design of ASME B31.3 metalic piping systems

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COMPLETE REVISION January 2009

Process Industry Practices Piping

PIP PNC00005 Design of ASME B31.3 Metallic Piping Systems

PURPOSE AND USE OF PROCESS INDUSTRY PRACTICES In an effort to minimize the cost of process industry facilities, this Practice has been prepared from the technical requirements in the existing standards of major industrial users, contractors, or standards organizations. By harmonizing these technical requirements into a single set of Practices, administrative, application, and engineering costs to both the purchaser and the manufacturer should be reduced. While this Practice is expected to incorporate the majority of requirements of most users, individual applications may involve requirements that will be appended to and take precedence over this Practice. Determinations concerning fitness for purpose and particular matters or application of the Practice to particular project or engineering situations should not be made solely on information contained in these materials. The use of trade names from time to time should not be viewed as an expression of preference but rather recognized as normal usage in the trade. Other brands having the same specifications are equally correct and may be substituted for those named. All Practices or guidelines are intended to be consistent with applicable laws and regulations including OSHA requirements. To the extent these Practices or guidelines should conflict with OSHA or other applicable laws or regulations, such laws or regulations must be followed. Consult an appropriate professional before applying or acting on any material contained in or suggested by the Practice.

This Practice is subject to revision at any time.

© Process Industry Practices (PIP), Construction Industry Institute, The University of Texas at Austin, 3925 West Braker Lane (R4500), Austin, Texas 78759. PIP member companies and subscribers may copy this Practice for their internal use. Changes, overlays, addenda, or modifications of any kind are not permitted within any PIP Practice without the express written authorization of PIP.

PRINTING HISTORY November 1996 Issued February 2002 Complete Revision

Not printed with State funds

January 2009 Complete Revision & Renumbering

COMPLETE REVISION January 2009

Process Industry Practices Piping

PIP PNC00005 Design of ASME B31.3 Metallic Piping Systems Table of Contents 1. Introduction................................. 2 1.1 Purpose............................................ 2 1.2 Scope ............................................... 2

2. References .................................. 2 2.1 Process Industry Practices .............. 2 2.2 Industry Codes and Standards ........ 2 2.3 Government Regulations ................. 3

3. Requirements.............................. 3 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9

General ............................................ 3 Design Conditions............................ 4 Design Practices .............................. 5 Hot Tapping ................................... 12 Piping Components........................ 12 Piping Flexibility ............................. 17 Piping Support ............................... 17 Specific Piping Systems................. 17 Fabrication, Assembly, and Erection .......................................... 22

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PIP PNC00005 Design of ASME B31.3 Metallic Piping Systems

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COMPLETE REVISION January 2009

Introduction 1.1

Purpose This Practice provides requirements for designing metallic piping systems to ASME B31.3, Process Piping (hereinafter referred to as the Code).

1.2

Scope This Practice provides requirements for piping systems arrangement, design conditions, components, and joints. This Practice shall be used in conjunction with the Code. The requirements of this Practice are more stringent than the Code for the purpose of standardization and not because the Code is considered unsafe. Piping systems designed in accordance with other piping codes are not included in this Practice.

2.

References Applicable parts of the following Practices, industry codes and standards, and references shall be considered an integral part of this Practice. The edition in effect on the date of contract award shall be used, except as otherwise noted. Short titles will be used herein where appropriate. 2.1

Process Industry Practices (PIP) – PIP PCCIA001 – Design of Instrument Air Systems – PIP PNC00001 – Pipe Support Criteria for ASME B31.3 Metallic Piping – PIP PNE00003 – Process Unit and Offsites Layout Guide – PIP PNC00004 – Piping Flexibility Analysis Criteria for ASME B31.3 Metallic Piping – PIP PNE00012 – Piping Examination and Leak Test Guide – PIP PNSC0001 – ASME B31.3 Metallic Piping Fabrication and Examination Specification – PIP PNSC0011 –Installation of ASME B31.3 Metallic Piping – PIP PNSC0021 –Leak Testing of Piping Systems – PIP PNSC0035 – Steam Tracing Specification – PIP REIE686 – Recommended Practices for Machinery Installation and Installation Design – PIP Piping Material Specifications

2.2

Industry Codes and Standards

• American Petroleum Institute (API) – API 570 – Piping Inspection Code: Inspection, Repair, Alteration, and Rerating of In-Service Piping Systems

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– API 602 – Compact Steel Valves – API 614 – Lubrication, Shaft-Sealing, and Control-Oil Systems for SpecialPurpose Applications – API 650 – Welded Steel Tanks for Oil Storage – API 2201 – Procedures for Welding or Tapping on Equipment in Service

• American Society of Mechanical Engineers (ASME) – ASME Boiler and Pressure Vessel Code Section VIII – Pressure Vessels, Division 1 – ASME B16.25 – Buttwelding Ends – ASME B16.36 – Orifice Flanges

– ASME B16.47 – Larger Diameter Steel Flanges: NPS 26 through NPS 60 – ASME B16.48 – Steel Line Blanks – ASME B16.5 – Pipe Flanges and Flanged Fittings – ASME B31.3 – Process Piping (Code) – ASME B36.10M – Welded and Seamless Wrought Steel Pipe – ASME B36.19M – Stainless Steel Pipe

• Crane Technical Publication

– Crane Technical Publication 410 – Flow of Fluids

• National Electrical Manufacturers Association (NEMA) – NEMA SM-23 – Steam Turbines for Mechanical Drive Service

• Manufacturers Standardization Society (MSS)

– MSS SP-6 – Standard Finishes for Contact Faces of Pipe Flanges and Connecting-End Flanges of Valves and Fittings 2.3

Government Regulations

• U.S. Department of Labor, Occupational Safety and Health Administration (OSHA) – OSHA 29 CFR 1910.147 – Control of Hazardous Energy Sources (Lockout/Tagout)

3.

Requirements 3.1

General 3.1.1

Piping systems shall be in accordance with this Practice and with all applicable federal, state, and local laws.

3.1.2

New piping systems within the scope of this Practice shall be in accordance with the Code.

3.1.3

Alterations to existing piping systems shall be in accordance with API 570. Changes in service or in design conditions shall be considered alterations.

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3.1.4

Items that are normally fabricated from piping components (e.g., strainers and devices that serve such purposes as mixing, separating, snubbing, distributing, and metering or controlling flow), if identified by the owner as specialty piping (SP) items, shall be designed in accordance with this Practice unless otherwise specified by the owner. Piping components such as pulsation dampeners, surge bottles, condensate collection pots, and like components may be furnished as piping, as permitted by ASME Section V111, U-1.

3.1.5

Design of piping at machinery shall be in accordance with PIP REIE686 and NEMA SM-23, as applicable.

3.1.6

All piping shall be identified by the owner as Category D, Category M, high pressure, or normal fluid services as defined in the Code. “Severe cyclic conditions” in accordance with the Code shall also be identified by the owner.

Design Conditions 3.2.1

The internal and external design pressure and temperature of piping shall be determined by considering the following conditions: a. Normal operations b. Start-up operations, including any start-up procedure, operation, routing, etc. c. Shutdown operations, including shutdown procedures, operations, pumpout, etc. d. Switching operations, including any cyclic regeneration, spare pump switching, coke drum switching, etc. e. Regeneration procedures f.

Equipment bypassing

g. Turndown operations h. Pump shutoff (deadhead) pressure i.

Any control valve in a fully opened or closed position

j.

Any block valve in a fully opened or closed position, except for locked or car-sealed valves

k. Blocked exits l.

Equipment trip or shutdown

m. Upset conditions n. Maintenance, repair, or neutralization procedures o. On-stream or purging operations p. Steamout or purging operations q. Solar temperature effects r.

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Heat-tracing effects

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3.2.2

The design minimum temperature shall be determined by considering the following: a. Normal conditions b. Expected autorefrigeration effects, including emergency depressuring. Comment:

The design minimum temperature shall be the coincidental temperature where the pressure reaches 25% of the design pressure.

c. One-day-mean low temperature in accordance with API 650, Figure 4.2 3.3

Design Practices 3.3.1

Basic Layout Piping layout shall be in accordance with PIP PNE00003.

3.3.2

Piping 3.3.2.1. Underground Piping

1. Except for the following services, piping should be located above grade: a. Firewater supply systems b. Cased road and tank dike crossings c. Lines in concrete trenches d. Oil-free compressed air lines e. Lines with secondary containment and a leak-detection method f.

Other lines as designated by the owner

2. All below-grade piping, including piping in trenches, shall be protected from external corrosion. 3. Buried steel piping in hazardous materials service shall be externally coated and cathodically protected. 4. The minimum cover over buried process piping shall be 18 inches (46 cm) in paved or unpaved areas and 30 inches (76 cm) under paved roads except under a reinforced concrete slab or other protective cover approved by the owner. 5. Sewers may be covered by this Practice if specified by the owner. 3.3.2.2 Block Valve Bypasses

1. If required, a block valve bypass shall be shown on the applicable Piping & Instrument Diagrams (P&ID). 2. Bypasses shall be integral with the valve or installed in the piping immediately adjacent to the valve.

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3.3.2.3 Dead Legs

1. A dead leg is a pipe section connected to a flowing stream where the pipe section is not self-draining and is not normally flowing. 2. Piping layouts in all services shall be designed to eliminate the presence of dead legs. 3. If dead legs cannot be avoided, either corrosion resistant materials or an approved coating system shall be used for the dead leg section. 4. Live dummy legs shall not be permitted. 3.3.2.4 Vibration

1. In locations where potentially severe vibration can occur, small piping branches (i.e., NPS 2 and smaller) shall be adequately designed to minimize its effects. 2. The following examples are acceptable practices/configurations for minimizing the effects of vibration on small piping branches, depending on the severity of the vibration: a. Brace all nipples (with reinforcing pads if required). b. Where bracing cannot be effectively provided, install schedule 160 nipples with reinforcing pads. c. Use an API 602 integrally reinforced extended body (IREB) valve. d. Brace all configurations that have a nipple between the welding boss and the root valve. 3.3.2.5 Blind flanges shall be used as end closures on flanged ends and valves, unless end caps are clearly required by design necessity. 3.3.2.6 Except for standard spectacle plates and blinds, flanged connections with long exposed bolts for sandwiched components (e.g., wafer type valves) should not be used in fire hazardous areas unless the bolting is protected by a fire-resistant shield. 3.3.2.7 Jackscrews

1. Jackscrews shall be used to facilitate flange separation for maintenance. Joint assemblies that often require frequent separation include orifice plates, spectacle plates, spacers, screens, and dropout spools. 2. Piping layout shall be designed such that flanges can be separated without excessive force. 3. Jackscrews shall be accessible from both sides of the pipe. 4. For orifice flanges, jackscrews shall be installed at three- and nine-o’clock positions. 5. If flange separators are provided, jackscrews shall not be required.

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3.3.3

Isolation (Block) Valves 3.3.3.1 Block valves shall be provided at vessel and storage tank nozzles as follows: a. In piping at all nozzles below the maximum operating liquid level of storage tanks b. In a liquid draw-off line of a vessel containing 10,000 pounds (4,550 kg) or more of a flammable liquid at the maximum operating liquid level if the line does not contain a block valve located within 30 feet (9 m) in a horizontal direction from the vessel 3.3.3.2 Block valves shall be provided for piping crossing the plant limits and operating unit limits as required for the planned operation, isolation, and maintenance of the plant as directed by the owner. 3.3.3.3 If positive isolation is required or cross-contamination cannot be tolerated, one of the following shall be used: a. Blanks b. Two block valves with a bleeder valve between them c. A double-seated valve (e.g., expanding gate or plug, trunnionmounted ball, through conduit slab gate, etc.) with body bleeder d. Removable spool 3.3.3.4 Valving of operating vent, drain, and sample connections shall have one block valve as a minimum. Additional block valves shall be provided as specified by owner. Comment: Operating vent, drain, or sample connections are used regularly when the source equipment or piping is in service and/or pressurized. 3.3.3.5 Equipment that may be removed from service during unit operation shall be furnished with single block valves with provisions for blinding or blanking. 3.3.3.6 Small Piping Root Valves

1. For all process services, branches NPS 2 and smaller shall have a root valve located as close as feasible to the run. 2. The root valve shall be no farther than three times the branch diameter (except for insulated lines) measured from the far end of the boss to the near end of the valve. 3. Unions shall not be installed in the pipe section between the main pipe run and the root valve. 3.3.3.7 Flangeless valves shall not be used as the first block valve against storage tanks or vessels containing hydrocarbons or hazardous materials.

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3.3.3.8 See Crane Technical Publication 410 for information on sizing valves. 3.3.4

Control Valve Manifolds 3.3.4.1 If specified, control valves shall be installed with a valved bypass and a block valve on each side of the control valve. 3.3.4.2 As a minimum, block and bypass valves shall be provided in the control valve manifolds for the following cases: a. If loss of control function for a service could adversely affect plant operations as determined by the owner b. If shutdown of a service cannot be tolerated (e.g., fuel lines to furnaces or boilers, steam reducing stations [main headers], etc.) c. If the absence of blocks and bypass valves would inhibit start-up efforts for a service as determined by the owner 3.3.4.3 Bleed Valves

1. Bleed valves shall be provided for each control valve manifold. 2. One bleed valve shall be located between the upstream block valve and the control valve. 3. If specified by owner, an additional bleed valve on the downstream side of the control valve shall be provided. 3.3.5

Vents, Drains, and Sample Outlets 3.3.5.1 Valved vent and drain connections shall be provided on all equipment that is not self-venting or self-draining. Connections shall be located on equipment, if practical, but may be located in connecting piping if there are no blocks between the vent or drain connections and the equipment. 3.3.5.2 Vent connections shall be provided for trapped high points of piping and shall be in accordance with one of the following configurations: a. Valved if required for operational purposes or removal of process fluid b. Plugged (valve omitted) if required for hydrostatic test purposes 3.3.5.3 Drain connections shall be provided for the low points of all lines located above grade and shall be in accordance with one of the following configurations: a. Valved if required for operational purposes or removal of process fluid b. Plugged (valve omitted) if required for hydrostatic test purposes 3.3.5.4 Unless otherwise specified, vent, drain, and sample outlet connections shall be NPS 3/4 minimum. 3.3.5.5 For services of fluids with suspended solids or of high viscosity materials, all piping connections shall be NPS 1 minimum.

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3.3.5.6 Unless otherwise specified, operating vent and drain connections shall be designed to drain liquid from equipment and piping in 2 hours or less. Comment: Operating vents and drain lines are used regularly when the source equipment or piping is in service and/or pressurized. 3.3.5.7 Hydrocarbon vapors or mixtures of hydrocarbon vapors and other vapors (e.g., steam) may be discharged to the atmosphere contingent on adequate safety and environmental considerations. 3.3.5.8 All vents and drains open to the atmosphere shall be provided with plugs or blind flanges. 3.3.5.9 Cooling shall be considered for sample outlets in piping or equipment operating at 140°F (60°C) or greater. One cooler may be used for multiple sample outlets. 3.3.5.10 Unless otherwise specified, for horizontal piping, sample connections shall be located at the side of the pipe for liquids and at the top of the pipe for gases. 3.3.5.11 If practical, discharge from drains emptying into open hubs (e.g., drain cups or sumps) shall be visible from the location of the drain valve. 3.3.5.12 If releasing controlled materials, operating vents and drain lines shall discharge into a closed system as specified by owner. 3.3.6

Check Valves 3.3.6.1 Unless otherwise specified, check valves shall be provided in discharge piping of centrifugal pumps. 3.3.6.2 Check valves shall be used where utility or chemical injection lines are permanently tied into process lines or equipment. 3.3.6.3 A check valve shall not be used as a substitute for a block valve for flow isolation purposes. 3.3.6.4 Check valves in vertical piping shall be installed for upward flow only and shall be installed with a drain connection immediately above the check valve. 3.3.6.5 If a lower pressure rated system flows into a higher pressure rated system, a check valve shall be installed in the lower pressure connection and the higher pressure rating shall extend to include the check valve. 3.3.6.6 If a sudden loss of pressure in a higher pressure system could lead to undesirable contamination from a lower pressure system, a check valve shall be considered for the higher pressure system. 3.3.6.7 Except for check valves in intermittent service or check valves in skid-mounted systems, for piping NPS 3 and greater, a turbulencefree minimum distance of five pipe diameters upstream and two pipe

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diameters downstream of every check valve should be maintained. Pipefittings (e.g., elbows, reducers, tees, etc.) or flow-restricting devices (e.g., orifices, control valves, etc.) should not be installed in these zones. 3.3.6.8 See Crane Technical Publication 410 for information on sizing check valves. 3.3.7

Blanks (Blinds) 3.3.7.1 The piping layout shall provide for the insertion of line blanks for flanged equipment isolation for maintenance, inspection, testing, and alternative operation. 3.3.7.2 If piping flexibility and equipment arrangement do not permit the insertion of temporary maintenance blanks at convenient flanges, permanent line blanks shall be provided in accordance with the following: a. At piping connections at equipment that can be physically entered b. At plant limits in process, utility, and auxiliary (e.g., fuel oil, fuel gas) piping connected to other piping outside plant limits that can be in use during shutdown of the plant 3.3.7.3 Figure-8 type blinds shall not be greater than 100 pounds (45 kg) or NPS 12. Figure-8 type blinds within these limits are shown in Table 1: Table 1 – Maximum Figure-8 Blind Sizes Class

Max. Figure-8 Size (NPS)

150 and 300

12

600 and 900

8

1500 and 2500

6

3.3.7.4 Circular blanks or spacers shall be provided for blind sizes greater than the limits of Section 3.3.7.3. 3.3.7.5 Circular blanks or spacers shall be used in place of figure-8 type blinds for cold-insulated piping less than 70°F (21°C). 3.3.7.6 Commercially available blinding systems in accordance with the Code shall be permitted. 3.3.7.7 See ASME B16.48 for guidance for the use of blanks in piping systems. 3.3.8

Strainers and Filters 3.3.8.1 If strainers are not furnished as part of the equipment, strainers in the piping shall be considered for the protection of the following equipment: a. Mechanical equipment in accordance with PIP REIE686

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PIP PNC00005 Design of ASME B31.3 Metallic Piping Systems

b. Steam traps and steam jet ejectors in steam inlet lines c. Burners in main fuel oil supply piping d. Upstream of low noise design control valves 3.3.8.2 If filters are not furnished as part of the equipment, filters shall be provided in the piping for the protection of the following equipment: a. Air supply piping for pneumatically actuated equipment b. Air piping upstream of air dryers c. Open-air intakes for blowers, compressors, or engines 3.3.8.3 Providing permanent strainers with plugged connections for the installation of differential pressure measurement across the strainer shall be considered. 3.3.8.4 Installation of spacer rings may be required after temporary strainers are removed. 3.3.9

Utility Piping Connections to Process Equipment 3.3.9.1 Firewater systems shall not be connected to process equipment except by using a temporary connection when the equipment is not in operation and not under pressure. 3.3.9.2 Except for air or steam, permanent connections shall not be made to process equipment operating above 212ºF (100ºC). 3.3.9.3 Water or steam shall not be permanently connected to equipment that operates below 32ºF (0ºC). 3.3.9.4 Permanent connections without a break tank shall not be made except if the required service is continuous or frequent (at least twice per week) or is needed for emergencies. 3.3.9.5 If air is injected as a reaction agent, all of the following shall be required: a. The hydrocarbon/air mixtures shall not be permitted to enter the flammable range unless otherwise required by the process b. Instrumentation shall be provided to shut off the airflow if the process flow fails c. A restriction orifice shall be provided 3.3.9.6 For all components of permanent connections, the pressure/temperature rating shall be suitable for either the process or the utility service, whichever is more severe. 3.3.9.7 For temporary connections, the pressure/temperature rating of the process side shall extend to the hose or breakaway spool. 3.3.9.8 If the process fluid requires internal lining or material other than that used in the utility system, the lining or the material shall extend from and include the check valve on the process side.

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3.3.9.9 Valves with bodies of gray cast iron, ductile iron, or low melting point alloys (e.g., brass or bronze) shall not be used in a permanent connection including the utility side. 3.3.9.10 The material selection of the valve bodies and trim in a permanent connection shall be suitable for both the process and the utility fluid. 3.3.9.11 Operator access shall be provided to the block valves on either side and to the blind or breakaway spool of the connection. 3.3.9.12 Chain-operated valves shall not be permitted. 3.4

Hot Tapping Hot tapping shall be in accordance with API 2201 and OSHA 29 CFR 1910.147.

3.5

Piping Components 3.5.1

General 3.5.1.1 Recommended piping components are shown in the PIP Piping Material Specifications. Other piping components and constructions that are in accordance with the Code, although not mentioned in the PIP Piping Material Specifications are permitted. 3.5.1.2 Minimum pipe size shall be NPS 3/4, except for the following applications: a. Category D fluid service b. Individual instrument leads c. Pump and compressor auxiliary piping d. Steam tracing e. Reduction at instruments or other equipment provided with smaller than NPS 3/4 connections

3.5.1.3 Pipe sizes NPS 1-1/4, NPS 2-1/2, NPS 3-1/2, and NPS 5 shall not be used, except for connections to equipment requiring these sizes and in jacketed pipe systems. In such cases, the transition to standard sizes shall be made as soon as practical. 3.5.1.4 Pipe sizes and schedules shown in the PIP Piping Material Specifications are in accordance with ASME B36.10M and ASME B36.19M. 3.5.2

Pipe 3.5.2.1 Nominal wall thickness for carbon and low-alloy steel piping joined by welding in new construction shall be, as a minimum, in accordance with the following requirements: a. Utility (Category D) fluid services (1) For NPS 1/2 – 2: Not normally welded (2) For NPS 3 – 6: Standard

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(3) For NPS 8 – 32: 0.250 inch (6.4 mm) (4) For NPS 34 and greater: Diameter/135 b. Normal and Category M fluid services (1) For NPS 1/2 – 1-1/2: Extra strong (2) For NPS 2 – 6: Standard (3) For NPS 8 – 32: 0.250 inch (6.4 mm) (4) For NPS 34 and greater: Diameter/135 3.5.2.2 Nominal wall thickness for nonferrous alloy and stainless steel (> 13% Cr) piping joined by welding in new construction shall be, as a minimum, in accordance with the following requirements: a. For NPS 1/2 – 3/4: Schedule 40S b. For NPS 1 and greater: Schedule 10S 3.5.3

Joints and Fittings 3.5.3.1 Unless otherwise specified, piping joints shall be of welded construction. Flanges, unions, and threaded connections shall be used minimally, except in Category D fluid services. 3.5.3.2 Butt-welded fittings shall be used for pipe greater than NPS 1-1/2, except as required at equipment or control valve connections. 3.5.3.3 Butt-welded or socket-welded fittings shall be used for pipe sizes not covered in Section 3.5.3.2, except as follows: a. Threaded fittings may be used downstream of a welded or flanged block valve to instruments, at equipment connections, and for terminal vent and drain connections. b. Threaded fittings may be used for Category D fluid services. 3.5.3.4 Socket-welded and threaded constructions should be avoided in services if corrosion is accelerated in crevices. 3.5.3.5 For lube oil and seal oil lines, only butt-welded or flanged joints shall be used between filters and equipment in accordance with API 614. 3.5.3.6 Butt-welded piping systems shall have long radius elbows. Short radius elbows may be used only if required because of space limitations. 3.5.3.7 Flush bushings, close nipples, locknuts, street elbows, and street tees shall not be permitted.

3.5.4

Branch Connections 3.5.4.1 Unless otherwise specified, branch connections shall be at a 90-degree intersection to the run pipe centerline.

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3.5.4.2 Unless otherwise approved by the owner, a welded branch connection shall not be designed with an intersecting angle of less than 45 degrees. 3.5.4.3 NPS 2 and Less

1. If the branch is the same size as the header, a straight tee shall be used. 2. For headers NPS 2 and less, one of the following configurations shall be used if the branch size is less than the header size: a. Reducing tees b. Straight tee with butt-welding reducer c. Swage nipple 3. For headers NPS 3 and greater, branch connections shall be provided with integrally reinforced branch connection fittings. 4. Integrally reinforced extended body (IREB) valves in accordance with API 602 may be used for valved piping connections (e.g., pressure gauges, vents, and drains). 3.5.4.4 NPS 3 and Greater

1. Branch connections shall be of all welded construction (e.g., unreinforced fabricated tees, reinforced fabricated tees, reducing tees, and forged integrally reinforced welded fittings). 2. If the branch is the same size as the header, a straight tee shall be used. 3. Branch connections for piping at reciprocating equipment shall be welding tees or forged integrally reinforced weld fittings. 3.5.4.5 Weep Holes

1. Weep holes of 1/4-inch (6-mm) diameter shall be provided in reinforcing pads for branch connections, in wear pads, and in support reinforcing pads if the pads cover welds that are not pipe manufacturing seam welds. 2. Weep holes shall also be provided to vent gases on piping that requires heat treatment after fabrication, or in special cases where hydrogen buildup could occur. 3. Weep holes shall be packed with heavy grease. 3.5.4.6 Branch tables in the PIP Piping Material Specifications provide reinforcing pads designed for full area replacement. 3.5.4.7 Branch tables in the PIP Piping Material Specifications are minimum requirements. Other equal or better configurations may be selected to suit a particular project need.

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3.5.5

Valves 3.5.5.1 General

1. Ball, butterfly, and plug valves shall have gear operators in accordance with the PIP Piping Material Specifications. 2. Block valves and bypass valves at control valve manifolds, equipment, and pressure-reducing stations shall be of the higher pressure rating. 3. For soft-seated valves, pressure-temperature ratings for the same class valve may vary between manufacturers and may be lower than the ratings shown in PIP Piping Material Specifications. 4. Screwed bonnet and screwed body valves shall not be used in any hydrocarbon or hazardous material services unless the bonnets/bodies are seal-welded. 5. Union bonnet valves shall not be used in any hydrocarbon or hazardous material services. 3.5.5.2 Gate Valves

Gear operators are recommended for wedge gate valves for the pressure ratings and sizes shown in Table 2. Table 2 – Gear Operator Applications for Gate Valves Pressure Class

Gate Valves Sizes (NPS)

150

14 and greater

300

12 and greater

600 and 900

8 and greater

1500 and greater

6 and greater

3.5.5.3 Check Valves

1. Dual- and single-plate wafer check and swing check valves shall not be used in reciprocating pump and compressor suction and discharge services or similar pulsating services. 2. In parallel pump or compressor systems, check valves installed at the discharge of pumps or compressors should be of a nonslam internal-spring-assisted type. Swing check valves should not be used in this service. 3. For parallel pump systems with individual pump discharge piping of NPS 20 and greater, a hydraulic analysis shall be conducted to verify that the selected check valves have the correct dynamic response to prevent slamming and limit pressure surge to an acceptable level. The analysis shall include consideration of the “worst case” operating mode scenario.

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3.5.5.4 Globe Valves

Gear operators are recommended for globe valves for the pressure ratings and sizes shown in Table 3: Table 3 – Gear Operator Applications for Globe Valves

3.5.6

Pressure Class

Globe Valves Sizes (NPS)

150

14 and greater

300

10 and greater

600

8 and greater

900

6 and greater

1500

4 and greater

2500

3 and greater

Flanges 3.5.6.1 Flanges NPS 24 and less shall be in accordance with ASME B16.5 for the listed materials. 3.5.6.2 Unless otherwise specified, steel flanges larger than NPS 24 shall be in accordance with ASME B16.47, Series B. 3.5.6.3 The use of flanges in piping shall be minimized. Flanges shall be typically used in the following applications: a. At flanged equipment b. At valves c. At blanks d. In removable sections of pipe e. Where frequent dismantling of piping is required f.

Where piping lined with nonmetals or nonmetallic piping cannot be bonded or otherwise joined

g. To provide for erection requirements h. To allow for modifications in areas where welding is not permitted i.

To provide clearance for dismantling of equipment (e.g., compressors, reactor heads, etc.)

j.

For maintenance cleaning, decoking, or slurry service

3.5.6.4 Slip-on flanges may be used in piping NPS 24 maximum for Classes 300 and less at design temperatures 800°F (430°C) or less. 3.5.6.5 Lap joint flanges may be used in piping for Classes 300 and less at design temperatures 500ºF (260ºC) and less. 3.5.6.6 Except for proprietary flanges, flange facing shall normally be raised-face for Classes 150 through 2500.

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PIP PNC00005 Design of ASME B31.3 Metallic Piping Systems

January 2009

3.5.6.7 Flat-faced flanges with full-faced gaskets shall be used for connecting piping to flat-faced flanged valves and equipment manufactured from nonductile materials. 3.5.6.8 Flange facing finish for cast iron, ductile iron, and bronze shall be in accordance with MSS SP-6. 3.5.6.9 Flange facing finish for steel, nickel alloy, and other alloys shall be in accordance with ASME B16.5. 3.5.6.10 Orifice flanges shall be in accordance with ASME B16.36. 3.5.6.11 Blind flanges shall not be drilled for connections (e.g., drain, vent) unless a stress calculation in accordance with ASME Boiler and Pressure Vessel Code, Section VIII, Appendix 2, shows that the flanges shall not be overstressed. 3.5.6.12 For pipe of minimum wall thickness, the bore of welding neck flanges shall not be greater than the inside diameter of the attached pipe, and shall be in accordance with ASME B16.25 tolerances. 3.5.6.13 Except as stated in Section 3.5.6.14, the design thickness of the flange hub at the welding end of flanges with a specified minimum yield strength (SMYS) less than that of the attached pipe shall be at a minimum equal to the pipe wall thickness multiplied by the pipeto-flange ratio of the SMYS if the SMYS ratio is from 1.0 to 1.5. See ASME B16.5, Figure 14. 3.5.6.14 The bore of welding neck flanges of the lower SMYS may be equal to the inside diameter of the attached pipe of the higher SMYS, if calculations in accordance with ASME Boiler and Pressure Vessel Code, Section VIII, Appendix 2, show that the flanged joint shall not be overstressed. 3.5.7

Gaskets Gasket selection shall be in accordance with the individual PIP Piping Material Specification.

3.5.8

Bolting Bolting selection shall be in accordance with the individual PIP Piping Material Specification.

3.6

Piping Flexibility Piping flexibility analyses shall be in accordance with PIP PNC00004.

3.7

Piping Support Piping supports shall be in accordance with PIP PNC00001.

3.8

Specific Piping Systems 3.8.1

Instrument Air 3.8.1.1 Instrument air systems shall be in accordance with PIP PCCIA001.

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3.8.1.2 Instrument air branch lines shall be taken from the top of the header. 3.8.1.3 Block valves shall be provided for branch connections less than NPS 2 and shall be located at the header. 3.8.1.4 The main instrument air header size should be NPS 1-1/2, as a minimum. 3.8.1.5 The instrument air supply to an individual user should be NPS 1/2, as a minimum. 3.8.2

Plant Air 3.8.2.1 Plant air branch lines shall be taken from the top of the header. 3.8.2.2 Block valves shall be provided for branch connections less than NPS 2 and shall be located both at the header and at the equipment.

3.8.3

Cooling Water 3.8.3.1 Block valves for every branch from cooling water supply and return headers shall be located either at the header or at the equipment being served. 3.8.3.2 Block valves shall not be provided in return lines operating at or below atmospheric pressure unless needed for equipment or system isolation. 3.8.3.3 If heat exchangers are provided with process isolation valves for inspection and cleaning during plant operation, block valves shall be provided in the cooling water inlet and outlet piping. In freezing climates, an antifreeze bypass from the inlet to the outlet or other means to prevent freezing shall be provided. 3.8.3.4 All aboveground cooling water supply and return branch lines shall be connected to the top of the headers.

3.8.4

Utility Water 3.8.4.1 Utility water branch lines shall be taken from the top of the header. 3.8.4.2 Block valves shall be provided for branch connections less than NPS 2 and shall be located both at the header and at the equipment.

3.8.5

Potable Water 3.8.5.1 Potable water shall not be connected to any other system unless isolated in accordance with state and local requirements. 3.8.5.2 Connections to the potable water system shall be in accordance with applicable ordinances and approved by the owner.

3.8.6

Steam and Steam Condensate Removal 3.8.6.1 Steam Headers

1. Steam headers shall run level or shall pitch downward in the direction of steam flow.

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January 2009

2. A vertical rise required in the direction of steam flow shall be designed with a vertical leg equipped with a drip leg at the low point. 3.8.6.2 Steam Branch Lines

1. Steam branch lines shall be connected to the top of the headers. 2. Branch lines shall run level or pitch downward in the direction of the steam flow. 3. A vertical rise required in the direction of steam flow, downstream of the connection to the steam header, shall be designed with a vertical leg equipped with a drip leg at the low point. 4. Block valves shall be provided in the branch lines from the steam headers located at and above the elevation of the steam header and installed in such a manner that no pocket is formed where condensate may collect. 3.8.6.3 Steam tracing shall be in accordance with PIP PNSC0035. 3.8.6.4 Steam traps discharging into the atmosphere shall be provided with upstream block valves. 3.8.6.5 Steam traps discharging to a condensate collection system shall be provided with both upstream and downstream block valves. 3.8.6.6 Condensate from vacuum steam systems shall be re-evaporated into the system by means of a condensate flash pot or removed by eductors, pumping traps, or other suitable means. 3.8.6.7 All steam traps shall be provided with an internal strainer or a strainer located upstream of the trap. The strainer shall be equipped with a blowdown valve piped to a safe location. 3.8.6.8 A steam separator or other means of condensate removal (e.g., pumping trap) shall be provided in the steam piping to each group of steam turbines operating on saturated steam and also to each group of steam-driven reciprocating compressors and other water-sensitive equipment. 3.8.6.9 A minimum of one steam trap shall be provided for each steam separator, header drip leg, branch drip leg, and low point where condensate may collect. 3.8.6.10 Each steam trap shall be sized and specified to operate at all anticipated pressures and condensate loads for the installed location. 3.8.6.11 Steam traps shall be sized and specified to discharge noncondensable gases at the maximum rates required to purge the steam system of these gases. 3.8.6.12 Staged large and small steam traps may be required to handle large flows of condensate from start-up and small flows of condensate from normal operations.

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PIP PNC00005 Design of ASME B31.3 Metallic Piping Systems

COMPLETE REVISION January 2009

3.8.6.13 Steam-trap discharge and other condensate lines shall be consolidated into headers and returned to the condensate collection system. 3.8.6.14 Condensate discharge to the waste system may be made only if a condensate collection system is not economically feasible or if condensate is contaminated. 3.8.6.15 Drip legs equipped with steam traps shall be installed at the bottom of steam headers at the following locations: a. Dead ends of steam headers and branch lines b. Low points c. Upstream of risers and vertical legs d. Upstream of expansion joints and raised expansion loops e. Upstream of block, reducing, and control valves f.

Intervals of approximately 150 feet (45 m) in straight, horizontal steam lines (i.e., without natural drainage points), but not greater than 300 feet (90 m)

3.8.6.16 Provisions shall be made to protect steam and condensate lines from freezing where freezing conditions are encountered. Freeze protection shall include provisions for operating locations and shutdown conditions. 3.8.7

Utility Stations 3.8.7.1 The following equipment shall have utility stations: a. Pump and compressor areas shall have permanent utility stations as follows: (1) Stations shall have steam, water, air, and nitrogen outlets as required for anticipated needs. (2) Station spacing shall be such that equipment can be covered with 50-foot (15-m) hose lengths. b. Columns and vessels shall have steam, water, air, and nitrogen, as required for anticipated needs. c. Exchangers and furnaces shall be provided with steam, water, air, and nitrogen connections as required for anticipated needs. The locations of the connections shall be as specified by the owner. 3.8.7.2 Each utility take-off connection for steam, water, air, and nitrogen shall be located at the top of the horizontal main header or auxiliary header. 3.8.7.3 Root valves shall be provided for each utility take-off connection from a main header or auxiliary header that cannot be taken out of service without shutting down a complete processing unit or operating facility.

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January 2009

3.8.7.4 Each utility line shall be provided with an isolation valve just upstream of the specified hose connector at the termination. 3.8.7.5 Pressure bleed-off valves shall be provided for each utility line in accordance with the owner’s requirements. 3.8.7.6 Each utility line shall have a service nameplate indicating the service. 3.8.7.7 The utility pipe and the ends of hoses provided with the station shall be color-coded. 3.8.7.8 Color-coding and type of connectors shall be in accordance with the owner’s location standard. 3.8.7.9 Hose connections, where applicable, shall be positioned approximately 4 feet (1.2 m) above finished plant grade or above platform of multilevel equipment. The piping shall be securely bolted to a supporting structure. 3.8.7.10 If an overhead system for water or steam is used in a freezing climate, either an additional block valve shall be provide at the header or other measures shall be taken to ensure that the piping is protected against freezing. 3.8.7.11 Hose connections to nitrogen systems shall have special fittings to provide positive segregation from the air system. 3.8.7.12 The nitrogen system shall have a check valve at each connection and at each utility station to prevent the introduction of air or hydrocarbons into the nitrogen system. 3.8.7.13 Other requirements for utility stations shall be provided in accordance with the owner’s location standard. 3.8.8

Burner Fuel Piping 3.8.8.1 Burner fuel piping shall be in accordance with the following requirements: a. Piping for fuel oil with viscosity greater than 20 centistokes shall be arranged for continuous circulation of the oil through the headers. b. Fuel gas supply piping shall be arranged to produce equal distribution of flow and to permit condensate drainage, unless dry gas is assured. 3.8.8.2 If a safety shutdown valve is required in fuel piping at furnaces or fired heaters, the valve shall have remote and local shutoff capability and shall be located in close proximity (i.e., within 50 feet [15 meters]) to the equipment. 3.8.8.3 An emergency shutoff valve in fuel piping at furnaces or fired heaters shall be provided at a safe distance (i.e., minimum of 50 feet [15 meters]) from the equipment.

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PIP PNC00005 Design of ASME B31.3 Metallic Piping Systems

3.8.9

COMPLETE REVISION January 2009

Heat Transfer Fluid Piping 3.8.9.1 The use of flanged and threaded connections should be minimized. Welded construction should be used wherever possible. 3.8.9.2 Any connection that is expected to be disassembled shall be provided with an upstream double block-and-bleed valve arrangement to protect personnel. 3.8.9.3 Some heat transfer fluids can freeze at ambient temperatures. If appropriate, heat tracing of the system should be provided to prevent freezing of lines when the system is shutdown. 3.8.9.4 If the piping system is cleaned or flushed using a water solution, the entire system shall be thoroughly dried. 3.8.9.5 Thermal fluids have a high coefficient of thermal expansion. Provisions shall be made to safely absorb the increased volume of thermal fluid at operating temperatures (e.g., an expansion tank).

3.9

Fabrication, Assembly, and Erection Fabrication, assembly, and erection of piping systems shall be in accordance with PIP PNE00012, PIP PNSC0001, PIP PNSC0011, and PIP PNSC0021.

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