-shielded or gas-shielded, depending on the type of flux-cored wire. Air-cooled welding guns are usually selected for low-current welding and for higher welding currents if a carbon dioxide shielding gas is used, since CO2 promotes cooling. Higher welding currents used with shielding gases other than CO2 often require welding guns that are water-cooled to avoid overheating. The curved head design is the most popular for welding steels (Figure 12). However, softer aluminum filler metal wire can often jam in a curved head so a straight head is preferred when welding aluminum (Figure 13).

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Figure 12. Curved Head Welding Gun

The basic components of the typical GMAW or FCAW gun include the following: • • • • • • • •

contact tip shielding gas nozzle (cup) shielding gas nozzle insulator (fibre spacer) filler metal electrode wire conduit (liner) shielding gas hose welding electrode cable assembly (one-piece composite cable) welding gun trigger shielding gas diffuser One piece composite cable Wire conduit (liner)

Fibre spacer Gas diffuser Contact tip Trigger

Shielding gas cup

Figure 13. Typical GMAW Welding Gun

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Contact Tip The contact tip is usually made of copper or copper alloy. It conducts welding current to the filler metal wire and directs the wire toward the work. The contact tip is connected electrically to the welding power source by the electrode lead cable. The inner diameter of the contact tip is very important, because the filler metal wire must feed easily through the tip but also make good electrical contact. The instructions supplied with every welding gun will list the correct contact tip for each filler metal wire size and material. The contact tip must be centered in the shielding gas nozzle (Figure 14). The contact tip is attached by an eccentric shaped slide contact or by a screw-type connection, depending on the design of the welding gun.

Electric cable

Gun tube

Insulator

Cable to contact tube adapter and gas diffuser Electrode contact tip

Gas nozzle

Electrode

Figure 14. Contact Tip Gas Nozzle Assembly

Contact tips become clogged or dirty easily. It’s important that you check them frequently and replace them once this occurs.

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Shielding Gas Nozzle The shielding gas nozzle directs an even-flowing column of shielding gas into the welding zone. An even flow is extremely important in providing adequate protection of the molten weld pool from atmospheric contamination. Different size shielding gas nozzles are available and should be selected according to the application. Use larger nozzles for high welding current work where the weld pool is large. Use smaller shielding gas nozzles for low welding current and short-circuit metal transfer welding. The most common shielding gas nozzle material is copper. An electrical insulation or insulator on the inside provides electrical insulation from the electrically hot contact tip.

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The filler metal wire exits through the contact tip, which is centred in the welding gun’s shielding gas nozzle (Figure 15).

Figure 15. Contact Tip and Shielding Nozzle Assembly

The inside and outside of the shielding gas nozzle can easily become spattered during welding. Spatter inside the nozzle disrupts the flow of shielding gas, resulting in contamination of the weld. You can prevent spatter buildup with a special anti-stick (anti-spatter) compound. This compound is available as a “dipin” paste or as an aerosol spray. If spatter does build up, it needs to be removed. Cleaning should be done with specially designed GMAW pliers or a nozzle cleaning reamer. The manufacturer rates all welding guns. The rating includes maximum welding amperage at 100% duty cycle and the filler metal wire diameters that can be fed through the gun. Some welding guns can be used for only one filler metal wire diameter. Others are more versatile and can be used with a variety of filler metal wire diameters. The liners must to be changed when you change the diameter of the filler metal wire.

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Welding Electrode Cable Assembly The electrode cable assembly leading to the welding gun can be made of several hoses and a welding lead cable, but more often, a single molded cable assembly encloses all the components. The major components of the assembly are the welding lead power cable, the filler wire conduit (liner), the shielding gas hose, and the coolant water hose (if required). Most cable assemblies are attached to the welding gun as a unit (Figure 16). The welding lead cable assembly conduit (liner) is the greatest source of resistance to the filler metal wire-feed drive system. Although a long conduit gives you more mobility and access for a larger work area, the resistance to feeding the filler metal wire rises sharply as the length increases.

Figure 16. Gun and Cable Assembly

Resistance against the filler metal wire results from the compressive force on the wire (which is greatest at the drive-unit end) and from friction (which rises proportionally with the length of the liner). Too much resistance can cause chattering and slippage at the wire-feed drive rolls or buckling of the wire. Friction and compression work as resistance to smooth wire-feeding (Figure 17).

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Conduit (liner)

NOTES

Point of resistance

Point of resistance Filler metal wire Figure 17. Resistance to Feeding Roller Wire

Accurate alignment of the filler metal wire-feed system components near the wire-feed drive rolls is essential to smooth wire-feeding. Misaligned parts or loose liners can cause high stresses in the filler metal wire and abrade the wire, especially near the wire-feed drive rolls. The liner must also provide continuous support for the filler metal wire from the wire-feed drive rolls through to the contact tip in the welding gun, as any unsupported length (particularly near the drive rolls) can lead to buckling. The larger diameter filler metal wires in particular require the liner to be fairly stiff. Because of their strength and rigidity, these wires will not feed properly if there are sharp bends or curves in the welding electrode cable assembly. To provide insulation from the hot weldment, the welding electrode cable assembly is covered with a high-quality rubber such as neoprene. Neoprene is used rather than plastic because it has both electrical insulation properties and superior heat resistance. Neoprene withstands being pulled over hot welded or flame-cut materials and also has good resistance to the solvents used to clean the liner. Most welding electrode cable assemblies have quick disconnect couplers (Figure 18) so that you can quickly and easily hook up the cable assembly to connections on the wire-feeder and welding gun.

Figure 18. Welding Electrode Cable Quick Disconnect Coupler

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Welding Electrode Cable Assembly Size Several types and lengths of welding electrode cable assemblies are available. Selection depends mainly on the welding current setting required.

Filler Metal Wire Conduits (Liners) The type of filler metal wire liner you use will depend on the type and diameter of the filler metal wire. Hardened steel liners are best suited for steel wires. The difference in hardness between the low-carbon steel filler metal wire being fed and the hardened steel liner provides the smoothest wire feed with the lowest friction. Plastic and nylon liners are best suited for the soft wires (such as aluminum), as the hardened steel liners will scratch these softer wires. In addition to choosing the correct type of liner for the type of filler metal wire, you must also choose a liner diameter that is suitable for the filler metal wire diameter. The manufacturer will specify the correct liner size in the operator’s guide supplied with the welding gun and cable assembly.

Weld Types and Positions Refer to Learning Task 12 for details on weld types and positions.

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SELF TEST 13

SELF TEST 13 1. What is the main advantage of the GMAW and FCAW processes? a. wide range of filler metals available b. low initial and operating costs c. minimal training required for operators d. high deposition rates (LT13, GMAW, GMAW-P, FCAW, and MCAW) 2. What set-up does the GMAW process normally use? a. DCEP b. DCEN c. DC/AC d. AC 3. What protects the arc from atmospheric contamination when GMAW? a. flux coating b. shielding gas c. oxygen d. carbon dioxide

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Describe Air Arc Gouging Air Carbon Arc Cutting The air carbon arc process is one of several arc-cutting processes. It’s abbreviated as “CAC-A.” In the past, it was abbreviated as “AAC.” The CAC-A process is widely used because it can cut and gouge all types of ferrous and non-ferrous metals more quickly than flame cutting. CAC-A is considered to be a cutting process, but it does much more. CAC-A can do a partial cut, gouge, or wash off a surface. This can prepare joints for welding, remove unwanted metal, remove weld faults, or remove bolts, pins, and other fasteners.

Principles of CAC-A Air carbon arc cutting works by melting the base metal with an electric arc (Figure 1). This arc is produced by a welding power source passing current through a carbon electrode held in a special holder. Jets of compressed air from holes in the lower jaw of the electrode holder blow the molten metal away to form a kerf or groove.

Carbon electrode

Electrode holder

Air jets

Figure 1. CAC-A Gouging

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CAC-A can be used on any kind of metal because it uses the intense heat of the arc to melt the metal. CAC-A does not cut the base metal by oxidizing it, as the oxy-fuel gas processes do. Unlike the oxy-fuel gas cutting processes, CAC-A can be used on any material that conducts electricity.

Components of the CAC-A The basic CAC-A system consists of a welding power source, an electrode holder, a carbon electrode, and a compressed air supply system (Figure 2). The power source can be any high-capacity welding power source that provides enough current. Air compressor

Electrode holder

Welding power source

Air line

Carbon electrode

–

+

Workpiece Ground clamp

Electrode lead Workpiece lead

Figure 2. Typical CAC-A System

To strike the arc, simply touch the carbon electrode to the work piece in the same as you would for SMAW. The circuit is now closed (or complete) and the welding current flows through the circuit. As the current crosses the arc, it creates tremendous heat. A small area of base metal just below the electrode melts. The CAC-A electrode holder has small holes or orifices that direct compressed air at the cut to blow the molten metal out of the gouge or cut area. The electrode holder is commonly called a “gouging torch” (Figure 3).

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NOTES Carbon electrode

Air control valve

Air jet holes (orifices)

Figure 3. Typical CAC-A Gouging Torch

Any standard welding power source, either AC or DC, can be used for CAC-A. It must be able to produce enough current for the size of the electrode.

Safe Work Practices for CAC-A CAC-A has additional safety hazards in addition to those for any arc welding process. Ventilation CAC-A is used to cut metals that are not usually cut with oxy-fuel gas. Many of these metals contain elements that produce toxic fumes when heated. Stainless steel, for example, contains chromium, which produces dangerous fumes when heated. Other metals, such as high-alloy steel and copper alloys, are also dangerous when heated. You must wear a respirator when cutting any metals that contain chromium, zinc, copper, or nickel. Never use CAC-A to cut beryllium, cadmium, or lead. These metals produce extremely toxic fumes. Heat from CAC-A can cause paint finishes and industrial coatings to produce toxic fumes. Grind or scrape the surrounding gouge area before gouging. Use active ventilation and a respirator. Noise Noise levels from the compressed air used with CAC-A are very high. Wear ear protection (earplugs and/or earmuffs) when cutting with CAC-A. Ear protection will also prevent a stray spark from entering your ear canal and possibly perforating your eardrum. In extreme cases, infection from this kind of injury can cause complete hearing loss.

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Radiation As with other arc processes, the high current and open arc used in CAC-A produce large amounts of radiation. When using this process, you will need a standard welding helmet that has a darker lens than you would use for SMAW with a comparable diameter electrode. A #12 filter lens shade is recommended for most jobs. Use a #14 filter lens shade for larger cutting jobs that require higher currents. You should also make sure that you properly cover all your skin surfaces. The best choice is leather or clothing treated with fire retardant. Fire The blast of compressed air can throw molten metal and sparks up to 6 m (20 ft.) from a work piece. The potential for fire is high. All combustible material must be removed from the area of the metal spray. You can control the spray of molten metal by placing a sheet-metal shield around the work piece. Make sure the spray points away from other workers and flammable materials. Always make sure you cut away from yourself. Follow standard safe practices when near flammable material: • •

Have a fire extinguisher or charged water hose nearby. Maintain a fire watch during the operation and after it is completed.

Applications of CAC-A Air carbon arc cutting (CAC-A) is widely used for the following reasons: • •

•

• • • •

242

CAC-A can remove metal much more quickly than oxy-fuel gas cutting or mechanical methods such as grinding or chipping. CAC-A equipment is relatively inexpensive because a standard welding power source can be used, and most shops have a compressed air supply. Proper cutting and gouging techniques can be learned in a short time. If they are done correctly, further edge preparation is not required. CAC-A is a very versatile process that can be used to cut metals that cannot be cut with the oxy-fuel gas cutting process. CAC-A can be used in situations where gas cylinders are not available or they are considered a safety hazard. Low heat input means fewer problems with distortion or surface hardening. CAC-A can be done manually or with an automated cutting machine.

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Manual Cutting For most CAC-A jobs, you’ll use a manual torch. The equipment is versatile and portable, and the process can be done in the shop or on the job site.

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Machine Cutting Machine cutting is more accurate than manual cutting. The cuts are straighter and cleaner than those produced manually. This is important when preparing a weld groove. CAC-A cutting machines have a motorized carriage mounted on a track. They are similar to the machines used for OFC. These machines are portable and can be mounted in a vertical, horizontal, or overhead position. On a semi-automatic machine, the electrode must be manually fed into the holder to produce the desired cut. The carriage moves along the track at a preset speed. The amperage and air volume are also preset. These semi-automatic machines are simple to operate and produce clean cuts. Fully automatic machines feed the carbon electrode automatically. They’re used when you want even greater accuracy. One type of automatic machine uses a spring-loaded device that maintains a constant distance between the electrode and the work piece. This provides a uniform groove depth. More sophisticated machines use a voltage-controlled electrode feed. This maintains a constant arc length and produces grooves with a depth tolerance of ± 0.6 mm (± 0.025 in.). Uses of CAC-A CAC-A can be used to cut metals that cannot be cut well with oxy-fuel gas. These metals include stainless steel, aluminum, cast iron, nickel, and copper alloys. For example, CAC-A is used in refineries and pulp mills where stainless steel pipe or other high-alloy steel pipe must be cut. Except for certain metals, CAC-A is seldom used for cutting through metals because there are other processes that can make these cuts more smoothly and accurately. The CAC-A process is used much more widely for gouging and for metal removal. When properly done, CAC-A gouged grooves are very clean, smooth, and suitable for welding with no further preparation (Figure 4). The groove itself is free of slag. Any minimal slag on the edge can be easily removed with a chipping hammer.

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NOTES

Figure 4. U-groove Prepared with CAC-A

Making high-quality cuts and gouges with a manual CAC-A gouging torch is difficult because it is hard to hold the torch perfectly steady. Automatic and semi-automatic motor-driven equipment produces better quality cuts and gouges. The CAC-A melting process does not produce sharp edges like oxy-fuel gas cutting does. When used correctly, CAC-A has very little adverse effect on the base metal. Since the CAC-A torch moves so rapidly over the work piece, little heat is built up and there is little distortion. CAC-A does produce changes in some base metals in much the same manner as the arc welding processes. In high-carbon steels and cast irons, CAC-A can produce a thin hardened zone. This hardened layer is only about 0.15 mm (0.006 in.) deep. Welding will re-melt this layer and reduce the hardness. Also, if you preheat high-carbon steels and cast iron, you can avoid much of the hardening effect. If the metal is to be machined after cutting or gouging, you need to remove any hardened areas. This is usually done with grinding. Weld Joint Preparation One of the most common uses of CAC-A is to prepare the edges of plates for welding. CAC-A can be used to bevel the edges of plates to make bevel and vee groove joints, but it is more commonly used to gouge U-groove joints. The plate is set up for a square butt joint, and a U-groove is cut into the joint in preparation for welding. The joint can be welded without further preparation.

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CAC-A is also used for back-gouging. This is often required on vee and U-groove joints in thick material. In this procedure, one side is prepared and welded. The base metal is turned over and a groove is gouged to the root of the first weld. This back-gouging is done to make sure that the weld penetrates completely. Notes on drawings will often say “back-gouge to sound metal.”

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NOTES

Weld Defects CAC-A is useful for removing defects in welds. A faulty weld can be gouged to sound metal and the joint can then be re-welded. Disassembly and Repair CAC-A is also commonly used in scrap yards to cut apart steel structures for demolition. Damaged or worn parts can be removed as the first step in a repair job. Railway maintenance workers use CAC-A to gouge cracks in railway tracks or rail cars before they are welded. Other applications include removing worn hardfacing material on equipment and removing the backing strips on completed welds. Because CAC-A is effective in cutting cast iron, it’s also used in foundries to remove cracks and defects, or excess metal from castings.

CAC-A Equipment CAC-A Power Sources Any standard welding power source, whether AC or DC, has the potential to be used as a power source for CAC-A. However, because CAC-A uses such high currents compared to SMAW, not all welding power sources are appropriate. Power Rating The welding power source must be able to satisfy the high current demands of CAC-A. The minimum recommended open circuit voltage (OCV) is 60 V. The arc voltage required is 28 V or higher. The actual welding current (amperage) and voltages depend on the electrode size and the type of cutting job. For most CAC-A applications, the welding power source should have a high current capacity at a 100% duty cycle rating. If your welding power source does not have a 100% duty cycle rating, check the manufacturer’s duty cycle specification chart to find out the amperage at which the power source can be operated at a 100% duty cycle.

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Because carbon arc cutting and gouging use such high current, the welding power source should have overload protection in the output circuit. If you are not sure whether a particular welding power source is suitable for CAC-A, check the manufacturer’s specifications to see the rated duty cycles and if the machine is recommended for CAC-A. Very few single-phase welding power sources produce enough current at a 100% duty cycle rating to be used for CAC-A. You are likely to permanently damage these units if you use them for gouging. For the best results when doing CAC-A, you should use an industrial welding power source with the highest possible current capacity rated at a 100% duty cycle. The preferred choice is a large, three-phase transformer rectifier unit that has massive transformer windings and can take the extreme and violent surges in current. Similarly, if you use an engine-driven welding power source, it should have plenty of current capacity rated at a 100% duty cycle. DC Versus AC Power Sources Both AC and DC welding power sources can be used for CAC-A. However, a DC welding power source is preferred for most CAC-A work because it produces a more stable arc and is more versatile. As for welding current efficiency, DC produces more current than AC for the same arc voltage (AC is only about 70% as efficient as DC). For most CAC-A applications on carbon, low-alloy, and stainless steels, the polarity of the welding power source should be set to direct current electrode positive (DCEP). For CAC-A on all cast irons, it’s recommended that AC or DCEN be used in combination with AC carbon electrodes. AC carbon electrodes are preferred as they have ingredients in them that let them work with AC. The end result of using AC carbon electrodes is a cleaner cut and less transfer of the carbon electrode to the base metal. Carbon transfer can be a nuisance during CAC-A on cast iron. However, in practice, most CAC-A on cast iron is done with DCEP using DC carbon electrodes and the carbon deposits are cleaned out as they build up. On copper and nickel alloys, AC or DCEN should be used in combination with AC carbon electrodes. As an alternative, DCEP using DC carbon electrodes can be used on copper alloys. Remember: For CAC-A on cast iron, copper alloys, or nickel alloys, AC produces cleaner cuts than DC. Also, when you are using AC current, you must use ACrated carbon electrodes.

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LEARNING TASK 14

The Electrode Holder The hand-held CAC-A electrode holder, commonly called a “torch,” is very similar to a heavy-duty SMAW electrode holder (Figure 5). The major difference is the air jet orifices in the lower jaw of the holder that direct the compressed air jets at the molten base metal.

NOTES

Clamp lever handle Air control valve Carbon electrode

Air jet holes (orifaces)

Griphead

Figure 5. Manual CAC-A Torch

The air control valve on-off button usually has a lock-open feature so you can keep the air flowing and still keep your hand in a comfortable position. The jaws are spring-loaded and hold the carbon electrode in place. A clamp lever handle opens the jaws. The electrode holder has a small, circular griphead with a vee groove that firmly grasps and locates the carbon electrode in relation to the air jet orifices. The griphead has two or three air jet orifices to direct the compressed air jet. This griphead rotates 360 degrees so that you can adjust it to different positions and directions, such as left to right or right to left (Figure 6).

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A-14 CUTTING/WELDING

NOTES

Figure 6. Swivel Griphead

CAC-A Air Supply It’s very important that the jets of compressed air have enough pressure to blow away the base metal as it melts. If the air pressure is too low, you’ll get a poor-quality cut. Although the cut edge or groove might look acceptable, it will contain too much carbon and slag. The carbon will appear as a black deposit in the bottom of the groove or cut. This carbon buildup is a particular problem on joints that are being prepared for welding. The carbon will combine with the weld deposit and create a brittle and crack-prone weld. The normal range for compressed air pressure in the CAC-A process is 550–690 kPa (80–100 psi). Light-duty torches designed for smaller diameter electrodes have smaller air jet orifices that require less air pressure, usually around 275 kPa (40 psi) (Figure 7).

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LEARNING TASK 14

Compressed air for CAC-A is normally supplied by an air compressor and is delivered through air hoses. Standard air hoses are used, but these must be large enough to deliver the required volume. A hose with a 13 mm (1⁄2 in.) inside diameter is suitable for most applications. If you use an extra-long run of hose, it will need to have a larger inside diameter, 16–19 mm (5⁄8– 3⁄4 in.), in order to deliver enough air.

NOTES

Sometimes compressed air cylinders are used, especially for smaller jobs or when portability is necessary. If compressed air is not available, an inert gas such as nitrogen can be substituted, but good ventilation must be available. Never use oxygen instead of compressed air. Oxygen will react violently in the CAC-A process and cause an explosion. Even when there is enough volume and pressure from the air source, the airflow can be restricted by clogged air passages or fittings. Check your equipment often and clean out any bits of metal slag or debris. Sometimes a flow problem can be as simple as a pinched hose. Service application

kPa

psi

L/min

cfm

Light

280

40

227

8

Medium industrial

550

80

708

25

Heavy industrial

550

80

934

33

Automated process

414

60

1303

46

Figure 7. Recommend Pressures and Volume Flows

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SELF TEST 14

A-14 CUTTING/WELDING

SELF TEST 14 1. Which metal should never be cut with CAC-A because it produces highly toxic fumes? a. aluminum b. lead c. stainless steel d. titanium 2. What is the purpose for the compressed air at the electrode holder? a. clean the kerf b. create the kerf c. clean the electrode holder d. remove the poisonous gasses 3. What is used to blow the molten metal away to form a kerf when carbon arc gouging? a. compressed air b. oxygen c. nitrogen d. carbon monoxide

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COMPETENCY A-15 PREPARE JOB ACTION

A-15 JOB ACTION

HEAVY MECHANICAL TRADES: LINE A—COMMON OCCUPATIONAL SKILLS

Goals Preparing a proper job action plan will help all employees understand the shop expectations and procedures when starting any job. When you have completed the Learning Tasks in this Competency, you will be able to: • •

describe the procedures to prepare a job action describe the risks of poor job action

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LEARNING TASK 1

LEARNING TASK 1

NOTES

Describe the Procedures to Prepare a Job Action Access Documentation When a job has been assigned, you’ll need to access and organize the documentation including: •

•

• • • •

Locating the work order and reading the details for the work to be performed. This will include organizing the different repairs on the equipment. Multiple repairs may conflict with each other. For example, you may need to perform an engine tune-up as well as removing a transmission. These tasks will need to be prioritized. Locating and previewing the equipment work history. Checking the work history can provide you with valuable information for solving a problem, or repairing a re-occurring failure. Locating any product bulletins for the equipment. These bulletins can identify the cause of problems and detail the needed repairs. Locating and completing the job safety report prior to starting work. This will ensure the equipment is safe to work on. Locating the service repair manual and checking the manufacturer’s suggestions for safety and procedures. Locating and completing a hazard assessment report (if required)

Personal Protective Equipment It’s important that you have proper protective equipment when working in any heavy mechanical environment, including: • • • • • • •

hard hat ear protection safety glasses face shield work boots work gloves reflective safety coveralls

Additionally, clean coveralls inspire confidence in customers that you work in an efficient and professional manner. You’re a representative of your company and maintaining a neat appearance can improve customer satisfaction.

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NOTES

A-15 JOB ACTION

Environmental Considerations You must always consider the environment before starting any job. Environmental conditions can change and this can affect safety. One example involves the blocking of a equipment during winter. Cold, hard ground can turn to mud during a thaw and this may result in the equipment sliding off the blocks. Some important points to consider: • • • • • • • • •

cold weather—are heaters required? hot weather—are shades needed? rain—are covers required? light—is additional lighting needed? air quality— is ventilation required? noise—is additional hearing protection needed? space—is there sufficient room to perform the required tasks? work site location—will you need extra clothing or supplies when working in the field? dangerous location—is the equipment located in a dangerous area such as an avalanche zone?

Every time you go to a job site, you must be aware of any special pre-job action considerations.

Tools and Equipment You need to make a list of basic and specialty tools required for a job. When working in the field, you may have to prepare and select the tools you’ll need while still at your shop. The work order will help you in determining exactly which tools you require. Tools that you must consider include: • • • • • •

specialty hand tools measuring instruments specialty testing equipment such as scanners, multi-meters, pressure gauges, and flow meters special pullers or pushers and their attachments special blocking special lifting equipment such as chains, cables shackles, and lifting eyes

It’s important that you consider the preparation and organization of tools and equipment before starting a job.

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Parts Many jobs will require that you order parts before commencing work. This is especially true for jobs conducted in the field. Remember that parts may be back-ordered and take several days for delivery. Organization is critical so that you have all the parts you need once you’re ready to start the job.

LEARNING TASK 1

NOTES

You should create an itemized list of all required parts. This will help you keep track of all parts you need, when they were ordered, where they were ordered from, and when they will be delivered. Before ordering parts, make sure you have all the relevant information for the equipment such as the serial number, unit number, etc. This helps ensure that you order the correct part as well as making sure that the right part is delivered.

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A-15 JOB ACTION

SELF TEST 1 1. What is the first thing that needs to be done when preparing a job action? a. locate the tools and equipment b. locate the personal protective equipment c. review the environmental situations d. review the documentation 2. You are asked to drive to a construction site and remove an engine from a machine. The crane is on site. What specialty tools might you collect at your shop? a. specialty measuring instruments b. specialty test equipment c. specialty lifting equipment d. specialty pullers

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A-15 JOB ACTION

LEARNING TASK 2

LEARNING TASK 2

NOTES

Describe the Risks of Poor Job Action Cost of Improper Job Action The cost of an improper job action can be many thousands of dollars. Poor communication with your supervisor can lead to mistakes. Therefore, most repair shops will establish a job action plan. Failure to follow this job action plan may result in: • • • • • • • • •

working on the wrong equipment working on the wrong component on the equipment locating the equipment in the wrong area to perform repairs using the wrong work order for the equipment driving to the wrong job site damage to shop equipment injuries to shop staff ordering incorrect parts frustration and embarrassment

Unhappy Customers Unhappy customers will be difficult to please once improper job action has occurred. Unhappy customers are reluctant to pay their bills and will scrutinize the job invoicing. Unhappy customers may request that you not work on their equipment in the future.

Lost Business If poor job action results in added expense for a customer, there’s a risk of losing that customer’s business. Lost business affects everyone at the shop. Lay-offs are more likely when there is insufficient work.

Time Management Repair shops want to perform best practices when completing repairs. Each job is different and may require more than one person to complete the work. Technicians are always looking for ways to do the work better and faster. Effective time management is important to accomplish these goals. Following a proper job action plan will minimize problems and help to improve time management.

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NOTES

A-15 JOB ACTION

Efficiency Efficiency is important when performing repairs. You must position the equipment/truck in a location that best suits the task at hand. Some considerations for this include: • • • • • • • •

location of parts departments location of cleaning areas location of work benches location of manuals access to blocking equipment proper storage areas for oil location of chains, cables, bolt bins, and fire extinguishers location of tools

It’s important that you make sure all these items are available and organized in a manner that will offer the best efficiency when you need them.

Damage to Components and Equipment Improper job action (such as poor planning, poor equipment, or tight deadlines) can result in damage to vehicles or shop equipment as well as personal injury. Damage may result from many actions including: • • • • •

260

improper location of equipment—trucks backing into other trucks improper use of forklifts—backing into other equipment improper use of blocking—falling equipment improper use of lifting equipment—chains or slings breaking improper use of pry bars or hammers—damage to components

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A-15 JOB ACTION

SELF TEST 2

SELF TEST 2 1. What may result by using the wrong work order to perform engine repairs? a. customer is happy, as he just received repairs he did not ask for b. service manager is happy, as the repair shop got some extra work c. service manager is unhappy as the repair shop will need to redo the job d. service manager is happy, as he will need to discuss this with the customer 2. Who is primarily responsible to discuss poor job actions with unhappy customers? a. the technician b. service manager c. shop foreman d. shop union representative 3. Who may be asked to make up for lost time for damaged components when you use improper tools? a. the technician b. service manager c. shop foreman d. the apprentice working under you 4. You drive to a construction site and repair the wrong final drive on a crawler dozer. You read the work order wrong. You install all new bearings and seals. The cost is $15 000.00. How should the repair shop approach this situation? a. repair the proper final drive and charge the customer the additional costs b. repair the proper final drive and only charge the customer the costs to repair that final drive c. repair the proper final drive and do not charge the customer anything d. repair the proper final drive and the service manager negotiates with the company for the wrong final drive repairs

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COMPETENCY A-16

DESCRIBE DIAGNOSTIC PROCEDURES

A-16 DIAGNOSTIC PROCEDURES

HEAVY MECHANICAL TRADES: LINE A—COMMON OCCUPATIONAL SKILLS

Goals When you have completed the Learning Tasks in this Competency, you will be able to: • •

describe the importance of following a diagnostic procedure describe diagnostic procedures used for troubleshooting

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A-16 DIAGNOSTIC PROCEDURES

LEARNING TASK 1

LEARNING TASK 1

NOTES

Describe the Importance of Following a Diagnostic Process A diagnostic process is a sequence of events used to logically guide you through the steps needed to identify a particular problem. Most service manuals include a diagnostic section.

Cost of Improper Diagnosis Improper diagnosis can lead to excessive costs, both in shop labour and lost revenue due to equipment down-time. These costs must be absorbed by either the shop or the customer. Improper diagnosis may result from: • • • •

not using a manual not understanding diagnostic steps in a manual following the wrong diagnostic steps not having the correct diagnostic test equipment

Unhappy Customers Although customers understand that mistakes can be made, they take a dim view when they’re the result of not following proper diagnostic processes. Unhappy customers are reluctant to allow you to repair their equipment if you’re known to disregard proper diagnostic procedures. It’s likely that such customers will seek other shops for future repair work. It can take years to regain a customer’s confidence resulting in much lost business.

Time Management Time management is very important. Manufacturers design their manuals with time management as a priority. Some will list approximate times that a particular repair should take. Your shop will usually give a customer a quote estimating the time it will take to complete the diagnostics. It’s important to stay within this time estimate where possible. Customers appreciate it when you follow a service manual diagnostic sequence. It gives them confidence that you’re following the proper procedure and not wasting time.

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NOTES

A-16 DIAGNOSTIC PROCEDURES

Efficiency Using a diagnostic process leads to quicker repairs and happier customers. As you become familiar with using diagnostic processes, your diagnostic times will become faster. Efficiency will come with experience. Once you’ve completed a diagnostic process, it’s worthwhile to re-check your work—you do not want to repair the wrong components.

Damage to Components Most components require specific steps to disassemble, inspect, test, and reassemble. Not following a proper diagnostic process may lead to damaged components. Damaging components during the diagnostic process can result in expensive repairs that have nothing to do with the original problem. This leads to frustrated and unhappy customers.

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A-16 DIAGNOSTIC PROCEDURES

SELF TEST 1

SELF TEST 1 1. Why is it important to follow a diagnostic process? a. because you were unable to talk with the operator b. because you do not understand the system c. because you are preventing lost time d. because you do not understand the complaint

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A-16 DIAGNOSTIC PROCEDURES

LEARNING TASK 2

LEARNING TASK 2

NOTES

Describe General Diagnostic Procedures Understand the System Familiarity with a system is very important when you’re following diagnostic procedures. Whether it’s electrics, hydraulics, transmissions, or engines, you’ll need a detailed knowledge of these systems. Constant training is necessary to understand all the different components on trucks and equipment. It’s advisable to read service manuals before starting diagnostic procedures.

Understand the Complaint Correctly communicating customer complaints is a major problem in the repair industry. The original customer complaint may pass through several people before you receive it. Miscommunication may result in you diagnosing the wrong problem. It’s important that there be sufficient information on the work order to direct you to the proper diagnostics. You may receive a description of a problem by email, phone, text, fax, or on a piece of paper. It can be difficult to understand the complaint with these methods of communication as they often do not give symptoms or operational irregularities.

Communicate with Operator Talking directly with the operator will allow you to decipher the problem more efficiently. Be sure to ask probing questions about the complaint: • • • • • • •

What are the symptoms? When did it first start to show these symptoms? Have the symptoms gotten worse over time? Is the equipment making any unusual sounds? Are there any unusual smells? Is there any unusual vibration? What do your dash gauges show?

Once you understand the complaint, you can focus on the area that requires operational tests and visual inspections.

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LEARNING TASK 2

NOTES

A-16 DIAGNOSTIC PROCEDURES

Operational Test When using diagnostic flow charts (some companies refer to these as “trees”), you will have to perform operational tests as part of your diagnosis. The purpose of this is to confirm the complaint and identify any other areas that need repairs. When performing an operational test, it’s important to know the equipment’s limitations. It’s likely that you’ll have limited experience actually operating the equipment so you may need the operator to help you with the test.

Visual Inspection Once you have confirmed the complaint, you can begin the visual inspection. Despite the name, this may involve smelling, hearing, and feeling in addition to sight. Some tasks that you may perform include: • • • • • • •

listen for any unusual noises inspecting linkages (binding or damage) inspect fluid levels inspecting for fluid leaks (oils, coolant, or fuel) inspect fluids for colour, smell, and feel inspect screens and magnets for contaminants inspect filters for contaminants

Determine Potential Causes Once you’ve finished the visual inspection, you should have enough information to make a list of potential causes. This list should be prioritized from the most likely to least likely. How you prioritize the list will also depend on how easy, or difficult, the particular test is. Your experience, combined with the troubleshooting guide, will direct you to test the most likely cause of the problem. Your list of potential causes should be included in the service report.

Test Potential Causes Once you’ve determined the potential causes of a problem, you must test each hypothesis. This may require special testing equipment such as electronic scanners, electrical test equipment, hydraulic flow meters, and hydraulic pressure gauges. It’s very important to follow the diagnostic guide as this can take considerable time. The diagnostic guide in Figure 1 will help you narrow down a diesel engine with a black or grey smoke problems.

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A-16 DIAGNOSTIC PROCEDURES

LEARNING TASK 2

BLACK OR DARK GREY SMOKE SYMPTOM

CAUSE

ACTION TO TAKE

COMMENTS

Smoke at high and Pump timing medium speed retarded under full load with engine quieter than normal

Check and adjust the timing to specifications

Pump timing can only be wrong if installed improperly, timing advance failure, or loose mounting fasteners

Smoke at low and medium speed under full load with engine noisier than normal

Pump timing advanced

Check and adjust the timing to specifications

Pump timing can only be wrong if installed improperly, timing advance failure, or loose mounting fasteners

Smoke at high and medium speed under full load with loss of power

Injection nozzle discharge holes partially blocked

Clean or replace nozzles as necessary

Can be caused from dirt or water in the fuel

Smoke at high speed under full load

Air cleaner restricted

Clean or replace air cleaner

Service at more frequent intervals

Intermediate or puffy smoke with white or bluish ting with engine knocking

Injection nozzles sticking intermittently

Clean, repair, or replace nozzles as necessary

Can be caused from dirt or water in the fuel

Smoke at low and medium speed under full load with hard start

Loss of compression from valves, rings, or other components

Check for engine overhaul, valve adjustments, or compression

May be caused from incorrect crankcase oil level

Figure 1. Diagnostic Guide

Figure 2 shows another example of a diagnostic guide, this one identifying steering problems. The guide identifies potential causes of the problem, where to look, and how to repair it.

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LEARNING TASK 2

A-16 DIAGNOSTIC PROCEDURES

TROUBLE SHOOTING CHART TROUBLE

PROBABLE CAUSE

REMEDY

FLUCTUATING PRESSURE

FAULTY OPERATION OF Fluctuating pressure or loss of pressure in RELIEF VALUE the system is usually caused by scale, chips, sludge, filings that have lodged between the relief valve and seat or by a damaged spring or worn valve. Flush and refill system. If condition still exists, overhaul valve assembly.

LOSS OF SYSTEM PRESSURE

SLIPPAGE OF PUMP DRIVE, OTHER PUMP MALFUNCTION, LACK OF HYDRAULIC OIL

Check pump according to manufacturer’s recommendations. Check oil level and fill tank to proper level.

CYLINDER PISTON ROD BINDING OR STICKING

CRAMPING OF LINKAGE

With hydraulic flow shut off from the unit and the rod end uncoupled, the rod should slide freely in or out by hand with a maximum force of 30 lbs. If binding is apparent, replace the unit and readjust pitman arm stops to prevent recurrence of damage.

CHATTER CONDITIONS

LOOSE MOUNTINGS OR LINKAGE, RELIEF VALVE SET TOO LOW, INSUFFICIENT PUMP FLOW

Make certain all ball stud mounting and other linkage is tight. Check pitman arm stops to be certain the arm strikes the stops slightly before the steering knuckles contact the stops on the axle. Set relief valve at least 150 PSI higher than normal steering requirements of the vehicle. Bleed air from system. Insufficient pump flow at idle speeds can be corrected by increasing engine idle rpm.

UNSATISFACTORY AIR IN SYSTEM, STEERING IN EITHER EXCESSIVE WEAR IN DIRECTION STEERING CYLINDER, INCORRECT SYSTEM PRESSURE, WORN PUMP

Check for air in system. Excessive noise or foamy condition of oil indicates aeration. Check to be sure air is not entering system through poor threads, hoses, pump seals, “O” rings, gaskets, and loose connections. Excessively worn cylinders result in leakage past the piston. Correct by replacing cylinder. Set relief valve at least 150 PSI higher than normal steering requirements of the vehicle. Repair or replace pump.

JERKY STEERING

STEERING VALVE MALFUNCTIONING BECAUSE OF WORN PARTS OR IMPROPER ADJUSTMENT

Adjust steering valve and/or install new valve parts.

STEERING WRONG DIRECTION

INCORRECT PLUMBING Check steering line plumbing. OF STEERING VALVE TO STEERING CYLINDERS LINES Reproduced with permission from Peterbilt Motors Company, truck repair manual Cat. No. 5233 (rev. 3/79). Figure 2. Truck Steering Diagnostic Guide

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System Component Isolation Once you’ve used the test equipment and isolated the component, you’ll follow the diagnostic guide to complete the repair.

LEARNING TASK 2

NOTES

When you’ve completed the repair, you’ll need to re-test the equipment to make sure that it has been fixed correctly and that there are no other problems. Retesting removes any doubt concerning your diagnosis and confirms that the complaint has been addressed.

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SELF TEST 2

A-16 DIAGNOSTIC PROCEDURES

SELF TEST 2 1. What is the first item in performing diagnostic procedures? a. talk with the operator b. perform an operational test c. perform the visual inspection d. know the system 2. What is the purpose for the operational test? a. get familiar with the machine b. confirm the complaint c. test your conclusions d. perform visual tests 3. Why is it important to communicate with the operator? a. they know the machine operation and complaint b. they can help you when you perform the operational test c. they will show you where to inspect d. they know the machine systems and subsystems

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LEARNING TASK 3

LEARNING TASK 3

NOTES

Describe the Importance of Following Manufacturer’s Diagnostic Procedures Time Saving The main reason for following a manufacturer’s procedures is to reduce the time it takes to repair equipment. Machinery produced for the heavy mechanical industry use computerized systems for the operation of the engine, hydraulics, steering, and controls. With such complex systems, it’s important to follow the specific manufacturer’s diagnostic procedures. Following diagnostic charts will result in less time spent identifying the cause of a problem. Using a computer can also assist in determining the problematic area. An example is the electronic injectors on a diesel engine. By checking the electronic measurement of the injector with the aid of a computer reader, you’ll have an idea of what’s going on with the injection system. The manufacturer’s diagnostic manuals will give the needed specifications that will help with the diagnosis.

Warranty Requirements When working for a dealership or distributor, the factory will require you to follow their diagnostic procedures for warranty purposes. By following the diagnostic charts, you’re removing all doubt as to what has occurred with the equipment. You’ll report back to the factory with your findings. The results are needed for warranty consideration which will determine who must pay for the repairs.

Diagnosis May Not Be Possible Any Other Way Equipment and components may be manufactured in such a way that following a manufacturer’s diagnostic chart is the only way to identify a problem. This is especially true due to the computerization of equipment which makes traditional techniques impractical with modern machinery. Diagnostic charts and computers are required to access the electronics in order to generate diagnostic codes or perform diagnostic functions.

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SELF TEST 3

A-16 DIAGNOSTIC PROCEDURES

SELF TEST 3 1. Why is it important to follow a manufacturer’s diagnostic procedure? a. help communicate with the operator b. help understand the complaint c. help meet warranty requirements d. help list the possible conclusions

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LEARNING TASK 4

LEARNING TASK 4

NOTES

Describe the Importance of Failure Analysis Failure analysis is the process by which you determine why a problem occurred.

Repeat Failure The main benefits of failure analysis are to ensure that a problem does not reoccur and to discover if a part is defective (defective parts will usually be covered under warranty). By identifying the cause of a problem, you decrease the chance of it happening again. Repeated failures are costly to owners and equipment down-time is a large expense for companies. Your goal as a technician is to diagnose the problem quickly and accurately to reduce repeated failures. Failure analysis may include examining and identifying causes of: • • • • • • • •

engine failures clutch failures shaft failures transmission failures differential failures final drive failures hydraulic failures fluid contaminations

Each time components are disassembled, you’ll need to isolate any causes of failures.

Extend Life Failure analysis can also reduce the possibility of future problems. One prime area of reducing failure is the use of oil analysis. By checking for metal content in oil, problems can be averted, costs can be reduced, and the life of components can be extended.

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LEARNING TASK 4

NOTES

A-16 DIAGNOSTIC PROCEDURES

Cost The cost of performing failure analysis is very low compared to the cost of performing future repairs. Fluid failure analysis is particularly cheap and helps maintain a file history for the equipment. You may also need to take photos or fill out documentation to support your failure analysis. This will become part of the record documenting the reason why a component failed.

Customer Satisfaction Customers are pleased when failure analysis prevents further repairs and equipment down-time. Failure analysis is a very subjective area and it can take years to acquire the knowledge needed to have an informed opinion on why things fail. When analyzing why things fail, use all available resources—your conclusion affects other issues, the most important being customer satisfaction.

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SELF TEST 4

SELF TEST 4 1. What is the primary purpose for failure analysis? a. prevent repeat failures b. meet warranty requirements c. provide proof of failure d. extend service life

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COMPETENCY A-17

PREPARE FOR EMPLOYMENT

A-17 EMPLOYMENT

HEAVY MECHANICAL TRADES: LINE A—COMMON OCCUPATIONAL SKILLS

Goals Heavy Mechanical Trades training includes four different mechanical trades: • • • •

Heavy Duty Equipment Technician Truck and Transport Mechanic Transport Trailer Technician Diesel Engine Mechanic

Heavy Duty Equipment Technician, Truck and Transport Mechanic, and Transport Trailer Technician are Red Seal Interprovincial recognized. Diesel Engine Mechanic is a Provincial Certificate of Trade Qualification for BC. All four trades have an apprenticeship which provides you the opportunity to be paid and learn on the job, as well as receiving technical training at one of the province’s training providers. The types of equipment and vehicles you will work on will vary depending on which trade and repair facility you work for. It may range from very large mining equipment to highway tractor trailer units to small skid steer units to diesel engines. The type of business you will be employed at could be a small shop with a few employees, or an original equipment manufacturer with several employees, or a large company with several hundred employees. The environment you work in could be in a shop, or outside in the weather, or in a shop underground at a mine, or in the field working out of a service truck. There’s legislation that describes working standards designed to protect you as an employee, and the environment you work in. You may be employed at a union or non-union shop—both have advantages and disadvantages. Employers are looking for workers with good work ethics and attributes. You must show a potential employer that you have something they desire and need. Writing a proper resume that showcases your talents is critical to finding the right job. When interviewing for a job, you must be prepared to demonstrate that you’re competent and would be an asset for the company. The job you’re hired for must work for both you and the employer.

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A-17 EMPLOYMENT

LEARNING TASK 1

LEARNING TASK 1

NOTES

Describe the Areas and Types of Vehicles and Equipment Maintained and Repaired Types of Equipment for Heavy Mechanical Trades Heavy Duty Equipment Technician As a Heavy Duty Equipment Technician, you’ll work with a wide range of equipment, from the very large to much smaller units: • • • • • • • • • • • • • • • • • •

loaders excavators dozers rock trucks shovels air compressors skidders wood processors feller bunchers logging trucks (off highway) farm tractors forklifts skid steers back hoes packers mobile cranes paving machines various working attachments

The locations that you’ll work in are also diversified. You could work in the mining, forestry, transportation, or road construction industry. Some machines are so large that you’ll need to work on them wherever they’re located. This means you could be working in a mine pit or on the side of a hill. If a machine has to be repaired in a shop, then it needs to be transported. Some mechanics buy a service truck and work as an independent mechanic.

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LEARNING TASK 1

NOTES

A-17 EMPLOYMENT

The types of jobs you’ll perform as a Heavy Duty Equipment Technician range from the very simple to the very complex. Servicing a machine includes greasing, oil and filter changes, adjustments, and simple repairs. Diagnosing a machine requires understanding how the system works, understanding the complaint or problem, and following diagnostic procedures. Repairing a machine includes replacing, adjusting, and even rebuilding of systems or components.

Truck and Transport Mechanic As a Truck and Transport Mechanic, you’ll work mainly on trucks and trailer units: Trucks: • single axle • tandem axle • tri-drive • dump truck (gravel truck) • logging • highway tractor • concrete mixer • van body • crane • garbage • tow truck • school bus • transit bus • coach Trailers: • highboy • chip • drop deck • van • load bed • logging • dump • refrigeration unit Truck and Transport Mechanics work in the service industry, forestry, construction, and mining. You’ll usually work in a shop, which can either be onsite or at a separate facility. Since trucks are relatively easy to tow, they’re usually taken to a shop for major repairs, but field-work is sometimes necessary. Some mechanics choose to buy a service truck and work as an independent mechanic.

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The types of jobs you’ll perform range from servicing to diagnosing to overhauling. Servicing includes checking oil levels, greasing, oil and filter changes, and minor repairs. Diagnosis includes understanding complex electronic system, following testing procedures and understanding the results. Repairs include replacing, adjusting, and rebuilding. In recent years, a greater emphasis has been placed on replacing components rather than rebuilding them.

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Transport Trailer Technician As a Transport Trailer Technician, you’ll work mainly with trailer units: • • • • • • • •

semi highboy dump refrigeration low bed chip logging van

Transport Trailer Technicians work in the service industry, forestry, construction, and mining. The work is usually done in a shop since trailers are easily transported. Service work includes greasing, adjustments, and minor repairs. Diagnosis includes understanding how the system works, understanding the complaint or problem, and following diagnostic procedures. Repairs include replacement, adjustments, and rebuilding systems or components. Electronically controlled systems have become much more common in the past few years.

Diesel Engine Mechanic As a Diesel Engine Mechanic, you’ll work on diesel engines from the truck, heavy equipment, or marine industries. Most of work is done in a shop, but some field work is also required. The engines can range from a small 3-cylinder engine to a large V16. Most Diesel Engine Mechanics work for a shop that specializes in the repair and overhaul of diesel engines. Servicing includes adjustments, and oil and filter changes. Diagnosis involves understanding the engine and electronic control systems, and following diagnostic procedures. Repairs include replacement, adjusting, and overhauling of complete diesel engines. Diesel engines have advanced electronic control systems controlling the engine and after treatment systems.

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Heavy Mechanical Trades In addition to the specific trades, you will often be required to work on your own shop equipment and vehicles. This may include items such as the shop pick-up or service truck, shop forklifts, or even chainsaws.

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SELF TEST 1

SELF TEST 1 1. What trade are rock trucks? a. truck and transport mechanic b. transport trailer technician c. diesel engine mechanic d. heavy duty equipment technician 2. What trade are gravel trucks? a. truck and transport mechanic b. transport trailer technician c. diesel engine mechanic d. heavy duty equipment technician 3. What trade focuses on diesel engine repairs? a. truck and transport mechanic b. transport trailer technician c. diesel engine mechanic d. heavy duty equipment technician

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Describe the Current Heavy Mechanical Trades Current Apprenticeship Training In British Columbia, the Heavy Mechanical Trades involves four trades, each of which has an apprenticeship. This combines paid workplace training as well as technical training with provincial training providers. Heavy Duty Equipment Technicians (HDE) and Truck and Transport Mechanics (TTM) have a four-year apprenticeship that leads to a Red Seal Interprovincial endorsement. A Diesel Engine Mechanic (DEM) has a four-year apprenticeship that leads to a provincial Certificate of Qualification. The Transport Trailer Technician (TTT) apprenticeship is three years and leads to a Red Seal Interprovincial endorsement. There are two ways to enter an apprenticeship: • •

direct entry when sponsored by an employer foundation training with a training provider

With direct entry, there will be up to four levels of apprenticeship training. When entering through the foundation training, there is Foundation, which includes Level 1 credit, then three more levels of apprenticeship training. The chart below breaks down the options and the in-school training times. Foundation Training

Direct Entry

Trades

Foundation with Level 1 credit (30 weeks)

Level 1 (10 weeks)

HDE, TTM, TTT, DEM

Level 2 (8 weeks)

Level 2 (8 weeks)

HDE, TTM, DEM

Level 3 (6 weeks)

Level 3 (6 weeks)

HDE, TTM

Level 4 HDE (4 weeks)

Level 4 HDE (4 weeks)

HDE

Level 4 TTM, TTT (4 weeks)

Level 4 TTM, TTT (4 weeks)

TTM, TTT

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In addition to technical training, you must accumulate workplace hours. Heavy Duty Equipment Technicians and Truck and Transport Mechanics must work a minimum of 6000 hours. Diesel Engine Mechanics have to work a minimum of 4500 hours. Transport Trailer Technicians have to work approximately 5000 hours prior to final certification. At the end of your apprenticeship, you need the following in order to become certified in your trade: • • • • • •

completion of all technical training completion of all level exams completion of competency log book completion of all workplace hours completion of the final exam (Red Seal or Certificate of Qualification) sign-off by employer

Physical and Mental Requirements If you’re considering employment in the Heavy Mechanical Trades, you should recognize that there are a number of qualities that will enhance your potential for success. Being in good health and having physical agility and strength is an advantage to a mechanic. Repairs to vehicles are made above, below, and inside equipment. At times, you’ll have to work in awkward positions for extended periods. Good hearing is essential for safety reasons as well as to diagnose knocks, squeaks, or rattles. Good eyesight is important for the examination of parts to determine their condition and make fine adjustments. Since mechanics use their hands extensively, good manual dexterity is also required. Your success as a mechanic requires that you have mechanical aptitude. This will allow you to picture in your mind the position and shape of objects and detect differences in the shape, size, and detail of objects or of pictorial material. Mechanical aptitude shows an ability to think through problems relating to objects and their relationship to other objects or devices. It also implies a high level of hand-eye coordination and an ability to manipulate objects, even small ones, with speed and accuracy. A career as a Heavy Mechanical Trades mechanic requires that you have mechanical interests. These interests will show themselves in your preference for dealing with mechanical systems and objects. Your success in the mechanical trades requires that you be able to read and understand technical papers and service manuals with ease. You also need to be a problem solver, understanding the complete system and then diagnosing the problem.

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Mechanics have to accept that they will get dirty during the day. Pressurewashing, parts washing, and working in dirty conditions are all part of the job and you have to be ready for that.

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As a mechanic, you may end up working in a wide variety of settings with other people. If you are an effective listener, are courteous and patient, and enjoy a professional activity that brings you into regular contact with others, you are likely well-suited for these mechanical trades. As well, the technical sophistication and precision of the mechanics’ trades make skills in effective communication important.

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SELF TEST 2 1. What are the total weeks of direct entry in-school apprenticeship training for TTT? a. 4 weeks b. 10 weeks c. 14 weeks d. 34 weeks 2. How many weeks in-school third year training for DEM? a. 0 weeks b. 4 weeks c. 6 weeks d. 8 weeks

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Describe the Range of Working Conditions Job Opportunities Upon entering the Heavy Mechanical Trades, you’ll find many opportunities. Resources such as coal, copper, gasoline, natural gas, and wood products are in demand. Getting them from the ground to the end user depends on equipment and vehicles—jobs are available throughout the process from start to finish. Pay scales and hours of work will vary as will the work environment and the quality of work.

Location Heavy mechanical jobs are available from one end of the province to the other. Mines, both open pit and underground, need mechanics to keep their equipment and vehicles moving in extreme conditions. Mining coal, copper, gold, and silver requires many pieces of equipment that require regular servicing and repairs. Forestry requires equipment to cut trees, move them to a truck, and then will carry the logs to a saw mill for processing. Wood chips are then transported to a pulp mill to make paper. Gasoline, diesel, and propane are carried from a bulk plant to filling stations. All of these methods of transportation require mechanics to service and repair equipment and vehicles. You may work in a shop on equipment and vehicles that are brought in by customers. You may travel daily to a mine to work in the on-site shop or in the field. You may travel by plane and stay on-site for one or two weeks at a time before returning home. You might work out of your own service truck repairing equipment for your clients. The locations for work in BC are endless.

Advancement and Specialization When you get your first job as a mechanic, you’ll be an apprentice. Subsequently, you’ll learn the trade from co-workers and technical training over the following years. You will then become a journeyperson. As you work and gather more and more knowledge, you’ll become more valuable to your company—they’ve invested time and money in you. After time, there may be opportunities for advancement to other positions. You may become a lead-hand and look after a work shift making work orders or supervising other mechanics. You may progress to a foreman who supervises a shop and all the mechanics. You may then become a service manager, responsible for an entire mechanical shop and all mechanical staff. You may even become a branch manager, looking after the

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operation of an entire business: parts, sales, and service. Other opportunities include becoming a service representative for an original equipment manufacturer. After years of service, you could also become an instructor at a private trainer or a provincial training provider. Some mechanics choose to remain at one position in a company, but are still very valuable. You may become a specialized mechanic. You could become the engine, gear, hydraulic, or electrical expert at a shop. By investing resources in you, you become very efficient at your job, making them more money as well as keeping their customers happy.

Types of Employment Opportunities There are many types of employment opportunities depending on your preferences. You may be hired by someone who has a fleet of equipment or vehicles. A dealership may hire you to work on one brand of vehicle or you could be hired by a shop that will work on all types of equipment. You may start with one type of employer and move to another gaining valuable experience from each.

Pay Scales Pay scale varies depending on where you’re employed. When you first start your apprenticeship, you will usually be paid approximately 50–60% of a journeyperson’s wages. Then, every six months you may receive a 5% pay increase. By the time you’re a fourth-year apprentice, you should be making close to the journeyperson’s wages. A journeyperson’s wage ranges from $30/ hr to $40/hr or more, depending on the specific location. In addition to wages, there is usually a package with health benefits, boot and tool allowance, retirement pension, and vacation pay. Each employer will have a different pay and wage package. Typically, a mechanic in the Heavy Mechanical Trades is wellpaid.

Hours of Work The traditional work week is eight hours a day, five days a week which adds up to 40 hours each week. However, there are many alternatives to the traditional 40hour work week. Some workplaces work four ten-hour days with a rotation that changes the days you work from week to week. Others use a twelve-hour day. Some have three twelve-hour shifts a week that rotates. Some shops work two twelve-hour day shifts followed by twenty-four hours off and then two twelvehour night shifts. If you’re flying into a camp and working for two or three weeks straight, you might be working at least twelve hours a day. There are all types of hours and shifts depending on where you’re working. There is also overtime, which is work done in addition to your regular hours. You’re usually paid extra for overtime hours. 298

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Working Environment Working environments in the Heavy Mechanical Trades will vary considerably depending on the workplace. When working in a shop atmosphere, you’re normally protected from the cold, heat, wind, and dust but you may also work in a yard or conduct field repairs. When working in the field, you must consider the conditions. Is it hot and dusty? Pouring rain? Extremely cold? You must be prepared for whatever mother nature throws at you. If it’s very cold, a portable heater and tarp can be used to allow you to work. Equipment and vehicles are often dirty and dusty and you may have to work on them without cleaning them completely. A workplace may be noisy, requiring that you protect yourself from hearing loss. When working alone, you must take extra precautions to prevent injury. There may be moving machinery in the area in which you are working which must be taken into consideration.

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Quality Control In today’s Heavy Mechanical Trades, there’s no room for mistakes or comebacks. The cost of parts and labour are expensive, as is the cost to the customer in lost revenue. Mistakes can cause the reputation of your workplace to suffer. Quality starts with you as a mechanic—you have to make correct diagnoses and complete repairs effectively and efficiently. The use of correct parts helps ensure a quality repair. As a mechanic, you must stay up-to-date with updates and changes from manufacturers. Managers must make sure that you receive proper training, whether it’s in-house or outside. All mechanics should work together to ensure that shop quality is high. If you see something that is being done incorrectly, you must bring it to your supervisor’s attention. The use of proper tools for a job will also help ensure a quality repair. Most mechanics and supervisors are available for consultations when you need another set of eyes to check things over. Some have years of experience and as an apprentice, you can draw on that knowledge to help complete a quality repair.

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SELF TEST 3 1. What are the traditional hours of work for the heavy mechanical trades? a. 4 ten-hour days per week b. 3 twelve-hour days per week c. 5 eight-hour days per week d. 5 twelve-hour days per week

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NOTES

Describe Types of Businesses There are various workplaces that a Heavy Mechanical Tradesperson may work— it depends on what the business is designed to do. Are they serving someone else’s needs, or their own? Do they sell equipment, vehicles, and parts or do they just provide labour? There are three main types of shops in the Heavy Mechanical Trades: • • •

independent dealership fleet

Independent An independent shop works on whatever comes in the door. Usually, it will have a contract with one or more companies to repair and maintain their equipment. Most of the work will be non-warranty, so it’s often on older equipment and vehicles. You will be required to learn various systems from different manufacturers because of this wide range of equipment. An independent shop may also be a single mechanic with his own service truck which travels to a work site. All tools and equipment are stored in this truck which requires that parts are picked up or delivered to the work site.

Dealership A dealership usually sells equipment or vehicles, and provides service and parts support. When working in a dealership, the main customer is usually the vehicle manufacturer in the form of warranty repair claims. Warranty coverage can range from one to five years depending on the component and manufacturer. For the customer to receive warranty service, the equipment needs to be repaired by mechanics at the dealership. A dealership mechanic has to be current in their product knowledge so that repairs are done quickly with no come-backs. Dealership mechanics are under pressure of meeting timelines and doing the job correctly the first time. In addition to warranty work, there is also regular service work and custom work that has to be performed.

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Fleet A fleet shop mechanic works on equipment owned by their employer. It may be a company with a fleet of trucks or trailers, a road building company, a logging show, or it could be a mine site. They need mechanics to keep their equipment and vehicles operational to complete their daily work. Usually, there’s a lot of preventative maintenance, servicing, and emergency repairs. If the fleet has newer equipment, the company that sold the equipment will perform any required warranty repairs. Some fleet shops will work on equipment outside of their company in order to make extra income. As a fleet mechanic, you’ll need to become familiar with all your equipment and vehicles. Even though they do the same job, they may not be from the same manufacturer.

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SELF TEST 4

SELF TEST 4 1. What type of business works mainly on original equipment manufacture’s equipment? a. dealership b. self employed c. small shops d. fleet 2. What type of business is a single employee and works out of their mobile truck? a. mobile b. dependent c. independent d. solo 3. What type of business mainly works on their own equipment? a. fleet b. solo c. franchise d. co-operative

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NOTES

Describe Labour Groups When working as a mechanic, you could be covered under a union collective agreement, or work with no union or collective agreement. It doesn’t matter if the employer is a fleet, dealership, or independent.

Union A union is an organization that works with the employees, who are union members, to work out an agreement on working condition with the employer. The union works on behalf of the union members to discuss issues with the employer. Issues include wages, hours of work, fringe benefits, health, and safety. Some unions may represent 10–20 members in a shop, or several hundred. Some businesses have both union and non-union employees. Normally, the mechanics are union members and the supervisors and managers are not. When applying for a job, you should ask if the business is part of a union. You’ll have to make the decision to work at a union business or a non-union business. When you’re a member of a union, you have to pay union dues. At times, there may be issues during the bargaining process that cannot be settled through normal negotiations requiring you to go on strike. When you go on strike, you withdraw your work and picket the business. The idea is to force the business and union to talk about the issues and come up with an agreement. The union has to follow the BC Labour Relations Code when negotiating with a business and working with the union members.

Non-union There are businesses which are non-union. This means that there is no union to act on the employees’ behalf. Typically, the employer and individual employee agree to wages, benefits, and vacations at the time of hiring. Then, after some years of service, the employee may request an increase in wages and benefits with the employer. Usually each employee is responsible for their own negotiations. Some non-union businesses will have wages and benefits comparable to a union business in order to keep employees satisfied and prevent a union from forming. Non-union businesses must follow the BC Employment Standards Act when dealing with their employees.

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SELF TEST 5 1. What regulations must the unions follow when working with union members? a. Provincial Labour Relations Code b. Provincial Employment Standards Act c. Federal Labour Relations Code d. Federal Employment Standards Act

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Describe Legislation Affecting Employment Provincial and federal legislation is in place to ensure that workers receive at least minimum standards of wages and terms of employment. The Employment Standards Act applies to most employees and employers in British Columbia except: •

Those working in occupations not covered by the Act such as doctors, lawyers, architects, chartered accountants, realtors, and those working in multiple provinces.

•

Employees whose jobs come under federal jurisdiction.

Federal Jurisdiction Federal labour laws cover employees who work for the Government of Canada, its Crown Corporations, and the Armed Forces. They also cover employees of railways, highway transport, telephone, interprovincial and international shipping and pipelines, radio and television broadcasters (including cable), air transport, and banks. Like the Employment Standards Act, the Canada Labour Code sets minimum standards for wages, annual vacations, holidays, maternity, parental and other leaves, hours of work, terminations, and wage recovery. In addition, it covers unjust dismissal and sexual harassment. For more information about the provisions of the Code, contact the regional office of Human Resource and Skills Development Canada, Labour Programs office, or visit the Labour Program website.

The Employment Standards Act BC’s Employment Standards Act, administered by the Ministry of Labour, sets the minimum legal standards that all employers must satisfy. Every employer must display a statement of employees’ rights in each workplace. About 60% of BC’s workers are non-union and come under the provisions of this legislation rather than those of a collective agreement. Collective agreements must meet or exceed the minimum standards of the Employment Standards Act. In addition, the provisions of the BC Labour Relations Code apply to workers in unionized workplaces.

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Payment of Wages Wages must be paid at least twice a month. A pay period cannot exceed sixteen days and payment must be received no more than eight days after the end of a pay period. If an employee quits, the employer has six days within which to pay all wages and holiday pay due. If the employer terminates the employee, all wages and holiday pay must be paid immediately on termination. An employer may deduct only those amounts from an employee’s wages that the employee has authorized or that the law permits or requires. Employers must deduct income tax, Canada Pension Plan contributions, and Employment Insurance premiums from an employee’s wages. No wages may be withheld to cover breakage, loss, or cash shortages. If an employer requires an employee to wear a uniform or special apparel, the employer must provide, clean, and maintain these items at no cost to the employee. If the employer and the majority of the affected employees agree that the employees will clean and maintain the special clothing, the employer must reimburse employees for these costs. An employer must honour an employee’s written authorization to deduct from the employee’s wages such things as: • • • • •

union dues contributions to charity contributions to a pension plan or superannuation plan premiums for medical or dental insurance maintenance required under the Family Maintenance Enforcement Act

Employers must also honour an assignment of wages authorized by a collective agreement or the terms of employment (e.g., group life insurance premiums). An employer may honour an employee’s written assignment of wages for the purpose of meeting a credit obligation. An employee is entitled to receive a statement of wages every payday. This statement must include the following information: • • • • • •

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employee’s name and address hours worked wage rate overtime hours and rate(s) amount for bonus or living allowance amount and purpose of each deduction

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If an employee is paid other than by salary or by the hour, the statement of wages must show how the wages were calculated for that period. A person who was a director or officer of a corporation at the time wages should have been paid is personally liable for unpaid wages, in an amount not exceeding two month’s wages for each employee affected.

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Hours of Work An employer must post a notice saying when work begins and ends, when each shift starts and ends, and when meal breaks occur. These notices must be posted where they can be read by all employees. An employer must give an employee at least 24 hours notice of a change in shift unless the employee is paid overtime for the time worked or the shift is extended before it is completed. After working for five consecutive hours, an employee is entitled to a halfhour meal break. An employer is not required to pay wages for the eating period unless the employee is expected to be available for work during the break. An employer is not required to provide coffee breaks. Coffee breaks are a benefit given at the employer’s discretion. An employee must have 32 consecutive hours free from work each week. If an employee works during the 32-hour rest period, all hours worked are payable at double the regular rate. An employer must ensure that each employee has at least eight hours free from work between each shift worked unless the employee is required to work because of an emergency. A split shift must be completed within 12 hours of the start of the shift. An employee who starts work on the call of an employer is entitled to a minimum of four hours pay at the regular rate. An employee who reports for work on the call of an employer but has not started working, is entitled to a minimum of two hours pay at the regular rate if work is not available. If work is suspended for reasons beyond the employer’s control (e.g., unsuitable weather conditions), the employee must be paid for two hours work or actual hours worked, whichever is greater.

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Overtime The maximum hours of work that an employer may permit or require an employee to work without overtime rates of pay are eight hours in a day or 40 hours in a week, unless a variance of hours or modified work week plan has been approved. These flexible work schedules must follow repetitive cycles which, over their course, average no more than eight hours a day, or 40 hours a week. Such schedules must: • •

•

run at least 26 weeks be approved by 65% of affected employees or, in firms covered by a collective agreements, by the trade union representing the affected employees conform to the requirements of the Employment Standards Regulations

Employers may cancel a flexible work schedule at any time. The Employment Standards Branch may also cancel the schedule if it receives a complaint from an affected employee and is satisfied that the employer either did not follow the required procedures in the regulations or unduly influenced, intimidated, or coerced employees to approve the schedule. Overtime means any hours worked over a normal workday of eight hours or a normal work week of 40 hours. The overtime rates of pay are time-and-a-half for all hours in excess of eight and up to 11, and double-time for all hours in excess of 11. On a weekly basis, overtime rates of pay are time-and-a-half for all hours in excess of 40 up to 48 and double-time for all hours in excess of 48 in the week, not including daily overtime. An employer can require an employee to work overtime, providing overtime rates are paid. Overtime rates do not apply to work done on a Saturday or Sunday if these days are part of a normal work week of 40 hours or less. At an employee’s written request, an employer may establish a time bank and credit overtime wages to the bank instead of paying the wages as they are earned. At any time, employees may request to have all or part of the banked wages paid out. The employee may also request time off with pay for some mutually agreed period. Upon termination, the outstanding balance must be paid to the employee. Banked wages must be drawn out within six months of being earned.

Minimum Wage The Act provides for a minimum hourly wage in the Province of British Columbia.

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Leaves and Jury Duty Employers are required under the Act to grant the following periods of unpaid leave: •

pregnancy leave of up to 18 consecutive weeks starting no earlier than 11 weeks before the expected birth date and ending no earlier than six weeks following the birthdate unless the employee requests a shorter period

•

parental leave for a birth or adoptive parents of up to 12 weeks

•

family responsibility leave of up to five days to meet responsibilities related to the care, health, or education of immediate family members

•

bereavement leave of up to three days on the death of an employee’s immediate family member

•

jury duty

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While an employee is on leave for any of these reasons, employment is considered to be continuous for the purposes of calculating annual vacation and termination entitlements and pension, medical, or other benefit plans. The employer may not terminate an employee on leave or jury duty or change the conditions of employment. When leave or jury duty ends, employees must be returned to their former or comparable positions.

Statutory Holidays The ten general holidays (statutory holidays) are New Year’s Day, BC Family Day (Feb.), Good Friday, Victoria Day, Canada Day, British Columbia Day, Labour Day, Thanksgiving Day, Remembrance Day, and Christmas Day. An employee with a regular schedule of hours who has worked for an employer for at least 15 out of the last 30 calendar days prior to a statutory holiday is entitled a regular day’s pay for the holiday. For employees who have worked irregular hours on at least 15 out of the last 30 calendar days, an average day’s wages are paid. This amount is calculated by dividing total wages during the last 30 days, excluding overtime, by the number of days worked. For employees who worked fewer than 15 out of the last 30 days, pro-rated statutory holiday pay is calculated by dividing total wages in the 30-day period, excluding overtime, by 15. If the holiday falls on a non-working day, the employee is entitled to an alternative day off with pay, no later than the employee’s next annual vacation or termination.

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An employee eligible for statutory holiday pay who works on the holiday must be paid time-and-a-half for the first 11 hours worked and double-time for additional hours. The employee must also be given an alternative day off with pay. The employee may credit the wages for the alternative day off to his or her time bank. The additional day must be scheduled before the annual vacation, before termination of employment, or within six months if credited to a time bank, whichever is earliest. In the week that a general holiday occurs, weekly overtime rates are paid after 32 hours, not 40. The rates are time-and-a-half for any hours in excess of 32 up to 40 and double-time for hours in excess of 40.

Annual Vacations with Pay Employees are entitled to an annual vacation of two weeks after 12 consecutive months of employment, and three weeks after five consecutive years of employment. Vacation entitlement can be taken in periods of one day or more, if the employee desires, but the employer cannot require the employee to take a vacation period shorter than one week. All vacation must be taken within 12 months of when it is earned. The employer may use a common date for calculating the annual vacation entitlement of employees, so long as no employee’s right to an annual vacation is reduced. The sale, lease, or transfer of the business does not affect the period of consecutive employment of its employees. Vacation pay is 4% of gross yearly wages for the first five years of employ-ment, and 6% of gross yearly pay for more than five years of employment. Vacation pay is counted as part of the total wages paid in a year. Vacation pay must be payable at least seven days before the vacation begins, or on regular pay days if agreed by the employer and employee, or by a collective agreement. Annual vacations or vacation pay cannot be reduced because the employee was paid a bonus or sick pay, or was previously given a vacation longer than the minimum. Vacation entitlements may be reduced if the employee took annual vacation in advance at his or her written request. If there is a statutory holiday during an employee’s vacation, the employee is entitled to an alternative paid day off sometime before the next annual vacation. If employment is terminated, the employee is entitled to accumulated vacation pay. Persons employed for less than five calendar days are not entitled to vacation pay.

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Termination of Employment Most employees who have worked for an employer for at least three months are eligible for compensation if their employment is terminated. The formula for compensation is: • • •

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after two months of consecutive employment—one week’s pay after one year—two weeks pay after three years—three weeks pay, plus one additional week for each year of employment to a maximum of eight years

A week’s pay is calculated by totalling the employee’s wages, excluding overtime, earned in the last eight weeks in which the employee worked normal hours and dividing this amount by eight. The period of continuous employment is not affected by the sale, lease, or transfer of the business. The employer may provide advance written notice equivalent in weeks to the number of weeks pay to which the employee is eligible in lieu of pay compensation. Employees cannot be on vacation, leave, strike or lockout, or be unavailable for work due to medical reasons during the notice period. If employment continues after the notice period ends, the notice is of no effect. During the notice period, the terms of employment may not be altered without the employee’s written consent. Notice or pay compensation is not required if the employee: • • • • • • •

•

retired or quit was dismissed for just cause worked on an on-call basis doing temporary assignments that could be accepted or declined was hired for specific work completed in 12 months or less was employed for a definite term was offered reasonable alternative employment and refused it was employed under a contract that is impossible to perform due to an unforeseen event or circumstance (e.g., fire or natural disaster, but not bankruptcy, receivership, or insolvency) was hired at a construction site by an employer whose principal business is construction

Notice or pay compensation is not required for temporary layoffs. A layoff becomes a termination when it exceeds 13 weeks in any period of 20 consecutive weeks or a recall period covered by a collective agreement is exceeded by more than 24 hours. A week of layoff is a week in which the employee earns less than 50% of his or her regular weekly wages, averaged over the last eight weeks. When a layoff becomes a termination, the date of layoff becomes the termination date and the employee becomes eligible for compensation as described above.

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Complaints and Appeals Any person may file a complaint against an employer under the Employment Standards Act. The complaint must be received within six months of the alleged contravention. If the complaint is from a terminated employee, it must be made within six months of the date of termination. The person making the complaint may request that her or his identity be kept confidential. The identity may only be disclosed if it is necessary for a proceeding under the Act, or if the Employment Standards Branch considers disclosure to be in the public interest. Once a complaint is filed, an Industrial Relations Officer of the Employment Standards Branch is appointed to inquire into and attempt to resolve the complaint. The officer consults with the employee, the employer, and any other person considered necessary for the dispute to be resolved. If the investigation finds that the Employment Standards Act or Regulations have been contravened, the Branch may issue a decision which may require compliance, reinstatement or compensation, or impose penalties. Decisions of the Branch may be appealed to the Employment Standards Tribunal. The appeal must be filed within eight days of the decision being served. Employers are required by the Act to refrain from terminating, disciplining, suspending, penalizing, intimidating, or coercing an employee because an investigation or action has been undertaken as a result of the employee’s complaint.

BC Labour Relations Code The BC Labour Relations Code regulates labour relations and collective bargaining. This statute is administered by the Labour Relations Board, which can be contacted through the Ministry of Labour offices. The Code guarantees that “every employee is free to be a member of a trade union and to participate in its lawful activities” [Section 4 (1)]. Employers are also free to join employers’ organizations. If a group of employees wants to be represented by a union, the Code provides the means for that union to be legally recognized as the exclusive bargaining agent for those employees. This recognition is called “certification.” A certified union has the right to bargain with the employer on behalf of the employees it represents and to bind them to a collective agreement setting out terms and conditions of their employment.

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According to Section 12 of the Code, the union has the duty to represent fairly all of the employees in the bargaining unit, whether or not they are members of the union. Once a union is certified, employers are forbidden to make individual deals with any employee in the bargaining unit.

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The Code contains provisions intended to promote collective bargaining and sets out basic standards for every collective agreement. If the union and the employer cannot reach an agreement, the Code allows strikes, lockouts, and picketing in order to enforce bargaining demands, as long as these do not occur during the term of a collective agreement. All disputes arising during the term of a collective agreement must be resolved by arbitration or some other method agreed upon by both parties. The Labour Relations Board is the final decision-maker on any questions that arise under the Code, including the following considerations: • • • • • • • •

a person is an employer or employee an organization is a union a collective agreement has been entered into a group of employees is a unit appropriate for collective bargaining a person is a member in good standing of a union a person is included in, or excluded from, an appropriate bargaining unit an activity constitutes a strike, lockout, or picketing an unfair labour practice has occurred

If the board finds that the Code, or a collective agreement under the Code, has been violated, it can remedy the situation by ordering those responsible to stop the violation, to pay compensation, or to reinstate an employee.

Collective Bargaining Collective bargaining is the process by which the union and the employer negotiate to reach an agreement about the terms and conditions of employment. This written agreement usually includes items such as salary, benefits, job security, seniority, and conditions of work. Collective agreements can benefit non-union workers as well, because these settlements often set the pattern for other employers in an industry. In collective bargaining, the two sides usually start preparing for negotiations long before they meet at the bargaining table. The management negotiators frequently consult lower-level management people about problems with the last agreement. Unions invariably have a procedure whereby members can ask that certain items be sought in the next contract. Each side has its negotiating committee.

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Both sides want room to maneuver in bargaining, so their opening stands are usually quite extreme. For example, you may read in newspapers that a certain group of employees is “demanding” a 10% increase, but the company says that, in order to remain competitive, it can only offer a 5% reduction. The final agreement will probably lie somewhere between these two extremes. Pay increases are the collective bargaining gains that receive the most publicity. In addition to wages, other items commonly covered in a collective agreement are: •

seniority clauses under which workers with long service are laid off only after employees hired more recently are let go

•

job security clauses, stipulating that an employee may be discharged only for “just cause,” and providing for severance pay for those who are not recalled to work

•

fringe benefits, including the costs of medical care plans, pension plans, dental care, and so on; fringe benefits include provisions for vacations and holidays

•

provisions for overtime pay or differentials, such as extra pay for evening or overnight shift work

The BC Labour Relations Code requires that a collective agreement be for at least one year. However, some run for two years and others for three years or longer, depending on the industry and the economic climate at that time. Either party to a collective agreement may serve written notice requiring the other party to commence bargaining at any time during the four months prior to the termination of the existing agreement. Negotiations can go on for a matter of days or weeks or months before the parties reach a tentative agreement. That tentative agreement must then be ratified or approved by the people they represent.

Ratification Sometimes, management negotiators have the authority to approve a tentative agreement, but frequently they have to refer it to their superiors. In private industry bargaining, it may have to be ratified by district or regional management or even a head office in another city or country. In the public sector, ratification may be by a board of education, a municipal council, or senior officials of provincial government departments or crown corporations.

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Union negotiators, with few exceptions, must go to the entire membership for ratification of the tentative agreement. In small bargaining units located in one community, ratification votes are held at membership meetings. In large, widelyscattered bargaining units, ratification may be by a mailed ballot. For example, the only way agreements covering the federal government’s 50 000 clerical employees can be ratified is by mail ballot, since these employees are located all across the country.

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Sometimes one or both parties will turn down the tentative agreement and the negotiators must return to the table to create another one.

Work Stoppages If the parties cannot reach an agreement, and they want to use the strike or lockout options to force one, they frequently call on government intervention called “mediation.” Either party can apply to the Ministry of Labour to appoint a mediation officer to help them reach an agreement. A mediator meets with the two parties separately and then tries to bring them together to reach a tentative agreement. If an agreement is still not reached, parties may resort to work stoppages. The parties must wait until the mediator has reported to the Minister of Labour before they can legally engage in a work stoppage. A strike is a refusal by employees to work in order to compel an employer to agree to terms and conditions of employment. A strike need not be a complete stoppage of work. For example, overtime bans and work slow-downs can constitute a strike. A lockout is a restriction by an employer of work that would normally be available for employees and is intended to compel those employees to agree to terms and conditions of employment. A bargaining unit is required by the BC Labour Code to hold a governmentsupervised secret ballot strike vote and get approval from a majority of the bargaining unit members. If an employer is contemplating a lockout, a government-supervised secret ballot lockout vote by the members of the accredited employer’s organization must be held. A strike or lockout can be called at any time during the three months after the date of a favorable vote. If the work stoppage is not called during that time, another vote must be held in order to renew the mandate.

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A union must give the employer 72 hours written notice of its intention to strike before actually engaging in strike activity. An employer must give 72 hours written notice of a lockout. In certain instances, as when perishable property is involved, the Labour Relations Board may lengthen the normal 72-hour period of strike or lockout notice. The Code provides that a withdrawal of services is not a strike if employees have stopped working because of a legitimate concern for their safety or health. A work stoppage normally continues until one side or the other finds the economic costs too high. The workers give in because they cannot meet their bills or the employer comes to terms because the work stoppage is costing too much in lost production.

Grievance and Arbitration Because the BC Labour Code prohibits all work stoppages during the life of an agreement, a method to resolve disputes is required. The Code allows the parties to negotiate through a grievance procedure. If the two parties are unable to resolve their dispute through this grievance procedure, then the dispute is taken to binding third-party arbitration. Arbitration with binding third-party adjudication as the final step must be provided for in the collective agreement. If the agreement does not provide for some method of resolving disputes during the life of the contract, the Code contains a provision for arbitration that is automatically included in the agreement.

Workers’ Compensation Act Employees (or their dependents) in most industries are entitled to compensation for personal injury arising out of and in the course of their employment. Workers disabled by specified industrial diseases are also entitled to compensation. Compensation is “no-fault” unless the injury results solely from a worker’s serious and willful misconduct. In this case, no compensation is payable unless the injury results in death or serious and permanent disability. The compensation is paid from a fund to which employers in the industries covered by the Workers’ Compensation Act must contribute. Employers cannot deduct from their employees’ wages any of the money that must be paid to the fund, which is administered by WorkSafeBC.

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Other Health and Safety Legislation The Occupational Environment Regulations under the Factory Act specify the purity and temperature of air that must be maintained, the amount of light that must be provided, the space that must be allowed for each employee, and the type of eating and washroom facilities that must be provided.

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Regulations made under the Health Act control camp location, bunkhouse construction, toilets, sewage disposal, and other sanitary aspects of industrial camps. These regulations apply to lumber, mining, and railway construction camps; sawmills; canneries; and “other similar places where labour is employed throughout the province.” The Workplace Hazardous Materials Information System (WHMIS) provides information about the identification, labeling, and safety of hazardous materials. This will help protect the health and safety of workers by promoting access to information on hazardous materials used in the workplace. WHMIS is governed by federal and provincial laws and regulations. Any person supplying or using controlled products must comply with it. Copies of these acts can be obtained through Crown Publications, or downloaded from the Internet. An employee who believes an employer is violating any health or safety standards can complain to the nearest office of the Ministry of Labour.

Human Rights Legislation Human rights legislation protects you against discrimination in all aspects of your life—at work, in public facilities, in housing, and so on. Fundamental or basic freedoms and rights are set out in the Canadian Charter of Rights and Freedoms, a section of the Canada Act (1980) or Constitution. Among many other things, this charter protects your right to move anywhere in Canada and to gain a livelihood or employment in any province (mobility rights). It also protects you from discrimination on the basis of race, national or ethnic origin, colour, religion, sex, age, or mental or physical disability (equality rights). If you feel your rights and freedoms have been denied or violated, you must go to court to get the matter resolved. In addition, the Canadian Human Rights Act prohibits discrimination in all federally-regulated agencies and institutions under federal jurisdiction. The Canadian Human Rights Commission is a federal agency established to deal with human rights complaints, issues, and education. If you feel your complaint might be covered, you can contact the nearest Commission by phone, in person,

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or by letter. The case will be investigated by the Commission if it falls within federal jurisdiction. If the investigation substantiates the complaint, a tribunal or conciliator can be appointed to settle the case. In British Columbia, your rights are also defined by the Human Rights Act. This Act prohibits discrimination in housing, public facilities and services, and employment. Under this Act, you cannot be refused employment or promotion or be forced to work under different conditions because of your race, colour, ancestry, place of origin, political belief, religion, marital status, physical or mental disability, sex, sexual orientation, age (45 to 65 years), or conviction for a criminal or summary conviction charge unrelated to employment. Complaints about possible human rights violations under the BC Human Rights Act can be made to the British Columbia Council of Human Rights. If you are unsure whether your complaint is a federal or provincial matter, contact either the Canadian Human Rights Coalition or the BC Human Rights Coalition, which are non-government agencies that help people with their human rights complaints.

Employers’ Rights Under human rights legislation, an employer has the right to: • • • • • • •

identify specific employment needs and priorities hire the most qualified applicant for a position set standards for work evaluate workers based on defined job descriptions and performance criteria set employment conditions, as long as they are within minimum labour standards and are applied equitably establish pay or salary scales, either independently or through negotiation discipline, demote, or dismiss incompetent, negligent, or insubordinate employees

Bona Fide Occupational Requirements The process of hiring employees should begin with establishing the job duties and qualifications. These qualifications must be bona fide (genuine) occupational requirements. This term means those requirements that persons should have to enable them to perform the job adequately and safely.

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For example, a mechanic may be required for a position that involves weekend work. The minimum qualifications may include holding an Interprovincial Red Seal and a number of years experience. These qualifications are acceptable because they do not discriminate against an individual or group of people.

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However, if you excluded persons of a particular religious group because you believe that these individuals would be unwilling to work on Saturdays, your actions could be considered discriminatory. Similarly, if you excluded parents of an infant because you believe that the individual would miss work due to the difficulty in finding weekend child care, this too would be considered discrimination. Sometimes a job may have a requirement or qualification that restricts individuals or groups who may apply. When strict guidelines have been met, this requirement may be permitted by human rights legislation.

Job Advertisement Employers must clearly indicate that jobs are open to both men and women. For example, an employer cannot advertise for a draftsman, maintenance man, or foreman. The ads must read draftsperson, maintenance person or repair worker, foreman (M/F), or supervisor. The letters “M/F” indicates male/female and that the word “man” in “foreman” is not intended to restrict the job to men only. Job advertisements cannot specify “single” or “married.”

Job Applications and Interviews Employers must be careful when taking job applications or interviewing candidates to reduce the chance that a complaint of discrimination when the applicant is denied an employment opportunity. Questions about age, race, colour, ancestry, place of origin, criminal or summary conviction, education, disability, political and religious belief, sex, sexual orientation, marital/family status should be limited to: • • • • • •

whether the person is of legal age to work in BC whether the person is legally entitled to work in Canada whether the person is eligible for bonding if this is required to perform the duties of the position whether the person is willing to authorize a criminal record check if this is required for the job educational qualifications directly related to the job job-related questions about the ability to perform the essential components of the job

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• •

job-related questions regarding the availability to work during the required work times job-related questions related to job mobility, travel, working in a camp, or other conditions required of the position

Employers who ask questions relating to the prohibited grounds under the Act, which are not related directly to the genuine occupational requirements of the job, may be open to complaints of discrimination by unsuccessful candidates. If you are asked questions that you think are discriminatory in an interview, you have several alternatives. You may wish to consider whether the question was asked to be friendly or make conversation, or whether the employer has made some assumption about your fitness for the job. You may choose to answer or attempt to answer what you think the underlying question really is. For example, you could say something like, “If you are asking whether I am willing to work evenings and weekends, the answer is yes. In my past two jobs, I routinely worked a four-on, four-off shift.” Another alternative is to ask for clarification: “I don’t understand how this question relates to the job. Could you rephrase it?” The key to maintaining your integrity while not costing yourself the job is to be calm and assertive in your responses.

Wage Discrimination The Human Rights Act requires that employees who perform work of a similar or substantially similar nature are paid the same rate. In deciding what is similar work, three factors are taken into account: skill, effort, and responsibility. Skill involves such factors as experience, education, training, and demonstrated ability. Effort includes both physical and mental energy. Responsibility includes the importance of the job, supervisory duties, and freedom to make individual decisions. Pay differences based on valid factors other than sex, race, and other prohibited grounds of discrimination are acceptable. Such factors include seniority systems, merit systems, and systems that measure earnings by quantity or quality of production. The Act also provides that no trade union, employer’s association, or occupational association can prevent any person from attaining full membership or can expel, suspend, or otherwise discriminate against any of its members because of race, sex, religion, colour, age, marital status, ancestry, place of origin, political belief, or criminal conviction unrelated to the job. Nor can any agreement be negotiated that would discriminate against any person contrary to the Human Rights Act.

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Everyone has the right to work in an environment which is free of discrimination and which is conducive to job performance. Workplaces in which workers are subjected to harassment are unhappy places resulting in individuals not performing to the best of their abilities. Harassment creates a “poisoned” atmosphere that does not contribute to cooperation and productivity. The people targeted for harassment may become ill and over-stressed. They may leave the department or workplace in order to escape the harassment. Coworkers may have reduced morale as a result of the lack of respect for others they witness. Ultimately, the effects of a less productive and cooperative workplace are felt by the customers of the establishment.

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Harassment Harassment is any physical or verbal conduct by a co-worker, supervisor, or customer that is discriminatory in nature and that offends or humiliates you. Although people often think only of sexual harassment, harassment includes any differential treatment of people on the basis of their gender, race, ethnic background, class, religion, sexual orientation, age, or disability. Harassment is a type of discrimination. It can take many forms, including: • • • • • • • • • • • •

threats, intimidation, or verbal abuse unwelcome remarks or jokes about subjects such as your race, religion, disability, or age displaying sexist, racist, or other offensive pictures and posters disparaging names or comments badgering and constant teasing offensive remarks unwanted touching making someone the constant target of practical jokes sexually suggestive remarks or gestures stereotyping on the basis of the group to which a person belongs unfair sharing of responsibilities physical assault, including sexual assault

Harassment can consist of a single incident or several incidents over a period of time. It is considered to have taken place if a reasonable person ought to have known that the behaviour was unwelcome. Racist and sexist jokes are sometimes perceived as just having fun. However, even if the person about whom you are joking laughs, it does not mean that he or she enjoys the experience. Jokes of this type can be intimidating and make people ill at ease. They may make people less willing to talk to you because they expect that you will turn their communication with you into more intimidating jokes. Racist and sexist jokes exclude people from your group. They show a lack of respect. They are also harassment. Constant use of racist or sexist expressions

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is also harassment. Comments such as “male chauvinist pig” or “Women should be kept barefoot, pregnant, and at home” are unacceptable and may be considered harassment.

Sexual Harassment Sexual harassment is harassment involving unwelcome conduct of a sexual nature. It can include a promise for reward in exchange for sexual favours or it might involve threats, either stated or unstated, that unfavourable consequences will result from not going along with the harassment. These consequences might include being demoted, losing a bonus, not getting the shifts you want, or being denied a promotion. Sexual harassment can also occur without promise of reward or threats. The harassment might make the workplace an intimidating, hostile, or offensive place where an employee cannot work comfortably. You do not need to intend to harass a person for harassment to take place. “It was just a joke” or “I just meant it as a compliment” are not excuses under the law.

Employer’s Obligations Employers are responsible for any harassment by supervisors, co-workers, or customers that occurs in the workplace. It is the employer’s responsibility to:

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•

make it clear that harassment will not be tolerated

•

establish a harassment policy

•

make sure that every employee understands the policy and the procedures for dealing with harassment

•

inform supervisors and managers of their responsibility to provide a harassment-free work environment

•

investigate and correct harassment problems as soon as they come to light, even if a formal complaint has not been received

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Company Policies on Harassment When a company has a strong policy on harassment and when it ensures that all employees know about the policy, employees get the message that the company means what it says. They also know exactly what to do if they are being harassed. A typical harassment policy contains: •

a strong statement that the company will not tolerate harassment

•

a definition of harassment

•

management responsibility

•

procedures for reporting harassment

•

an explanation of the mediation and investigation procedures and the rights of all parties

•

a discussion of the sanctions (discipline) which may be applied

•

time limits for complaints

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Samples of policies on harassment which companies can use as models are available from the Human Rights Council.

Checking Your Own Behaviour In most workplaces, discrimination and harassment are serious offences. They can cost you your reputation or even your job. To ensure that you treat your fellow employees fairly and equitably, you should: •

Monitor your own behaviour to check whether you are being fair or whether you are singling others out for different treatment.

•

Check for signs of nervousness or discomfort on the part of co-workers, especially more subtle cues such as a nervous laugh, shifting eyes, or avoidance of contact.

•

Check out your observations in a non-threatening way. (e.g., “I’ve noticed that you seem nervous around me. Am I doing something that you find uncomfortable?” said in a pleasant, non-confrontational way.)

•

Ask for honest feedback from your co-workers about your behaviour.

•

Be sensitive to the impact your authority or the environment can have on the impact of your words and actions. (e.g., Many women feel uncomfortable being alone with a man they do not know well.)

•

Never assume that you know what others think, feel, or how they will react.

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Physical or Mental Disability People with physical or mental disabilities are protected under the Human Rights Act. This protection covers those individuals whose prospects of getting a job and advancing in that job are reduced or affected because of a disability. During the hiring process, all applicants should be evaluated on the basis of their ability to carry out the essential components of the job. The employer should: • • • •

concentrate on the person’s capabilities, not disabilities assess persons as individuals, not as members of a group avoid making generalizations about disabilities consider reasonable modifications which permit people with disabilities to perform essential job tasks

Job Accommodations Modifications to the job or facility to employ persons with disabilities are called job accommodations. For example, people who are hearing impaired may require a simple light system to alert them to new orders. Often, the person with a disability can tell you exactly what job accommodations are needed. Some government funding may be available for more extensive accommodations. If an employee is already employed when he or she becomes temporarily or permanently disabled, the employer cannot fire, lay off, or demote the person because of the disability, unless the individual can no longer perform the essential components of the job. The employer is required to reasonably accommodate the disability. This responsibility is sometimes called the duty to accommodate. Accommodations may include: • • • • •

reassigning non-essential work duties flexible work schedules physical alteration of facilities training technical aids

The BC Human Rights Council would look at such factors as how much the accommodation will cost, the size of the work force, the impact of a collective agreement, and safety considerations.

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Gas Safety Branch The Safety Standards Act states the regulations in regards to everyone who installs, alters, maintains, or operates gas technologies. If you are working with any gas technology (such as natural gas, propane gas, or liquid natural gas), you must comply with the following regulations: • • •

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Safety Standards Act Safety Standards General Regulation Gas Safety Regulation

Before you are able to work on any gas system, you must first receive training and obtain a certificate of qualification.

Motor Vehicle Act The Motor Vehicle Act states all the rules, regulations, and laws that govern the operation of all motor vehicles on the roads in BC. It defines rules of the road, offences, and infractions. As a mechanic who inspects and repairs vehicles, you should be familiar with this Act.

ICBC The Insurance Corporation of British Columbia is delegated under the Motor Vehicle Act to provide direct services to people who operate vehicles in BC. Some of their services include: • • • • • •

vehicle registration and licensing driver training, testing, and licensing administrative processes maintaining driving records and applying penalty points receiving payments and applications for reviews of certain sanctions commercial vehicle safety enforcement (CVSE)

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SELF TEST 6 1. What Act sets the minimum legal standard that all employers must satisfy? a. BC Unemployment Standards Act b. BC Employment Standards Act c. Federal Employee Act d. BC Fare Standards Act 2. Unless there is a variance, what is the normal hours worked in a week before you may receive overtime pay? a. 20 hours b. 40 hours c. 60 hours d. 80 hours 3. What code guaranties that every employee is free to be a member of a trade union and to participate in its lawful activities? a. BC Labour Relations Code b. BC Code of Conduct c. BC Union Rights Code d. BC Federation Code 4. What does Workplace Hazardous Materials Information System (WHMIS) provide information about? a. colour of material b. labelling c. size of Contaminates d. storage 5. What Act requires that employees who perform work of a similar or substantially similar in nature are paid the same rate? a. Fair Wage Act b. Equal Rights Act c. Human Rights Act d. Equality Act

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SELF TEST 6

6. What Act states all the rules, regulations and laws that govern the operation of all motor vehicles on the roads in BC? a. Motor Vehicle Act b. Rules of the Road Act c. ICBC Act d. Vehicles and Road Act 7. Who is delegated to provide vehicles registration services, driver testing and CVSE? a. Motor Vehicle Centres b. Insurance Corporation of BC c. Co-ops of BC d. Motor Vehicle Insurance Centres

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Describe Positive Employee Attributes Mechanical skills are only part of what employers seek in an employee. For most employers, commitment, enthusiasm, dependability, honesty, the willingness to learn, and the ability to accept criticism are at the top of their list of expectations. Employers want people who can communicate effectively with other co-workers, work as a team, and respect others in the workplace. As a mechanic, you need to have the ability to solve problems and look into the causes instead of just the repair. With the constant changes in the Heavy Mechanical Trades, you must be open to learning new concepts and technologies. When working on equipment, you must maintain a high level of quality and professionalism. How you present yourself to employers, coworkers, and customers (both visually and verbally) affects your career as a mechanic.

Communication Maintaining good communication is important for any company. Any breakdown in communication can have far-reaching effects on your ability to do your job and on the company’s ability to reach its objectives. If directions are not fully or clearly given, you may not understand the exact procedures that must be followed or may not be aware of the specific materials that should be used. In order for work to be done correctly, you need to seek clarification if you have not understood or are unsure about certain procedures or methods. In small businesses where the owner-manager runs all aspects of the business, communication is usually informal and mainly by word of mouth. The employees are given their assignments by the owner and report back when the work is done. As companies get bigger and develop separate departments or divisions, much more information is conveyed in writing. Written communication enables employees to re-read complex information and to deal with it at their own convenience. It makes it possible for copies to be distributed to a variety of interested parties, serves as evidence of instructions given, and provides a written record for later verification. For efficiency, companies also develop procedures and policies to clarify how the information is passed. This process is called establishing channels of communication. For example, a purchase order you fill out may have to be signed by your supervisor for authorization before it can be handled by the purchasing office.

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For a company to work effectively, information must flow in all directions. It must flow from management to the worker, between co-workers, and from the workers back to management. As an employee, you have a right to expect clear directions from your supervisor on work assignments and accurate information on company policies and procedures that affect you. It is your responsibility to report on work progress and to make suggestions to your supervisor. Skill in communication is of great value in any organization and is vital in getting along with others. Knowing how to say what you want tactfully yet forcefully and asking questions in a positive way are the basis of good communication skills. Effective communication is honest and direct and should state your needs and wants in a clear and objective manner. Negative or accusatory statements set you up for potential conflicts and other forms of uncooperative behaviour on the part of your co-workers. This can impair your ability to do your job well. At times, you must deal directly with customers—it may be necessary to help them understand the problems encountered and provide alternatives. This type of communication is necessary to ensure that the customer knows that you’re performing only work that is requested and required. You must write clear and complete reports on work being performed. These reports may be used by a service manager to explain to the customer what repairs have been completed. Unclear reports can create misunderstandings that cause the customer to lose faith in the company. The success of a company relies a great deal on customer’s goodwill and word-of-mouth recommendations. The customer’s feelings and perceptions must always be taken into account.

Thinking The Heavy Mechanical Trades involve much problem solving. Any mechanic can replace a part with a new one, but a quality mechanic will be able to diagnose a problem and determine what needs to be repaired or replaced. They will also be able to find the cause of the failure and recommend procedures to prevent the failure from happening again. Many systems are computer controlled, which involve following diagnostic procedures and performing reprogramming of computers. You must be able to learn new technologies and adapt to various operating systems. If you can do this, you will be very successful.

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Desire to Continue Learning Modern equipment and vehicles have come a long way in the last 100 years. In the last 20 years, computer control systems have evolved and are now in nearly every type of equipment or vehicle. As a mechanic in this trade, you have to keep up with changes. You have to seek out new technology and stay current. Upgrading your skills makes you more valuable to your employer.

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Positive Attitude One of the most important qualities for getting along with co-workers is a positive attitude. Having a good attitude involves several things: a willingness to work diligently, pursuing definite goals, being pleasant to the public, and being courteous, respectful, and helpful to your co-workers. By maintaining a good attitude, you’re telling people that you care. Honesty and integrity are important qualities in the workplace. Employers are always looking for someone they can trust and depend upon. Employers also look for people with initiative and a drive to advance their careers. The right attitude can help you move into a supervisory or management position.

Responsibility You are responsible for the decisions you make in your life. As a mechanic, you’ll make many decisions every day—some simple, others complicated. A simple decision is the one to show up on time and begin your work right away. More complex decisions involve deciding what parts need repairing or replacement. You’re responsible for managing your time, working effectively, and completing jobs on schedule.

Adaptability One constant in the Heavy Mechanical Trades is change. Changes can be daily, such as the type of equipment you work on or the type of repair. Changes can be more gradual, such as technology, types of equipment, working conditions, or your job status. The ability to adapt to change is another attribute employers want to see in their employees.

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Team Skills Every employer is looking for a team player. A team player is person who can work with others to get a job done, or share new ideas or concepts with coworkers. Team players listen to others and respect their opinion. At times, you may be a team leader whereas other times, you’ll be a follower. In both situations, it’s important that you work with the team towards your objective.

Care for Quality As a mechanic in the Heavy Mechanical Trades, the quality of your work must be one of your highest priorities. The vehicles and equipment you will work on can cost in the hundreds of thousands, or even millions, of dollars. If you do a poor job, it can be costly to your company to correct the mistakes, it can cost the equipment owner lost revenue, it may even cost someone their life. Make sure that whatever job you do, no matter how small or large, it’s done to the best of your ability.

Personal Care Appearance can affect your acceptance in any organization. Remember that you have only one chance to make a first impression. Give thought to your clothes and grooming before starting a new job. After you’re hired, remember that you’re representing not only yourself, but the company you work for. What you wear and how you handle yourself can affect how you’re perceived by others. Wearing clean coveralls, safety attire, and keeping clean are good habits to have. Make sure that you’re prepared to work your full shift, even when that’s a 12hour day. Being well-rested and leaving any “baggage” at home makes sure your head is clear and focused on the job at hand. Drug or alcohol abuse cannot be tolerated on the job site—any substance abuse can result in serious personal or equipment damage. Many large work sites have random testing to ensure everyone is “clean.” If drugs or alcohol are found in your system, you are usually fired on the spot and escorted off the property.

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Following Safety Regulations Following workplace safety regulations is your responsibility. You do not want to be responsible for an injury to yourself or a co-worker. After being hired, you’ll undergo safety training. Your employer will explain the safety regulations you must follow. Safety is everyone’s responsibility so if you see something unsafe, you must correct the situation. WorkSafeBC has province-wide safety standards and your employer may have their own additional procedures.

NOTES

The following chart clarifies some attributes: Acceptable Attributes

Unacceptable Attributes

Workers who are committed:

Workers who lack commitment:

• try to make the company look good

• criticize their organization to outsiders

• work hard for the organization • do their best • dress appropriately

• are mostly concerned about what the organization can do for them

Workers who are enthusiastic:

Workers who are unenthusiastic:

• are interested in their work

• do only enough to get by

• share their ideas

• do not care about the quality of the work

• are cheerful • give others help

• may be uncooperative

Workers who are dependable:

Workers who are not dependable:

• arrive at work on time

• arrive at work late

• finish assigned work on schedule

• do not finish assigned work

• call when they miss work due to illness

• miss work without notifying employer

• fulfill commitments

• make excuses to not follow through on commitments

• use sick days only for legitimate illness or injury

• are complainers

• are often absent from work

Workers who are honest:

Workers who are dishonest:

• admit their mistakes

• take tools or materials for their own use

• express their opinions

• try to get away with as much as they can

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Acceptable Attributes

Unacceptable Attributes

Workers who are willing to learn:

Workers who are unwilling to learn:

• listen carefully to instructions

• ignore instructions

• ask questions when they do not understand

• dislike taking advice

• try new things • learn from their own mistakes Workers who are willing to accept criticism: • are open to suggestions made by others

Workers who are unwilling to accept criticism: • get angry or sulk when criticized

• use constructive criticism to improve the quality of work

• are not receptive to learning new things

• learn from suggestions

• reject suggestions • tend to repeat their mistakes

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SELF TEST 7

SELF TEST 7 1. What are some key attributes a mechanic must have to be successful in this trade? a. steady hands, nerves of steel, and a strong back b. likes to get dirty, small in stature, and a high tolerance to pain c. dependability, willingness to learn, and good communication skills d. loud talker, flexible, and willingness to do whatever it takes to complete the job 2. Who sets the province wide safety standards? a. BC Working Safely b. ICBC c. Safety BC d. WorkSafeBC

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Describe Employer Responsibility Your employer has certain responsibilities when it comes to dealing with employees. They must treat their employees with respect, and trust they’re going to perform their duties as instructed. The employer is responsible for maintaining a healthy and safe work environment. Some of the responsibilities are: •

establish and maintain a joint health and safety committee, or instruct workers to select at least one health and safety representative

•

take every reasonable precaution to ensure the workplace is safe

•

train employees about potential hazards; how to safely use, handle, store, and dispose of hazardous substances; and how to handle emergencies

•

supply personal protective equipment and ensure workers know how to use it safely and correctly

•

immediately report all critical injuries to the government department responsible for Occupational Health & Safety

•

appoint a competent supervisor who sets the standards for performance, and who ensures safe working conditions

The employer is responsible for payment of wages and benefits to the employee. The employer has to keep track of all the hours an employee works and pay any overtime. The employer is also responsible for deducting income tax, Canada Pension Plan, Employment Insurance, and union or professional dues. They also pay for uniforms (coveralls), cleaning, and maintenance. The employer has to follow the applicable legislation concerning workplace issues. They may have to follow the BC Labour Relations Code or The Employment Standards Act depending on whether it is a union or non-union company. There is no Self Test for this learning task.

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LEARNING TASK 9

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Prepare a Resume An effective resume is critical to acquiring a job. There are different types of resumes depending on your work history and the type of job for which you’re applying. The resume you create for your first job will be different than the resume you create when looking for a change of jobs. However, in both cases, you’re trying to highlight your skills and abilities to the prospective employer. You’re also demonstrating your potential to become the employee the employer is looking for. Generally, a resume should be about two pages long, highlighting your skills, experience, and education.

Gathering Information Before writing a resume, you must first consider all the types of information you’ll need to include: • • • • •

personal information education skills work experience references

Personal Information Include personal information such as your full name, permanent address, and telephone number (home and cell). You want to make it easy for the employer to contact you in case of further questions or a job offer.

Education Your resume should provide details of your education including certificates such as foundation training or Red Seals. List any diplomas or degrees you have achieved. If you’ve attended more than one training provider, list them starting with the most recent. Include the training provider’s address, the dates you attended, and the certificate, diploma, or degree you received. Note any certificates from specialized training such as forklift, WHMIS, air endorsement, or original equipment manufacturer’s training.

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Skills List any relevant skills or abilities you’ve developed over the years. See below for a list of skills that may be added to your resume. Technical or Specialized: • critical thinking • evaluate situations • solve math problems • interpret results of diagnosis • computer skills • quick learner • committed to lifelong learning Communication: • speak and write the language of the industry • listen to learn • listen to understand • understand schematics and diagrams • contribute to the team • work with a team • respect the opinion of others • be a leader Personal Management Skills: • positive attitude • self-confidence • accept responsibility • learn from others • set goals and priorities • self-motivated • suggest new ideas It’s best if you can demonstrate your particular skills with an example, e.g., rather than stating “I can work with a team,” describe how “I worked with a volunteer organization to build a race car.”

Work Experience Your resume should list your work history. Your list may be short if you’re just starting out, or it could be quite long if you’ve changed jobs often. Start with your most recent employer. Include the company name, address, your title, and your starting and ending dates. You may want to list any accomplishments made or work performed while at that company.

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References Your resume should include a list of references—people who will vouch for your character, abilities, and past work experience. Common references include coworkers, past employers, and educators. Before listing anyone, make sure they have agreed to be a reference. You should contact them beforehand and inform them of the type of job you’re applying for. Most employers will contact your references and so it’s a good idea to let them know to expect a call. You should supply the following information about your references: • • • • •

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NOTES

name job title employer address telephone number

It’s best to include at least three references.

Organization of the Resume Your resume should showcase your most important qualifications first. This will help maintain the interest of the person reading it. Remember that you will not be the only person applying for a job. Depending on the number of applicants, your resume has a very short time to make an impression. Your personal information such as name and contact information is always presented first. You then have options as to how you order your education, skills, and work experience sections. This will depend on your strengths, and what the employer is looking for. •

If your education is recent and you’ve received specific training for the job you are applying for, place your education section first.

•

If your work experience is more relevant to the job, place your work experience section first.

•

If you have extensive activities related to the job, then place your skills section first.

Putting the most relevant section first will help the employer realize that you’re a good candidate for the job. Your three references make up the final section. Remember to contact them to ask permission to use them as a reference.

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Consider the following tips when writing your resume: •

Make sure it’s easy to read and organized.

•

The standard length for a resume is two pages, with references listed on a third. A single-page resume will not contain enough information.

•

Use point form to list responsibilities and accomplishments.

•

Edit the resume for spelling and punctuation. (It’s recommended that you have someone else proofread your resume.)

•

Use white standard size paper (8½ x 11 in.).

Types of Resume There are two basic resume formats: • •

chronological functional

A chronological resume highlights your work history by date, and a functional resume highlights your skills.

Chronological A chronological resume lists education and work experience entries in order from latest to earliest. Most students who are seeking their first job use this type of resume. For the work experience section, make an entry for each job you’ve had. List each job title explaining your duties and responsibilities, the skills you learned, and what you achieved. In the education section, list your most recent schooling first. On the next page is a sample of a chronological resume:

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  John  Smith   1234  Main  St.   (604)  555-­‐1234  (home)   (604)  555-­‐9989  (cell)  

NOTES

 

Education   2011  –  present                

BC  Training  Institute   Vancouver  BC   Intermediate  Metal-­‐working  

 

2009  –  2011          

     

Cameron  College   Kamloops  BC   Introductory  Mechanical  Training  

     

Kitsilano  High  School   Majored  in  Mechanics   Graduated  with  honors  

 

2006  –  2009            

Work  Experience   2010  –  present                

A1  Garage   459  Elm  St.,  Vancouver  BC   Junior  Mechanic  

 

2008  –  2010          

     

Family  Food  Mart   890  Johnson  Ave,  Kamloops  BC   Stockboy,  cashier  

 

Awards  and  Recognition   • Top  mechanic  student  bursary  $500   • Top  vocational  trades  student  2009    

Interests  and  Activities   • Riding  quads   • Hiking   • •

Camping   Rebuilding  old  cars    

References   Mr.  Fred  Jones   A1  Garage   (604)  555-­‐6282    

Mr.  Gerry  Smith   Kitsilano  High  School   (604)  555-­‐7452    

Ms.  Janet  Gilmour   Family  Food  Mart   [email protected]  

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Functional A functional resume focuses on what skills you’ve developed rather than what jobs you’ve had. It does not matter whether you acquired these skills at a volunteer position or at a paid job. If you have limited job experience, or have had several jobs in a short period of time, a functional resume is recommended. Job titles, dates, and employers may be left out. Instead, you’ll list a summary of your abilities: • • • •

skills accomplishments experience areas of competence

Combination The combination resume combines the chronological and the functional resumes. You highlight your skills, but you also add the employers and dates. List the skills you’ve gained from work experience and then list your work history from latest to earliest. This format includes the best of both types of resumes. On the next page is a sample of a functional resume:

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  JOHN  SMITH   1234  MAIN  ST.   (604)  555-­‐1234  (home)   (604)  555-­‐9989  (cell)  

NOTES

 

JOB  TARGET:    

Automotive  Partsperson  Apprentice  

 

EXPERIENCE:   Customer  service  

Greeted  and  served  customers   Handled  cash  and  credit  sales   Resolved  customer  complaints  and  handled            returns  

 

Inventory  Control  

Maintained  inventory  control  procedures   Analyzed  sales  history  information  to  project  sales          volumes   Ordered  goods  to  replenish  stock   Used  a  computerized  inventory  management          system  to  maintain  stock  levels  and  reduce  waste.  

 

Warehousing    

Received  goods     Filled  customer  orders   Prepared  goods  for  shipping   Operated  forklift  truck  and  pallet  jacks  

 

WORK  HISTORY:   2010  -­‐  2012  

Sales  Clerk   Sardis  Hardware   357  Main  Street   Sardis,  BC  

 

2007  -­‐  2010  

Warehouseman   Stevens’  Manufacturing   Box  373   Prince  George,  BC  

 

EDUCATION:   2005     2000  

Partsperson  Entry  Level  Trades  Training   University  College  of  the  Fraser  Valley   Graduated  from  Grade  12,  Sardis  Secondary  School  

 

REFERENCES:   Mr.  Bob  Johnston   Sardis  Hardware   (250)  555-­‐5351    

Mr.  Frank  Miller   Prince  George  Secondary   (250)  555-­‐7826    

Mrs.  Margaret  Peterson   (250)  555-­‐1900  

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SELF TEST 9 1. What should be in your resume? a. education, skills, and experience b. age, sexual orientation, and education c. height, weight, and religion d. references, medical history, and wage required 2. How many references should be included in your resume? a. 1 b. 3 c. 5 d. 7 3. What are the two main types of resumes? a. paradigm and logical b. anthology and prodigy c. chronological and functional d. reasonable and extreme

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LEARNING TASK 10

LEARNING TASK 10

NOTES

Prepare a Cover Letter The purpose of a cover letter is to introduce yourself and your resume to a potential employer. It’s intended to show that you have the skills and abilities necessary for the job. It also demonstrates your ability to communicate effectively. The cover letter gives you an opportunity to sell yourself and encourage the prospective employer to invite you for an interview. A solicited letter is in response to an advertisement for a job posting. You should focus on the skills listed in the advertisement. An unsolicited letter is given to a company even though they may not be looking to hire at that time. It may be given to a company you want to work for in the future. An unsolicited cover letter should tell the company what you can do for them and why you’re qualified to work for them.

Composition Composition is a key to a successful cover letter. The letter should be no more than one page. The first paragraph will be an opening introduction. The middle paragraphs should cover your knowledge of the company, your training, and your work experience. Finally, you have a closing paragraph.

Opening Paragraph The opening paragraph should concern the advertisement you’re responding to, or the job you’re seeking. You should briefly describe your qualifications for the job. If you’re writing a solicited letter, you should mention the competition number in this paragraph, or where you saw the advertisement. If you’re writing an unsolicited letter, you should mention how you became aware of the company, and why you want to work there.

Middle Paragraphs The middle paragraphs show you’re interested in their company and to give them a reason to invite you for an interview. You need to demonstrate that you have skills and abilities that would be a benefit to them. Briefly list your relevant training, education, and experience. These paragraphs should answer the two questions a prospective employer will be thinking: • •

Why do you wish to work for us? Why should I hire you?

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To answer these questions, you need to do some homework on the company. You also need to highlight your skills and training relevant to the job. Although a lot of the information is the same, you do not want to include everything on your resume in a cover letter. Rather, you want your cover letter to be an invitation for the employer to read your resume.

Closing Paragraph The closing paragraph is your opportunity to request an interview and leave contact information. You want to be clear you’re hoping for an interview. You may suggest a follow-up phone call or visit to the company. Finally, mention that you’re including your resume. Tips for writing an effective cover letter: • • • • •

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address the letter to an individual, position, or department use a word processor, unless the employer has asked for a hand-written letter use positive statements about your education and experience avoid using the word “I” too often—instead mix in “my” tailor each cover letter to the company and job you are applying for

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SELF TEST 10

SELF TEST 10 1. What is a solicited cover letter? a. the employer has requested the letter b. response to an advertisement for a job posting c. requesting a job position d. requesting a job interview

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NOTES

Identify Job Search Sources There are many sources you can use to find a job: • • • • • • •

newspapers internet networking industry publications job fairs direct approach head hunters

Newspapers At one time, newspaper classified ads were the main source of job leads. However, as internet use has increased, the importance of want ads has declined. Want ads can still be helpful for some types of job-seekers, particularly those seeking entry-level positions. It’s worth noting that career experts do not place great value on want ads since these positions are often filled by the time the ads are published. You can check your local newspaper or newspapers from larger cities.

Internet Recent trends in job-hunting have been to use the Internet to search for openings and post resumes. There are hundreds of thousands of jobs listed on thousands of job websites. Search for either a particular job description, or for the company for which you want to work. A benefit of these sites is that many also include company profiles and other important information you can use to gain an understanding of each employer. Many job-seekers have received interviews from these postings. Tips for online job-searching: •

On the search line, enter combinations of words to refine your search. Try “employment advertisements,” “job listings,” “careers,” “Canada,” “British Columbia.” Use different combinations of the words and different search engines. Bookmark pages that you find useful.

•

Once you have found a useful site, check out any links.

•

Check how frequently the website is updated. Websites that are updated daily or weekly will be more useful than ones that are updated less frequently.

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•

Check to see whether the companies, organizations, or institutions charge fees for the services they list on their websites. For example, there may be a cost to post your resume. Read the terms of use thoroughly before using a service the website provides. Websites maintained by educational institutions and government ministries or departments do not charge for their services.

•

The Internet is used by millions of people each day. Be extremely careful about providing any personal information such as your name, address, or telephone number over the Internet.

Networking Networking provides the vast majority of job leads. The phrase “it’s not what you know, it’s who you know” still rings true. More job leads are found through networking than any other method. Networking involves using the people you know: your family, friends, neighbours, colleagues, customers, vendors, and associates. The more people in your network, the greater number of job prospects you have. Even when you’re not currently searching for a job, you should be working on growing and strengthening your network.

Industry Publications Every field has at least one professional organization that publishes magazines. Truck and heavy duty machinery magazines are two types of publications where employers may post their advertisements. There may be postings in magazines that sell machines, trucks, and trailers. Many of these magazines are distributed across Canada.

Job Fairs Industries also participate in job fairs. Companies attend these fairs to meet and recruit top prospects. Your goal is to prepare beforehand and identify the key employers in attendance and then develop a strategy for breaking through the clutter of other job-seekers. Even if the employer is not in the market for someone with your mix of skills and experience, you can still get your foot in the door through this method.

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Direct Approach The direct approach has become something of a lost art, but one that can uncover a “hidden job market.” This method involves compiling a list of potential employers. This list can come from numerous sources, including business and trade periodicals, company directories, even the phone book. Once you’ve prepared a specific cover letter and resume, you’ll go to each company and talk with the manager or owner. You may not always get the opportunity to talk directly to them, but always leave your resume and then follow up a few days later. Persistence pays off, and if you’re visiting their company regularly, they will become familiar with you. If, at a later date, they’re looking for someone, they may contact you before using other methods to find an employee. If the company is out of town, mail your cover letter and resume to them.

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NOTES

Head Hunters Head hunters are intermediaries who are paid to get job-seekers and employers in contact with each other. Sometimes, companies will hire a head hunter to find suitable applicants for a job opening. You’ll find head hunters using many of the same methods you use to find a job. To be successful in your job-search, you need to develop as many job leads as possible, and to follow-up each one. Once you submit your cover letter and resume, be sure to follow-up a short time later to confirm that your material was received. Be professional in your follow-up. You may want to consider developing a “follow-up log.” This will help you keep track of each job lead, the date you followed-up, and the name of the person you spoke with.

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SELF TEST 11 1. What is networking referring to when finding a new job? a. using the internet b. using the television c. using people you know d. using the newspaper

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NOTES

Prepare for an Interview Most employers compile a short-list of candidates from the applications they receive, and then interview these people. You have to be prepared for an interview. It’s critical that you present yourself in a professional manner.

Research the Organization Preparing for an interview begins with finding out as much as possible about the company. Find out as much as you can about the position, the employer, and its needs. What do they sell? Who are their clients? Are they a fleet? What type of equipment do they use? Knowing these facts will help you demonstrate how your background meets their needs. Research the company on the Internet and at your local library. Employers are as interested in your questions as they are in your answers. It’s an advantage if you ask intelligent questions about the position, the company, and the industry.

Review of Job Qualifications You must be familiar with the job qualifications. The employer will be referring to the job posting and the type of skills or certificates required for the job. You’ll have to explain your qualifications and how they compare to the company’s requirements. It might seem simple, but if you stumble at the basics, you’ll never get to the more complicated questions. You may be asked about your work experiences and skills acquired. Don’t be afraid to admit mistakes, but turn it into a positive by explaining what you did to overcome that situation.

Prepare for Broad Personal Questions Employers use interviews to gauge whether you have the qualities to perform the job well. They’re looking for ability and aptitude, a willingness to work, a desire to achieve goals, maturity, and compatibility. Employers will also watch to see how you react when difficult questions are asked. You may be asked how you handled a particular situation in the past. (This is a good indicator to the employer as to how you will handle yourself in the future.) When answering questions, look the prospective employer in the eye. Show enthusiasm as this can enhance your chances of success. You want appear confident with yourself and your background.

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Interviews use a question and answer format. You should be prepared to answer questions such as: •

Can you tell me something about yourself?

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What are your future plans?

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Why do you want to work here?

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Can you work under pressure and deadlines?

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Why did you leave your last employer? or Why do you want to leave your present employer?

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What are your strengths?

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What are your weaknesses or limitations?

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Why should I hire you?

They may even ask questions specific to the Heavy Mechanical Trades.

Review of Resume You should bring a copy of your cover letter and resume to the interview even though they will have your original. The interviewer may ask specific questions about your resume and it’s important that you answer without needing to read it. If there are gaps in your work experience, you must be able to explain those.

Interview Practice It may seem strange to practice for an interview, but you need to give the best impression you can. Have a friend interview you and practice answering questions you think you’ll be asked. Practice your posture, explanations, and body language. Make the situation similar to what would happen in an actual interview. Place a table and chairs in a room just as it would be in an interview. Prepare questions that you’d like to ask the interviewer. If possible, video-tape your practice interview so you can see how you look and act during the process. The more prepared you are, the better your chance of success.

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A-17 EMPLOYMENT

Personal Appearance In an ideal world, you’ll be hired based solely on your skills and abilities. However, it’s human nature to judge based on appearance and so first impressions are critical to your success. Most employers form a first impression within the first seven seconds of meeting. Since very little is said during these seven seconds, early judgment is often based strictly on appearance. Studies reveal that employers consistently ask the question, “Does the individual look right for the job?” Your personal appearance may not get you a job, but it can definitely cost you a job. A positive impression at the start usually makes the rest of the interview confirm that impression. Starting with a negative first impression makes the rest of the interview that much more difficult.

LEARNING TASK 12

NOTES

Although there are no absolute rules regarding dress, you should wear clothes appropriate to the position for which you’re applying. Your selection will vary based on your occupation, location, and preference. Inappropriate wear includes a business suit when applying for a construction job, or wearing overalls when applying for an office job. The goal is to look the part, and your appearance should be consistent with your occupation. Neat, clean work clothes are appropriate for assembly, production, or warehouse positions. Sales and office positions require business clothes. A conservative suit is the recommended style for professional and managerial positions. Common sense and good taste are the best guides in selecting clothing for an interview. Avoid faddish styles and loud colours. Jewelry should be conservative and kept to a minimum. Clothing should fit comfortably. You want the employer to focus on your skills, not your clothes. Some basic guidelines to follow: •

be clean and neat, including your fingernails, teeth, hair, and face

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have empty pockets—no bulges or rattling coins/keys, etc.

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do not chew gum, eat candy, or smoke cigarettes

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carry a light briefcase or portfolio case

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remove visible body piercings (nose, eyebrow, tongue, etc.)

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wear minimal jewelry and cologne

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LEARNING TASK 12

NOTES

A-17 EMPLOYMENT

Arriving Ahead of Time Being punctual is critical during an interview. If you’re late for an interview, the employer will suspect that you’ll be late for work as well. Prior to the interview, check its location and determine how long it will take you to get there. On the day of the interview, allow extra time in case of traffic problems—arriving early is much better than arriving late. Applicants can be rejected for many reasons: •

poor personal appearance and hygiene

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an overbearing, conceited attitude

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poor communication skills

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lack of clear career goals

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lack of interest, commitment, and enthusiasm for the job

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lack of confidence and poise

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overemphasis on what the employer offers them (salary, benefits, vacation)

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lack of tact, maturity, and courtesy

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poor attitude about the job, previous employers, or school

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failure to look interviewer in the eye

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a limp handshake

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inability to relate skills and experience to the job

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lack of knowledge about the company

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obvious personal problems

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lack of tolerance, strong prejudices, and narrow interests

There is no Self Test for this learning task.

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A-17 EMPLOYMENT

LEARNING TASK 13

LEARNING TASK 13

NOTES

Follow up on an Interview Before the end of the interview, you should request a follow-up phone call or email. Ask the interviewer for a business card so you have contact information. That evening, send the person a thank you email. You should also send a letter in the mail thanking them for the interview and pointing out that you’re very interested. If you haven’t heard from the interviewer after four or five days, make a follow-up phone call. State that you’re still interested in working for their company and ask if they have any further questions. If you get a voice mail, leave a message. After these initial steps, call or email once a week until they tell you that you’re hired or that the position is filled. Although some people may feel that you’re hounding them, other employers wait to see who contacts them to determine who really wants to work for them. On the next page is a sample of a follow-up letter.

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LEARNING TASK 13

NOTES

A-17 EMPLOYMENT

John  Smith   1234  Main  St.     Vancouver,  BC    V5Y  1V4     (604)  555-­‐7625     [email protected]   2012/06/25     Harold  Jones   Shop  Foreman   ABC  Construction  Ltd.   480  Commercial  Dr.     Vancouver,  BC    V7T  1G8       Dear  Mr.  Jones,   Thank  you  for  taking  the  time  out  of  your  busy  schedule  to  talk  with   me  about  the  mechanical  position  with  ABC  Construction  Ltd.  I   appreciate  your  time  and  consideration  in  interviewing  me  for  this   position.   After  speaking  with  you  and  the  group,  I  believe  that  I  would  be  a   perfect  candidate  for  this  job,  offering  the  quick  learning  and   adaptability  that  is  needed  for  an  entry  level  position.   In  addition  to  my  enthusiasm  for  performing  well,  I  would  bring  the   technical  and  analytical  skills  necessary  to  get  the  job  done.   I  am  very  interested  in  working  for  you  and  look  forward  to  hearing   from  you  once  the  final  decisions  are  made  regarding  this  position.   Please  feel  free  to  contact  me  at  any  time  if  further  information  is   needed.  My  cell  phone  number  is  (604)  555-­‐7625.   Thank  you  again  for  your  time  and  consideration.   Sincerely,    

 

John Smith  

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A-17 EMPLOYMENT

SELF TEST 13

SELF TEST 13 1. What should be done after your job interview with a prospective employer? a. buy coffee and doughnuts b. email or call back c. send flowers d. wait for a reply

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Answer Key Line A: Common Occupational Skills Competencies A-14 to A-17 Table of Contents

Competency A-14: Use Cutting and Welding Equipment . Self Test 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 8. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 12 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Competency A-15: Prepare Job Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .367 Self Test 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 Self Test 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367 Competency A-16: Describe Diagnostic Procedures . . . . Self Test 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Competency A-17: Prepare for Employment . . . . . . . . . Self Test 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 4. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 5. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 7. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 9. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Self Test 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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HEAVY MECHANICAL TRADES— FOUNDATION / LEVEL 1

365

ANSWER KEY

COMPETENCY A-14: USE CUTTING AND WELDING EQUIPMENT

Competency A-14: Use Cutting and Welding Equipment Self Test 1 1. d. to protect every person in the workplace from work-related risks 2. b. minimum legal standard Self Test 2 1. a. ability to withstand forces pulling apart 2. c. iron Self Test 3 1. b. steel, iron, or yellow brass 2. a. 103 kPa (15 psi) Self Test 4 1. d. close both the oxygen and acetylene cylinder valves 2. c. crack the cylinder valves 3. c. carburizing Self Test 5 1. b. draglines 2. c. a rounded top edge Self Test 6 3. c. weld bead 4. c. to add metal 5. b. 6 mm to 19 mm (¼" to ¾") Self Test 7 1. c. 40% copper 60% zinc 2. c. capillary action 3. b. 427°C (800°F) 4. c. 60% copper, 40% zinc Self Test 8 1. d. 40% tin and 60% lead 2. b. rosin core solder Self Test 9 1. c. the arc is struck 2. c. #10 lens 3. b. skin burns from welding radiation 4. c. 10

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HEAVY MECHANICAL TRADES— FOUNDATION / LEVEL 1

COMPETENCY A-15: PREPARE JOB ACTION

ANSWER KEY

Self Test 10 1. a. AC current only 2. c. one cycle 3. a. electrode .5 cycle negative, .5 cycle positive 4. b. 10 minutes Self Test 11 1. b. electromagnetism 2. c. 70000 psi/ all positions/ low hydrogen 3. c. composition of coating and current requirements Self Test 12 1. c. on the same material to be welded 2. a. lap joint 3. b. tap method 4. d. lap 5. b. plug Self Test 13 1. d. high deposition rates 2. a. DCEP 3. b. shielding gas Self Test 14 1. b. lead 2. b. create the kerf 3. a. compressed air

Competency A-15: Prepare Job Action Self Test 1 1. d. review the documentation 2. c. specialty lifting equipment Self Test 2 1. c. service manager is unhappy as the repair shop will need to redo the job 2. c. shop foreman 3. a. the technician 4. d. repair the proper final drive and the service manager negotiates with the company for the wrong final drive repairs

HEAVY MECHANICAL TRADES— FOUNDATION / LEVEL 1

367

ANSWER KEY

COMPETENCY A-16: DESCRIBE DIAGNOSTIC PROCEDURES

Competency A-16: Describe Diagnostic Procedures Self Test 1 1. c. because you are preventing lost time Self Test 2 1. d. know the system 2. b. confirm the complaint 1. b. they can help you when you perform the operational test Self Test 3 1. c. help meet warranty requirements Self Test 4 1. a. prevent repeat failures

Competency A-17: Prepare for Employment Self Test 1 1. d. heavy duty equipment technician 2. a. truck and transport mechanic 3. c. diesel engine mechanic Self Test 2 1. c. 14 weeks 2. a. 0 weeks Self Test 3 1. c. 5 eight-hour days per week Self Test 4 1. a. dealership 2. c. independent 3. a. fleet Self Test 5 1. a. Provincial Labour Relations Code Self Test 6 1. b. BC Employment Standards Act 2. b. 40 hours 3. a. BC Labour Relations Code 4. b. labelling 5. c. Human Rights Act 6. a. Motor Vehicle Act 7. b. Insurance Corporation of BC 368

HEAVY MECHANICAL TRADES— FOUNDATION / LEVEL 1

COMPETENCY A-17: PREPARE FOR EMPLOYMENT

ANSWER KEY

Self Test 7 1. c. dependability, willingness to learn, and good communication skills 2. d. WorkSafeBC Self Test 9 1. a. education, skills, and experience 2. b. 3 3. c. chronological and functional Self Test 10 1. b. response to an advertisement for a job posting Self Test 11 1. c. using people you know Self Test 13 1. b. email or call back

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369

Heavy Duty Mechanical Lines and Competencies Line A A-1 A-2 A-3 A-4 A-5 A-6 A-7 A-8 A-9 A-10 A-11 A-12 A-13 A-14 A-15 A-16 A-17

Common Occupational Skills Use Safe Work Practices Apply Occupational Health and Safety Use Environmental Practices Use Hand Tools, Power Tools, and Shop Equipment Use Fasteners and Fittings Lift and Support Loads Operate Equipment Use Shop Resources and Record Keeping Practices Service Winch Wire Rope Identify Lubricants Service Bearings and Seals Apply Math and Science Use Electronic Media Use Cutting and Welding Equipment Prepare Job Action Describe Diagnostic Procedures Prepare for Employment

Line B B-1 B-2 B-3 B-4

Brakes Service and Repair Hydraulic Brakes Service and Repair Hydraulic Power Brakes Service and Repair Air Brakes Diagose and Repair Advanced Brake Systems

Line C C-1 C-2 C-3

Hydraulics Describe Hydraulic Systems Service Hydraulic Components Diagnose and Repair Advanced Hydraulic Systems

Line D D-1 D-2 D-3 D-4 D-5 D-6 D-7 D-8 D-9

Electrical Describe Electricity Use Electrical Testing Instruments Service and Diagnose Batteries Service Charging Systems Diagnose and Repair Charging Systems Service Starting Systems Diagnose and Repair Starting Systems Service Electrical and Electronic Circuits Diagnose and Repair Electrical Components and Systems Diagrnose and Repair Electronic Compoments and Systems Diagrnose and Repair Vehicle Management Systems Service, Diagnose, and Repair Hybrid Systems Service, Diagnose, and Repair Electric Drive Systems

D-10 D-11 D-12 D-13 Line E E-1 E-2 E-3 E-4 E-5 E-6 E-7 E-8 E-9 E-10

Suspension and Steering Service and Diagnose Tires, Wheels, and Hubs Service Steering Systems Diagnose and Repair Truck Hydraulic Assisted Steering Systems Service, Diagnose, and Repair Machine Suspension Systems Remove and Install Undercarriage Diagnose and Repair Frames Align Vehicle Diagnose and Repair Wheeled Equipment Steering Diagnose and Repair Track Machine Steering Diagnose and Repair Undercarriage

Line F F-1 F-2 F-3 F-4

Trailer Service Landing Gear and Trailer Accessories Service and Repair Coupling Systems Service, Diagnose, and Repair Trailer Body Components Service, Diagnose, and Repair Trailer Heating and Refrigeration Systems

Line G Heating, Ventilation and Air G-1 Describe Heating and Air Conditioning Fundamentals G-2 Diagnose and Repair Heating and Air Conditioning Systems Line H H-1 H-2 H-3 H-4 H-5 H-6 H-7 H-8 H-9 H-10 H-11 H-12 H-13 H-14 H-15 H-16

Line I I-1 I-2 I-3 I-4 I-5 I-6 I-7 I-8 I-9 I-10 I-11 I-12 I-13 I-14 I-15 I-16 I-17 I-18 I-19 I-20 I-21 I-22 Line J J-1 J-2 J-3 J-4 J-5

Engines and Supporting Systems Describe Engine Fundamentals Service Engine Support Systems Diagnose and Repair Engine Support Systems Service Diesel Fuel Supply Systems Diagnose and Repair Diesel Supply Systems Service Gasoline Fuel Systems Describe Alternative Fuel Systems Diagnose Engines and Components Remove and Install Diesel Engines Repair Engines and Components Describe Diesel Fuel Injection Fundamentals Diagnose and Repair Mechanical Fuel Injection Systems Diagnose and Repair Electronic Diesel Fuel Systems Diagnose and Repair Diesel Emission Systems Diagnose and Repair Engine Brakes Service, Diagnose, and Repair Electronic Ignition Systems Powertrain Describe Power Transfer Systems Service Clutches Diagnose and Repair Clutches Service Manual Transmissions Diagnose and Repair Manual Transmissions Diagnose and Repair Automated Transmissions Service Torque Converters and Dividers Service Powershift and Automatic Transmission Diagnose and Repair Automatic Transmissions and Torque Converters Diagnose and Repair Powershift Transmissions Service Drivelines Diagnose and Repair Drivelines Service Drive Axles Diagnose and Repair Drive Axles Service Final Drives Diagnose and Repair Final Drives Diagnose and Repair Driveline Retarders Diagnose and Repair Winches Diagnose and Repair Power Takeoffs and Transfer Cases Remove and Install Transmissions Remove and Install Driveline and Differentials Remove and Install Final Drives Structural Components and Accessories Indentify Protective Structures Service Cab Structures Repair Advanced Cab and Body Structures Diagnose and Repair Working Attachments Diagnose and Repair Pnuematic System