Guidelines for Process Safety in Batch Reaction Systems [1 ed.] 0816907803, 9780816907809

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Guidelines for

Process Safety in Batch Reaction Systems

CENTER FOR CHEMICAL PROCESS SAFETY of the

AMERICAN INSTITUTE OF CHEMICAL ENGINEERS 3 Park Avenue, New York, New York 10016-5991

Copyright © 1999 American Institute of Chemical Engineers 3 Park Avenue New York, New York 10016-5991 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise without the prior permission of the copyright owner. ISBN 0-8169-0780-3

This book is available at a special discount when ordered in bulk quantities. For information, contact the Center for Chemical Process Safety at the address shown above.

It is sincerely hoped that the information presented in this document will lead to an even more impressive record for the entire industry; however, the American Institute of Chemical Engineers, its consultants, CCPS Subcommittee members, their employers, their employers’ officers and directors, and Arthur D. Little, Inc., disclaim making or giving any warranties or representations, express or implied, including with respect to fitness, intended purpose, use or merchantability and/or correctness or accuracy of the content of the information presented in this document. As between (1) American Institute of Chemical Engineers, its consultants, CCPS Subcommittee members, their employers, their employers’ officers and directors, and Arthur D. Little, Inc., and (2) the user of this document, the user accepts any legal liability or responsibility whatsoever for the consequence of its use or misuse.

CCPS and members of the Batch Reaction Subcommittee dedicate this book to the memory of Felix Freiheiter and Al Noren

Preface

The Center for Chemical Process Safety (CCPS) was established in 1985 by the American Institute of Chemical Engineers (AIChE) for the express purpose of assisting the Chemical and Hydrocarbon Process Industries in avoiding or mitigating catastrophic chemical accidents. To achieve this goal, CCPS has focused its work in four areas: • Establishing and publishing the latest scientific and engineering practices (not standards) for the prevention and mitigation of incidents involving hazardous materials, • Encouraging the use of such information by dissemination through publications, seminars, symposia and continuing education programs for engineers, • Advancing the state-of-the-art in engineering practices and technical management through research in prevention and mitigation of catastrophic events, and • Developing and encouraging the use of undergraduate education curricula which will improve the safety knowledge and consciousness of engineers. The Center for Chemical Process Safety (CCPS) identified the need for a publication dealing with process safety issues unique to batch reaction systems. Guidelines for Process Safety in Batch Reaction Systems, is the result of a project begun in 1997 in which a group of volunteer professionals representing major chemical, pharmaceutical and hydrocarbon processing companies, worked with Arthur D. Little Inc., to produce a book that attempts to describe the safe design and operation of batch reaction systems. The objectives of the book are to • Identify safety concerns unique to batch reaction systems; • Provide a how-to guide for the practicing engineer to identify, define and address unique safety issues in batch reaction systems; xi

xii

PREFACE

• Provide a range of criteria and techniques to be considered in the development, design, operation, and maintenance of batch reaction systems to reduce risk and ensure safety of people, environment, and property; • Provide an aid to identify potential sources of unsafe conditions encountered in batch reaction systems; • Provide guidance in applying appropriate practices to prevent accidents; and • Identify sources for specific expertise and reference them accordingly. The book does not focus on occupational safety and health issues, although improved process safety can benefit each area. Detailed engineering designs are outside the scope of the book. This book intends to identify issues and concerns in batch reaction systems and provides potential solutions to address these concerns. This should be of value to process design engineers, operators, maintenance personnel, as well as members of process hazards analysis teams. While the book offers potential solutions to specific issues/concerns, ultimately the user needs to make the case for the solutions that best satisfy their company’s requirements for a balance between risk reduction and cost. In many instances the book provides one or more sources of additional information on the subject which could be of value to the reader.

Acknowledgments

The American Institute of Chemical Engineers (AIChE) wishes to thank the Center for Chemical Process Safety (CCPS) and those involved in its operation, including its many sponsors whose funding and technical support made this project possible. Particular thanks are due to the members of the Batch Reaction Subcommittee for their enthusiasm, tireless effort and technical contributions. Members of the subcommittee played a major role in the writing of this book by suggesting examples, by offering failure scenarios for the major equipment covered in the book and by suggesting possible solutions to the various Concerns/Issues mentioned in the tables. AIChE and CCPS would also like to express their appreciation to Arthur D. Little, Inc. for their contribution in preparing this book for publication. It is the collective industrial experience and know-how of the subcommittee members plus the experience and expertise of Arthur D. Little, Inc. that makes this book especially valuable to the process and design engineer. Dr. Georges A. Melhem was the Director-in-Charge of this project, for Arthur D. Little, Inc.; Dr. Sanjeev Mohindra of Arthur D. Little, Inc. was the author; and Christina Hourican handled the somewhat complex word processing for this project. The Batch Reaction Subcommittee was chaired by Walter L. Frank of EQE International. Current members of the subcommittee, listed alphabetically are: David J. Christensen, Union Carbide Corporation; Warren Greenfield, International Specialty Products; Philip P. Malkewicz, Nalco Chemical Company; Peter F. McGrath, Olin Corporation; Louisa A. Nara, Bayer Corporation; Leslie A. Scher, CCPS Staff Consultant; Robert Schisla, Eastman Chemical Company; Anthony Torres, Eastman Kodak Company; Dr. Jan C. Windhorst, Nova Chemicals; and Paul Wood, Eli Lilly & Company. Former subcommittee members who contributed much in getting this project started were Felix Freiheiter, CCPS Staff Consultant (deceased); Al Noren, Monsanto Company-Searle (deceased); John Noronha, Eastman Kodak Company (retired) and Robert Stankovich, Eli Lilly & Company. xiii

xiv

ACKNOWLEDGMENTS

The Batch Reaction Subcommittee would also like to acknowledge the following peer reviewers for their meaningful suggestions and contributions: Robert E. Hollenbeck, Fred Maves, Gary Paulu, Arlyn H. Poppen, and Monica R. Stiglich of 3M; Pete Lodal of Eastman Chemical Company; Michael Hofler, Lisa Morrison and Peter Monk of Nova Chemicals; Stanley S. Grossel of Process Safety & Design, Inc.; Linda Hicks of Reilly Industries, Inc.; Gary York of Rhodia, Inc.; Steve Getz of Union Carbide Corporation; and John Davenport, CCPS staff consultant. Lastly, the members of the Batch Reaction Subcommittee would like to thank their employers for providing the time and support to participate in this project.

Acronyms and Abbreviations

ACGIH ACS AGA AIChE AIHA AIT ANSI APFA API APTAC ARC ASM ASME ASNT ASSE ASTM AWS BLEVE BPCS CAA CAAA CART CCPS CEM CFR CGA

American Conference of Government Industrial Hygienists American Chemical Society American Gas Association American Institute of Chemical Engineers American Industrial Hygiene Association Autoignition Temperature American National Standards Institute American Pipe Fittings Association American Petroleum Institute Automated Pressure Tracking Adiabatic Accelerating Rate Calorimeter American Society for Metals American Society of Mechanical Engineers American Society for Nondestructive Testing American Society of Safety Engineers American Society for Testing and Materials American Welding Society Boiling Liquid Expanding Vapor Explosion Basic Process Control System Clean Air Act Clean Air Act Amendments Computed Adiabatic Reaction Temperature Center for Chemical Process Safety Continuous Emissions Monitor Code of Federal Regulations Compressed Gas Association xv

xvi CIA CMA CSTR DCS DIERS DIPPR DOT DPC DSC DTA EPA ERD ERPG ERRF ERS ESD FC F&EI FIBC FL FMEA FMEC FO FRP HAZOP HSE HVAC IChemE IDLH IEC IEEE IRI ISA ISO LEL LFL LNG LOC LPG MAWP MEC MIE

ACRONYMS AND ABBREVIATIONS

Chemical Industries Association Chemical Manufacturers Association Continuous-Flow Stirred-Tank Reactor Distributed Control System Design Institute for Emergency Relief Systems Design Institute for Physical Property Data Department of Transportation Deflagration Pressure Containment Differential Scanning Calorimetry Differential Thermal Analysis Environmental Protection Agency Emergency Relief Design Emergency Response Planning Guideline External Risk Reduction Facilities Emergency Relief System Emergency Shutdown Device Fail Closed Fire and Explosion Index Flexible Intermediate Bulk Containers Fail Last Position Failure Mode and Effects Analysis Factory Mutual Engineering Corporation Fail Open Fiber Reinforced Plastic Hazard and Operability Study Health and Safety Executive Heating, Ventilation, and Air Conditioning The Institution of Chemical Engineers Immediately Dangerous to Life or Health International Electrotechnical Commission Institute of Electrical and Electronics Engineers Industrial Risk Insurers Instrument Society of America International Standards Organization Lower Explosive Limit Lower Flammable Limit Liquefied Natural Gas Limiting Oxidant Concentration Liquefied Petroleum Gas Maximum Allowable Working Pressure Minimum Explosible Concentration Minimum Ignition Energy

Acronyms and Abbreviations

MOC MSDS NACE NBIC NDE NEC NEMA NESC NFPA NIOSH NPSH NTIAC OSHA P&ID PEL PES PFD PFR PHA PID PLC PPE PRV PSD PSI PSS PSV PVRV RP RSST RT RTD SADT SAE SCBA SCC SIL SIS SFPE SRS TGA TEMA

Management of Change Material Safety Data Sheet National Association of Corrosion Engineers National Board Inspection Code Nondestructive Examination National Electrical Code National Electrical Manufacturers Association National Electrical Safety Code National Fire Protection Association National Institute of Occupational Safety and Health Net Positive Suction Head Nondestructive Testing Information Analysis Center Occupational Safety and Health Administration Piping and Instrumentation Diagram Permissible Exposure Limit Programmable Electronic System Process Flow Diagram Plug Flow Reactor Process Hazard Analysis Proportional Integral Derivative Programmable Logic Controller Personal Protection Equipment Pressure Relief Valve Process Safety Device Process Safety Information Process Safety System Pressure Safety Valve Pressure-Vacuum Relief Valve Recommended Practice Reactive Systems Screening Tool Radiographic Testing Resistance Temperature Detector Self Accelerating Decomposition Temperature Society of Automotive Engineers Self-contained Breathing Apparatus Stress Corrosion Cracking Safety Integrity Level Safety Instrumented System Society of Fire Protection Engineers Safety Related Systems Thermogravimetric Analysis Tubular Exchanger Manufacturer Association

xvii

xviii THA TLV UBC UEL UFL UL UPS UT VCE VDI VDE VOC VSP

ACRONYMS AND ABBREVIATIONS

Thermal Hazardous Analysis Threshold Limit Value Uniform Building Code Upper Explosive Limit Upper Flammable Limit Underwriters Laboratory Inc. Uninterruptible power supply Ultrasonic testing Vapor Cloud Explosion Verein Deutsche Ingenieure Verein Deutsche Elektrotechnike Volatile Organic Compound Vent Sizing Package

Contents Preface

xi

Acknowledgments Acronyms and Abbreviations

xiii xv

1 Process Safety in Batch Reaction Systems 1.1. Scope 1.2. Special Concerns of Batch Reaction Systems 1.3. Approach Used in Guidelines

1 1 2 3

2 Chemistry

7

2.1. Introduction 2.2. Case Study 2.3. Key Issues 2.4. Process Safety Practices Table 2: Chemistry Appendix 2A. Chemical Reactivity Hazards Screening A.1. A.2. A.3. A.4.

Understand the Problem Conduct Theoretical Screening Conduct Experimental Screening Conduct Experimental Analysis

7 8 9 9 11 21 21 21 23 25 vii

viii

CONTENTS

3 Equipment Configuration and Layout 3.1. Introduction 3.2. Case Studies Pump Leak Incidents Tank Farm Fire

3.3. Key Issues 3.4. Process Safety Practices Table 3: Equipment Configuration and Layout

27 27 28 28 28 29 29 30

4 Equipment 4.1. Introduction Vessels Including Reactors and Storage Vessels Centrifuges Dryers Batch Distillation Columns and Evaporators Process Vents and Drains Charging and Transferring Equipment Drumming Equipment Milling Equipment Filters

4.2. Case Studies Batch Pharmaceutical Reactor Accident Seveso Runaway Reaction Pharmaceutical Powder Dryer Fire and Explosion

4.3. Key Issues 4.4. Process Safety Practices Table 4.0: General Table 4.1: Reactors and Vessels Table 4.2: Centrifuges Table 4.3: Dryers Table 4.4: Batch Distillation and Evaporation Table 4.5: Process Vents and Drains

35 35 36 38 39 40 40 41 41 42 42 43 43 44 44

45 45 48 54 64 70 73 75

ix

Contents

Table 4.6: Transferring and Charging Equipment Table 4.7: Drumming Equipment Table 4.8: Milling Equipment Table 4.9: Filters Appendix 4A. Storage and Warehousing

76 90 96 100 105

5 Instrumentation/Control Systems 5.1. Introduction 5.2. Case Study 5.3. Key Issues 5.4. Process Safety Practices Table 5: Instrumentation/Control Systems

109 109 112 113 114 115

6 Operations and Procedures 6.1. Introduction 6.2. Case Studies Initiator Overcharging Incident Reactant Stratification Incident

6.3. Key Issues 6.4. Process Safety Practices Table 6: Operations and Procedures

125 125 129 129 130 131 131 132

References

143

Glossary Index

159 167

1 Process Safety in Batch Reaction Systems 1.1. Scope The Center for Chemical Process Safety (CCPS) has identified the need for a publication dealing with process safety issues unique to batch reaction systems. This book, Guidelines for Process Safety in Batch Reaction Systems, attempts to aid in the safe design, operation and maintenance of batch and semi-batch reaction systems. In this book the terms “batch” and “semi-batch” are used interchangeably for simplicity. The objectives of the book are to: • Provide a how-to guide for the practicing engineer to identify, define, and address unique safety issues typically encountered in batch reaction systems. • Provide a range of criteria and techniques to be considered in the development, design, operation, and maintenance of batch reaction systems to reduce risk and ensure safety of people, environment, and property. • Provide an aid to identify potential sources of unsafe conditions encountered in batch reaction systems. • Provide guidance in applying appropriate process safety practices to prevent accidents. • Identify sources for specific expertise and reference them accordingly. The book does not focus on occupational safety and health issues, although improved process safety can benefit these areas. Detailed engineering designs are outside the scope of this work. This book intends to identify issues and concerns in batch reaction systems and provide potential solutions to address these concerns. This should be of value to process design engineers, operators, maintenance personnel, as well as members of process hazards analysis teams. While this book offers potential solutions to specific issues/concerns, ultimately the user needs to make the case for the solutions that provide a balance between risk 1

2

1. PROCESS SAFETY IN BATCH REACTION SYSTEMS

reduction and cost. The solutions presented in the book, are possible approaches for dealing with a particular issue. The authors of this book could not anticipate all the possible issues, or all applicable solutions for a specific issue. Therefore, it is intended that the use of the suggested solutions be combined with sound engineering judgment and consideration of all relevant factors. Furthermore, all the solutions presented may not be applicable to a given situation. It should also be recognized that the solutions presented might themselves introduce potential hazards that were not originally present. Therefore, it is necessary to use the information in the context of the total design concept to ensure that all hazards have been considered, and that all applicable laws and regulations have been complied with.

1.2. Special Concerns of Batch Reaction Systems Batch reaction systems present unique challenges for process safety (Hendershot 1987). Batch operations consist of a series of processing steps, which must be carried out in the proper order, and at the proper time. By their very nature, batch-type processes do not operate in a steady state. As the process is being carried out, the holdup of materials in the vessel varies with time as materials are charged, reacted and perhaps withdrawn, thus changing mixing characteristics and effective heat transfer area. There is a continuous variation in the physical properties, chemical compositions, and physical state of the reaction mixture with time. This makes it more difficult, both for the operators and control systems, to monitor and diagnose the process. The sequence of processing steps, and frequent start-ups and shutdowns increase the probability of human errors and equipment failures. Moreover, batch reaction systems often handle multiple processes and products in the same equipment. This can also lead to increased probability of human error. Batch plants are often designed for general use, rather than dedicated to a specific process. The piping and layout of the equipment is often modified to meet the needs of the current process, or the process is modified to use the existing equipment. Use of the same equipment in different campaigns, complex process piping, and the use of shared auxiliary equipment, such as columns and condensers, presents greater challenges in preventing cross contamination; in selecting materials of construction; and in selecting instrumentation and control systems. Additionally, the complexity of equipment and the frequency of changes complicate the process documentation task. These frequent changes often result in complex management of change (MOC) issues. The nature of batch operations (unsteady-state), frequently involving manual intervention, creates significant issues pertaining to the design of control systems, design of operating procedures, and the interaction between the

1.3. Approach Used in Guidelines

3

control system and the operators. The operator is a more integral part of the process control, supervision loop, and the safe operation of the process. The operator managing a batch process has a greater number of duties and responsibilities than his counterpart in a continuous system. Several of these duties are either specific to batch operations or are done more often in batch operations than in continuous processes. The number and variety of functions that the operator has to perform during a batch process requires effective management systems, including more rigorous training, to minimize human error. Furthermore, the batch operator is more involved and is often in closer proximity to the process. This close proximity puts the operator at increased risk to direct exposure to the hazards associated with larger inventory of raw materials and semi finished products than continuous systems with comparable throughput. All of these issues make batch reaction systems unique, in terms of the challenges they pose for managing process safety. Figure 1 shows a typical batch reaction system.

1.3. Approach Used in Guidelines The book presents information pertaining to the safety issues in batch reaction systems in five chapters. Each chapter starts with a description of the topic covered in the chapter. This is followed by a short example highlighting a reported incident involving a batch reaction system. The case study is followed by a listing of key issues and process safety practices unique to the topic. The issues and concerns presented in this book, as well as potential design solutions and sources of additional information are presented in the tables. This format concisely conveys the necessary and relevant information in a familiar and convenient format. The organization of the tables is described below. • Concern/Issue: Identifies a specific safety issue or concern and its safety implications. • Potential Solutions and Control Mechanisms: Lists the potential solutions and control mechanisms that may be employed to reduce the risk of a specific issue or concern. • Additional Resources: Provides additional sources of information on the concerns/issues identified in the tables. Please note that the “Additional Resources” column does not attempt to include all sources of additional information. It should be recognized that the solutions and control mechanisms presented in the table are possible approaches for dealing with a particular issue.

4

Figure 1. Typical batch reaction system.

1.3. Approach Used in Guidelines

5

They are solely meant to create awareness and assist designers and operators, and are not meant to imply that these solutions and control mechanisms are Recognized and Generally Acceptable Good Engineering Practices (RAGAGEP). The authors of this book could not anticipate all the possible issues, or all applicable solutions for a specific issue. The potential solution and controls are intended to stimulate thought and initiate discussions about the appropriateness of the potential solutions presented, and potentially stimulate the generation of other solutions not included in the table. It is intended that the use of the tables should be combined with sound engineering judgment and consideration of all relevant factors. Furthermore, all the solutions presented may not be applicable to a given situation. It should also be recognized that the solutions presented could introduce potential hazards that were not originally present. Therefore, it is necessary to use the table in the context of the total design concept to insure that all hazards have been considered. The information pertaining to the safety issues in batch reaction systems is presented in the following chapters:

Chapter 2. Chemistry Understanding the behavior of all the chemicals involved in the process—raw materials, intermediates, products and by-products, is a key aspect to identifying and understanding the process safety issues relevant to a given process. The nature of the batch processes makes it more likely for the system to enter a state (pressure, temperature, and composition) where undesired reactions can take place. The opportunities for undesired chemical reactions also are far greater in batch reaction systems due to greater potential for contamination or errors in sequence of addition. This chapter presents issues, concerns, and provides potential solutions related to chemistry in batch reaction systems.

Chapter 3. Equipment Configuration and Layout Proper equipment configuration and layout can make a significant contribution to the safety of a processing facility. In batch processes, where the material handled by the process can change frequently, providing safe separation distances presents an even greater challenge than continuous processes. Other important considerations for facility layout are the electrical classification and fire protection requirements. It also is quite common for batch processes to be located inside buildings. This leads to the need to provide adequate building ventilation to avoid buildup of hazardous vapors/gases due to leaks. This chapter presents issues/concerns, and provides potential solutions related to equipment configuration and layout in batch reaction systems.

6

1. PROCESS SAFETY IN BATCH REACTION SYSTEMS

Chapter 4. Equipment Frequently a piece of equipment is used in different processes during its lifecycle. This could result in process conditions that exceed the safe operating limits of the equipment. Equipment inspection may provide a poor prediction of the equipment’s useful life and reliability, due to the change of material handled or change in process chemistry over the life of equipment. Batch operations are also characterized by frequent start-up and shut-down of equipment. This can lead to accelerated equipment aging and may lead to equipment failure. This chapter presents issues and concerns related to the safe design, operation, and maintenance of various pieces of equipment in batch reaction systems, and provides potential solutions.

Chapter 5. Instrumentation/Control Systems The fact that batch processes are not carried out at steady state conditions imposes broad demands on the control system. The instrumentation and control system have to be selected to provide adequate control for a wide variety of operating conditions and a wide variety of processes. In addition, basic process control and shutdown systems have to deal with sequencing issues. This chapter presents issues and concerns related to safety of instrumentation and control in batch reaction systems, and provides potential solutions.

Chapter 6. Operations and Procedures The operator is an integral part of the process in a batch reaction process. Some of the functions a typical operator working in a batch processing facility may have to perform are scheduling, equipment setup, cleaning, charging, executing and controlling procedure, monitoring, fault diagnosis and corrective action, sampling, handling of finished and off-spec/partially finished products, maintenance, emergency response, process logging and communication. Several of these are either specific to batch operations, or are done more often in batch operations than in continuous processes. The greater number and variety of functions that the operator has to perform during a batch process presents more opportunities for errors than for continuous operations. This chapter presents issues related to operations and procedures in batch reaction systems, and provides potential solutions.

2 Chemistry 2.1. Introduction Understanding the behavior of all the chemicals involved in the process—raw materials, intermediates, products and by-products is a key aspect of understanding the process safety issues relevant to a given process. A knowledge of how these chemicals behave individually and how they interact with other chemicals, utilities, materials of construction, potential contaminants or other materials that they can come in contact with during shipment, storage, and processing is essential for understanding and managing process safety. Understanding the chemistry of the process also provides the greatest opportunity in applying the principles of inherent safety at the chemical synthesis stage. Process chemistry greatly determines the potential impact of the processing facility on people and the environment. It also determines such important safety variables as inventory, ancillary unit operations, by-product disposal, etc. Creative design and selection of process chemistry can result in the use of inherently safer chemicals, a reduction in the inventories of hazardous chemicals and/or a minimization of waste treatment requirements. Reactors often represent a large portion of the risk posed by a batch chemical operation. A better understanding of the reaction behavior and kinetics allows for an optimization of reactor control and safety systems. Knowledge of the reaction behavior includes desired reactions as well as undesired sidereactions that can take place in the reactor itself and other parts of the process. Knowledge of the physical properties of the materials involved in the process and the effects of physical phenomena such as mass transfer, heat transfer, mixing, phase of reaction on the overall reaction rate may be used to identify designs that maximize the economical benefits while reducing risk. As outlined in Chapter 1, batch chemical reactors present unique challenges to the designers in terms of process safety. The transient nature of the batch processes makes it more likely for the system to reach a condition (pressure, temperature, and composition) where undesired reactions could take place. The opportunities for 7

8

2. CHEMISTRY

undesired chemical reactions also are far greater in batch reaction systems due to greater potential for contamination. The importance of understanding the chemistry of the process is not limited to the research and development phase of the process lifecycle. It manifests itself again and again in all the lifecycle stages ranging from research and development to plant decommissioning. Process development in the conceptual design stage and the pilot plant stage can identify opportunities for inherent process safety in selecting the process chemistry and simplifying, i.e., improving control and operation schemes to keep the chemical reactants within safe operating limits. Knowledge of chemistry also can be used to design mitigation measures for releases of hazardous chemicals to the environment (CCPS-G12). In the detailed engineering stage, engineers and chemists can identify safety issues and provide design solutions to reduce the risk posed by the process. During the construction and start-up phase, knowledge of process chemistry can be used to identify operations that need to be strictly followed to reduce potential hazards. Special attention needs to be focused on cleaning to prevent cross contamination. It also can be used to provide safer equipment layout and ergonomics. The operator of the process needs to have an understanding of the process chemistry and the hazards associated with the various chemicals in order to perform routine operations and to identify, diagnose and respond to incipient hazardous situations. Plant modifications, plant expansions, proposed catalysts modifications and changes to the feedstock composition, or other raw materials need to undergo a management of change review. It is also important to analyze the effect of such modifications on the by-product and waste streams. During shutdown and decommissioning, attention needs to be focused on hazards associated with the residues left in the unit after shutdown. There are several issues that are unique to batch reaction system design. The process development time is often shorter due to the need to respond quickly to market demands. The small-scale batch process development may not receive the same effort and rigor as larger batch or continuous processes. Moreover, batch processes are often made to fit the existing facilities. This could lead to operating key equipment and emergency relief systems at the edge of their original design limits.

2.2. Case Study A weigh tank containing chlorosulfonic acid needed to be cleaned to remove salt deposits. The salt deposits precipitated from the material and occasionally plugged the downstream control valve. Since the material was water reactive, heptane was chosen to clean the vessel. Chemists had not anticipated the material would be reactive with heptane. While cleaning the vessel the pressure

2.4. Process Safety Practices

9

started to rise from the reaction, causing the vessel bottom head to fail at the weld seam. The force from the escaping gases propelled the tank into the ceiling and overhead structural steel. A small fire erupted which was quickly brought under control by the automatic sprinkler system. Even though the chemists had reviewed the chemistry and did not anticipate any problems, use testing could have identified this problem in the laboratory rather than the plant.

2.3. Key Issues Process chemistry issues and their effects on batch reaction systems safety are presented in Table 2, beginning on page 11. This table is meant to be illustrative but not comprehensive. Some key issues are listed below. • The hazardous materials used in the process may be raw materials, intermediates, products, by-products, cleaning materials, decomposition, or unintended products. • Inadvertent contact between two or more chemicals may lead to a hazardous condition. • Process materials may be pyrophoric, water reactive, strong oxidizers or strong reducers. • Process chemistry should be selected to fit existing batch equipment. • Disposal issues pertaining to unreacted batches, incomplete batches or off-spec products.

2.4. Process Safety Practices Listed below are safety practices aimed at minimizing the incidents caused by process chemistry issues. • Select a process chemistry or synthesis route that is inherently safer. • Perform chemical reactivity testing, including the analytical verification of reactants, catalyst, quenchers, initiators, and inhibitors. More details are provided in Appendix 2A of this chapter. • Use reactor calorimetry testing to determine thermodynamics and kinetics of process. See Appendix 2A (Chemical reactivity hazards screening). • Pilot process before putting into operation. • Provide system to maintain process safety information (PSI) – Systems for the identification, compilation, and update of information – Assign responsibility for developing new PSI, updating existing PSI and approval of changes to PSI.

10

2. CHEMISTRY

•

•

• • • •

• • • • •

– Controls to verify and/or cross check completion and accuracy of development and update of PSI. Maintain Process Safety Information (PSI) related to chemistry such as: – Information pertaining to the hazards of the chemicals used in the process. This should contain at least the following information: toxicity, flammability, permissible exposure limits, physical data, reactivity data, corrosivity data, thermal and chemical stability data, and hazardous effects of inadvertent mixing of different materials that could occur. – Document safety issues pertaining to process chemistry – Share knowledge between chemists, engineers and operators. Use chemical interaction matrices to identify potential incompatibilities between combinations of materials (not just binary reactions) and interactions with cleaning solvents, heat transfer fluids and other utilities, equipment lubricants, scrubbing media, materials of construction, etc. Implement management of change procedures for changes in design, operation, equipment and chemistry. Provide emergency relief where needed. Provide for addition of diluent, poison, or inhibitor directly to reactor. Provide for automatic or manual actuation of bottom discharge valve to drop batch into a dump tank with diluent, poison or inhibitor, or to an emergency containment area. Design equipment to accommodate maximum operating envelope. Appropriate use of Safety-Related Systems (SRS) such as Safety-Instrumented Systems (SIS). Inert equipment where appropriate. Specialized training or technical literature by raw material suppliers to address special use or handling requirements. Careful analysis of cleaning practices, especially nonperiodic or special purpose cleaning.

11

Table 2: Chemistry

Table 2: Chemistry

No.

Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Selection of Chemistry/Process Chemistry 1.

2.

Raw materials, interme- • Select a process chemistry or synthesis route diates, products, that is inherently safer (e.g., nontoxic, nonby-products, decompoflammable materials, less severe operating sition or unintended condition) products are hazardous. • Use Process Safety Management techniques Use of the hazardous to minimize the risk to people, and the materials poses a potenenvironment tial risk to the people Select equipment design for high integrity • and the environment. containment

CCPS G-1

Use of materials sensitive to shock, high temperature or high pressure. If the material is inadvertently exposed to an unsuitable condition, or if the process moves out of the safe operating limits, it could result in a loss of containment.

• Select a process chemistry that is inherently safer (e.g., replace shock sensitive, high temperature sensitive and high pressure sensitive materials with more benign materials, less severe operating conditions)

ASME VIII Div I and II

• Prevent exposure to shock, high temperature or pressure

CCPS G-23

• Design for pressure containment

CCPS G-41

• Provide adequately designed relief device

DIERS

• Use less severe operating conditions

NFPA 68

CCPS G-6 CCPS G-10 CCPS G-21 CCPS G-24 CCPS G-25 CCPS G-31 CCPS G-41

CCPS G-11 CCPS G-13 CCPS G-30

NFPA 69 3.

Chemical/materials that • Use inherently safer chemistry (e.g., when may potentially come in phosgene is cooled in a heat exchanger, contact are incompaticonsider use of an inert oil as the coolant ble. Inadvertent contact rather than water as heat exchanger tubes between two or more may fail) chemicals may lead to a • Use chemical interaction matrices to identify hazardous condition. potential incompatibilities between chemicals including utilities, solvents and materials of construction • Use chemical reactivity testing to identify and evaluate the hazards • Use written operating procedures and provide training • Use consistent labeling system • Select equipment to minimize inadvertent contact as a result of equipment failure • Isolate process from sources of incompatible material

API RP750 CCPS G-1 CCPS G-13 CCPS G-22 CCPS G-3 CCPS G-30 CCPS G-32 CCPS G-41 Hendershot 1987 Kletz 1991 Lees 1996

12

No.

2. CHEMISTRY

Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Selection of Chemistry/Process Chemistry 4.

Ingress of air into reactor containing pyrophoric material. Possibility of fire / deflagration.

• Use management systems (tagging) or interlocks to prevent opening of reactor during reaction progress • Provide emergency purge and/or isolation activated on detection of oxygen • Provide isolation valves to isolate equipment

AGA-XK0775 CCPS G-29 NFPA 2001 NFPA 68 NFPA 69

• Design system to accommodate deflagration pressure • Provide fire and/or deflagration suppression system • Provide closed feed system • Provide explosion venting 5.

Water reactivity of chemicals involved in reaction. Possibility of runaway.

• Avoid use of water as cooling/heating medium • Avoid use of water/steam for cleaning of reactor • Avoid direct water connection to reactor • Prevent backflow from scrubber into reactor • Eliminate water as a mechanical seal barrier fluid • Clean and chemically dry vessel prior to charging water reactive material • Provide dry compressed gas feeds • Ensure that alternate sources of inert gas feeds are dry • Confirm that raw materials feeds are dry • Preplan fire protection requirements and procedures • Use inherently safer equipment (e.g., jacketed vessels instead of tube heat exchangers) • When water or steam is used as a utility, insure appropriate mechanical integrity program for equipment

CCPS G-13 CCPS G-41

13

Table 2: Chemistry

No.

Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Selection of Chemistry/Process Chemistry 6.

Raw materials, interme- • Test suspect materials for undesired proper- CCPS G-11 diates, products, ties, (e.g., endothermic compounds, comDIERS by-products and/or pounds containing oxidizing and reducing IEC 61508 undesired byproducts group such as ammonium nitrate) are subject to runaway • Substitute or attenuate hazardous materials reactions that produce (inherently safer alternative) extreme heat and/or Construct equipment to handle extreme • extreme amounts of temperatures and or pressures gaseous/vapor products. • Provide emergency relief systems • Provide process monitoring and control systems • Provide External Risk Reduction Facility (ERRF)

7.

Unknown intermediate / • Test suspect materials to characterize undeside reaction. Unknown sired properties thermal hazards. Possi- • Conduct thermal hazards analysis bility for runaway • Evaluate methods for controlling runaway reaction. reactions (e.g., short stop, inhibitors)

CCPS G-13 DIERS

• Determine consequences of runaway reactions and ensure mitigation techniques are in place

8.

Chemicals for use in the • Carefully and deliberately select process CCPS G-23 process are selected chemicals and synthesis route CCPS G-41 because they are conve- • Emphasize consequences of chemical nient and not necessarchoices to Research and Design Engineering ily because they are the most suited. Nonoptimal system design in terms of safety and economics.

14

No.

2. CHEMISTRY

Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Selection of Chemistry/Process Chemistry 9.

10.

Process chemistry selected to fit in existing batch equipment. Nonoptimal process design in terms of safety and economics. Possibility of operating close to, or outside of, the safe operating envelope of the equipment and the relief capability.

• Use inherently safer chemistry

CCPS G-1

• Consider the consequences of using existing CCPS G-8 equipment for new processes (e.g., batch CCPS G-23 size, corrosion, cost) CCPS G-41 • Anticipate future product needs before purchase of equipment • Match batch sizes to equipment capabilities • Provide equipment with comparable pressure rating for the entire system • Implement management of change procedures

Short development time • Allocate enough time for development may result in a less than • Use more time-efficient PHA techniques complete knowledge of • Use administrative controls to decide when the hazards. to go to full scale production

API RP 750 CCPS G-1 CCPS G-10 CCPS G-25

• Establish minimum requirements “transfer package” for process knowledge • Require development chemist to be present during initial product runs Chemical Identification 11.

Trade name of process chemical changes or trade name prevents immediate recognition of harmful effects/ interaction of chemical. Sometimes different vendors use different names for chemicals. Use of incorrect chemicals leads to hazardous conditions.

• Establish procedures for testing and verifica- CCPS G-13 tion of raw materials, including use testing CCPS G-22 • Implement management of change procedures

NFPA 325M

• Implement operating procedures and training

NFPA 704

• Use consistent internal labeling system

NFPA 401

15

Table 2: Chemistry

No.

Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Use dedicated feed tank and reactor

API RP 750

• Implement procedure for double checking reactant identification and quality

CCPS G-13

• Implement procedure for double checking addition of correct reactant in correct order

CCPS G-29

Composition 12.

Addition of incorrect reactant or unanticipated material to the reactor. Possibility for runaway reaction.

• Develop operating instructions on the correct or permitted connections between tanks and vessels

CCPS G-22 CCPS G-30

• Color code and label lines • Provide dedicated storage areas/unloading facilities for reactants • Use dedicated connections and/or unique couplings • Physically separate points of connection of incompatible materials • Use interlocks which prevent addition of certain combination of chemicals • Use batch sequencing in control systems when possible • Require certificate of analysis for raw material 13.

Change in feed composition. This may happen due to change in suppliers or due to introduction of reworked material. Unwanted effect on reaction products, by-products. Varying inhibitor concentrations in monomers from different vendors. Potential for runaway reaction.

• Design for feed variations

CCPS G-1

• Obtain certificate of analysis

CCPS G-11

• Establish purity limits for each feed

CCPS G-13

• Bench scale use testing

CCPS G-23

• Sample and analyze feed stocks before addition

CCPS Y-28

• Design system to accommodate maximum expected pressure • Provide adequately designed emergency relief device • Implement procedure for double checking reactant identification and quality • Implement management of change

DIERS

16

No.

2. CHEMISTRY

Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Runaway Reaction 14.

Runaway reaction • Provide automatic or manual addition of dil(caused by, e.g., generauent, poison, or inhibitor directly to reactor tion of excessive heat • Provide automatic or manual actuation of during “fast” charging). bottom discharge valve to drop batch into a dump tank with diluent, poison or inhibitor, or to an emergency containment area

CCPS G-11 CCPS G-13 CCPS G-23 DIERS Kletz 1991

• Provide automatic/manual isolation based on detection of undesired reaction rate • System design accommodating maximum expected pressure and temperature • Provide adequately designed relief device • Provide emergency cooling • Design equipment to limit excessively fast feedrate 15.

Overcharge/overfeed of • Use of dedicated reactant charge tank sized reactants Possibility of only to hold amount of reactant needed overfilling vessel, or ini- • Interlock reactant feed charge ed via feed tiating runaway totalizer or weight comparison in charge tank reaction. • Provide automatic/manual response to level or other indication of abnormal quantity of vessel contents

CCPS G-13 CCPS G-23

• Monitor reaction initiation and progress during charging • Provide batch sequencing interlocks that demand operator action • Provide adequately designed relief device 16.

Undercharge/ underfeed • Use dedicated reactant charge tank sized to of reactants. Possibility hold correct amount of reactant needed of unreacted mixed • Interlock reactant feed charge via feed reactants left at end of totalizer or weight comparison in charge tank batch, leading to a sub• Provide automatic/manual response to level sequent runaway or other indication of abnormal quantity of reaction. vessel contents • Provide means for detecting reaction completion before proceeding • Design reactor and/or downstream system to accommodate maximum expected pressure • Install adequately designed emergency relief device • Establish procedure for disposal of materials

CCPS G-11 CCPS G-13 CCPS G-23 DIERS Kletz 1991

17

Table 2: Chemistry

No.

Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Runaway Reaction 17.

Overcharge of catalyst • Use dedicated catalyst or initiator charge or initiator, too much tank sized to hold only the amount of cataor too fast. Possibility of lyst needed runaway reaction. • Limit quantity of catalyst or initiator added by flow totalizer

CCPS G-15 CCPS G-23 CCPS G-29

• Implement procedural controls on the amount or concentration of catalyst or initiator to be added • Use staging area for preweighed single catalyst charges • Design equipment to prevent excessively fast feed. Do not oversize pumps or control valves • Install flow restriction orifice • Provide means of detecting reaction progress and completion before proceeding further • Design reactor and downstream system to accommodate maximum expected pressure

18.

Undercharge of catalyst. • Use dedicated catalyst charge tank sized to Potential for accumulahold only the amount of catalyst needed tion of reactants and • Implement administrative (procedural) consubsequent runaway trols for catalyst on the amount or concenreaction. Possibility of tration to be added no reaction resulting in • Use staging area for preweighed single cataa waste disposal issue. lyst charges • Provide means of detecting reaction progress and completion before proceeding further • Design reactor and downstream system to accommodate maximum expected pressure • Provide adequately designed relief device • Establish procedure for disposal of unreacted materials

CCPS G-11 CCPS G-13 CCPS G-23

18

No.

2. CHEMISTRY

Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Runaway Reaction 19.

Overactive and/or • Use dedicated catalyst charge tank sized to wrong catalyst. Possibilhold only the amount of catalyst needed ity for runaway • Passivate fresh catalyst prior to use or use reaction. prediluted catalyst

CCPS G-3 CCPS G-11 CCPS G-13

CCPS G-22 • Establish procedures for testing and verificaCCPS G-29 tion of catalyst activity and identification CCPS G-32 including use testing. Include procedure to monitor shelf life of catalyst to maintain DIERS activity • Develop and install emergency system and procedures to shortstop runaway reaction. • Establish administrative (procedural) controls on the amount or concentration of catalyst to be added • Use staging area for preweighed single catalyst charges • Provide means of detecting reaction progress and completion before proceeding • Design reactor and downstream system to accommodate maximum expected pressure • Provide adequately designed relief device • Establish procedure for disposal of unreacted materials • Require certificate of analysis for catalyst

20.

Inactive and/or wrong catalyst. Possibility for accumulation of reactant and subsequent runaway reaction in reactor or downstream vessel. Possibility of no reaction resulting in a waste disposal issue.

• Establish procedures for testing and verifica- CCPS G-11 tion of catalyst activity and identification CCPS G-13 including use testing CCPS G-23 • Provide means of detecting reaction comDIERS pletion before proceeding Kletz 1991 • Design reactor and/or downstream system to accommodate maximum expected pressure • Provide adequately designed relief device • Establish procedure for disposal of unreacted reactant mixture

19

Table 2: Chemistry

No.

Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Provide automatic control of inhibitor/initiator addition

CCPS G-11

• Provide analytical verification of inhibitor / initiator effectiveness including use testing (including shelf life issues)

CCPS G-23

Runaway Reaction 21.

Incorrect inhibitor / initiator composition or concentration or amount. Reaction proceeds too rapidly.

CCPS G-13 DIERS

• Avoid conditions for precipitating, or other- Kletz 1991 wise separating inhibitor from reacting species • Design system to accommodate maximum expected pressure and temperature • Provide emergency cooling • Provide adequately designed relief device 22.

23.

Insufficient diluent due to under feed or excessive evaporation resulting in insufficient heat sink. Possibility of runaway reaction due to high temperature excursion or high concentration of reacting species

• Provide automatic control of diluent addition

Incomplete reaction due to insufficient residence time, low temperature, overactive inhibitor etc. Possibility of no reaction. Possibility of unexpected reaction in subsequent processing steps. Problem of disposing of unreacted mixture.

• Auto/Manual response to low reaction progress

CCPS G-11

• Decision not to proceed to next step based on detection of low reactor temperature and/or reactor composition sampling

CCPS G-15

• Design reactor or downstream vessel to accommodate maximum expected pressure

CCPS G-23

• Provide adequately designed relief device

DIERS

CCPS G-11 CCPS G-23

• Select diluent less susceptible to evaporation • Install automatic/manual isolation based on detection of unexpected reaction rate • Provide emergency cooling • Provide adequately designed relief device • Monitor liquid level

CCPS G-13 CCPS G-22 CCPS G-31

• Implement procedure for disposing of unreacted mixture

Contamination 24.

Chemical reaction due to • Develop written procedures to clean and equipment not being verify reactor readiness properly cleaned/ drained • Implement checklist verification from previous run. Possibility of unwanted reac- • Analyze used cleaning solvent tion or insufficient desired reaction.

CCPS G-15 CCPS G-22 CCPS G-29

20

No.

2. CHEMISTRY

Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Contamination 25.

Contamination from leakage of heating/cooling media or introduction of other foreign substances (e.g., corrosion) or possibility of unwanted reaction between the heating/cooling medium and the reactor contents, leading to runaway reaction. Possibility of no reaction or inhibited reaction resulting in accumulation of reactants and delayed runaway.

• Use heating/cooling medium which does not CCPS G-23 react with or inhibit reactor contents • Use external heater/cooler (panel coil) • Use electrical heating with proper consideration of maximum possible heating element temperature • Use lower pressure heating or cooling medium to avoid flow into reactor in the event of a leak • Consider impact of reactor contents leaking into utility • Implement procedures for leak/pressure testing of jacket, coil or heat exchanger prior to operation • Provide emergency cooling • Transfer reactor contents to dump tank with diluent quench.

Off-spec product/intermediate raw material 26.

The raw materials are off-spec resulting in generation of excessive waste products.

• Implement effective quality control program CCPS G-29 • Employ good operating procedures • Provide procedures to safely handle the unplanned waste generation and/or neutralize off-spec materials.

Waste Minimization 27.

• Implement strict quality control program Variation in waste by batch. Feed variability • Employ good operating procedures to downstream waste • Develop effluent handling procedures processing equipment. Possibility of reaction in waste streams, flammable/ toxic hazard.

CCPS G-29 CCPS G-32

Appendix 2A. Chemical Reactivity Hazards Screening

21

Appendix 2A. Chemical Reactivity Hazards Screening Characterizing chemical reactivity hazards involves a review of the inherent thermal hazards of the pure process materials as well as the thermal hazards of the materials under processing conditions. Gaining this understanding and characterizing thermally hazardous systems is a multistep process.

A.1. Understand the Problem The first step is to understand the context in which the thermal hazard information is needed. This might include information on materials, reactions, processing conditions, previous incidents, if any, and any other available information that can help with the characterization.

A.2. Conduct Theoretical Screening After understanding the problem, the second step is to conduct a theoretical screening to determine the expected thermal hazards of a system. Table A.1 identifies properties of materials to be considered, and some potential sources of information, in formulating an opinion about the thermal hazards of particular materials and reactions. The first place to look for information describing the physical properties and known reaction hazards of an individual chemical or process is the literature. Once literature sources have been exhausted, theoretical information should be developed. This determination of theoretical values involves the development of worst-case theoretical estimates based on chemical compatibility information and thermophysical properties such as formation energies, heats

22

2. CHEMISTRY

Table A.1: Potential Sources of Theoretical Screening Data Material Properties

Potential Sources

1. Basic chemical data

MSDSs, manufacturer’s data, The Merck Index

2. Reactivity data

Bretherick’s Handbook, NFPA 49, 325 and 432 hazard ratings, Sax, Handbook of Hazardous Chemical Properties, Kirk–Othmer Encyclopedia of Chemical Technology or as determined

3. Incident data

Open literature

4. Chemical compatibility matrix

Literature or as determined

5. Chemical structure

Supplied by research scientist, CRC Handbook of Chemistry and Physics

6. Formation energies

Literature (e.g., Pedley’s Handbook) or as determined, Perry’s Chemical Engineers’ Handbook, DIPPR, CRC Handbook of Chemistry and Physics

7. Heats of reaction, decomposition, solution

Literature or as determined CRC Handbook of Chemistry and Physics

8. Chetah hazard criteria

ASTM Chetah Software (see discussion)

9. Computed Adiabatic Reaction Temperature (CART) at constant pressure and/or volume

As calculated

of reaction, decomposition and solution, hazard criteria, and computed adiabatic reaction temperature (CART). Chemical Compatibility

Chemical incompatibility charts can help in organizing available data on the incompatibilities existing between expected mixtures. Frurip (Frurip et al., 1997) gives one procedure for developing a chemical compatibility chart while describing some of the tools available. CCPS G-13 also provides a table of known incompatibility hazards. Data can also be gathered experimentally on the compatibility of materials. Incompatibility charts have been published by the U.S. Coast Guard (1994), ASTM (1980) as well as others. See Frurip (Frurip et al., 1997) for a description of experimental tests and published compatibility charts.

23

Appendix 2A. Chemical Reactivity Hazards Screening

Thermophysical Properties

Much information can be understood by a review of certain thermophysical properties of materials and mixtures. In comparing the values of heats of reaction, heats of decomposition and CART to values for known hazardous compounds, an estimation of thermal hazard potential can be made. Table A.2 outlines thermal hazard ranking values that could be used in classifying materials and processes based on heats of reaction and CART determinations (Melhem and Shanley 1997). Two standard estimation methods for heat of reaction and CART are Chetah 7.2 and NASA CET 89. Chetah™ Version 7.2 is a computer program capable of predicting both thermochemical properties and certain reactive chemical hazards of pure chemicals, mixtures or reactions. Available from ASTM, Chetah 7.2 uses Benson’s method of group additivity to estimate ideal gas heat of formation and heat of decomposition. NASA CET 89 is a computer program that calculates the adiabatic decomposition temperature (maximum attainable temperature in a chemical system) and the equilibrium decomposition products formed at that temperature. It is capable of calculating CART values for any combination of materials, including reactants, products, solvents, etc. Melhem and Shanley (1997) describe the use of CART values in thermal hazard analysis.

A.3. Conduct Experimental Screening Experimental screening involves conducting experimental tests to gauge the thermal hazard of materials and processes. The goal of these tests is to provide information by which the materials and processes may be characterized. Experimental screening can be performed for the following: • • • •

Self-reactivity Mechanical sensitivity Thermal sensitivity Deflagration and explosion, including dust explosibility and ignitability

Table A.2: Theoretical Hazard Rankings Hazard Ranking

Heat of Reaction (∆Hr ) Estimate

CART Estimate

Negligible to Low

Less exothermic than –1.2 kJ/g (–0.28 kcal/g)

< 700 K

–-1.2 kJ/g < ∆Hr < –3.0 kJ/g

1600 K

24

2. CHEMISTRY

Self-Reactivity Hazards

Self-reactivity can be defined as the potential for a material to decompose or undergo energetic changes. Some of the methods for characterizing selfreactivity hazards are listed in Table A.3. Mechanical Sensitivity

Mechanical sensitivity can be divided into two categories—mechanical friction and mechanical shock. Mechanical friction can be defined as mechanical energy imposed by materials being wedged between surfaces and mechanical shock can be defined as mechanical energy imposed by materials undergoing an impact. Several tests for measuring the sensitivity to friction and the impact of materials are detailed in CCPS G-13. Thermal Sensitivity

Thermal sensitivity is the potential for a material to explode under a thermal stimulus. Test methods are outlined in CCPS G-13. Explosion Testing, Including Dust Explosibility and Ignitability

Explosion testing should be performed to establish safe operating limits. Dust explosibility and ignitability are measurements of the potential for a combustible material, in dust form, to explode or ignite. Any combustible material has the potential to cause a dust explosion if dispersed in air as a dust and ignited. Further details on explosibility testing can be found in Palmer (1973), Bartknecht (1989) and Eckhoff (1997). Table A.3: Methods for Conducting Self-Reactivity Experimental Screening Method

Information Gained

Differential scanning calorimetry (DSC)

Onset temperature of exotherms, heat of reaction

Thermogravimetric analysis (TGA)

Onset temperature of weight loss

Differential thermal analysis (DTA)

Onset temperature of exotherms, heat of reaction, Cp, approximate kinetics

Reactive Systems Screening Tool (RSST™)

Temperature history of runaway reaction, rates of temperature and pressure rise (for gas producing reactions)

ARC ™

Temperature history of runaway reaction, rates of temperature and pressure rise (for gas producing reactions)

25

Appendix 2A. Chemical Reactivity Hazards Screening

A.4. Conduct Experimental Analysis Experimental analysis involves the use of thermal hazard analysis tests to verify the results of screening as well as to identify reaction rates and kinetics. The goal of this level of testing is to provide additional information by which the materials and processes may be characterized. The decision on the type of experimental analysis that should be undertaken is dependent on a number of factors, including perceived hazard, planned pilot plant scale, sample availability, regulations, equipment availability, etc. Table A.4, taken from the CCPS Guidelines for Chemical Reactivity Evaluation and Application to Process Design, shows the questions which need to be asked regarding the safety of the proposed reaction, the data required to answer those questions and some selected methods of investigation. The experimental analysis is extremely specialized, and companies should consider outsourcing the tests if they do not have specialists in this area. Table A.4: Essential Questions on Safety Aspects of Reactions Question

Data Required

1. What is the potential temperature rise by the desired reaction? What is the rate of the temperature rise? What are the consequences? What is the maximum pressure?

• Enthalpy of desired reaction

Selected Methods of Investigation • Table of data • Thermodynamic data

• Specific heat

• Calculations; estimations • Vapor pressure of • Differential Thermal Analysis solvent as a function (DTA) / Differential Scanning of temperature Calorimetry (DSC) • Gas evolution • Dewar flask experiments • Reaction calorimetry with pressure vessel • Thermometry/manometry • APTAC™ /ARC™ /RSST/VSP

• Enthalpy of unde2. What is the potential temperature rise by undesired reactions sired reaction or thermal decomposi- tion, such • Specific heat as from contaminants, impuri• Rate of undesired ties, etc.? reaction as a funcWhat are the consequences? tion of temperature What is the maximum pressure? 3. Is reactant accumulation possible? What are the consequences?

4. What is the safe storage temperature for shelf life?

• DTA/DSC • Dewar flask experiments • APTAC™ /ARC™ /RSST/VSP

• Steady state concentrations

• Reaction calorimetry combined with analysis

• Kinetic data

• Potential energy by DSC/DTA

• Data from 1 and 2

• VSP / APTAC™

• Kinetic data

• Isothermal Storage Test

• Data from 1 and 2

3 Equipment Configuration and Layout 3.1. Introduction Proper equipment configuration and layout can make a significant contribution to the safety of a processing facility. Safe separation distances are usually based on hazard considerations, but often the demands for safe access during construction, operation, and maintenance are governing factors. In batch processes, where the material utilized in the process can change frequently, providing safe separation distances presents an even greater challenge. In general, larger spacing between equipment leads to a safer layout. However, this may lead to an increase in pipe work, which in itself may increase the probability of accidental releases. The larger spacing between equipment may also increase operator effort and workload in operating the process. Often batch process equipment needs to be located inside buildings. This is usually the case when the process needs to be shielded from extreme heat/cold conditions, the elements, and/or needs to be kept sterile. This leads to the need to provide adequate building ventilation to avoid buildup of hazardous material due to leaks and other process emissions. When the operation of a process involves opening, cleaning, charging etc., point source ventilation may also need to be provided. Layout also has a significant role in minimizing the probability of ignition of a flammable release. Area electrical classification provides the basis for the control of electrical ignition sources. This classification is also used to determine the areas that require protection from vehicular access, etc. Frequently, highly hazardous processes that can result in overpressure (e.g., hydrogenation) are placed behind blast resistant structures/walls. Another important issue in layout is the provision of safe access to equipment for emergency response needs such as fire-fighting etc. The layout also needs to provide for safe escape and rescue routes. As far as off-site population is concerned, the most important siting factor is the distance between the process 27

28

3. EQUIPMENT CONFIGURATION AND LAYOUT

and the off-site receptors. Physical effects of accidental releases, fires and explosions decay rapidly with distance. Low population density in the immediate vicinity of the plant reduces the number of people potentially affected by the accidental releases.

3.2. Case Studies Pump Leak Incidents A high-pressure reciprocating pump, originally used for pumping heavy hydrocarbons, was put into service to pump propylene in an unventilated building. A leak occurred from the gland due to failure by fatigue of the studs holding the gland in position. The escaping liquid vaporized and was ignited by a furnace 76 meters away. Four men were badly burned and the glass windows on the buildings were broken. The failure was attributed to the fact that plant management had not implemented effective management of change procedures. As a result of the deflagration, gas detectors and remote isolation capability were provided. Also, the pump was moved to an open building where small leaks would be dispersed by natural ventilation (CCPS G-39).

Tank Farm Fire In November 1990 a fire occurred at a flammable liquid tank farm supporting Denver’s Stapleton international airport. Eight of the farm’s twelve storage tanks contained jet fuel, totaling almost 4.2 million gallons. The fire burned for 55 hours, destroying seven tanks. Investigators concluded that a damaged pump in a valve pit near the storage tanks may have caused the initial leak and also may have ignited the fuel. In addition, the investigators concluded that a pipe simultaneously cracked, thus releasing fuel into the fire area. The subsequent fire fed on the fuel collecting in the pit and spewing from the two leaks, and impinged on piping and related equipment in the valve pit. As this fire continued to burn, flange gaskets deteriorated, causing more leaks and allowing more fuel to flow out of the storage tanks. The growing fire encroached on two storage tanks adjacent to the valve pit. Approximately 12 hours into the incident, a friction coupling parted, allowing fuel from one storage tank to suddenly increase the fire size. The fire spread to an impounding area and involved two more fuel tanks. The following changes to the tank farm site would have mitigated the outcome of this incident: • Increased distance between the tanks and the pumping/valve area • Increased tank-to-tank separation

3.4. Process Safety Practices

29

• Installation of internal excess flow or fail-safe remotely operated valves for tanks at locations where piping connects • Provisions for the removal of fuel in the event the storage tanks’ primary discharge means becomes inoperable • Simple and recognizable means for fire fighters to shut off fuel flow into the facility • Increased structural support for piping (CCPS G-39)

3.3. Key Issues Safety issues in batch reaction systems relating to equipment configuration and layout are presented in Table 3. This table is meant to be illustrative but not comprehensive. A few key issues are presented below. • Shared vent systems, utility systems, or equipment may result in incompatible materials coming together. • Potential for fire traveling through the shared vent system. • Possibility of combining incompatible materials in drainage and dikes. • There is a greater need to provide ready access to equipment in batch plants because these require more manual operations. If the access is difficult, it may lead to operator injury and/or inability of operator to carry out responsibilities. • Close proximity of hazardous processes may result in releases or other hazardous conditions in one process affecting the neighboring process areas, thereby resulting in escalation of the hazard.

3.4. Process Safety Practices Listed below are safety practices aimed at minimizing hazards due to equipment configuration and layout. • Provide safe separation distances for normal operation, maintenance, emergency egress, ergonomics • Design systems to prevent incompatible materials coming together • Provide appropriate area electrical classification • Provide appropriate building, and point source ventilation • Provide ignition source control • Monitor utility systems for contamination • Proper control room design • Use damage limiting construction • Provide spill control • Install adequate sprinkler protection

30

3. EQUIPMENT CONFIGURATION AND LAYOUT

Table 3: Equipment Configuration and Layout

No.

Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Design to avoid incompatible materials present in the same vent system

ACGIH 1986

• Install deflagration suppression systems

NFPA-69

• Design vent to prevent backflow/accumulation

NFPA-91

Shared Systems 1.

Shared vent systems. Possibility of incompatible materials coming together.

CCPS G-11

• Prescrub vent discharge before transfer to vent header • Monitor circulating utility systems for contamination 2.

Shared utility supply • Design to avoid common utility supply systems. Possibility of headers and/or systems to processes with incompatible materials incompatible materials coming together via • Install backflow protection on supply lines contamination of the • Implement mechanical integrity program shared utility system to prevent contamination of utility systems • Monitor circulating utility systems for contamination

3.

4.

Shared equipment • Design to avoid or minimize use of (e.g. auxiliary processcommon equipment for incompatible ing “scrubbers”). Posmaterials sibility of incompatible • Implement proper cleaning procedure materials coming between incompatible uses to prevent together. cross contamination

Shared transfer systems.

API RP 750 CCPS G-7 CCPS G-22 CCPS G-29 CCPS G-57 NFPA-91

API RP 750 CCPS G-11 CCPS G-22 Kletz 1991 Lees 1996

• Prescrub or treat process streams before transfer to common equipment

NFPA-91

• Avoid the use of incompatible materials in shared transfer systems

API RP 750

• Ensure cleaning procedures are followed

Lees 1996

• Avoid pockets in lines

NFPA-91

• Install dedicated transfer system

Kletz 1991

31

Table 3: Equipment Configuration and Layout

No.

Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Ignition Sources 5.

Ignition of flammable • Provide safe separation distances release resulting in fire • Develop appropriate area electrical or explosion. classification

API RP 500 BS 5345 BS 5958

• Provide ignition source control

NFPA-70

• Place ignition sources in positive pressure enclosure and buildings

NFPA-77

• Provide adequate ventilation Fire/Explosion 6.

Shared vent systems. Potential for fire traveling through the shared vent system.

• Design vent system to prevent backflow/accumulation

33 CFR 154

• Prescrub or treat vent discharge before transfer to the vent header

NFPA-91

NFPA-69

• Install detonation and / or deflagration arresters • Install deflagration suppression system • Provide explosion venting and isolation mechanism • Provide vent system inerting or purging • Install dedicated vent systems 7.

Liquid spills. Possibility of accumulation of flammable liquids resulting in fire or explosion hazard.

• Provide spill control through adequate drainage and curbs or dikes

API RP 750

• Provide adequate ventilation

CCPS G-24

• Wash down systems

CCPS G-30

• Minimize possibility of ignition

Lees 1996

• Minimize possibility of spills

NFPA 69

CCPS G-22

NFPA-15 8.

Liquid spills. Possibil- • Provide segregation storage of incompatiity of combining ble materials incompatible materials • Don’t put incompatible materials in the in drainage and dikes. same dike • Use segregated drainage & sewer systems • Wash down systems • Minimize possibility of ignition • Minimize possibility of spills

API RP 750 CCPS G-22 CCPS G-22 CCPS G-24 CCPS G-30 NFPA-328 NFPA-329

32

No.

3. EQUIPMENT CONFIGURATION AND LAYOUT

Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Proper location of air intake

API RP 752.

Fire/Explosion 9.

Control room sited closer to the batch process due to need for more operator interaction with batch processes. Infiltration of flammable/toxic release from outside. Possible overpressure from external explosion.

• Provide adequate control room ventilation CCPS G-26 system NFPA-101 • Provide positive control room pressure to prevent inflow of hazardous material • Provide flammable/toxic detection systems in buildings • Provide control room or facility alarm to warn occupants • Provide personal protective equipment • Provide sufficient bottled air / SCBA • Provide doors on the side of the control room opposite to expected hazard sources • Provide wind direction indication visible from inside the building / control room • Employ damage limiting construction • Develop emergency response procedures • Develop evacuation plans • Provide exterior (and interior) fire extinguishing equipment • Design control room to withstand blast overpressure

10.

Batch equipment located indoors. A release of flammable/toxic material tends to disperse slower than if the release is outdoors. May lead to large concentration buildup and result in operator exposure. Confined flammable releases are also more likely to result in explosion with larger overpressures.

• Provide adequate building ventilation

ACGIH 1986

• Install flammable/toxic detection systems in buildings with alarms to warn building occupants of hazardous accumulations

CCPS G-3

• Provide personal protective equipment • Provide sufficient bottled air/SCBA • Develop emergency response procedures • Develop evacuation plans • Install explosion venting for room and/or building • Damage limiting construction of processing building

CCPS G-13 CCPS G-26 NFPA-68

33

Table 3: Equipment Configuration and Layout

No.

Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Install point source ventilation

API 2007

• Install building ventilation

CCPS G-22

• Install flammable/toxic detection systems in buildings with alarms to warn building occupants of hazardous accumulations

CCPS G-32

Operator Exposure 11.

Operating equipment is opened, cleaned, emptied, or charged frequently. Operator exposure to toxic or flammable materials during normal process operation.

• Use personal protective equipment • Provide sufficient bottled air/SCBA • Develop emergency response procedures • Develop appropriate evacuation plans

General 12.

13.

Close proximity of feed chemicals for different processes resulting in possibility of using wrong material. Close proximity of process equipment and process areas impedes emergency response and evacuation. Possibility of operator exposure and/or reduction in efficiency of emergency response.

• Provide segregated storage

CCPS G-29

• Separate the processes

CCPS G-3

• Provide unique loading devices See also Chapter 6 • Design equipment layout to accommodate emergency needs—response, ingress, egress • Maintain good house keeping • Schedule materials used • Investigate alternate methods of delivery to occupy less workspace (pipeline instead of drums) • Perform prestartup walk-through • Perform audits/inspection • Clearly mark and maintain the integrity of routes and pathways • Schedule processes to reduce amount of material • Redesign and modification • Use dedicated staging and storage areas

CCPS G-29 Kletz 1991 NFPA-101 Mecklenburgh 1985

34

No.

3. EQUIPMENT CONFIGURATION AND LAYOUT

Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Provide shortest, most direct and safest route to items requiring most frequent attention

CCPS G-23

General 14.

15.

16.

Operator access to equipment. There is a greater need to provide ready access to equipment in batch plants because these require more manual operations. If the access is difficult, it may lead to operator injury and/or inability of operator to carry out responsibilities.

NFPA-101

• Consider ergonomics during layout design

Mecklenburgh 1985

Close proximity of hazardous processes. Possibility of releases or other hazardous conditions in one process affecting the neighboring process areas resulting in escalation of the hazard.

• Maintain safe separation distances

API RP 752

• Consider the need for fire walls, solid floors, etc. in building design and construction

CCPS G-26

Close proximity of hazardous process. High pressure vessels which may fail explosively.

• Maintain safe separation distances

• Provide emergency relief design to vent to safe location

CCPS G-24 CCPS G-11 DIERS Dow F&EI

API RP 750 CCPS G-26 Dow F&EI

4 Equipment 4.1. Introduction This chapter discusses safety issues related to the design and operation of key equipment used in the batch reaction systems. Some of the equipment covered includes: • • • • • • • • •

Vessels, including reactors and storage vessels Centrifuges Dryers Batch distillation columns and evaporators Process vents and drains Charging and transferring equipment Drumming equipment Milling equipment Filters

Batch process systems impose an additional dimension to the design of equipment. A piece of equipment in batch operations is frequently used in different processes during its life cycle. Surplus equipment or existing equipment is often reused for a different purpose. These practices introduce the possibility of equipment being inadvertently used outside its intended operating envelope. In addition, using existing equipment for new process may overtax existing ancillary units such as utilities, disposal facilities, fire protection etc. Inspection alone may be an inadequate predictor of the equipment reliability due to change of material handled or change in process chemistry over the life of the equipment. Batch operations are characterized by frequent start-up and shutdown of equipment. This can lead to accelerated equipment aging, and may lead to unexpected equipment failure. Some of the types of equipment used in batch reaction systems are discussed in more detail below. 35

36

4. EQUIPMENT

Vessels Including Reactors and Storage Vessels (Table 4.1) Vessels are key components of a batch reaction process facility. While reactors may be the first type of vessel to come to mind, vessels also include storage tanks for feedstocks, intermediates, products, waste streams, etc. Vessels can vary widely in design with respect to factors such as size, pressure and temperature ratings, and materials of construction. However, some common concerns result from the inventories of hazardous materials present in the vessels, the potentially severe operating conditions (e.g., high temperature and pressure) that might pose hazards, and the fact that, in the case of reactors, we are intentionally releasing the chemical potential energy of the process, with the attendant risks of doing so. Reactors are generally, but not always, of robust construction in keeping with the elevated temperatures and pressures commonly associated with the process chemistry. Significant emphasis is placed on integrity of containment, with key considerations including proper temperature and pressure ratings for design, and proper consideration of materials of construction. Adequate mixing and heat exchange capabilities are important with respect to both the intended process function of the vessel, and the safe operation of the vessel; inadequate cooling and/or mixing are common causal factors for runaway reactions that can lead to vessel rupture. Reactors also often share the safety significant performance issues described below for storage vessels. As previously discussed, the flexibility of processing, typical in batch facilities, can complicate the provision of design features that address all of these above concerns for all potential uses of the reactor. Storage tanks are generally designed based upon the vapor pressure of their contents, and can range from low pressure (API-type) tanks to high pressure tanks for compressed gases or pressurized liquids. Nonrefrigerated, pressure-liquefied gases such as liquefied petroleum gases (LPGs) will flash upon release and cool equipment to the extent that the equipment may fail due to cold embrittlement. Boiling liquid expanding vapor explosions (BLEVEs) can result when vessels containing these materials are exposed to external fires. Releases of flammable liquefied gases can also give rise to fires, vapor cloud explosions, and fireballs (e.g., during BLEVEs). Refrigerated liquefied gases are stored at much lower pressures and, accordingly, generally pose much less of a hazard. However, BLEVE hazards still exist for fire exposure situations. Both pressurized and refrigerated liquefied gases pose concerns of exposure to personnel to extremely cold liquids and vapors upon release, along with any toxicity or asphyxiation hazards inherent to the particular liquid. Pressurized and refrigerated storage is covered in detail by industry standards, codes and guidelines, specifically by the NFPA for smaller quantities and API for larger quantities. Atmospheric storage tanks are normally used for liquid materials that are below their boiling point at ambient conditions. Hazards associated with

4.1. Introduction

37

atmospheric tanks (ambient pressure to 15 psig) include overpressure and underpressure, vapor generation, spills, tank rupture, fire, and product contamination. In addition, settling of foundations, and seismic and wind loadings are important concerns. (See API RP 620 and RP 650.) Although atmospheric storage tanks are not subject to BLEVEs, releases of flammable or combustible liquids can lead to pool fires. Since the potential consequences of fires increase as inventories increase, it is advisable to apply principles of inherent safety through reduction of inventories and elimination, where possible, of known ignition sources. The contamination of material in tanks by the introduction of incompatible materials or material of the wrong temperature can cause runaway reactions, polymerization, high temperature excursions, or underpressurization of the tank. To avoid potential contamination of products or routing wrong materials to tanks, safeguards should be implemented, such as clearly labeling piping, valves and manifolds to the tank; use of clear and well-defined operating procedures; and provision of periodic operator training. For vessels containing flammable liquids, where the vessel design pressure is insufficient to contain a deflagration or open loading is performed, consideration should be given to providing an inert gas blanket (e.g., nitrogen) to reduce the oxygen concentration and prevent fires or explosions. Storage vessels also include bins and silos used for the storage of solid materials such as pellets, granules, or dusts. The primary hazard in the storage of such materials comes from the dust that is generated during the mechanical handling of these materials. Suspensions of combustible dusts in the vessel vapor space above the material can be ignited leading to fires and explosions. Since dust production typically cannot be prevented, other means of explosion prevention must be applied. Ignition sources should be minimized, and explosion venting of vessels (including bin vent filters or baghouses) should be considered. Care should be taken during the design of a bin to reduce horizontal surfaces inside the bin where material can remain and create a hazard when the bin is opened for maintenance; the air above such areas has been known to explode while work inside the bins was being performed during normal repairs. Additionally, the vessels can be inerted in a manner similar to that used for atmospheric storage tanks (NFPA 68 and 69). The pneumatic transfer of solids can also be performed using an inert or a reduced oxygen concentration gas with a closed loop return to the sending tank. Among the principal reasons for providing inerting on reactors and vessels is the desirability of eliminating flammable vapor–air mixtures that can be caused by: • Addition of solids through the manhole. • Materials having low minimum spark ignition energies, or autoignition temperatures

38

4. EQUIPMENT

• Potential ignition sources that cannot be controlled adequately, such as: – spontaneous combustion – reactive chemicals: pyrophoric materials, acetylides, peroxides, and water-reactive materials – static electricity: material transfer where lines and vessels are not grounded properly, agitation of liquids of high dielectric strength (low conductivity), addition of liquids of high dielectric strength to vessels, addition to or agitation of liquids in vessels having nonconductive liners Another purpose of inerting is to control oxygen concentrations where process materials are subject to peroxide formation or oxidation to form unstable compounds (acetylides, etc.) or where materials in the process are degraded by atmospheric oxygen. An inert gas supply of sufficient capacity must be ensured. The supply pressure must be monitored continuously. The designer should consider the need for additional measures to supply inert gas. Particular attention must be given to the following situation: In the case of locally high nitrogen consumption (i.e., when a large kettle is inerted), the pressure in the main line may drop so far that the mains could be contaminated by gases or vapors from other apparatus connected at the same time. Depending upon the application, the quality of inert gas (e.g., water content, contaminants) can be important to process safety. The required level of inerting must be ensured by technical and administrative measures, for example: • control and monitoring of inert gas flow and inert gas pressure • continuous or intermittent measurement of oxygen concentration • explicit information in the standard operating procedures or in the process computer program for the correct procedure to achieve a sufficient level of inerting A rigorous mechanical integrity program to ensure the proper design, construction, and maintenance of reactors and storage vessels is essential in order to prevent leaks or more serious vessel failures arising from corrosion or other mechanical failure. The leaking of flammable and toxic liquids can have serious safety and environmental consequences, which are compounded by the large inventories that can be held in these vessels.

Centrifuges (Table 4.2) Since centrifuges are subject to the hazards inherent in all rotating equipment, the designer should first consider whether other, safer methods of separation (such as decanters or static filters) can be used. If it is determined that a

4.1. Introduction

39

centrifuge must be used, the design should be reviewed to ensure that it is as safe and reliable as possible. A good discussion of centrifuge safety design features and operating practices is found in an IChemE publication (1987). Potential problems associated with centrifuges include mechanical friction from bearings; vibration; leaking seals; static electricity; and overspeed. Vibration is both a cause of problems and an effect of equipment problems. The potential destructive force of an out-of-balance load has led to setting lower shutdown limits on the magnitude of vibration than other rotating equipment. Flexible connections for process and utility lines become a must so these vibration problems are not transmitted to connected equipment. Flexible hoses with liners having concentric convolutions (bellows type) avoid the sharp points inherent with spiral metallic liners. By avoiding the sharp point the liner is less likely to cut the exterior covering. Grounding of all equipment components, including internal rotating parts, must be ensured initially and periodically thereafter. Grounding via some type of brush or other direct contact is preferred to grounding via the bearing system through the lubricating medium (unless conductive greases are used). Use of nonconductive solvents complicates the elimination of static electricity concerns; use of conductive solvents or antistatic additives should be considered where feasible. For flammable and/or toxic materials all of the precautions for a pressurized system should be considered. For example, when a centrifuge is pressurized, overpressure protection is required, even if the pressurization is an inert gas. Relieving of the pressure to a closed system or safe location must be considered.

Dryers (Table 4.3) The choice between different types of dryers is often guided by the chemicals involved and their physical properties, particularly heat sensitivity. As when selecting other equipment, the designer should first ask if the step is necessary; if so, whether this is the correct or safest process step. Does the material being processed have to have all of the liquid removed? Can the downstream step or customer use the material in a liquid, slurry or paste form? Some of the hazards in drying operations are: vaporization of flammable liquids; presence of combustible dusts; overheating leading to decomposition; and inerting leading to an asphyxiation hazard. For heat sensitive material, limiting the temperature of the heating medium and residence time of the material are used to prevent decomposition. Inventories of hazardous materials should be minimized. Preventive measures include adequate ventilation and explosion venting, explosion containment, explosion suppression, inerting, elimination of ignition sources, and vapor recovery. Instrumentation may include oxygen

40

4. EQUIPMENT

analyzers and sensors for temperature, humidity, etc. Effluent gases should be monitored for flammability limits. The IChemE book (1990) should be consulted for a thorough review of fires and explosions in dryers. Several general principles may be applied to equipment handling combustible dusts: • design equipment to withstand a dust explosion; • minimize volume filled by dust suspension; • minimize (monitor) mechanical failure and overheating (bearing, rollers, mills); • eliminate static electricity and other sources of ignition; • minimize passage of burning dust by isolating equipment; • provide explosion prevention (e.g., by inerting) and protection (e.g., suppression, venting, or isolation); • provide fire protection; • maintain design operating conditions via management of change.

Batch Distillation Columns and Evaporators (Table 4.4) Batch distillation equipment can range from a free-standing column with a reboiler, condenser, receiver, and vacuum system, to the use of a jacketed reactor with a condenser. Distillation often involves the generation of combustible vapors in the process equipment. This necessitates the containment of the vapor within the equipment, and the exclusion of air from the equipment, to prevent the formation of combustible mixtures that could lead to fire or explosion. Since distillation is temperature, pressure, and composition dependent, special care must be taken to fully understand the potential thermal decomposition hazards of the chemicals involved. Other potential hazards can result from the freezing or plugging in condensers, or blocked vapor outlets, which may lead to vessel overpressurization if the heat input to the system is not stopped. Emphasis should be placed upon the use of inherently safer design alternatives using concepts such as: limiting the maximum heating medium temperature to safe levels; selecting solvents which do not require removal prior to the next process step; using tempered heat transfer medium to prevent freezing in the condenser; and locating the vessel temperature probe on the bottom head to ensure accurate measurement of temperatures, even a low liquid levels.

Process Vents and Drains (Table 4.5) Process vents and drains, including emission control devices, are often overlooked but are important elements in the safety of batch systems. Inadequate attention to these items can result in incompatible chemical mixtures within the

4.1. Introduction

41

system; formation of combustible atmospheres, or overloading of emission control equipment. Some items requiring special attention are: • elimination of pockets or traps in pipelines; • identification and consideration of all process fluids or equipment that could simultaneously drain or vent into common pipelines or equipment; • the potential need to prescrub the stream being vented prior to mixing with other streams; • proper selection of materials of construction. In addition to the information presented in this chapter, refer to Chapter 3, Equipment Configuration and Layout, for further discussions on shared vent and drain systems.

Charging and Transferring Equipment (Table 4.6) Due to the nature of batch operations, transferring and charging of process materials is a common activity. This can entail gas, liquids, and/or solids handling via open equipment. This may include pumping of liquids from drums or dumping of solids from other containers into an open vessel, shoveling material into a dryer, or making temporary connections such as at hose stations. Primary concerns include the of loss of containment and the potential for exposure of operating personnel to hazardous materials; the potential for other hazards such as fires or explosions; and the ergonomic issues inherent in manipulating large, heavy containers. The first two concerns are of particular significance in batch operations, since operating personnel are often more frequently and more intimately exposed to the batch processes than is typically the case with continuous processes. Some commonly applied controls include • • • • • •

providing enclosed charging systems, where feasible; use of localized ventilation; proper selection and use of personal protective equipment; use of mechanical assists for handling drums and other containers; procedures and training; and interlocking vessel openings to prevent opening while the vessel is pressurized.

Drumming Equipment (Table 4.7) Many of the material hazards present in batch processing are also present during the drumming of materials out of the process. However, there are additional considerations unique to this operation, including the mechanical handling of massive objects, potential for puncture of containers, and loss of liner integrity. Some of the hazards present in the drumming stage have the potential for overpressurization leading to release of chemicals and operator exposure,

42

4. EQUIPMENT

underpressurization of drums, or uncontrolled reactions occurring after drumming, leading to potential fires or explosions. Special consideration needs to be given to drummed materials that are shock/heat sensitive as well as drummed materials that degrade over time.

Milling Equipment (Table 4.8) Milling equipment may be used in batch systems where it is necessary to reduce particle size or product agglomeration. A primary hazard associated with milling equipment is the temperature increase that can be imparted to the material during the milling operation, particularly when product flow through the mill is significantly reduced or interrupted (similar concerns exist for other solids handling operations such as blending and, to a lesser degree, particle size separations such as screening or sieving). This can lead to ignition or decomposition of combustible or unstable materials that could lead to fires or explosions in the milling equipment. Additionally, fires or explosions can result from the presence of combustible dusts typically present in the milling equipment, should other ignition sources be present. Other concerns include the potential for exposure of operating personnel to chemical hazards. A number of design alternatives should be considered when milling materials that are combustible or are temperature sensitive, such as • monitoring of milling temperature; • shaft speed sensors to detect pluggage in the mill; and • instrumentation or inspections to ensure product flow, thus limiting material temperature rise to a safe level. Other ignition sources should be identified and excluded through consideration of • • • •

static electricity concerns, including proper bonding and grounding; proper area electrical classification; proper selection, location, and maintenance of bearings; and removal of tramp materials from the feed to the milling equipment.

Milling of impact-sensitive materials should generally be avoided.

Filters (Table 4.9) One of the primary concerns for filters is the loss of containment of flammable and toxic materials and operator safety during the frequent opening and closing of the equipment (e.g., for changing filter elements or unloading filters). Inherently safer process alternatives should be considered to eliminate or lessen the need for filtration. Self-cleaning, automatic backwashing, or sluicing filters should be considered for pyrophoric or toxic materials as they do not have to be

4.2. Case Studies

43

opened or disassembled to remove the filter cake. Filters for liquid service should be provided with fire-relief valves and safe operating procedures for out-of-service conditions. Bag house filters are normally low-pressure units. They can vary in operating conditions from hot and chemically aggressive to cool and inert. Hot feed may lead to exceeding the temperature rating of the filters and could even result in a bag house fire. As with all filters, not exceeding the design differential pressure is important to both the process stability and safety. As the solid is removed from the gas stream and is subsequently handled for recovery or disposal, all of the conventions and concerns for handling dust, powders and other solids apply. The system should be protected from the potential of dust deflagration by the use of pressure relief or suppression devices. A discussion of safety considerations for these types of systems is found in Dust Explosion Prevention and Protection Part 1–3. (IChemE 1992). In summary, it must be remembered that both design and operations are important in maintaining the integrity of the process and equipment.

4.2. Case Studies Batch Pharmaceutical Reactor Accident While two operators were charging penicillin powder from fiber drums into a reactor containing a mixture of acetone and methanol, an explosion occurred at the reactor manhole. The two operators were blown back by the force of the explosion, and were covered with solvent-wet powder. The incident was initiated by the ignition of solvent vapors, which resulted in a dust explosion of the dry powder. The solvent mixture in the reactor did not ignite. Tests on the polyethylene liners inside the fiber drums showed that they were nonconducting; while an attempt had been made to ground the liners, this would not have been effective for the nonconductive polyethylene. The most probable cause of the ignition was an electrostatic discharge from the polyethylene liner during reactor charging. which had been grounded at the time of the incident After this accident, the company instituted the following procedures (Drogaris 1993): • Requiring nitrogen inerting when pouring dry solids into flammable solvents • Adding dry powder to the reactor by means of grounded metal scoops, where possible, rather than by pouring in directly from drums with polyethylene liners • Using only conductive polyethylene liners

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4. EQUIPMENT

• Using a closed charging system rather than pouring dry powders into flammable solvents directly via an open manhole • Performing an electrostatic hazard review of the whole plant and all the processes whenever powders and flammable solvents are used Ed. Note: Even though this incident involved a reactor, it applies as well to any vessel, open-manhole, charging operation. Most likely the liners were loose and the operators not grounded. If fixed liners were in place and the operators grounded, the accident might not have occurred. Another problem that can be avoided by using closed charging systems is the volumetric displacement of fluids from the vessel during addition of solids.

Seveso Runaway Reaction On July 10, 1976 an incident occurred at a chemical plant in Seveso, Italy, which had far-reaching effects on the process safety regulations of many countries, especially in Europe. An atmospheric reactor containing an uncompleted batch of 2,4,5-trichlorophenol (TCP) was left for the weekend. Its temperature was 158°C, well below the temperature at which a runaway reaction could start (believed at the time to be 230°C, but possibly as low as l85°C). The reaction was carried out under vacuum, and the reactor was heated by steam in an external jacket, supplied by exhaust steam from a turbine at 190°C and a pressure of 12 bar gauge. The turbine was on reduced load, as various other plants were also shutting down for the weekend (as required by Italian law), and the temperature of the steam rose to about 300°C. There was a temperature gradient through the walls of the reactor (300°C on the outside and 160°C on the inside) below the liquid level because the temperature of the liquid in the reactor could not exceed its boiling point. Above the liquid level, the walls were at a temperature of 300°C throughout. When the steam was shut off and, 15 minutes later, the agitator was switched off, heat transferred from the hot wall above the liquid level to the top part of the liquid, which became hot enough for a runaway reaction to start. This resulted in a release of TCDD (dioxin), which killed a number of nearby animals, caused dermatitis (chloracne) in about 250 people, damaged vegetation near the site, and required the evacuation of about 600 people (Kletz 1994).

Pharmaceutical Powder Dryer Fire and Explosion An operator had tested dryer samples on a number of occasions. After the last sampling, he closed the manhole cover, put the dryer under vacuum, and started rotation of the dryer. A few minutes later an explosion and flash fire occurred, which self-extinguished. No one was injured. Investigations revealed that after

4.4. Process Safety Practices

45

the last sampling, the dryer manhole cover had not been securely fastened. This allowed the vacuum within the dryer to draw air into the rotating dryer and create a flammable mixture. The ignition source was probably an electrostatic discharge (the Teflon® coating on the internal lining of the dryer could have built up a charge). No nitrogen inerting had been used (Drogaris 1993). After this incident, the following precautions were instituted to prevent similar incidents from occurring in the future: • Nitrogen purging is carried out before charging or sampling of the dryer • If the absolute pressure rises to about 4 psia, the rotation stops, an alarm sounds, and a nitrogen purge starts automatically

4.3. Key Issues Safety issues in batch reaction systems relating to equipment are presented in Tables 4.0 through Table 4.9. The various tables are organized as follows: Table 4.0 Table 4.1 Table 4.2 Table 4.3 Table 4.4 Table 4.5 Table 4.6 Table 4.7 Table 4.8 Table 4.9

General Reactors and Vessels Centrifuges Dryers Batch Distillation columns and evaporators Process Vents and Drains Charging and Transferring Equipment Drumming Equipment Milling Equipment Filters

Tables 4.0, 4.1, and 4.6 contain information that may be applicable to the whole range of equipment and operations. These tables are meant to be illustrative but not comprehensive.

4.4. Process Safety Practices Listed below are practices that should be considered in the design and safe operation of equipment in batch reaction systems. • When using inert gas, provide protection against personnel asphyxiation hazards • Protect against the accumulation of electrostatic charges which can cause ignition. This may include the bonding and grounding of the tank, piping,

46

4. EQUIPMENT

•

• • •

• •

• •

•

•

• • • • • • • •

and other ancillary equipment and the use of bottom or diptube addition of liquids to minimize material splashing in the tank. Provide adequate fixed fire protection for tanks and vessels containing flammable, unstable or reactive materials. This can include fire loops with hydrants and monitors in the storage area, foam systems for individual tanks, and deluge spray systems to keep the exposed surfaces of tanks cool in case of fire in an adjacent tank. Install flame arresters on atmospheric vents to prevent fire on the outside of the tank from propagating back into the vapor space inside the tank. Provide fire resistant insulation for critical vessels, piping, outlet valves on tanks, valve actuators, instruments lines, and key electrical facilities. Provide remote controlled, automatic, and fire-actuated valves to stop loss of tank contents during an emergency; provide fire protection to these valves. Valves should be close-coupled to the tank, and must be resistant to corrosion or other deleterious effects of spilled fluids. Vessels should be provided with overpressure relief protection. Provide the capability to add a considerable amount of coolant or diluent to reduce the reaction rate if required. This measure requires: – choice of an appropriate fluid which does not react with the reaction mixture – sufficient free volume in the reactor – piping, instrumentation, etc. to add the fluid in the time required Provide the capability to rapidly depressurize the reactor to a safe location, if needed. Add an inhibitor to stop the reaction. This measure requires intimate knowledge of how the reaction rate can be influenced and whether effective mixing/inhibition is possible. Dump the reactor contents into a vessel which contains cold diluent. This option also requires particular care that the dumping line is not blocked or does not become blocked during the dumping procedure. For reactors containing flammable liquids, where the reactor design pressure is insufficient to contain a deflagration, consideration should be given to providing an inert gas blanket (usually nitrogen). Match batch size to container size of critical components, using an integral number of whole containers, where possible Double check materials being added to reactor Complete batch loading sheets for each batch run Use of operator sign-off sheets Preweigh reactants before transferring to reactor Verify raw materials (certificate of analysis for critical materials) Use of a staging area Use of dedicated and proper storage and unloading areas that don’t expose other operating and production facilities

4.4. Process Safety Practices

47

• Maintain safe handling and storage practices • Provide fire suppression deluge protection in areas having high concentrations of flammables or combustibles • Test reactive and critical raw materials prior to use • Sample to confirm concentrations • Label all containers • Use unique containers (e.g., colors, shapes) where appropriate • Identify all process and utility lines (written material name and color coded) • Indicate direction of flow, where applicable • Use unique fittings/connections/couplings (e.g., colors or sizes) where needed • Match batch size to equipment capabilities • Use appropriate materials of construction • Consider Inherently Safer Design alternatives (e.g., to withstand maximum upset conditions—temperature, pressure, flow) • Use hard piping where possible • Minimize pipe lengths where possible • Use heating media that will not exceed the safe temperature limits for the process • Design for ease of cleaning • Remove abandoned lines and equipment • Install valves and local instrumentation where they will be accessible and visible • Where used, include check valves in mechanical integrity program • Provide adequately designed relief devices • Provide separate vent systems for incompatible materials

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Table 4.0: General

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Overpressure 1.

Blockage of • Size piping system to maintain minimum piping, valves or required velocity to avoid deposition flame arresters due • If appropriate, eliminate flame arrester or use to solid deposiparallel switchable flame arresters with flow tion. Potential for monitoring system Monitor flow in line • overpressure. • Remove solids from process stream (use knockout pot, filter, etc.)

API 2028 CCPS G-11 ASME VIII Liptak 1982 Wilday 1991

• Install insulation/tracing of piping to minimize solid deposition (freezing/precipitation) • Recirculate material in lines prone to solid deposition • Use flush mounted valves where required • Periodically clean via flushing, blowdown, internal line cleaning devices (e.g., “pigs”) • Design piping for maximum expected pressure • Install adequately designed emergency relief device (ERD) Underpressure 2.

Failure of vacuum system control resulting in possibility of vessel collapse.

• Design vessel to accommodate maximum vacuum (full vacuum rating) • Provide vacuum relief device/system (can be a source of oxygen in vapor space resulting in flammable atmosphere)

API 2000 CCPS G-11 DIERS FMEC 7-59 NFPA 69

• Provide a vacuum alarm • Interlock to inject inert gas • Select vacuum source to limit vacuum capability 3.

Uncontrolled condensation/absorption of vapor phase component resulting in vacuum creation inside vessel.

• Design vessel to accommodate maximum vacuum (full vacuum rating)

ASMG VIII

• Use blanketing gas pressure control system to minimize vacuum

NFPA 99C

• Provide vacuum relief device/system • Blanket the condenser • Insulate equipment to mitigate effect of ambient temperature changes, e.g., thunderstorm • Interlock cold liquid feeds with heat source (e.g., distillation column)

FMEC 7-59

49

Table 4.0: General

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Fire/Explosion 4.

Deflagration of • Design vessel to accommodate maximum vapor caused by expected deflagration pressure air leakage into • Provide deflagration pressure relief equipment operatdevice/system ing under vacuum. • Provide oxygen analyzer with activation of inert Possibility of gas addition on detection of high oxygen fire/explosion. concentration

NFPA 68 NFPA 69

• Provide continuous inert purge to check for leaks before start-up • Operate below the Lower Flammable Limit (LFL) 5.

Ignition of • Design system to prevent condensation in condensed ductwork or buildup of deposits by providing flammable vapor smooth surfaces, elimination of potential points or solid deposits in of solids/liquid accumulation. ductwork/ piping. • Periodically flush and/or steam clean piping/ducts Possibility of • Include cleaning procedure in process write-up fire/explosion. • Provide written cleaning procedure and responsibility • Provide provision for drainage of ducts (e.g., sloped, low point drains) • Eliminate ignition sources within the ductwork • Bond and ground all pipe and duct work • Eliminate flammables or combustibles • Provide inert atmosphere • Install dilution system to keep flammable concentration below lower flammable limit (LFL) • Install on-line flammable gas detection and activation of inerting system • Install automatic sprinkler system • Install deflagration vents • Provide automatic isolation of associated equipment via quick closing valves • Provide design system to contain overpressure where practical • Provide weak sections in piping and duct work • Operate above dew point or sublimation point • Avoid use of static generating materials (plastic or rubber) for piping and ductwork systems in hazardous service

CCPS G-41 FMEC 7-59 NFPA 69 NFPA 77 NFPA 68

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4. EQUIPMENT

Potential Solutions and Control Mechanisms

Additional Resources

Inadequate ventilation in ducts due to partial obstructions or closed dampers leading to creation of flammable atmosphere. Possibility of fire/explosion.

• Design dampers so that system will handle the minimum safe ventilation rate at maximum damper throttling • Provide damper mechanical position stop to prevent complete closure of damper • Eliminate ignition sources within the ductwork • Use bonding and grounding • Eliminate flammables or combustible by material substitution • Use inert atmosphere • Design ventilation system to keep flammable concentration below lower flammable limit • Provide on-line flammable gas detection and activation of inerting system • Install automatic sprinkler system • Install deflagration vents • Provide automatic isolation of associated equipment via quick closing valves • Provide weak sections (for pressure relief) in piping and duct work • Design system to accommodate maximum expected deflagration pressure • Provide prescrubbers/condensers to reduce load in duct

CCPS G-41

Inadequate circulation in equipment causing accumulation of flammable pockets. Possibility of fire/explosion.

• Design where natural circulation is sufficient to prevent accumulation of flammables • Eliminate flammable solvent (e.g., substitute water-based solvent) • Design system for deflagration pressure containment where practical

CCPS G-41

No. Concern/Issue Fire/Explosion 6.

7.

8.

NFPA 13 NFPA 15 NFPA 16 NFPA 68 NFPA 69

NFPA 69

Premature shut• Design where natural circulation is sufficient to NFPA 69 down of fans/ventiprevent accumulation of flammables and/or crelation system ation of hot spots immediately fol• Design to contain overpressure where practical lowing shutdown of heat input (prior • Provide postventilation interlocks and/or operating procedures to keep fans running for a suffito sufficient coolcient time after shutdown of heating system ing) resulting in hot spots and flammable pockets (dryers, carbon beds, and thermal oxidizers). Possibility of subsequent ignition resulting in fire or explosion.

51

Table 4.0: General

Potential Solutions and Control Mechanisms

Additional Resources

Production of fine powder during auxiliary processing. Possibility of a dust or dust/hybrid explosion.

• Operate below minimum oxygen concentration • Maintain good housekeeping • Grind/blend under inert atmosphere • Provide damage limiting construction • Provide design to contain overpressure where practical • Maintain inlet temperature of heating medium sufficiently below the minimum ignition temperature

NFPA 68

Manifolding of ventilation exhaust ducts of several pieces of equipment from several processes. Possibility of spread of fire or deflagration from one location to the next.

• Use dedicated exhaust ducts • Vent individual pieces of equipment through conservation vents to prevent back flow • Install flame arresters at vessel vents, where applicable • Design to contain overpressure where practical • Maintain ignition source control • Maintain use of inert atmosphere • Provide automatic isolation via quick closing valves of manifold duct system on detection of fire/flammable atmosphere or overpressure in duct system • Provide automatic sprinkler system/inerting gas • Provide deflagration vents • Provide deflagration suppression system • Monitor flammable atmosphere/fire • Provide nitrogen blocks (nitrogen injection to stop flame propagation) or other explosion isolation measures

NFPA 13

Pyrophoric material exposed to air when equipment is opened for cleaning/maintenance. Possibility of fire and operator exposure.

• Maintain good operating and cleaning procedures CCPS G-32 • Provide fixed water spray, if appropriate CCPS G-41 • Use inherently safe material, where possible NFPA 15 • Provide inert purge • Deactivate pyrophoric material prior to exposing to air • Purchase/design equipment that does not require opening • Ensure operating procedures are in place to purge with inert gas prior to opening

No. Concern/Issue Fire/Explosion 9.

10.

11.

NFPA 69 NFPA 650 NFPA 654

NFPA 15 NFPA 16 NFPA 68 NFPA 69

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4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Operator Exposure 12

Emission of toxic, flammable or corrosive vapors when equipment is opened for cleaning/maintenance or during charging of hazardous material. Possibility for operator exposure.

• Provide local exhaust ventilation connected to a CCPS G-41 disposal system (vent condenser, adsorber, scrubber or incinerator) • Operator shuts down operation in response to vapor detection alarm • Develop and implement appropriate operating procedures • Provide operation to remove operator from zone of danger • Purge vessel prior to opening • Use inherently safer materials, where possible

Management of Change 13.

Equipment used in different processes during its lifecycle. Surplus equipment or existing equipment reused for different use. Possibility of equipment being used outside its safe operating envelope.

• Procure equipment that can be used in other processes (current or future) without operating close to its design envelope

CCPS Y-28

• Design equipment for the entire system to accommodate the maximum expected pressure • Select a material of construction that has a wide application range • Verify suitability of equipment for new service (material of construction, pressure and temperature rating, etc.) • Verify suitability of relief device for new service • Develop and implement appropriate cleaning and decontamination procedures

14.

• Ensure that the equipment is able to handle the Using existing equipment for new process chemistry, and that the demands of new process may the new process on ancillary units are also met overtax existing • Perform process hazards analysis ancillary units e.g., • Perform management of change review utilities/disposal/ fire protection etc. Possibility of hazardous event.

15.

Use of temporary equipment for processing

• Implement management of change procedure

CCPS G-1

53

Table 4.0: General

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Management of Change 16.

Equipment inspec- • Reevaluate and possibly reset inspection intervals tion may provide a when equipment is used for handling different poor prediction of chemistry equipment safety • Perform management of change review due to change of material handled or change in process chemistry over the life of equipment.

17.

Not “in-kind” • Ensure that the replacement satisfies the requirereplacements (e.g., ments of duty gaskets, rupture • Implement management of change review disks, packing, process mechanical seals) resulting in failure. Possibility of hazardous release. Loss of Containment

18.

Cyclic nature of • Implement mechanical integrity program batch process (e.g., • Design equipment for easy replacement start/stop, thermal cycling). Possibil- • Consider demand of cycling while designing equipment and controls ity of mechanical wear and tear. Possible loss of containment.

19.

• Procure equipment that can be used in other Available equipment determines processes (current or future) without operating the process chemclose to its operating envelope. istry selected. • Provide equipment with comparable pressure Operating close to rating for the entire system the safe operating • Match batch sizes to equipment capabilities envelope of the equipment and the relief capability.

20.

Frequent start/stop • Minimize frequent start/stop by proper sizing of of equipment may equipment (e.g. pump capacity) lead to equipment • Implement mechanical integrity program failure. • Develop procedure to investigate causes for frequent reset of control • Minimize frequent start/stop of equipment

CCPS G-22 CCPS G-27 CCPS Y-28 OSHA 1910.119

54

4. EQUIPMENT

Table 4.1: Reactors and Vessels

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Use open vent or overflow line discharged to a safe location

API 2350

Overpressure 1.

Overfill, resulting in vessel overpressure.

ASME VIII

• Install level device interlocked to prevent overfill • Install independent high level alarm with instructions to prevent overfilling • Prepare and implement instructions to monitor level and fill rate during transfer and verify that vessel has sufficient free board prior to transfer • Install emergency relief device (ERD) • Design vessel to accommodate maximum supply pressure

2.

Inadvertent or • Ensure that utility connections do not exceed uncontrolled pressure rating of vessel opening of high • Use incompatible utility couplings to prevent pressure utility connections of high pressure utilities system resulting in • Use fixed piping and adequate labeling to avoid vessel coupling errors overpressure. • Install mechanical flow restriction (e.g., restriction orifice) of utility with open vent on vessel • Provide pressure control regulator and pressure relief device • Provide sensor interlocked to isolate utility pressure • Install pressure indication and alarm • Design vessel to accommodate maximum utility pressure • Install emergency relief device/system on vessel and/or utility line • Install emergency relief/device/system on utility service set at or below vessel pressure rating

ASME VIII CCPS G-11 CCPS G-41 ISA S84.01

55

Table 4.1: Reactors and Vessels

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Develop and implement procedure to remove and inspect relief device after suspected operation

ASME VIII

Overpressure 3.

Blockage of relief device by solids deposition (polymerization, solidification). Possible loss of overpressure protection.

CCPS G-11

• Perform visual inspection and scheduled replacement of relief devices periodically • Provide flow sweep fitting at inlet of relief device • Heat trace/insulate vessels and critical piping, as needed • Design to accommodate maximum expected system pressure • Provide a periodic or continuous flush of relief device inlet with purge fluid • Use rupture disks alone or in combination with safety valves with appropriate rupture disk leak detection

4.

Ignition of • Use nonflammable solvents flammable • Provide ignition source controls (e.g., permanent atmosphere in grounding/bonding, nonsplash filling, etc.) vessel vapor space. • Store or process material below its flash point • Use instrumentation that does not provide an ignition source, and/or minimizes the probability of air ingress into vessel. • Inert vapor space • Install oxygen analyzer with alarm • Install flame arrester in vent path • Provide emergency purge and/or isolation activated by detection of flammable atmosphere or high oxygen concentrations • Install deflagration pressure relief • Design vessel to accommodate device/system maximum deflagration pressure

API 2028 NFPA 30 NFPA 68 NFPA 69

56

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Design vessel to accommodate maximum vacuum (full vacuum rating)

AGA XK0775

• Use blanketing gas pressure control system to minimize vacuum

FMEC 7-59

Underpressure 5.

Uncontrolled condensation/absorption of vapor phase component resulting in vacuum creation inside vessel.

ASME VIII

• Install vacuum relief system • Blanket condenser with inert gas • Insulate equipment to mitigate effect of ambient temperature changes, e.g., thunderstorm • Interlock cold liquid feeds with heat source (e.g., distillation column)

6.

Excessive liquid withdrawal rate resulting in possibility of pulling vacuum.

• Design vessel to accommodate maximum vacuum (full vacuum rating)

ASME VIII

• Provide open automatic/manual vent or install a restriction orifice

FMEC 7-59

CCPS G-30

• Size pump to limit withdrawal rate • Interlock pump rate to vessel pressure • Interlock pressure or pump power to shutoff pump • Use inert gas blanket to minimize vacuum • Install vacuum relief system

High Temperature 7.

High temperature material fed to vessel. Temperature excursion outside the safe operating envelope resulting in a runaway reaction.

• Install high temperature alarm, and interlock to activate cooling or shut off feeds at desired temperature • Install interlocks to prevent deadheading of pumps (e.g., high temperature shut-down) • Develop and implement operating instructions to control feed temperature and shut off feed when temperature rises above a certain level • Provide emergency relief device (ERD) • Design system to accommodate maximum expected temperature and pressure

ASME VIII CCPS G-11

57

Table 4.1: Reactors and Vessels

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

High Temperature 8.

ASME VIII Loss of effective • Provide back-up source of cooling cooling. Tempera- • Measure, alarm and/or interlock low coolant CCPS G-11 ture excursion flow, low coolant pressure, high differential temCCPS G-41 outside the safe perature between inlet and outlet operating envelop. • Low coolant flow or pressure or high reactor temperature to actuate secondary cooling medium via separate supply line • Use large inventory of naturally circulating, boiling coolant to accommodate exotherm (e.g., refluxing solvent) • Use antifouling agents and corrosion inhibitors in heat transfer systems • Perform functional test of cooling system prior to batch reaction addition • Ensure automatic isolation of feed on detection of loss of cooling • Install automatic or manual activation of bottom discharge valve to drop batch into a dump tank with diluent, poison, or inhibitor, or to an emergency containment area (May not be effective for systems such as polymerization reactions where there is a significant increase in viscosity.) • Provide for automatic or manual addition of diluent, poison, or inhibitor directly to reactor • Install emergency relief device (ERD) • Design system for maximum expected pressure

9.

Reaction/Ignition or thermal decomposition due to high temperature at unwetted internal heating element surface. Possibility of runaway reaction, vapor phase deflagration or thermal decomposition.

• Limit temperature of heating medium • Use split heating/cooling system to eliminate heat transfer to unwetted surface • Heat with sparged steam/tempered water • Avoid splashing of material onto unwetted heating surface • Use external heating system with process recirculation • Implement operating instructions to maintain liquid level above heating surface at all times • Install automatic level control with low level alarm and shutdown of liquid withdrawal system to ensure liquid is above heating surface at all times • Provide inert vapor space to prevent vapor phase deflagrations • Install emergency relief device (ERD) • Design system to accommodate maximum expected temperature and pressure

ASME VIII CCPS G-11 CCPS G-30 FMEC 7-59 NFPA 68 NFPA 69

58

4. EQUIPMENT

Potential Solutions and Control Mechanisms

Additional Resources

High reactor temperature due to failure of temperature control. Temperature excursion outside the safe operating envelope.

• Limit temperature of heating media and provide automatic shut-off of heat above a present temperature • Provide independent interlocks to shut-off heating media on high temperature • Provide emergency cooling • Provide automatic or manual activation of bottom discharge valve to drop batch into a dump tank with diluent, poison, or inhibitor, or to an emergency containment area • Provide automatic or manual addition of diluent, poison, or inhibitor directly to reactor • Design system to accommodate maximum expected pressure • Install emergency relief device

ASME VIII

Hot spot develops in reaction medium. Temperature excursion outside the safe operating envelope, possibly resulting in a runaway reaction or decomposition. Potential mechanical failure of reactor wall.

• Ensure proper mixing in reactor • Monitor exterior wall temperature with infrared optical detection system, and operating instructions for operator response if high temperature signal occurs • Install high temperature sensors interlocked to shut down reactor • Provide automatic or manual introduction of quench fluid on detection of high local temperature • Shutdown/depressure reactor upon detection of high temperature • Design system to accommodate maximum expected pressure and temperature • Install emergency relief device • Ensure utility temperature does not exceed runaway reaction temperature or vessel maximum design temperature

CCPS G-11

Inadequate heat transfer rates, (e.g., loss of agitation in jacketed vessels). Undesirable reactor temperature leading to either too high or too low reaction rates.

• Provide high/low temperature alarms to shut off feed • Monitor heat removal rate or coolant outlet temperature • Provide adequate heat transfer surface area or temperature gradient (keeping in mind that fluid properties and temperature change as the reaction progresses) • Provide agitator monitoring to alert operators • Design to allow for internal and external fouling resulting in reduction of heat transfer capacity

CCPS G-23

No. Concern/Issue High Temperature 10.

11.

12.

CCPS G-11 CCPS G-22 CCPS G-23

CCPS G-12 CCPS G-23 CCPS G-36 Fisher 1990

59

Table 4.1: Reactors and Vessels

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

High Temperature 13.

14.

15.

External fire expo- • Fireproof insulation (limits heat input) sure resulting in • Slope-away diking with remote impounding of runaway reaction spills and/or system • Locate batch operation outside of affected fire overpressure. zone • Provide safe separation distances • Install fixed fire protection and alarms, water sprays (deluge), and/or foam systems activated by flammable gas, flame, and/or smoke detection devices • Install fire safe bottom valves • Install fire safe valves on major solvent lines • Install remote shut off of fuel sources • Eliminate points of leakage (flanges, hoses). Replace with fixed/welded pipes • Move flammable material storage away from vessel (e.g., pallets, etc.) • Eliminate sources of fuel • Blank unused lines at switching station • Provide emergency cooling activated by external fire (e.g., fusible link, plastic tubing) • Install depressurizing system • Install emergency relief device • Develop emergency response plan

CCPS G-11

High temperature • Limit agitator power input and provide proper due to excessive impeller design agitator shaft work • Limit shaft speed resulting in high • Monitor shaft speed reaction rates. • Provide adequate cooling system • Design system to accommodate maximum expected temperature, and pressure

CCPS G-7

Hot bearing/seals causing ignition of flammables in vapor space. Localized initiation and possible propagation of decomposition or loss of containment.

• Develop alternative agitation methods to eliminate shaft seal as a potential hot spot • Train operators to visually check mechanical seal fluid on regular basis • Inert vapor space • Provide nitrogen buffer zone around seal using enclosure around seal • Install mechanical seal fluid reservoir low level sensor with alarm • Install vibration or temperature sensor with alarm • Install emergency relief device (ERD) • Provide adequate preventive maintenance

FMEC 7-44 NFPA 1 NFPA 11 NFPA 15 NFPA 16 NFPA 25 NFPA 68 NFPA 69 NFPA 204 NFPA 704 OSHA 1910.119. 106

CCPS G-29 Lees 1996

CCPS G-22 CCPS G-29 CCPS G-39 CCPS G-41

60

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Monitor temperature

CCPS G-23

• Provide adequate heating

CCPS G-29

• Design system to accommodate minimum expected temperature

Lees 1996

Low Temperature 16.

Low ambient temperature resulting in embrittlement and/or mechanical failure of reactor.

• Provide freeze protection/heat tracing Mixing 17.

18.

19.

Excessive mixing of reactants or impurities which promotes emulsification. Poor phase separation resulting in problems in subsequent processing steps or in downstream equipment.

• Limit agitator power input and provide proper impeller design

Viscosity of reactor contents increases dramatically with the extent of reaction. Mixing becomes more difficult as reaction proceeds. This may lead to hot spots due to insufficient mixing or inadequate heat transfer rates resulting in runaway initiation.

• Design process to work within agitator limitations

CCPS G-29

• Design agitator to account for property variations with reaction progress

Lees 1996

Incompletely submerged agitator impeller resulting in excessive forces on reactor wall and heads. Possible loss of containment.

• Monitor agitator power input

CCPS G-29

• Design agitator to be stable during filling and emptying operation (e.g., stiffer shaft, foot bearing)

Kletz 1991

CCPS G-29 Lees 1996

• Return process to pilot or development to redesign process to eliminate or minimize this problem • Limit shaft speed • Monitor shaft speed • Test for phase separation • Install de-emulsifiers

Kletz 1991

• Monitor shaft speed • Design system to accommodate maximum expected pressure and temperature • Provide emergency relief device • Monitor viscosity • Add diluent to reduce viscosity • Monitor agitator power input

• Install low level shutoff preventing further liquid withdrawal from vessel • Install low level alarm with interlock to automatically shutdown the agitator • Provide instructions to manually stop agitation at predetermined level in vessel

Lees 1996

61

Table 4.1: Reactors and Vessels

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Use compatible/mutually soluble materials • Provide agitator monitor (shaft speed, load, etc.) to alert operators. • Implement procedures to dispose of unreacted materials • Implement procedure and/or back-up equipment for dealing with imminent danger relating to agitator failures • Interlock agitator power consumption to cutoff feed of reactants or catalyst or activate emergency cooling • Provide emergency power supply backup to motor • Porvide automatic or manual actuation of bottom discharge valve to drop batch into a dump tank with diluent, poison, or inhibitor, or to an emergency containment area • Provide in-vessel agitation (velocity) sensor with alarm • Activate inert gas sparging into reactor liquid to effect mixing • Provide emergency relief device (ERD) • Design system to accommodate maximum expected pressure

CCPS G-11

• Design upstream system to accommodate maximum expected pressure • Provide positive displacement feed pump instead of centrifugal pump or pressurized transfer • Elevate feed vessel above reactor • Provide check valve(s) in feed line (secondary control) • Provide for automatic/manual closure of isolation valve(s) in feed line on detection of low or no flow • Provide for automatic/manual closure of isolation valve(s) in feed line on detection of reverse pressure differential in feed line • Install surge pot between feed vessel and reactor to minimize effects of inadvertent mixing • Install emergency relief device (ERD) on feed vessel or feed line • Feed through vessel top with antisiphon device in feed line • Utilize double block and bleed pipe and valving system

CCPS G-11

Mixing 20.

Loss of agitation causing stratification of immiscible layers. Insufficient mixing of reactants results in unwanted accumulation of unreacted reactants. Possibility of runaway reaction upon resumption of agitation.

CCPS G-23 CCPS G-29 Kletz 1991 Lees 1996

Runaway Reaction 21.

Reactor contents inadvertently admitted to upstream feed vessel. Possibility of reaction in piping and vessel.

CCPS G-23 CCPS G-29 Kletz 1991 Lees 1996

62

4. EQUIPMENT

Potential Solutions and Control Mechanisms

Additional Resources

Corrosion prod• Understand process and do not use materials of ucts lead to catalyconstruction that may lead to problems sis of unwanted • Use corrosion inhibitor reaction. • Implement corrosion monitoring and correction program

ASME VIII

No. Concern/Issue Runaway Reaction 22.

• Implement mechanical integrity program

CCPS G-7 CCPS G-11 CCPS G-22 CCPS G-29

CCPS G-56 • Upgrade material of construction or use resistant Kletz 1991 liner • Implement procedure for testing liner with con- Lees 1996 tinuity meter • Provide emergency dump of reactor contents. • Design system to accommodating maximum expected pressure • Install emergency relief device (ERD) (UPS G-11) • Ensure that pickling or passivation of the system is complete prior to starting the system 23.

Corrosion of equipment and piping. Possible loss of containment.

• Use less corrosive chemistry (inherently safer principles)

CCPS G-29

• Consider addition of corrosion inhibitor

CCPS G-41

• Consider corrosion testing before design • Use corrosion resistant materials of construction • Use resistant liner • Consider procedure for testing liner • Consider use of protective coatings and paints on exterior • Design vessel with double wall and inert space between walls for sampling • Implement scheduled nondestructive testing at key points to monitor corrosion as part of a mechanical integrity program • Evaluate potential for external corrosion from environmental factors such as chloride bearing insulation, chemical spills, sea mist, road salt, etc.

CCPS G-32

63

Table 4.1: Reactors and Vessels

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Loss of Containment 24.

Loss of sealing CCPS G-23 • Circulate vessel contents via external, seal-less fluid for vessel agipump tator seal. Possible • Use double or tandem mechanical seal with inert seal failure and seal fluid emission of flam• Include requirements for operators to visually mable or toxic check seal fluid reservoir levels on a regular basis vapors. in written operating procedures • Provide seal fluid reservoir with low level sensor and alarm • Install flammable and/or toxic vapor sensors where needed • Include operator emergency response to indications of a seal leak in written operating procedures Phase Separation in Vessel

25.

Missing Interface: wrong material sent to next step wrong material sent to waste treatment

• Check both phase layers before proceeding (e.g., add water to “aqueous” phase and/or nonmiscible phase to identify properly) • Analyze samples of each phase at critical steps • Provide drain value with level interphase shutoff

64

4. EQUIPMENT

Table 4.2: Centrifuges

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Implement routine checks of vent lines for plugging

Kletz 1991

Overpressure 1.

Centrifuge vent system blocked, (e.g., flooding of effluent collecting line, freezing, polymerization, and accumulation of solids).

• Monitor pressure drop across vent system (e.g., local indication, alarm or interlock) • Eliminate sources of pressure drop by redesign • Check for solid formation in vent condensers operating below freezing point • Implement thawing cycle • Heat trace vent line (e.g., electrical, steam, glycol)

2.

Gas pressurized feed overpressurizes centrifuge system when feed vessel empties.

• Monitor tank level and provide interlock for feed shut-off • Use alternate fluid delivery system (e.g., pump) • Limit delivery gas pressure to maximum safe working pressure of downstream system (e.g., pressure regulation) • Restrict feed flow rate to be consistent with vent capacity • Ensure adequate vent capacity for maximum possible gas flow

3.

• Provide level switches for effluent collection Blocked liquid vessels effluent line resulting in flooding. • Provide high level alarm in liquid effluent line • Implement preventive maintenance checks

4.

Blockage of liquid effluent line due to closed valves, results in flooding of basket and overflow from basket to solid collection system in base. Possibility of liquid spill.

• Monitor pressure drop across vent system (e.g., local indication, alarm or interlock) • Interlock valve in feed line to centrifuge • Equipment/line-up checks • Remove unnecessary valves • Seal valves open

Lees 1996

65

Table 4.2: Centrifuges

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Maintain nonflammable atmosphere (e.g., inert gas purging)

NFPA 69

Underpressure 5.

Exhaust system introduces a negative pressure in the centrifuge, can introduce air into casing resulting in flammable atmosphere.

• Maintain integrity of gaskets and seals • Check mating faces for corrosion/unevenness particularly on clad components • Use gaskets compatible with materials being processed

High Temperature 6.

Hot feed (increases fire/explosion risk with flammable solvents).

• Provide and maintain an automated inerting system—oxygen concentration or pressure controlled

NFPA 69

• Eliminate leakage sources (fumes/air) • Use alternative solvents (nonflammable or less flammable) • Reduce feed temperature and/or monitor temperature of feed and interlock with feed shutdown

7.

Bowl or shaft bearings running hot. Possibility of ignition of vapor or thermal decomposition of the material.

• Use sealed or purged bearings (to stop ingress of solvent)

FMEC 7-59 NFPA 69

• Establish optimal gearing lubrication program • Introduce feed after centrifuge reaches desired speed to prevent solvent from reaching bearings • Monitor bearings for excess (high) temperature. • Provide and maintain an automated inerting system—oxygen concentration or pressure controlled

Runaway Reaction 8.

Centrifuging of unstable material, shock sensitive material could result in decomposition.

• Test material for impact/shock sensitivity and thermal hazards • Use alternate (low energy) separation process for shock sensitive/unstable material

CCPS G-13

66

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Eliminate interconnections

CCPS G-15

• Interlock feed valves so only one can be open

CCPS G-32

Runaway Reaction 9.

Multiple feeds to single machine, two feeds open at once. Incompatible materials come in contact, possibly leading to runaway reaction.

• Install three-way valve • Implement appropriate operating procedures and training

Corrosion 10.

Failure of clad• Implement routine inspections ding, allowing sub- • Implement periodic nondestructive testing strate to be exposed, leading to corrosion and potential failure.

CCPS G-7

11.

Inappropriate materials of construction lead to corrosion and potential failure.

Dillon 1992

• Select compatible materials of construction for the specific process • Change process parameters (e.g., different acid, reduce temperature). Evaluate changes with test coupons off-line

Loss of Containment 12.

Solvent/fume leak- • Maintain integrity of gaskets and seals age from casing • Use gaskets compatible with process materials joints resulting in • Check mating faces for corrosion/unevenness, loss of particularly on clad components containment.

13.

• Use bottom unloading or inverting (basket) Loss of containment during solids machines discharge. • Provide dump interlock to ensure material is transferred to safe location • Install flexible containment around discharge opening • Enclose centrifuge in self-contained room or enclosure

67

Table 4.2: Centrifuges

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Loss of Containment 14.

Leakage or failure • Use materials of construction compatible with of flexible connecprocess tions between • Implement routine inspections, monitoring and centrifuge and preventive maintenance programs receiving • Design flexible connections and their attachment container. methods to accommodate expected process pressures (positive and negative), system movements and vibrations

15.

Lids and/or inspec- • Interlock so that it is not possible to operate cention ports opened trifuge if lids and/or inspection ports are open while in operation leading to loss of containment, loss of inerting, operator exposure. Ignition Sources

16.

Static electricity generation in machines due to bowl rotation or high feed velocity.

• Use alternate solvent with reduced static potential

BS5958

• Use conductive materials of construction

FMEC 7-59

• Add antistatic agent to nonpolar solvent

NFPA 77

• Check conductivity prior to feeding

Pratt 1997

• Use static dissipating linings if applicable • Use unlined machine with adequate corrosion resistance; If lining is required, it should be conductive • Provide adequate bonding and grounding • Use ant-static drive belt • Reduce linear flow velocities to eliminate static charge buildup during feed • Provide oxygen monitored inerting • Bowl drive shaft requires grounding other than through gear box/bearings (e.g., brushes, slip rings) 17.

Foreign bodies embedded in cake cause heat/sparks during removal (plowing out).

• Provide captive retention of tramp metal in upstream equipment (e.g., magnetic separators, scalping screens) • Install coarse filter in feed line • Minimize tramp metal generation at the source (e.g., lock nuts, washers)

68

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Ignition sources 18.

Loose or misplaced internal hardware causes heat/sparks during plowing out.

• Preventative maintenance and operator prestart checklist

CCPS G-22

19.

Loose drive belts generating frictional heat/static electricity.

• Preventative maintenance checks, tightness and protection from contaminants

CCPS G-29

Hot running bearings.

• Preventive maintenance

20.

• Check belt tension

• Monitor bearings temperature • Purging and sealing to keep solvents out, if solvent (even vapor) exposure is possible • Use improved bearing lubricant

Fires/Explosions 21.

See ignition sources, all these can lead to fire or explosion.

• Oxygen monitored inerting system • Explosion suppression devices

Operator Exposure 22.

Operator exposure • Use bottom unloading or inverting (basket) machines during solids discharge and manual • Design flexible containment around discharge removal residual opening heel. • Enclose centrifuge in contained room or enclosure • Use nitrogen knife to scrape centrifuge General

23.

Vibration during plowing out—can lead to premature equipment failure and a potential ignition source— see above.

• Check plow and linkage for loose components/wear • Sharpen plow or use serrated blade for hardened heels • Manually remove heel more frequently • Plow at lower bowl speed • Advance plow more slowly • Make sure plow system is well damped • Avoid air actuated plows • Avoid use of full depth plows with hard cakes • Use nitrogen knife to scrape centrifuge

CCPS G-29

69

Table 4.2: Centrifuges

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

General 24.

25.

Running unbalanced, vibration due to worn bearings or other mechanical problem such as product accumulation behind filter screen.

• Preventive maintenance and operator checklist inspections

Running unbalanced—vibration due to uneven feeding.

• Redesign feed distributor

• Use effective vibration monitor/shutdown device

• Feed at different bowl speed (usually slower) • Install effective vibration monitor/shutdown device • Adjust feed rate to get uniform distribution

26.

27.

28.

External corrosion • Implement mechanical integrity program of high-energy • Implement proper selection of material of equipment. Loss construction of containment and damage due to flying debris. Continued feed after basket is full.

• Install automatic cut-off (weight activated) • Monitor process

• Interlock feed to bowl rotation Liquid feed continues after basket of centrifuge stops spinning.

CCPS G-23 CCPS G-29 CCPS G-39

70

4. EQUIPMENT

Table 4.3: Dryers

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Design dampers so that system will handle the minimum safe ventilation rate at maximum damper throttling

API 2028

• Bond and ground ducts and equipment

CCPS G-29

• Eliminate flammables, wherever possible

CCPS G-36

• Use inert atmosphere

CCPS G-41

• Design ventilation system to keep flammable concentration below lower flammable limit

FMEC 7-43

• Install on-line flammable gas detection and activation of inerting system

NFPA 13

• Provide automatic sprinkler protection

NFPA 68

• Install deflagration vents

NFPA 69

• Provide automatic isolation of associated equipment via quick closing valves

SFPE 1998

General 1.

Inadequate ventilation in ducts due to partial obstructions or closed dampers leading to creation of flammable atmosphere. Possibility of fire/explosion.

API RP 750

Bossart 1974 • Provide damper mechanical position stop to preCCPS G-11 vent complete closure of damper CCPS G-22 • Eliminate ignition sources within the ductwork

FMEC 7-59 NFPA 15

• Install weak sections in piping and duct work to provide overpressure relief • Design system to accommodate the maximum expected deflagration pressure, where practical • Use prescrubbers/condensers/kilns to reduce load in duct 2.

Batch dryer operation resulting in a high peak evaporation rate of flammable solvent causing buildup of flammables. Possibility of fire/explosion.

• Inert/purge dryer

FMEC 7-43

• Design ventilation system to handle the peak sol- FMEC 7-59 vent evaporation rate SFPE 1998 • Replace flammable solvent (e.g., water based) • Develop and implement system and operating procedure designed to allow for unsteady evaporation rates

General 3.

Inadequate circulation in equipment causing accumulation of flammable pockets. Possibility of fire/explosion.

• Design so that natural circulation is sufficient to prevent accumulation of flammables

ACGIH 1986

• Eliminate flammable solvent (e.g., water-based)

CCPS G-29

• Design system to accommodate maximum deflagration pressure, where practical

CCPS G-39

CCPS G-23

CCPS G-41

71

Table 4.3: Dryers

Potential Solutions and Control Mechanisms

Additional Resources

Premature shut• Design so that natural circulation is sufficient to down of fans/venprevent accumulation of flammables and/or cretilation system ation of hot spots immediately fol• Design system to accommodate maximum deflalowing shutdown gration pressure, where practical of heat input Use postventilation interlocks and/or operating • (prior to sufficient procedures to keep fans running for a sufficient cooling) resulting time after shutdown of heating systems in hot spots and flammable pockets (dryers, carbon beds, thermal oxidizers). Possibility of subsequent ignition resulting in fire or explosion.

CCPS G-11

Production of fine powder during auxiliary processing. Possibility of a dust or dust/hybrid explosion.

• Operate below minimum oxygen concentration

AGA XK0775

• Practice good housekeeping

CCPS G-23

• Grind/blend under inert atmosphere

CCPS G-41

• Provide damage limiting construction

Eckhoff 1997

• Design system to accommodate maximum deflagration pressure, where practical

FMEC 7-59

Drying thermally unstable chemicals: thermal decomposition resulting in vessel overpressure or rupture.

• Control temperature of heating media below expected initiation temperature

API RP 750

• Use isothermal aging tests to monitor stability at desired drying temperature

CCPS G-29

No. Concern/Issue General 4.

5.

6.

CCPS G-23 CCPS G-39 NFPA 68 NFPA 69

Lees 1996 • Maintain inlet temperature of heating medium to NFPA 69 equipment sufficiently below the minimum igniNFPA 654 tion temperature Palmer 1973 • Eliminate flammable solvent

CCPS G-23

CCPS G-30 • Use inert atmosphere/purge to eliminate combusCCPS G-41 tion that could serve to initiate bulk thermal Lees 1996 decomposition • Screen chemicals to be dried for thermal stability NFPA 654 • Evaluate and design for pressure consequences of NFPA 86 thermal decomposition Palmer 1973 • Evaluate potential for solid phase deflagration (Continued on next page)

72

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

General 6.

(Continued)

• Eliminate “tramp metal”, broken parts, and “lumping” materials in dryer that may cause localized overheating (particularly agitated pan and auto-filter dryers) • Evaluate heating due to sustained agitation in agitated pan dryers • Use alternate drying method (ex. vacuum drying instead of atmospheric drying; vacuum tray dryer, freeze drying, cryogenic CO2 drying, instead of vacuum rotary dryer) where material is subdivided in multiple locations • Implement preventive maintenance on bearings for rotary, autofilter, and agitated pan dryers • Monitor temperature of material being dried by infrared, resistance temperature device, (RTD) etc. • Monitor heating media inlet and outlet temperature

7.

8.

Vapor–air deflagration inside dryer: thermal decomposition resulting in vessel overpressure or rupture.

• Use inert atmosphere/purge

Material sent to next step too hot from dryer:

• Cool material adequately before emptying from dryer

• thermally unstable material leading to violent decomposition • combustible material leads to fire/explosion in downstream equipment.

NFPA 86

• Evaluate and design for pressure consequences of NFPA 654 thermal decomposition NFPA 69 • Evaluate potential for solid phase deflagration • Design system to accommodate the maximum expected deflagration pressure

See also Drumming Equipment (Table 4.7)

73

Table 4.4: Batch Distillation and Evaporation

Table 4.4: Batch Distillation and Evaporation

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Consider downstream processing that does not require that the intermediate be stripped to dryness

API RP 750

General 1.

Removal of liquid from phase that is a known thermal decomposition hazard (“strip-todryness”), i.e. liquid/solid level falls below temperature sensing device leading to overheating of thermally unstable material resulting in decomposition.

• Use vacuum distillation to obtain lower boiling point of solvent to allow lower distillation temperature

CCPS G-13 CCPS G-23 CCPS G-29 CCPS G-30

• Consider co-distillation (replace one liquid with CCPS G-41 another in portionwise distillation) or azeotropic Cronin 1987 distillation Eckhoff 1997 • Consider incorporating inert material to act as NFPA 36 heat sink NFPA 491 • Implement in-process analysis to determine if thermally unstable component is consumed or converted • Provide temperature measurement in bottom of vessel to insure temperature monitoring • Limit maximum utility temperature by choosing different heating/cooling medium (e.g.. tempered water in atmospheric loop vs. high pressure steam) • Provide redundant independent temperature monitoring instrumentation

2

Removal of liquid • Evaluate thermal stability characteristics of reacfrom phase that is tion mixture an unknown ther- • Conduct thorough evaluation of process modifimal decomposication using management of change review tion hazard (due procedure to contamination, unreacted thermal See also item 1 above decomposition hazard material, or change in starting material) leading to overheating of thermally unstable material resulting in decomposition.

CCPS G-13 CCPS G-22 CCPS G-29 CCPS G-30 CCPS Y-28 Cronin 1987

74

4. EQUIPMENT

Potential Solutions and Control Mechanisms

Additional Resources

Freezing/plugging of condenser, with continued heating or process feed, leading to overpressure of vessel.

• Use cooling medium that will not cause freezing (e.g., tempered water instead of chilled water)

API RP 750

• Monitor pressure drop across condenser

CCPS G-29

Drawing distillate back into the distilling vessel.

• Do not use sub-surface inlet to receiver from condenser

API RP-75

• Use “weep-hole” (siphon break) in sub-surface inlet piping

CCPS G-10

No. Concern/Issue General 13.

4.

CCPS G-10

• Provide “thawing cycle” • Provide high pressure interlock to shutdown heating and/or process feed

• Ensure valves are in correct position • Incorporate batch distillation into written procedure for the process • Fill vacuum vapor space of vessel with inert gas prior to cool down

Bossart 1974 CCPS G-22 CCPS G-25 CCPS G-27 CCPS G-29 FMEC 7-59

• Install check valve in distillate discharge line 5.

6.

Inadequate • Sample and analyze prior to proceeding to next removal of solvent step leading to unwanted reaction in downstream equipment or in subsequent steps.

API RP 750

Co-distillation • Evaluate isothermal aging characteristics of therleads to long mally unstable components at the maximum period of time expected utility temperature under heat result- • Consider using the same solvent in the next step ing in exceeding (i.e. eliminate the co-distillation) the isothermal aging characteristics for a thermally unstable material which leads to thermal decomposition and overpressure of the vessel.

CCCPS G-1

CCPS G-6 CCPS G-13 CCPS G-27 CCPS G-29

CCPS G-6 CCPS G-13 Cronin 1987

75

Table 4.5: Process Vents and Drains

Table 4.5: Process Vents and Drains

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Design vent lines to prevent low point traps (pockets)

CCPS G-11

• Provide adequate drainage

CCPS G-23

General 1.

Low point traps (pockets) in vent lines.

CCPS G-22

• Design and maintain drainage system for trapped sections of vent lines 2.

Prescrubbing (vessel containing scrubber solution between vacuum source and batch vessel). High concentration of off-gases resulting in overpowering abatement equipment.

• Provide subsurface addition to prevent “bypassing” of prescrubber solution

API RP 750

• Implement pH monitoring to determine useful life of scrubbing solution

CCPS G-22

• Consider the thermal effects of reaction mixture transfer to prescrubber

CCPS G-25

• Install high temperature interlock on discharge of condenser to shutdown reactor and initiate emergency cooling

FMEC 7-43

• Use “large volume” prescrubber to minimize potential for overcoming and/or by-passing it

NFPA 36

Bringing scrubbing • Provide vacuum break to prevent siphoning of solution back into prescrubber solution back to reactor reactor.

4.

Uncontrolled release of flammable, toxic, or environmentally detrimental vapors from atmospheric vents.

Hendershot 1987

• Route to scrubber, quench, or other control device

CCPS G-3

• Install differential pressure or flow monitoring device to indicate flow into/out of vent

CCPS G-11

• Use conservation vent to minimize releases • Provide flame arrester in/on vent line • Ensure vents relieve to a safe location. If vented to atmosphere, ensure proper classification and controlled access

Drawing reaction mixture into vacuum system or scrubbing system.

CCPS G-23

• Provide agitation, cooling jacket, and temperature CCPS G-29 control for prescrubber to improve operation CCPS G-41

3.

5.

CCPS G-13

• Provide empty vessel between vacuum source or scrubbing system and reaction vessel to act as liquid trap • Investigate incompatibility of various process streams going to the same vacuum or scrubbing system • Monitor vacuum level between source and reaction vessel

CCPS G-4 CCPS G-13 CCPS G-23 CCPS G-29

CCPS G-13 CCPS G-23 CCPS G-30

76

4. EQUIPMENT

Table 4.6: Transferring and Charging Equipment Potential Solutions and Control Mechanisms

Additional Resources

Temporary connections offer a lot of flexibility to operations but also creates concerns about increased operator exposure, loss of containment, and the ability to add the incorrect material or charge to the incorrect vessel.

• Use permanent piping, wherever possible

CCPS G-3

• Provide clear labeling on all lines entering and exiting vessels

CCPS G-10

• Provide and require use of personal protective equipment (PPE)

CCPS G-20

Open manway/ addition port results in release of flammable, toxic, or environmentally detrimental vapors.

• Limit opening of manholes

ACGIH 1986

• Use localized ventilation (flexible ventilation pick-up close enough to manway/addition port to effectively capture emissions)

API std. 653

No. Concern/Issue General 1.

2.

• Implement appropriate procedures and training

CCPS G-15 CCPS G-22 CCPS G-29 CCPS G-30 CCPS G-32

• Lower batch temperature to 20°C below boiling point before opening

API std. 2000 API std. 2015 CCPS G-29 NFPA 328

Overpressure 3.

4.

Overfill resulting in vessel overpressure.

Excessive fill rate.

• Use sensors/alarm/interlocks (i.e., weight, level sensors)

API RP 750

• Ensure vessel has room for transfer

CCPS G-29

• Install high-high level switch in receiving vessel interlocked to feed and/or emergency dump

CCPS G-30

CCPS G-3

• Install flow restriction orifice in fill line

API RP 750

• Install fill line control with high flow alarm and/or shutdown

ASME VIII

• Provide interlock activated by high pressure or high flow

CCPS G-22

• Develop and implement procedures to monitor level and fill rate during transfer and verify that vessel has sufficient free board prior to transfer

CCPS G-29

• Provide emergency relief device (ERD) • Design vessel to accommodate maximum expected supply pressure

CCPS G-11 CCPS G-23 DIERS

77

Table 4.6: Transferring and Charging Equipment

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Check for improperly labeled partial containers

API RP 750

Overpressure 5.

Incorrect amounts charged.

• Ensure correct amount is on hand before starting CCPS G-22 • Use control devices (flow, level, etc.)

CCPS G-29

• Modify recipe to use whole containers • Modify recipe to use whole pallet or container 6.

Pumping of heat sensitive material. Exothermic decomposition leading to overpressure.

• Design casing to contain decomposition overpressure

CCPS G-1

• Provide deadhead protection (hydraulic relief)

CCPS G-11

• Use jacketed cooled pumps

CCPS G-23

• Avoid the use of positive displacement pump

FMEC-1974

• Select pump to minimize heat input

Lees 1996

• Provide high temperature/pressure alarm and shutdown

NFPA 496

CCPS G-8

• Provide emergency relief device (ERD) 7.

8.

Decomposition of heat sensitive process material due to heat generated from mechanical input (i.e., plugging of rotary feeders, paddle dryers, screw conveyors).

• Use equipment types which minimize mechanical CCPS G-11 heat input CCPS G-28 • Install deflagration venting and/or suppression NFPA 68 system NFPA 69 • Eliminate tramp metal in feed to grinder, screw, etc.

NFPA 654

• Eliminate tramp metal generated due to equipment breakage

• Design to accommodate for maximum expected Pump used for higher than design pressure density fluid ser• Verify suitability of pump for service; replace if vice resulting in necessary high discharge • Provide emergency relief device (ERD) pressure. • Provide interlock to shutdown pump on detection of high discharge pressure • Ensure management of change procedures are followed • Monitor power and install high current shutdown

CCPS G-11 CCPS G-23 CCPS G-29 CCPS Y-28

78

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Overpressure 9.

Pump deadheaded. • Check for downstream closure

CCPS G-11

• Use minimum flow recirculation lines piped back CCPS G-29 to feed vessel • Consider use of internal relief valve as applicable 10.

Vent system inoperable or plugged.

• Check and open vents by scheduled preventive maintenance

AGA-X0775

• Monitor flow through vent system; provide steady purge if needed

CCPS G-22

• Make sure vent system is sloped to drain to knock-out pot (separator)

CCPS G-11 CCPS G-29

• Perform periodic maintenance and inspection 11.

12.

13.

Inert gas or other pressure source is open.

• Install a pressure regulator to control source pressure • Install pressure indicator and relief valve

Adding volatile • Indication and alarm on high temperature phase on top of • Interlock additions valves to vessel temperature hot phase (or vice versa) resulting in • Provide adequately sized emergency relief device (ERD) rapid phase transition and overpressuring of vessel.

API RP 750

Blockage of • Size piping system to maintain minimum piping, valves or required velocity to avoid build-up of solids flame arresters due • Eliminate flame arrester or use dual (parallel) to build-up of flame arresters with on-line switching solids. Potential capabilities for system • Remove solids from process stream (knockout overpressure. pot, filter, cyclone separator, etc.)

CCPS G-11

• Provide insulation/tracing of piping to minimize solid deposition (freezing/precipitation) • Provide recirculation line to minimize deposition • Install flush mounted valves • Implement periodic cleaning via flushing, blowdown, internal line cleaning devices (e.g., “pigs”) • Design piping for maximum expected pressure • Install emergency relief devices where appropriate

CCPS G-11 CCPS G-22 CCPS G-29

CCPS G-54 DIERS FMEC 1974 IRI 1990 Lees 1996 NFPA 54 NFPA 69

79

Table 4.6: Transferring and Charging Equipment

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Increase pressure at source

CCPS G-23

Underpressure 14.

Low pump head pressure.

• Verify pump design will achieve needed pressure • Check for restrictions in suction and discharge lines

15.

Failure of vacuum system control resulting in possibility of vessel collapse.

• Design vessel to accommodate maximum vacuum (full vacuum rating)

ASME VIII

• Install vacuum relief system

CCPS G-39

CCPS G-23

• Provide low pressure alarm and interlock to inert gas supply • Select/design vacuum source to limit vacuum capability

High Temperature 16.

17.

Temperature control failure on lines/equipment.

• Perform periodic maintenance and inspection

CCPS G-22

• Install redundant control system

CCPS G-29

Line or equipment • Include hydraulic relief in line exposed to direct • Provide adequate insulation for solar protection sun or heat source. • Clear lines after each use

CCPS G-11

Low Temperature 18.

Cold ambient temperature.

• Provide insulation, heating, etc.

19.

Temperature control failure on lines or equipment.

• Check heat tracing

CCPS G-29

• Perform periodic maintenance and inspection

Corrosion 20.

Incorrect/incompatible materials of construction used in transferring/charging line or equipment.

• Review material of construction requirements vs. CCPS G-23 existing equipment before changing service • Use corrosion coupons during pilot/development/scale-up

80

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Check label versus process requirements

CCPS G-22

• Check correct step in operating procedure

CCPS G-29

• Label materials, lines pumps and valves

CCPS G-30

• Use staging area

Hendershot 1987

Corrosion 21.

Incorrect concentrations of material are charged resulting in a corrosive environment, (i.e., diluting acid).

• Check labels against batch sheets • Use double check system • Set valves to correct flow path • Use procedures and training

Runaway Reaction 22.

Unwanted reaction • Clean and inspect equipment after each use due to • Design with compatible materials contaminants. • Maintain integrity of the system • Design emergency relief system (ERS) for runaway scenario

23.

Accumulation of • Design system to accommodate maximum reactive material expected pressure in section of auxil- • Use inherently safer chemistry iary equipment or piping. Possibility • Implement on-line measurement (e.g., level, temperature, composition) and side draw-off of of runaway reactive material reaction. • Eliminate pockets where material could accumulate

CCPS G-13 CCPS G-22 CCPS G-23 CCPS G-29

CCPS G-11 CCPS G-23 CCPS G-29 CCPS G-41 Kletz 1991

• Design piping and equipment to drain to a safe location • Provide emergency relief design (ERD) • Provide procedures to clean pipes 24.

Incorrect chemicals used.

• Label materials, lines, pumps and valves

API RP 750

• Use staging area

CCPS G-3

• Check labels against batch sheets

CCPS G-22

• Set valves to correct flow path

CCPS G-30

• Use double check system

CCPS G-33

• Use procedures and training • Use different packaging for different chemicals

81

Table 4.6: Transferring and Charging Equipment

Potential Solutions and Control Mechanisms

Additional Resources

Charging thermally unstable material to warm reactor results in decomposition.

• Install local indication and alarm on high temperature

CCPS G-23

Poor distribution of solids or liquid charge. Potential for excessive reaction rates due to localized overconcentrations of reactants.

• Implement appropriate procedures and training

No. Concern/Issue Runaway Reaction 25.

26.

• Provide emergency cooling

CCPS G-22

Loss of Containment 27.

Pump is operated at a fraction of capacity. Possibilities of excessive internal recirculation, frequent seal and bearing failure resulting in loss of containment.

• Match pump capacity to the service

CCPS G-23

• Install minimum flow recirculation line to heat sink to ensure adequate cooling of the pump

CCPS G-29

• Provide interlock to shutdown pump on minimum flow indication • Implement procedural controls to avoid operating at too low a flow • Provide deadhead protection

28.

Transfer path is • Verify open and clear transfer path before initiblocked due to ating transfer closed valve, blind • Utilize pressure and flow sensors etc. Pressure is built up in system and leaks in piping occur.

29.

Release of toxic/flammable material from piping due to leak, flange leak, valve leak, pipe rupture, collision, or improper support.

CCPS G-29

• Implement procedure for line breaking

API RP 1623

• Select materials of construction for pipes and gaskets to be compatible with all materials to be transferred

ASME B31.3

• Install fireproof/spiral wound gaskets where applicable • Install new hose gaskets for each batch connection (Continued on next page)

CCPS G-22 CCPS G-23 CCPS G-24 CCPS G-29 CCPS G-39

82

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Loss of Containment 29.

(Continued)

• Maximize use of welded pipe vs. screwed or flanged and minimize use of unnecessary fittings • Avoid use of underground/hidden piping • Use double walled pipe with annular nitrogen purge and monitoring capabilities • Provide flange shields to prevent operator exposure • Account for thermal cycling of lines • Use minimum diameter pipe for physical strength • Use proper design and location of piping supports • Provide physical collision barriers • Provide isolation on detection of high flow, low pressure, or external leak • Install excess flow valves • Use fusible link fire safe valves for automatic closure under fire conditions • Develop and implement procedural restrictions to avoid damage (crane restrictions, climbing restrictions) • Use totalizing meters on each end of line to detect leak • Adhere to design requirements for seismic zone

NFPA 30

• Perform piping flexibility studies • Install pressure relief for thermal expansion 30.

• Eliminate hose, use hard pipes wherever possible Degradation of hose results in leak • Consider use of higher integrity hose (e.g., and release of metallic braided) toxic/flammable • Use hoses rated for required maximum system material. pressure and pressure test before use • Periodically replace hoses • Provide excess flow check valve upstream and check valve downstream of hose • Isolation based on detection of high flow, low pressure or external leak • Use fusible link fire safe valves for automatic closure under fire conditions (Continued on next page)

CCPS G-22 CCPS G-23 CCPS G-29 Kletz 1991 NFPA 30 NFPA 70

83

Table 4.6: Transferring and Charging Equipment

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Loss of Containment 30.

(Continued)

• Provide crush protection (e.g., ramp) when laying hoses across roadway • Avoid sharp angle changes in direction • Implement procedure for cleaning hoses and inspection • Use a dedicated hose for each material transferred • Install appropriate bonding and grounding with periodic testing • Select appropriate material of construction • Avoid the use of transfer hoses in hidden areas

31.

Deterioration of pipe/hose lining due to chemical attack or electrostatic discharge.

• Use pipe material of construction which does not API RP 1632 require lining Britton 1999 • Use conductive liner to reduce potential for deg- CCPS G-23 radation due to static discharge CCPS G-29 • Use thicker liner material NFPA 69 • Limit liquid velocity to minimize static buildup NFPA 77 • Perform periodic thickness testing of metal pipe wall • Perform periodic process stream analysis for metals content • Ensure proper care is used during lined pipe installation

32.

Piping erosion.

• Limit fluid velocity

Crane’s Fluid Flow Handbook

33.

Portable equipment and temporary connections for processing receive more wear than fixed system. This may lead to hazardous release, ignition or explosion.

• Pressure test connections

CCPS G-29

• Provide manual bonding and grounding

NFPA 70

• Analyze hazards before using portable equipment • Evaluate procedure for installation/hook-up to ensure proper safety is achieved • Provide double protection of quick connects • Follow mechanical integrity program • Conduct process hazards analyses • Implement management of change controls

84

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Loss of Containment 34.

Frequent disassembly/assembly of equipment increases mechanical wear resulting in possible loss of containment.

• Follow mechanical integrity program

CCPS G-29

• Implement testing of equipment prior to each use or change of service

IRI 1990

• Implement procedures to verify change of service

Lees 1996

Kletz 1991

• Interlock procedures to verify safety before opening • Ensure maintenance procedures are followed • Select equipment for ease of assembly/disassembly • Implement procedures for line breaking/cleaning • Provide correct tools for assembly/disassembly

Fire and Explosion 35.

Ignition of condensed flammable vapor or solid deposits in ductwork/piping resulting in possibility of fire/explosion.

• Design system to prevent condensation

API RP 750

• Design system with smooth surfaces to minimize buildup of deposits

CCPS G-11

• Eliminate potential points of solids/liquid accumulation

CCPS G-23

• Implement good housekeeping procedures • Provide for drainage of piping/ducts (e.g., sloped, low point drains)

CCPS G-22 CCPS G-24 CCPS G-29 CCPS G-41

• Eliminate ignition sources within the ductwork

Lees 1996

• Provide adequate bonding and grounding

NFPA 13

• Eliminate flammables or combustibles

NFPA 15

• Use of inert atmosphere

NFPA 68

• Design ventilation system to keep flammable concentration below lower flammable limit

NFPA 69

• Install on-line flammable gas detection system that activates an inerting system • Provide automatic sprinkler system • Use deflagration vents • Design for automatic isolation of associated equipment via quick closing valves • Design system to accommodate maximum expected pressure, where practical • Design for operation above dew point or sublimation point

85

Table 4.6: Transferring and Charging Equipment

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Fire and Explosion 36.

Electrostatic spark discharge and ignition during charging of liquids, or during mixing, cleaning etc. resulting in possibility of fire/explosion. Excessive addition rate (linear flow velocity) can result in electrostatic charge. Potential for explosion to start a thermal decomposition of reaction mass.

• Use nonsplash addition methods for liquids (e.g., API RP2003 subsurface addition, addition along the wall, BS 5958 etc.) CCPS G-11 • Use “antistat” with nonpolar solvents NFPA 13 • Ensure that cooling solvent temperature is suffiNFPA 68 ciently low to operate outside flammable limits NFPA 69 • Control velocity/turbulence of liquid addition • Avoid filters on addition lines close to inlet to reduce turbulence and charge generation

NFPA 70

• Inert vessel and verify safe atmosphere before charging

Pratt 1997

NFPA 77

• Control humidity in operating area (as humidity increases, static potential decreases) • Avoid use of nonconductive materials of construction for both installed equipment and charging containers, funnels, etc. • Provide ground indicator with interlock to prevent manhole opening if ground connection to solids container is faulty • Implement procedures for manual grounding and bonding of additions container and funnel to vessel • Ground the operator and provide operator with proper clothing/attire (e.g., conductive shoes with periodic testing) • Install permanent bonding/grounding of equipment system with periodic testing • Install fire/deflagration suppression system

37.

Electrostatic spark discharge and ignition during charging of solids resulting in possibility of fire/explosion. Potential for explosion to start a thermal decomposition of reaction mass.

• Eliminate addition of materials as solids (e.g., use slurry)

AGA XK0775

• Consider charging solids before solvents

BS 5958

• Charge solids materials by means of a closed system (e.g., hopper and rotary airlock, screw feeder, double-dump valve system, etc.)

CCPS G-22

• Inert vessel and verify safe atmosphere before charging

CCPS G-29

• Control humidity in operating area (as humidity increases, static potential decreases) (Continued on next page)

NFPA 68 (Continued)

API RP 2003

CCPS G-23 CCPS G-32

86

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Avoid use of nonconductive materials of construction for both installed equipment and charging containers, funnels, etc.

NFPA 69

Fire and Explosion 37.

(Continued)

• Avoid use of nonconductive liners in charge containers

NFPA 70 NFPA 77 Pratt 1997

• Provide ground indicator with interlock to prevent manhole opening if ground connection to solids container is faulty • Implement procedures for manual grounding and bonding of solids container and funnel to vessel • Ground the operator and provide operator with proper clothing/attire (e.g., conductive shoes with periodic testing) • Install permanent bonding/grounding of equipment system with testing • Install fire/deflagration suppression system 38.

39.

Tramp materials introduced into manway, leading to impact or frictional spark, igniting vapors.

• Install scalping screen on vessel charge hatch

CCPS G-22

• Remove tramp materials prior to charging vessel

CCPS G-23

Inert gas not pres- • Determine process requirements ent leading to cre- • Implement correct procedures ation of flammable • Install vapor space analyzers with alarm atmosphere.

CCPS G-29

Bossart 1974 CCPS G-1 CCPS G-22 CCPS G-23 CCPS G-29 CCPS G-32 ISA RP 12.13

40.

Incorrect electrical • Check area classification and verify that electrical equipment is properly rated classification for equipment or auxiliary equipment, lighting, etc., possibly leading to unsafe conditions.

API RP 500 CCPS G-23 CCPS G-29 NFPA 70 NFPA 497

87

Table 4.6: Transferring and Charging Equipment

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Control rate of addition of solids, so as not to exceed inerting capacity • Charge solids by means of a closed system (e.g., hopper and rotary airlock, screw feeder, doubledump valve system, etc.), with solids purged with inert gas prior to addition to vessel

AGA XK0775

Fire and Explosion 41.

42.

Solids addition entrains air into inerted head space, creates flammable mixture.

Vacuum transfer • Install low level interlock on supply vessel to into reactor, drum shut down transfer or feed tank runs • Monitor oxygen level in head space dry, resulting in air being pulled into vessel, creating flammable atmosphere. Potential for fire/explosion.

CCPS G-23 CCPS G-29 FMEC 1997

CCPS G-23 CCPS G-29 Fisher 1990 ISA S84.01

Also, potential for static charges generation due to misting of liquid at end of transfer. 43.

44.

Static charge gen- • Charge solids by means of a closed system (e.g., eration due to too hopper and rotary airlock, screw feeder, doublerapid transfer out dump valve system, etc.) of drum or flexible • Control rate of solids addition (e.g., size of intermediate bulk opening in super sack) container (super • Procedures and training sack).

CCPS G-22

Inadequate ventilation in ducts due to partial obstructions or closed dampers leading to creation of flammable atmosphere and possibility of fire/explosion.

ACGIH 1986

• Design dampers so that system will handle the minimum safe ventilation rate at maximum damper throttling • Provide damper mechanical position stop to prevent complete closure of damper • Eliminate flammables or combustibles • Provide inert atmosphere • Design ventilation system to keep flammable concentration below lower flammable limit • Install on-line flammable gas detection system that activates an inerting system • Provide automatic sprinkler protection • Use deflagration vents • Design for automatic isolation of associated equipment via quick closing valves • Design system to contain overpressure if practical • Install prescrubbers/condensers to reduce load in duct

CCPS G-23 CCPS G-29 CCPS G-32

API 2028 Bossart 1974 CCPS G-12 CCPS G-23 CCPS G-29 CCPS G-41 ISA S84.01 NFPA 11 NFPA 13 NFPA 15 NFPA 68 NFPA 69

88

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Follow safe procedures for drum stacking and moving

CCPS G-3

• Use lockout/tagout procedures

CCPS G-29

Operator Exposure 45.

46.

Palletizing/moving drums incorrectly-drum falls and breaks or opens.

CCPS G-22 CCPS G-32

Material released • Blow (purge) system, clean lines, before breaking AGA XK0775 the connection when transfer lines CCPS G-22 are disconnected. • Minimize use of hoses CCPS G-29 FMEC 1997

47.

48.

49.

50.

51.

Lines are not depressurized before disconnecting.

• Follow proper operating instructions

CCPS G-22

• Install or use small bleed valves

CCPS G-23 CCPS G-29

Nitrogen pressur- • Check line integrity and all fittings, couplings, ization of lines or etc. before transfer is started equipment that are not sealed tight.

CCPS G-22

Pressurization due • Stop transfer and de-pressurize before breaking to plugged transfer line and clearing plug lines.

CCPS G-22

Sampling spills.

Blowing down lines for cleaning.

CCPS G-29

CCPS G-29

• Wear proper personal protective equipment (PPE)

CCPS G-22

• Follow proper sampling procedures

CCPS G-29

• Use safe sampling design

Lovelace 1979

• Verify flow path before starting the flow.

CCPS G-22

• Blow (purge) lines to safe location which protects the operator and environment

CCPS G-23

• Wear proper personal protective equipment (PPE) • Follow proper sampling procedures • Use safe blow-down design

CCPS G-23

CCPS G-29

89

Table 4.6: Transferring and Charging Equipment

Potential Solutions and Control Mechanisms

Additional Resources

Vapor escaping from open manway, engulfs operator, could ignite resulting in flash fire.

• Provide local ventilation at charge hatch

ACGIH 1986

• Charge solids materials by means of a closed system (e.g., hopper and rotary airlock, screw feeder, double-dump valve system, etc.), connected to vent system

CCPS G-22

Runaway reaction with manway open—foam out (can be acid based), operator contacted by process materials.

• Interlock manway with vessel pressure

CCPS G-22

• Design system for closed manual operation

CCPS G-23

No. Concern/Issue Operator Exposure 52.

53.

54.

CCPS G-23 CCPS G-29

CCPS G-29 Fisher 1990 ISA S84.01

Operator exposure • Charge liquids and solids materials by means of a ACGIH 1986 to fumes or inerts. closed system (e.g., hard piping, hopper and CCPS G-22 rotary airlock, screw feeder, double-dump valve CCPS G-23 system, etc.) CCPS G-29 • Provide local ventilation • Use proper personnel protective equipment (PPE)

55.

Operator comes into contact with agitator through manway.

• Implement procedures and training

CCPS G-22

• Interlock manway with agitator rotation

CCPS G-23

• Install scalping screen on manway

CCPS G-29 Fisher 1990 ISA S84.01

56.

• Provide mechanical assists for handling and Ergonomic issues during charging, dumping of containers handling of heavy and unwieldy containers, potential for personnel injury.

CCPS G-23 CCPS G-29

90

4. EQUIPMENT

Table 4.7: Drumming Equipment Potential Solutions and Control Mechanisms

Additional Resources

Contaminants/ foreign material in drum, leading to reaction in drum.

• Inspect drum before filling

CCPS G-3

Nitrogen blow through into drum from feed vessel during pressure transfer leading to loss of containment.

• Provide level indicator in feed vessel with alarm/interlock

No. Concern/Issue Overpressure 1.

2.

CCPS G-15 CCPS G-29 CCPS G-30 AGA XK0775 CCPS G-3 CCPS G-15 CCPS G-22 CCPS G-23 CCPS G-29 FMEC 1997

3.

Use of pumps to transfer material to drum leading to overpressure.

• Limit filling rate to not exceed vent rate

ACGIH 1986

• Use metering pumps

CCPS G-3 CCPS G-15 CCPS G-22 CCPS G-23 CCPS G-29

4.

Vent bung cap not removed prior to filling.

• Vent around feed nozzle through 2″ bung opening

ACGIH 1986

• Select container designed to fail at low pressure

CCPS G-22

• Follow proper drum filling procedure/checklist

CCPS G-23

CCPS G-3

CCPS G-29 5.

Vent system inoperable or clogged.

• Test system back pressure before use

ACGIH 1986

• Flow indication or pressure drop indication

CCPS G-3 CCPS G-22 CCPS G-23 CCPS G-29

Overpressure 6.

Vent system not balanced with inlet, or undersized.

• Reduce feed rate or redesign vent system

ACGIH 1986 CCPS G-22 CCPS G-23 CCPS G-29

91

Table 4.7: Drumming Equipment

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Store drum at proper temperature

CCPS G-3

• Keep drum away from heat source

CCPS G-15

• Ensure reaction is complete before drumming

CCPS G-22

• Allow adequate freeboard for material

CCPS G-29

Overpressure 7.

Overpressure of material in drum due to external heat input or self heating.

• Provide adequate sprinkler protection • Thermally initiated venting (e.g., melt-out bungs) Loss of Containment 8.

9.

10.

11.

Thermal expansion due to liquid overfill leading to loss of containment.

• Drum at proper temperature

CCPS G-3

• Keep drum away from heat source

CCPS G-14

• Ensure reaction is complete before drumming

CCPS G-22

• Allow adequate freeboard for each material

CCPS G-29

Palletizing/moving • Follow proper palletizing and drumming drums incorprocedures rectly—drum • Stretch wrapping/strapping pallets falls and breaks or opens.

CCPS G-3

Drum not sealed properly.

• Seal containers as directed in operating procedures

CCPS G-3

• Use new gaskets

CCPS G-22

• Provide correct tools for sealing drums

CCPS G-29

Drum not intact— • Inspect drum before use holes, cracks, etc. • Pressure check drums for leaks

CCPS G-14 CCPS G-22 CCPS G-29

CCPS G-15

CCPS G-3 CCPS G-22 CCPS G-29

12.

13.

Overfill drum due • Calibrate weighing devices and maintain equipto operator error ment in good working order or valve failure, • Use metering pumps can lead to operator exposure, slip- • Interock fill operation with weighing device pery floors, spread of flammable liquids. Material escapes when filters are changed.

CCPS G-3 CCPS G-15 CCPS G-22 CCPS G-29

• Blow (purge) system, clean lines before changing filters

AGA XK0775

• Isolate and drain filters

CCPS G-14

CCPS G-3 CCPS G-22 CCPS G-29 FMEC 1997

92

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Loss of Containment 14.

15.

Leaks in various system components, hoses, valves, swivel joints in arm, lance, etc. Lines are not depressurized before checking, changing filters.

• Periodic replacement of components

CCPS G-3

• Pressure test all lines

CCPS G-22

• Ensure proper materials of construction

CCPS G-29

• Follow operating procedures

CCPS G-3

• Install pressure indication instrumentation and vent valves

CCPS G-22 CCPS G-23 CCPS G-29

16.

In solid drumming • Check liner position and integrity before filling systems, failure of liner allowing powder to blow out of the container.

CCPS G-3 CCPS G-22 CCPS G-29

Underpressure 17.

Thermal contrac- • Drumming at proper temperatures tion vacuum cre• High integrity walls ated which can suck air, moisture, • Store to prevent water accumulation on drum tops etc., into drum creating unwanted reaction; or collapse of the drum.

CCPS G-3 CCPS G-15 CCPS G-22 CCPS G-29

Corrosion 18.

Drum not sealed properly allowing reaction with moisture, air, etc.

• Follow proper sealing instructions

CCPS G-3 CCPS G-15 CCPS G-22 CCPS G-29

19.

Unsuitable materials of construction.

• Follow proper drum selection guidelines

CCPS G-1 CCPS G-22 CCPS G-23 CCPS G-29

93

Table 4.7: Drumming Equipment

Potential Solutions and Control Mechanisms

Additional Resources

Transfer system contaminated, (i.e., piping, pumps, filters, etc.)

• Clean system on service changes

CCPS G-3

External corrosion.

• Inspect drums before use

No. Concern/Issue Corrosion 20.

21.

CCPS G-22 CCPS G-29

CCPS G-3 CCPS G-22 CCPS G-29

22.

Contaminants/ foreign material in drum.

• Inspect drum before use

CCPS G-3 CCPS G-22 CCPS G-29

Runaway Reaction 23.

Unsuitable materials of construction.

• Select drum made of suitable material of construction

CCPS G-3 CCPS G-22 CCPS G-23 CCPS G-29

24.

Drum not sealed properly and foreign material enters.

• Seal drum per operating procedures

CCPS G-3

• Use drum covers

CCPS G-15 CCPS G-22 CCPS G-29

25.

26.

Filters are dirty and/or need changing— incompatible chemicals, etc.

• Increase frequency of filter changes during service changes

System not cleaned properly.

• Increase frequency of cleaning

CCPS G-3

• Clean system during service change

CCPS G-15

• Visually inspect system

CCPS G-22

CCPS G-22 CCPS G-29 CCPS G-30

CCPS G-29 27.

Reaction not complete before transfer/ drumming.

• Verify final batch analysis and conditions before drumming

CCPS G-15 CCPS G-22 CCPS G-29 CCPS G-30

94

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Ignition Sources 28.

Incorrect electrical • Check area electrical classification classification for equipment or auxiliary equipment, lighting, etc.

NFPA 70

29.

Ignition from static charges; nongrounded drums (i.e., fiber, plastic liners).

• See that workers are equipped with static resistant clothing

API RP 2003

• See that workers use nonsparking tools

CCPS G-22

• Use subsurface feeds for organic liquids

CCPS G-29

• Ground and bond equipment

CCPS G-32

• Use of conductive or static dissipative drums and drum liners whenever possible

NFPA 77

• Follow operating procedures

ACGIH 1986

• Cool adequately before drumming

Bossart 1974

• Don’t seal drums until material has cooled down sufficiently

CCPS G-15

• Provide adequate fixed fire protection

CCPS G-29

• Insure good ventilation

CCPS G-30

CCPS G-13

Pratt 1997

High Temperature 30.

Drumming at incorrect temperature. Possibility of flammable atmosphere, or initiation of thermally unstable materials.

CCPS G-22

• Check heat tracing for excessive heat input 31.

32.

Density is lower and drum may be overfilled due to high material temperatures. Contact with operator due to spill, over flow, hot drum, etc.

• Verify proper temperatures before drumming.

CCPS G-15

• Use volumetric measurement

CCPS G-22 CCPS G-29

• Drum at temperatures low enough to protect operator against thermal injury

CCPS G-15 CCPS G-22 CCPS G-29

Fire/Explosions 33.

Air, water drawn into drum.

• Seal drums properly

CCPS G-15

• Drum at correct temperatures

CCPS G-22 CCPS G-29

95

Table 4.7: Drumming Equipment

Potential Solutions and Control Mechanisms

Additional Resources

Elevated drum temperatures reaching Self Accelerating Decomposition Temperature (SADT).

• Evaluate thermal stability parameters of material (isothermal aging tests, SADT, etc.)

CCPS G-15

• Keep drums away from source of heat

CCPS G-29

• Drum and store at required temperature

CCPS G-30

Vapors in vent collection system in flammable range.

• Design to be outside the flammable region in the vent system (N2 purge, dilution air, etc.)

ACGIH 1986

• Monitor flammable concentration

API 2028

• Monitor oxygen concentration

Bossart 1974

• Install flame/detonation arresters

CCPS G-23

No. Concern/Issue Fire/Explosions 34.

35.

CCPS G-22

AGA XK0775

CCPS G-29 CCPS G-30 FMEC 1987 NFPA 69 Low Temperature 36.

Material solidifies or is too viscous and plugs lines. Potential for exposure while correcting problem.

• Monitor and control temperature in feed system

CCPS G-23

• Heat trace and/or insulate lines

CCPS G-29

• Use proper line break procedures

Fisher 1990

• Use personal protective equipment (PPE) • Use proper lockout-tagout and confined space entry procedures

Operator Exposure 37.

• Design operation to minimize/eliminate dusts or Dusts from solid filling, vapors vapors from liquid filling. • Use proper personal protective equipment • Ensure proper design of local ventilation

ACGIH 1986 CCPS G-3 CCPS G-22 CCPS G-23 CCPS G-29

96

4. EQUIPMENT

Table 4.8: Milling Equipment

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Overpressure 1.

Pressure build-up • Provide adequate venting and dust filtration on downstream of receiving vessel vent mill (risk of com- • Where liquefied gas (nitrogen or CO ) is used 2 ponent failure, for milling, ensure adequate vent sizing and limit particularly in gas liquefied gas feed-rate to mill conveying systems). Internal pressure may also force product out of the mill.

CCPS G-11 CCPS G-22 CCPS G-23 CCPS G-29

Underpressure 2.

Failure of compo- • Ensure all system components, including flexible nents in connectors are rated for maximum feasible subatmospheric vacuum conditions pressure convey- • Ensure adequate pressure control system and ing operations. back-up (e.g., vacuum relief devices)

API 2000 CCPS G-3 CCPS G-11 CCPS G-22 CCPS G-29 CCPS G-39

High Temperature • Limit feed-rate, design for uniform feed-rate (e.g., CCPS G-12 screw feeder or rotary valve) CCPS G-23 • Measure temperature at strategic points in mill CCPS G-29 casing to detect and alarm product temperature NFPA 654 rise

3.

Overfeeding resulting in plugging of mill and subsequent heat buildup.

4.

• Replace screen with one correctly sized and/or Heat build-up clean screen due to too fine or blocked outlet • Install pressure indicator downstream and screen. upstream of mill for conveyed systems

CCPS G-12 CCPS G-23 CCPS G-29

• Measure temperature at strategic points in mill casing to detect and alarm product temperature rise 5.

Heat build-up due to worn or overloaded bearings.

• Ensure frequent preventive maintenance checks on bearings

CCPS G-12

• Monitor and alarm bearing temperature

CCPS G-29

• Ensure proper belt tension

CCPS G-23

97

Table 4.8: Milling Equipment

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Design discharge to avoid bridging, provide reliable instrumentation to detect full receiver (load cells or level probe)

CCPS G-12

High Temperature 6.

Heat build up due to plugged discharge line.

• Check lines to ensure they are clear before startup • Monitor and alarm temperature 7.

8.

9.

CCPS G-23 CCPS G-29 CCPS G-39

Heat build-up due to loss of cooling.

• Monitor and alarm temperature

CCPS G-12

• Use coolant flow/temperature sensors or product temperature sensors.

CCPS G-23

Heat build-up due to mill running too fast.

• Use shaft speed sensor

CCPS G-12

• Implement administrative controls on adjustable speed drives

CCPS G-23

Nonuniform feedstock causes variation in operating conditions resulting in overheating.

• Feedstock should be blended before milling

CCPS G-1

• Test feedstock before commencing milling operation (e.g., moisture content)

CCPS G-23

• Ensure all materials of construction exposed to low temperatures are suitable (carbon steel, plastics, elastomers in seals, lubricants, etc.)

CCPS G-29

CCPS G-29

CCPS G-29

CCPS G-29

Low Temperature 10.

Component failure when cryogenic cooling is used.

• Provide adequate control system to maintain design temperature

CCPS G-12 CCPS G-23 CCPS G-39 Fisher 1990 NFPA 55

Runaway Reaction 11.

• Screen for thermal hazards prior to milling Product in mill exceeds temperamaterial ture at which • Consider slurry milling prior to product isolation thermal runaway is initiated, result- • Measure temperature in mill casing and product outlet to monitor for hot spots and interlock to ing in explosion. shut system down and if appropriate initiate (This condition quenching operation can also occur in • Provide cooling jackets on mill or use cryogenic mill feeding cooling with liquefied gas such as nitrogen or equipment such carbon dioxide as screw feeders; similar countermeasures are appropriate.)

CCPS G-1 CCPS G-12 CCPS G-27 CCPS G-29 Fisher 1990 ISA S84.01 Liptak 1982

98

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Corrosion 12.

Internal corrosion • Use appropriate materials of construction in mill can occur • Maintain dry or inert atmosphere in mill at all if feed is high in times corrosives, such as halogens, and is hygroscopic.

CCPS G-1 CCPS G-23 CCPS G-39 Perry 1984

Ignition Sources 13.

14.

15.

Hot bearings pro- • Avoid by regular preventive maintenance (PM) viding a source of inspections, lubrication and belt checks ignition. • Use improved lubrication

CCPS G-23 CCPS G-29 CCPS G-34

Tramp metal reaching mill resulting in frictional heating/mechanical spark which provides an ignition source.

• Provide suitable protection (e.g., magnetic separa- CCPS G-23 tors, screens, etc.) CCPS G-29 • Secure all potential sources of tramp metal (e.g., CCPS G-34 fasteners etc.) in upstream equipment

Static electricity generation both in mill and conveying equipment.

• Inert milling system

CCPS G-12

• Control/interlock with oxygen concentration monitoring

CCPS G-23

• Ground, bond all electrically conductive components

CCPS G-32

• Use enclosed feed systems, not operator fed system

• Use conductive materials of construction

CCPS G-29 ISA S84.01 NFPA 654

Fire/Explosion 16.

Leakage from mill ignited by spark or hot surface.

• Use adequate shaft sealing (mechanical or multiple gas purged lip or chevron seals). Harden shafts in seal area • Use pressure tight flexible connections and clamps on mill inlets and outlets • Provide adequate fixed fire protection where appropriate

CCPS G-23 CCPS G-29 NFPA 13 NFPA 15 NFPA 16

99

Table 4.8: Milling Equipment

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Operator Exposure 17.

Operator expo• Use closed equipment wherever possible (hoppers sure to hazardous and intermediate bulk containers (IBCs)). materials or • Where product is exposed at transitions or packbroken mill parts ing operations: use containment devices such as during feeding gloveboxes; provide airflow control (laminar flow and packaging booths); or as a last resort use the room as conoperations.. tainment and provide suitable personal protective equipment for the operators

ACGIH 1986 CCPS G-3 CCPS G-22 CCPS G-23 CCPS G-29

• Provide local ventilation • Design charging chute to eliminate “line-of-sight” from mill to operator to reduce the possibility of a broken mill part flying out of the charging chute and causing injury. • Provide scalping screens

Management of Change 18.

Running different • Develop procedures to characterize feedstock CCPS Y-28 products through whenever changes have been made and reevaluate mill, or change in milling conditions upstream process, • Implement management of change review resulting in differprocedure ent feed charac• Use adequate cleaning procedures teristics and unsuitable milling conditions, e.g. overheating due to blocked outlet screen. General

19.

Thermal decomposition of material during milling.

• Perform thermal and shock hazards analysis prior to milling

CCPS G-1

• Consider milling under different conditions, e.g., slurry milling

CCPS G-27

• Use liquid nitrogen injection as a coolant 20.

Tramp metal from mill causes downstream problems.

• Provide screens or magnetic separator on mill outlet

CCPS G-23 CCPS G-29 CCPS G-41 CCPS G-23 CCPS G-29

100

4. EQUIPMENT

Table 4.9:

Filters

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• For closed filters, purge filter with inert gas

AGA XK0775

Overpressure 1.

Ignition of combustible or flammable material with filter closed or filter box lid closed.

• For open filters, use alternate closed filtering methods such as plate and frame

ARI RP 500

• Add antistatic agent to nonconducting solvents

API RP 2003

• Bond and ground the piping and equipment

CCPS G-22

• Provide appropriate area electrical classification

CCPS G-23

• Heat activated device triggers CO2 or inert gas blanket

CCPS G-29

• Loss of filter box ventilation shuts off solvent feed

NEC 70

• For filter boxes, use drop tube with dam for subsurface addition to minimize static generation

NFPA 497

• For filter boxes, provide internal filter box ventilation

FMEC 7-59 NFPA 77 Pratt 1997

High Temperature 2.

3.

Feed slurry tem• Use alternate closed filtering methods perature is high, • Check and adjust source temperature prior to resulting in excestransfer sive flammable • Design filter box ventilation for excessive flamvapors for open mable vapors filters.

CCPS G-1

Friction from contact of moving parts, tramp metal, bearings or seals initiating thermal decomposition or igniting flammable vapors.

CCPS G-23 CCPS G-27 CCPS Y-28

• Maintain proper clearances

CCPS G-1

• Screen chemicals to be filtered for thermal stability

CCPS G-23

• Evaluate and design for pressure consequences of thermal decomposition

CCPS G-39

• Evaluate potential for solid phase deflagration • Eliminate tramp metal and broken parts that may cause localized overheating

CCPS G-27 CCPS G-41

Table 4.9:

101

Filters

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Clean and inspect equipment after each change

API 750

• Segregate incompatible materials • Label material, lines, pumps and valves

ASTM Proposal 168

• Use double check system

CCPS G-15

• Check labels against batch sheets

CCPS G-22

• Use procedures and training

CCPS G-27

• Set valves to correct flow path

CCPS G-29

Runaway Reaction 4

Unwanted reaction due to contaminants in equipment or solvent wash.

CCPS G-32 Frurip 1997 Sutton 1995 Fire/Explosion 5.

Improper cloth or • Include proper handling and disposal in operating filter media disprocedures posal may result • Use high temperature filter media in fire and explo• Use flame retardant personnel protective sion hazard. equipment • Inert/purge filter with nitrogen

6.

7.

AGA- XK0775 CCPS G-22 CCPS G-23 CCPS G-29 CCPS G-31 FMEC 1997

Spontaneous combustion of pyrophoric material in the filter after opening or blowing dry.

• Rinse filter with water (or other appropriate solvent) prior to opening

For open filters, or when opening closed filters, solvent is flammable and may be above flash point with air present. For open filters, vent system failure may increase solvent vapor concentration, resulting in a fire or explosion.

• Rinse filter and cake with cool solvent prior to opening filter

ACGIH 1986

• For closed filters, purge filter with nitrogen prior to opening, cleaning or starting solvent slurry

Bossart 1974

AGA- XK0775 CCPS G-29

• Upon opening, immediately transfer cake to safe shipping container while still wet

• Use nonflammable solvent where ever possible • Use alternate closed filtering methods • Design internal filter ventilation for excessive flammable vapors

AGA- XK0775 CCPS G-22 CCPS G-23 CCPS G-29 CCPS G-31

• Provide adequate building ventilation

ISA RP 12.13

• Install local air exhaust pickup points at filter (e.g., elephant trunks) (Continued on next page)

(Continued)

102

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Provide combustible gas analyzers

NFPA 13

• Provide automatic area sprinkler/deluge protection

NFPA 15

• For filter boxes, interlock filter box ventilation with solvent feed

NFPA 30

Fire/Explosion 7.

(Continued)

NFPA 16

• For filter boxes, keep closed whenever possible and keep solvent in bottom pumped out • For filter boxes, provide remote and automatic filter box lid closing on trip of appropriate fire detection device. Fire detection device may also be interlocked to stop solvent feed, trip deluge internal to filter box and/or trip inert gas blanket for filter box (caution, be aware inert gas is a potential asphyxiation hazard) • For filter boxes, use flexible, conductive plastic film on surface of cake to minimize fumes • Use flame retardant personnel protective equipment Ignition Sources 8.

Ignition of flammable atmosphere for open filters or solvent may be above flash point with air present when cleaning or unplugging closed filters. This may necessitate tight control of ignition sources to prevent a fire/explosion.

• Cool and/or rinse filter prior to opening filter

API RP 2003

• Check area electrical classification

API RP 500

• Control humidity of air in operating area to reduce accumulation of static electricity

CCPS G-22

• Use conductive floors

CCPS G-29

• Ground the operator with proper clothing (conductive shoes, gloves, etc.)

CCPS G-31

• Periodic testing of conductive shoes • Implement procedure for manual bonding and grounding of tools to filter box

CCPS G-23

CCPS G-32 CCPS G-41 NFPA 498

• Avoid use of nonconductive materials of construction

NFPA 70

• Use nonsparking tools

Pratt 1997

• Perform conductivity tests on slurry before feed to filter • Use antistatic agent with nonpolar solvents • On filter boxes, use drop tube with dam for subsurface addition to minimize static generation • Control velocity/turbulence of solvent addition • Provide adequate fixed fire protection where required

NFPA 77

Table 4.9:

103

Filters

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Loss of Containment 9.

Overfill by plugging, blinding cloth, failure to start underflow pump, loss of vacuum or by operator error.

• Use alternate filtering methods

CCPS G-15

• Provide combustible gas analyzers

CCPS G-22

• Provide high level cut-off interlocked with solvent feed

CCPS G-23

• Provide level control system on filtrate receivers with bottoms pumps

CCPS G-31

• For vacuum transfer of filtrate, alarm on loss of vacuum

Lees 1996

CCPS G-29 ISA RP 12.13

• Provide overflow line from filter to drain • Provide area diking and containment • For filter boxes, provide overflow line to safe location • Provide pressure drop monitor for closed filters 10.

Leakage of flammable or toxic chemical from equipment.

• Provide vapor-tight enclosure around filter and run at negative pressure with exhaust fans

API RP 500

• Implement frequent maintenance of sealing surfaces and clamping systems

CCPS G-23

• Use new gaskets where appropriate • To protect clamping system, use dissimilar metals to prevent galling on threaded fasteners

11.

Leakage of flammable or toxic chemical from rotary vacuum filter.

CCPS G-22 CCPS G-29 CCPS G-31 CCPS G-39

• Check area electrical classification

Lees 1996

• Provide emergency ventilation

NFPA 497

• Provide vapor-tight enclosure with adequate lighted viewing window around filter and run at negative pressure with exhaust fans

API RP 500

• Route solid discharge directly into receiver tank • Provide catchment trough and routine maintenance to minimize valveplate leakage

CCPS G-22 CCPS G-23 CCPS G-29 CCPS G-31

• Provide overflow/high level shutoff on feed trough

CCPS G-39

• Check area electrical classification

NFPA 497

• Provide emergency ventilation • Provide adequate fixed fire protection where appropriate

Lees 1996

104

4. EQUIPMENT

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Test material prior to filtering

ACGIH 1986

• Use appropriate personnel protective equipment

CCPS G-3

• Design filter box ventilation for excessive flammable vapors

CCPS G-1

• Segregate incompatible materials

CCPS G-23

• Clean and inspect equipment after each batch

CCPS G-29

• Use procedures and training

CCPS G-31

Operator Exposure 12.

Incomplete conversion of material or contaminated material could lead to operator exposure.

CCPS G-22

Gibson 1991 Lees 1996 Lovelace 1979 NFPA 498 13

Operator exposure to toxic vapors during opening and cleaning.

• Purge prior to opening or cleaning

ACGIH 1986

• Use appropriate personnel protective equipment

AGA- XK0775

• Use alternate closed filtering methods

CCPS G-3

• Use cleaning methods which don’t require opening the filters

CCPS G-15

• Provide adequate building ventilation

CCPS G-23

• Provide local air exhaust pickup points at filter (e.g. elephant trunks)

CCPS G-29

CCPS G-22

CCPS G-31 NFPA 1993

14

Improper disposal of filter media may result in operator exposure.

• Include proper handling and disposal in operating CCPS G-15 procedures CCPS G-22 • Use appropriate personnel protective equipment CCPS G-29 • Provide local air exhaust pickup points at filter

CCPS G-31 CCPS G-32 CCPS Y-28

15.

Ergonomic issues • Use alternate filtering methods in manual wash• Provide ergonomic design, mechanical assist ing, unloading, setup, cleaning, shoveling of filter boxes, moving of portable units e.g. plate and frame filter press.

CCPS G-15 Sanders 1993

Appendix 4A. Storage and Warehousing

No. Concern/Issue

Potential Solutions and Control Mechanisms

105 Additional Resources

Operator Exposure 16.

Manual operation • Use alternate filtering methods places operator in • Use appropriate personnel protective equipment close proximity to potential hazards.

Brandt 1992 CCPS G-15 CCPS G-22 CCPS G-31 Mecklenburgh 1985 NFPA 1993

Appendix 4A. Storage and Warehousing Storage areas in the plant usually contain the largest volumes of hazardous materials. Frequently storage areas contain flammable liquids or liquefied gases. The main concern in the design of storage installations for such liquids is to reduce the hazard of fire by reducing the amount of spillage, controlling the spill, and controlling the ignition sources. It cannot be emphasized enough that reducing the quantities of hazardous materials is the single greatest method for reducing the hazards of fire or explosion. Minimizing storage quantities also reduces the potential for large spills and further damage. Pipeline feeds from a reliable source can eliminate the requirement for large storage areas. Solid chemicals may be stored in bulk in bins, hoppers, piles or containers. Liquid chemicals may be stored in tanks, reservoirs or specified shipping containers. Gases may be stored in low-pressure gas holders, in high pressure tanks or cylinders; or in liquid form in tanks or containers under pressure, refrigeration or both. Pressure and temperature of storage greatly affects dispersion/ emission of liquid or vapor in case containment is lost. Important considerations are separation distances and diking arrangements. The primary additional safety concern when hazardous materials are stored in containers is the large amount of vehicle and employee traffic associated with the use of containers combined with the hazard caused by constant handling. Storage areas should be designed to allow the smooth flow of traffic without the need to constantly maneuver a forklift or truck. The storage area should be arranged to allow personnel access to inspect all containers for leakage or other damage on a regular basis. The storage of compressed gases and flammable and combustible liquids should meet the requirements and applicable guidance contained in industry consensus standards and regulations. Incompatible materials

106

4. EQUIPMENT

should be kept separated so that any spills cannot mix. The storage of containers in rack areas may require specialized fire control systems such as individual sprinkler lines to deliver water or foam directly to each rack level. The placement of drums in processing area for the dispensing of the contents may not need to meet the same stringent storage specifications, but it will still be necessary to meet all pertinent safety requirements. The process drums area may include safety barriers to prevent traffic from hitting the drums, portable drum sumps to contain any spills, a ventilation system to control fumes, and double valving or a valve and plug to minimize drum leakage. During batch operations most materials will require one or several steps of warehousing or other storage outside of tanks or vessels. This type of goods storage can occur in warehouses or buildings (roof and walls), open air, under a roof (no walls), in a tent or inflatable enclosure or simply in the staging area. Large warehouse storage of hazardous materials in particular may present a danger to people, the environment or plant operations. Warehouse fires at Sandoz (Basel, 1986) and in North America have resulted in strict requirements in most European jurisdictions and a reappraisal of North-American requirements. Fire and fire-fighting consequences that relate to the storage of large amounts of hazardous materials as in certain warehouses, need to be evaluated to determine if fire-fighting is appropriate. Environmental and fire fighter safety need to be taken into consideration and sometimes the decision could be to let a fire burn itself out. Storage and receiving are activities that can greatly contribute to a safe and economic operation. It is here that quality control can be achieved at minimal cost. Label verification and other quality assurance measures can increase the confidence level that the correct chemicals have arrived, thereby potentially circumventing the use of wrong chemicals. Wrongly shipped chemicals can be returned to the manufacturer with minimal or no cost to the batch operation owner. As with all processes and activities it is of great importance to apply the principles of inherent safety, in particular the minimization and attenuation principles (CCPS G- 41). Materials that can react with each other should be stored in segregated areas. Special attention is needed for corrosive materials which upon leakage from their primary containment (e.g., a plastic bag) can corrode their main container as well as other containers holding different chemicals in adjacent areas. Proper material handling procedures need to be developed and followed and correct tools should be used. For example, the use of forklift trucks with rounded forks to avoid puncturing drums/bags could be considered. Hazards associated with stacked pallets loaded with shrink-wrapped bags of freeflowing materials that can topple over when bags have been punctured should be recognised. Storage areas should be inspected on a regular basis and damaged bags,

Appendix 4A. Storage and Warehousing

107

drums and other type of containers should be isolated and properly discarded by staff using appropriate personnel protective equipment (PPE). Example: A warehouse in the UK stored large numbers of metal drums holding bagged pesticides. In order to spot torn bags, quickly and easily, holes had been drilled in the bottom of the metal drums. While this helped the housekeeping efforts it negated the containment function of the drums. The bags melted during a fire and the pesticide ended up in the firewater, creating a considerable environmental problem. Reactive chemicals are often stored under an inert material or atmosphere, stored in a diluted form, or stabilized by a chemical additive. These situations require special care; for example: • Vaporization of solvents covering alkali metals during storage can expose the metals to moisture. • Vaporization of diluting solvents may increase the concentration of reactive chemicals to unsafe levels. • Low temperatures can cause a phase separation in stabilized solutions in which case one phase can become deficient in stabilizer and subject to runaway reactions. Acrylic acid can crystallize out of stabilized solution, and subsequent thawing of these essentially pure acrylic acid crystals can initiate runaway reactions, often with severe consequences. Thawing of crystallized (frozen) materials needs to be accomplished using established procedures in thaw boxes or similar devices. If established procedures are not available, a safety review needs to be conducted and a procedure developed prior to thawing the material. • Heat sensitive materials need to be stored away from heat sources such heaters and windows where they are subject to solar radiation. • Shelf life of stabilizers or inhibitors may be limited • Some stabilizers or inhibitors require a certain oxygen concentration in the tank head space atmosphere in order to function. Where inerting is required, careful control is necessary to maintain this minimum oxygen concentration in inerting gas while still staying below the minimum oxygen concentration required for combustion. • Phase changes also mean that pressure and or vacuum relief needs to be considered in order to maintain the mechanical integrity of the container. Correct storage requirements, procedures (e.g., first in, first out) and conditions such as temperature control issues including insulation, cooling, heating and ventilation need to be determined and implemented. Potential ignition sources need to be eliminated or protected against by proper bonding, grounding, and lightning protection (NFPA 77, NFPA 780, Pratt 1997). Good housekeeping is another essential ingredient for the

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prevention of mix-ups and unanticipated adverse consequences, e.g., fire caused by smouldering dirty rags. A number of codes, standards, guidelines, and recommended practices promulgated by organizations such as NFPA and API are provided in the reference section. Additional guidance applicable to warehousing includes • A Guide to Safe Warehousing for the European Chemical Industry, Conseil Europeen des Federations de l’Industrie Chimique, April 15, 1987. • General Storage Safeguards, Loss Prevention Datasheet 8-0, Factory Mutual Engineering Corp. • Warehousing of Chemicals, Loss Prevention Bulletin 088, IChemE, August 1989. • Protection of Warehouses Against Fire, Loss Prevention Bulletin 084, IChemE, 1989, pp. 2–6. • The Forgotten Hazards: Services in Warehouses, Loss Prevention Bulletin 084, IChemE,1989, pp. 7–12. • Opslag van Gevaarlijke Stoffen, Comite Europeen des Assurances, September 1988. • CCPS G-3. Guidelines for Safe Storage and Handling of High Toxic Hazard Materials. American Institute of Chemical Engineers, New York • CCPS G-30. Guidelines for Storage and Handling of Reactive Materials. American Institute of Chemical Engineers, New York. • CCPS G-33. Guidelines for Safe Warehousing of Chemicals. American Institute of Chemical Engineers, New York.

5 Instrumentation/Control Systems

5.1. Introduction The safe operation of a chemical process requires continuous monitoring of the operation to stabilize the system, prevent deviations, and optimize system performance. This can be accomplished through the use of instrumentation/control systems, and through human intervention. The human element is discussed in Chapter 6. Proper operation requires a close interaction between the operators and the instrumentation/control system. To a large extent, batch operations have simple control systems and are frequently operated in the manual mode. The instrumentation system is the main source of information about the state of the process. Some of the typical functions of the instrumentation/control system are • • • • • •

Information Management Recipe Management Production Scheduling Process Management Equipment Related Control Safety Interlocking

Figure 5.1 defines the activities that are important in batch control systems. This drawing shows the control activities in a hierarchical fashion starting with the safety interlocks and proceeding up to higher level activities such as recipe management, scheduling, and information management. Information Management

The goal is to maintain a history of data associated with previously executed batches, equipment operating rates, etc. and provide this information to other 109

110

5. INSTRUMENTATION/CONTROL SYSTEMS

Figure 5.1 Batch control activities (ISA).

5.1. Introduction

111

functions in the organization. This requires the control activity to interface with the process management, recipe management, and scheduling control activities. Recipe Management

This control activity includes creating, editing, storing and retrieving recipes and interfacing with the process management control activity. Some interfacing is also needed between this control activity and with the scheduling and information management control activities. Production Scheduling

This control activity is primarily concerned with determining what products will be made in the batch plant and when those products will be made. This requires the control activity to interface with the process management, recipe management, and information management control activities. Process Management

One of the main functions of this control activity is to select a master recipe from the recipe management control activity, edit that recipe and transform it into a control recipe suitable for downloading to the equipment-related control activity, downloading the recipe (i.e., initiating the batch), and then to supervise the execution of the recipe. Equipment-Related Control

This control activity includes process control and unit management. Process control includes those loops and devices that perform sequential control, regulatory control, and discrete control. Unit management is responsible for coordinating the activities associated with the batch units (e.g., allocating resources within the unit, ensuring that batch sequences proceed in the proper order, etc.). Safety Interlocking

These control functions prevent abnormal process actions that would jeopardize personnel safety, harm the environment, or damage equipment and/or property. An excellent source of reference on the topic of Batch Control systems is the Instrument Society of America’s (ISA’s) Batch Control Systems Standards SP88 document (ISA SP88). Basic process control system (BPCS) loops are needed to control operating parameters like reactor temperature and pressure. This involves monitoring and manipulation of process variables. The batch process, however, is discontinuous. This adds a new dimension to batch control because of frequent start-ups and shutdowns. During these transient states, control-tuning parameters such as controller gain may have to be adjusted for optimum dynamic response.

112

5. INSTRUMENTATION/CONTROL SYSTEMS

By the very nature of batch processing, it is inevitable that process equipment will have idle time between batches. The idle time also could occur if the controller is not being used at all times during the execution of the batch (e.g., a flow controller may only be used during the feed of one of the reactants). During the idle time, control considerations such as reset windup must be considered to prevent the control signal from going outside of the control limits. There also may be frequent changes in recipes, product grades, and in the process itself. All of these things put increased demands on the control loops in a batch process. Different control strategies are often necessary for the same piece of equipment. This could involve changing to a different controller or changing the control algorithm. The choice of which controller or control algorithm to use may be product dependent and should be specified in the recipe. Due to variable operating environments and their cyclic nature, batch processes may be subjected to higher instrument failure rates than continuous systems. Instrumentation failure or malfunctions and software/hardware failures are generally among the most common concerns—next to human errors—in the safety and reliability of batch processes. One of the most common issues in batch process control system is failure of sensors, which can easily lead to loss of control system and safety system functionality. Some other common concerns are simply the failure of the basic measurements, loss of signals during transmission, failure of control loop, or leakage from instrumentation. Thus, failure of any one component could compromise the overall control system, provide spurious signals, and generate off-spec products. Ultimately, it could result in unsafe operation or even a loss of containment. Proper design and selection of instruments based on equipment reliability and potential consequences are some of the most effective strategies to maintain safe operation. This is very crucial due to the nature of the batch process, which involves a high degree of variability. Some other common practices are providing appropriate redundancy, procuring fault diagnosis and shutdown systems, implementing independent Safety Instrumented System (SIS), or providing permissives and interlocks.

5.2. Case Study A polymerization process involving a monomer, an organic peroxide initiator and an organic solvent underwent an energetic runaway reaction. All the contents in the polymerization reactor were lost. The emergency relief system prevented major damage to the equipment. The process equipment train consisted of a storage tank farm, an initiator pot, some small addition pots and a reactor. Multiple processes were run in the system and the equipment and instrumentation had to handle a variety of

5.3 Key Issues

113

conditions. To minimize contamination, the equipment and lines were cleaned between campaigns. During the changeover process, air or nitrogen was often introduced into the lines. The volumetric, positive displacement meter used for the key monomers required a considerable amount of maintenance, as it was not designed to handle nitrogen or air gas pockets. The meter was replaced with one more suited to this service and calibrated for monomer A and performed satisfactorily for Monomer A. In a rapid changeover to make another product the meter was not recalibrated for the new monomer, monomer B. This led to a large overcharge of monomer B and the subsequent runaway reaction. In a multiproduct batch manufacturing facility, production changes and the need to make new products occurs frequently and fast responses are often demanded. The need to do a thorough management of change (MOC) analysis and the need to check all equipment, instrumentation and controls for proper design and settings should not be circumvented in an attempt to meet ‘tight’ schedules.

5.3 Key Issues Safety issues in batch reaction systems relating to instrument/control systems are presented in Table 5. The table is meant to be illustrative but not comprehensive. Some key issues are presented below: • Batch processes may require more monitoring in order to take supervisory action (e.g., put the system on hold if a particular manual valve is not closed). • Discontinuous operation (idle periods) of instruments such as flow meters, pH meters, analyzers, etc., could lead to failure as a result of plugging, drying out, etc. • Change in service may lead to inappropriate instrumentation for the current process. • Same sensor used for basic process control system and safety instrumented system. Failure of sensor leads to loss of control system and safety system functionality. • Variety of instrumentation leads to complex maintenance and calibration procedure, e.g., different types, different manufacturer, and ages of instrumentation leading to problems in maintenance. • Manual mode control operation is very common leading to increased potential for human error. • Process equipment function changes with different steps in process sequence (e.g., same vessel used as feed tank, reactor, crystallizer; pump

114

5. INSTRUMENTATION/CONTROL SYSTEMS

used to pump in/out). Instrumentation and controls not kept in phase with the current process step (e.g., control set points, interlocks etc.) • Excessive number of alarms resulting in confusion and reduction in efficiency of pinpointing the root cause of the upset.

5.4. Process Safety Practices Listed below are some process safety practices which can help reduce accidents due to instrumentation and control systems. Use intrinsically safe instrumentation. Provide appropriate safety integrity level (SIL) level. Consider ergonomics in the design of displays and control panels. Implement abnormal situation management. Clean and decontaminate instrumentation before changing service. Frequently recalibrate and test all instruments, read-out devices, sensors and alarms. • Implement pre-use verification of instrumentation and control. • • • • • •

115

Table 5: Instrumentation/Control Systems

Table 5: Instrumentation/Control Systems Potential Solutions No. Concern/Issue

and Control Mechanisms

Additional Resources

• Use corrosion resistant material of construction

CCPS G-12

• Perform regular inspections, testing and maintenance

IEC 61508 ISA S84.01

• Verify suitability of instrumentation to service

VDI/VDE 2180, Part 1

Corrosion 1.

2.

Material of construction of sensor not suited for operating environment. Loss of sensing capability, leading to unwanted consequences such as spurious trips, overt (announced) and covert (unannounced) faults.

• Use multiple voting with plausibility analysis • Avoid equipment/systems subject to covert (unannounced) faults

Corrosion of • Relocate vulnerable components to a more conpneumatic lines, trolled environment electronics, electri- • Provide purging for electronics to prevent extercal equipment. nal corrosion Loss of signal. • Use corrosion resistant material of construction • Implement mechanical integrity program to prevent leaks of corrosive material • Use multiple voting with plausibility analysis

VDI/VDE 2180 ISA S71.04

Loss of Containment 3.

• Avoid use of vulnerable instruments in hazardLeakage from ISA S84.01 instrumentation or ous service breakage of instru- • Use instruments of same or higher pressure ments resulting in rating as vessel release of hazard• Provide proper support of small lines ous material. • Provide gussets on nozzles and small lines, where appropriate • Consider use of thermowells instead of temperature probes • Use instruments judiciously; more instruments can lead to more leak sources • Provide operator training and administrative controls (No standing on pipes/fitting, holding of piping/tubing etc.) • Provide protective cages/shields to minimize human exposure (e.g., avoid sight glasses) • Choose inherently safer instrumentation • Locate vulnerable instruments within protective enclosures to prevent accidental breakage

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5. INSTRUMENTATION/CONTROL SYSTEMS

Potential Solutions No. Concern/Issue

and Control Mechanisms

Additional Resources

Ignition Sources 4.

Instrumentation • Base area electrical classification on range of and/or ancillary chemicals used equipment provide • Ensure proper design and selection of instrumena source of tation as per area electrical classification ignition. • Consider the use of intrinsically safe instrumentation

API RP 2003 Britton 1999 Gruhn 1998 ISA S84.01 ISA-S12.6

• Encapsulate, and seal potential ignition sources

NFPA 70

• Locate instruments in purged/pressurized enclosure

NFPA 77 NFPA 496

• Use pneumatic/hydraulic system where necessary NFPA 497 in hazardous environments VDI/VDE 2180 • Locate instruments away from potential leak sources • Provide for proper bonding and grounding General 5.

6.

7.

Instrumentation used in different processes during its lifecycle. Surplus instrumentation or existing instrumentation reinstalled for different use. Possibility of instrumentation being used outside its design limits.

• Procure instrumentation that can be used in ISA S84.01 other processes (current or future) without operating close to its design limits

Changing type of instrument in same service leading to an incident.

• Verify suitability of new instrumentation to service

Novel materials and/or less well-known chemistry may lead to measurement of inappropriate parameters.

• Select materials of construction that can be used in a wide range of services • Verify suitability of instrumentation to new service; make sure original specifications are documented • Clean and decontaminate instrumentation before changing service • Perform Management of Change review CCPS Y-28

• Perform process hazard analyses • Perform Management of Change review • More development/characterization of chemistry CCPS G-13 and determination of physical properties • Measure diverse parameters (e.g., measure temperature and pressure) • Implement functionality testing • Perform Thermal Hazards Analysis (THA)

117

Table 5: Instrumentation/Control Systems

Potential Solutions No. Concern/Issue

and Control Mechanisms

Additional Resources

General 8.

Change in service may lead to inappropriate instrumentation for the current process.

• The system should be designed so as to provide levels of protection appropriate to the hazard potential • Ensure proper location of sensors • Ensure hazard analysis of process is done to provide proper level of protection • Install appropriate instrumentation • Perform Management of Change review

9.

Failure of basic process control system (BPCS) resulting in loss of control.

CCPS G-12 Gruhn 1998 IEC 61508 ISA S84.01 OSHA 1910.119 CCPS Y-28

• Design for reliability and availability

CCPS G-12

• Take common cause failures into account while evaluating reliability

IEC 61508

• Perform periodic proof testing of systems

VDI/VDE 2180

• Use staggered proof testing to reduce chances of common cause failure • Design for safe shutdown on failure or loss of BPCS • Provide independent safety instrumented system (SIS) with periodic testing • Monitor BPCS for deviations and provide operators with ability to assume safe manual control • Implement detailed operating procedures and training 10.

Same sensor used • Provide independent sensors for use in BPCS and CCPS G-12 for BPCS and safety instrumented system with a plausibility IEC 61508 safety instruanalysis ISA S84.01 mented system. • Provide appropriate redundancy for risk classifiFailure of sensor cation of system leads to loss of • Provide on-line self-diagnostic system control system and safety system functionality.

11.

Failure of sensor critical to monitoring and supervision of the process. The critical sensor may vary from process to process or stage to stage in the same vessel.

• Define critical operating parameters for each process and/or stage • Provide adequate reliability by using redundant/diverse sensors • Provide local independent readout • Install a SIS, where warranted • Install on-line self diagnostic system • Provide appropriate preventive maintenance of instruments and field sensors

IEC 61508 ISA S84.01

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5. INSTRUMENTATION/CONTROL SYSTEMS

Potential Solutions No. Concern/Issue

and Control Mechanisms

Additional Resources

• Provide reliable sources of motive power with appropriate level of backup where required.

VDI/VDE 2180

General 12.

Loss of motive power for instruments.

• Eliminate common cause electrical failures for supply and backup • Ensure that control systems are fail safe; both individually and collectively • Provide reliable and high-quality supply of instrument air (oil, dust and moisture free) • Provide nitrogen backup to instrument air (caution: be aware of potential asphyxiation hazards) • Use uninterrupted power supply, where necessary, to allow time for orderly shutdown or time to get alternate power from reliable sources

13.

Gauges, meters, or • Relocate/redesign the gauges so that operator CCPS G-15 recorders are not can read them easily Gruhn 1998 easily read by • Provide ergonomic design of displays ISA RP 60.3 operators. • Avoid instruments that have minimum and maximum readings at same position on scale • Design instruments to read normal conditions at midrange • Standardize gauge and instrument displays • Train operators to understand the units that are displayed

14.

Loss or corruption • Select proper material of construction of signal during • Implement procedures for proper installation, transmission. support and protection for transmission lines • Protect cables from steam, water, oil leaks, corrosive or flammable atmosphere, heat sources etc. • Minimize transmission distance • Use high-quality instrument air (oil, dust and moisture free) • Protect against electromagnetic interference (EMI), electrical interference and radio frequency interference (RFI) • Use fiber optic cable in preference to wires to reduce interference, crosstalk, and difference in ground potential at different location • Employ periodic testing of system grounding

IEC 61508 NFPA 75

119

Table 5: Instrumentation/Control Systems

Potential Solutions No. Concern/Issue

and Control Mechanisms

Additional Resources

General 15.

16.

17.

18.

Electrical, electromagnetic, or radio frequency interference causes malfunction of the BPCS and SIS. Potential for common cause failure.

• Minimize the effect of electrical interference by the design, installation and selection of instrumented systems • Remove/isolate interference sources • Periodically test grounding • Provide adequate lightning protection

API RP 2003 IEC 61508 NFPA 75 NFPA 77 NFPA 780

• Provide signs to indicate areas where use of portable electronic devices are controlled

Process equipment function changes with different steps in process sequence (e.g., same vessel used as feed tank, reactor, crystallizer; pump used to pump in/out). Instrumentation and controls not kept in phase with the current process step (e.g., control set points, interlocks etc.).

• Use automated sequencing with operator acknowledgment

BPCS and SIS located closer to the processes than continuous systems, possibly leading to environmental attack from corrosion, dust, humidity, temperature, etc.

• House logic-solver components of BPCS, and safety instrumented systems (SIS) in a controlled environment

Discontinuous operation of instruments such as flow meters, pH meters, analyzers, etc., due to idle periods could lead to failure as a result of plugging, drying out, etc.

• Use instruments that resist degradation during idle periods

VDI/VDE 2180

• Provide periodic testing

VDI/VDE 3542

CCPS G-29 CCPS G-32

• Provide independent verification • Provide proper training and procedures • Provide process write-ups • Use log book and checklists • Provide limit switches to verify physical valve positions

NFPA 75 VDI/VDE 2180

• Provide clean-air purge • Maintain good housekeeping • Provide robust systems suitable for environment

• Implement preuse verification and calibration • Periodically flush/purge of instruments • Provide recirculation during idle periods

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5. INSTRUMENTATION/CONTROL SYSTEMS

Potential Solutions No. Concern/Issue

and Control Mechanisms

Additional Resources

General 19.

20.

Large instrument spans required to address variety of operating conditions/requirements may result in inadequate measurement and control at the low or high end of their spans.

• Recalibrate sensor for smaller ranges when greater accuracy is required

Temperature control systems incapable of handling multiple media/duty (e.g., cooling/tempered water/steam). Sensor may not be accurate in the range used. Switchover time between media may result in loss of control.

• Select temperature sensors that can be used with multiple heating/cooling media over a wide temperature range without loss of performance

ISA S84.01 Liptak 1982

• Use smart instruments that allow quick change of span • Use multiple parallel instruments/control valves of different ranges for the for same service • Install instruments that are appropriate for the current operation

Liptak 1982

• Use separate control valves for heating/cooling • Use same media for heating/cooling • Design for rapid change over of services

21.

Calibration unsuit- • Calibrate for every batch ISA S84.01 able for current • Check calibration before change of service Liptak 1982 process/step. Some • Purchase and install instrumentation whose resoprocesses require lution is high enough for the most sensitive progreater accuracy of cess/step measurements.

22.

DCS sampling frequency too low or the response time for some analog instruments may be too slow for proper control of transient nature of batch processes and may lead to a process upset.

• Verify suitability of sampling frequency for process dynamics (can vary from process to process) • Use different instruments • Minimize dead time • Use a Fast Data Logger for critical pieces of equipment that can change states quickly, e.g., major rotating equipment where the usual one-minute data storage interval is not adequate in case of trips

Stephanopolous 1984

121

Table 5: Instrumentation/Control Systems

Potential Solutions No. Concern/Issue

and Control Mechanisms

Additional Resources

General 23.

24.

25.

26.

Variety of instrumentation leads to complex maintenance and calibration procedure, e.g., different types, different manufacturer, and ages of instrumentation leading to problem in maintenance.

• Standardize instrumentation while utilizing diverse measurements or instruments, where necessary

Same equipment can be controlled from different location (e.g., pneumatic in field and digital in control room).

• Eliminate multiple control locations, if possible

Physically different controls on similar equipment in different locations.

• Standardize equipment and controls where possi- ISA RP 60.3 ble when designing new facilities or upgrading old ones

Frequent change in tuning parameters and alarm points provides more opportunities for human error.

• Design system which does not require frequent changes in tuning parameters

Liptak 1982

• Provide instrumentation technician training • Ensure maintenance and design teams work together on specification • Exercise proper warehousing, (i.e., maintain a paper trail between items and their operating/maintenance procedures)

ISA RP 60.3

• Provide local hand/off/auto switch to prevent control room operation during field activities with indication of status in control room

• Provide training and procedures VDI/VDE 2180

• Provide formal tuning procedures for controllers • Implement authorization levels for changing tuning parameters • Provide programmed recipes with built-in tuning parameters • Provide checklist for product & process changeover • Record and communicate all changes (manual or automatic)

27.

Modification/ changing of software execution and sequencing module such as “PURGE VESSEL” in a PLC. May impact other recipes.

• Review impact of change/modification of software on all its applications • Implement Management of Change Procedures (MOC) • Proof run process using nonhazardous materials after software change • Perform a common mode failure analysis

Gruhn 1998 VDI/VDE 3542

122

5. INSTRUMENTATION/CONTROL SYSTEMS

Potential Solutions No. Concern/Issue

and Control Mechanisms

Additional Resources

• Provide operating procedures /checklists

CCPS G-15

• Provide scheduled operator training

ISA RP 60.3

General 28.

29.

Operator has to observe the process more frequently as a result of nonsteady state operating conditions. This requires more frequent control interventions, leading to an increased potential for human error.

• Design system to minimize frequent changes • Record and communicate all changes (manual or automatic) See Chapter 6 for more details

Common use of CCPS G-12 • Minimize use of manual mode control through manual mode conwell designed automatic mode of operation ISA RP 60.3 trol increases • Ensure that SIS is not disabled when operating in potential for manual mode human error. • Provide operating procedures /checklists • Provide operator training • Log all changes • Provide reliable and appropriate measurement of all critical process variables

30.

Manual sampling/ analysis is part of control scheme resulting in a large “lag time” in determining when to proceed and what to do (heat/cool, etc.).

• Use on-line sampling/analysis, where appropriate • Ensure that safety is not compromised by using manual sampling/analysis as part of the control scheme, e.g., increasing hold times • Provide timely sample test results • Provide instructions to put system in safe mode while waiting for sample results

123

Table 5: Instrumentation/Control Systems

Potential Solutions No. Concern/Issue

and Control Mechanisms

Additional Resources

• Eliminate unnecessary alarms

Nimmo 1995

General 31.

Excessive number of alarms resulting in confusion and reduction in efficiency of pinpointing the root cause of the upset. Operators may miss or ignore critical alarms.

• Eliminate causes of spurious alarms • Log all changes to alarm settings • Identify critical alarms and put on separate panel • Log critical alarms and causes for the alarms • Alarm system design should consider which measurements are to be alarmed; the number, type, and urgency of alarm; type of alarm (i.e., visual/audible) etc. • Alarm should be easily recognized from a previously acknowledged alarm • Provide operator training for response to alarm conditions • Use of automated fault diagnosis systems • Reset alarms with process cycle, but only after all alarms have been acknowledged • Implement first out system • Alarm management prioritization of BPCS and different categories of SIL alarms • Alarms should require an operator intervention otherwise they should not be classified as alarms • Implement abnormal situation management

32.

Software failure resulting in hazardous event.

• Follow strict controls throughout the software life cycle including requirement specifications, software design, coding, testing, and modification • Install system to prevent unauthorized software access and changes • Document and log all changes • Provide redundant software—(software diversity) with a plausibility control • Provide manual backup—control independent of software • Provide critical alarms and safety systems independent of BPCS • Proof testing using non hazardous chemicals after making software changes • Install separate (independent) hardwired safety systems

CCPS G-12 IEC 61508 ISA S84.01

6 Operations and Procedures

6.1. Introduction The primary focus of this chapter is on the operator, since he or she is often closest to the process and provides the last line of defense during a process upset. In the typical batch type system the operator is an integral part of the process control. Operators implement the procedural safeguards needed for the safe operation of the process. The reliability of procedural safeguards (standard operating procedures) are dependent on the effectiveness of training, operator experience, the strength of managerial implementation and process documentation. Not only are these hard to measure, but they can change significantly due to a wide variety of factors, such as personnel turnover or change in management. Complicating matters is the fact that a typical operator working in a batch processing facility may have to perform a number of diverse functions during a routine shift. Moveover, most of these functions must be performed in a specified sequence and timeframe. Some of these functions are listed below: • • • • • • • • • • •

Equipment setup Cleaning Charging Executing and controlling procedures Monitoring, fault diagnosis, and implementing corrective actions Sampling, testing, and controlling Handling of finished products Handling of off-spec/partially finished products Conducting maintenance Providing emergency response Process logging, communication 125

126

6. OPERATIONS AND PROCEDURES

Several of these functions are either specific to batch operations or are done more often in batch operations than in continuous processes. Batch operators also make more frequent control decisions and manipulations than their counterparts in continuous processes. This increased number and variety of functions presents more opportunities for salvaging a process when something goes wrong or alternately for introducing errors (van der Schaaf, 1996). This greater potential for human error has important safety implications because human error is responsible for a large percentage of all incidents. The estimates range from 50% to 85%. Indeed some researchers have gone so far as to conclude that human error in either the design, operation, or management is the root cause of all incidents. Introducing stress by tight production schedules can introduce an environment that further promotes errors. From a safety and reliability perspective, it is important to design a process and its controls around the strengths and capabilities of the operation and avoid situations where it would be physically and mentally impossible for an operator to execute his or her task. The management systems that support the operator should focus on enhancing the operator’s capabilities, for example, by providing appropriate training. In general, the risk of human error can be reduced by properly designing the equipment, procedures, and the work environment and by proper staffing, training, and implementation of management controls. Selecting people with the appropriate capabilities and skills will result in fewer errors being made. Operator selection is important because the operator is a participant in batch processes whereas in continuous plants he/she performs more of a monitoring role. The most experienced and well qualified operators should be assigned to the more hazardous processes. Pair new operators (even experienced operators who are new to the process) with operators experienced in the process. Proper training of personnel is one of the most effective strategies for reducing error. A high level of training is required for batch processes. There is a wide variety of tasks to teach and master. It should be kept in mind that people could forget or revert to old habits acquired before training. Refresher training is a useful way to deal with such situations. Comprehensive additional training should also be required prior to the implementation of campaign changes. The training should ensure that tasks are performed as required by procedure, even under stress. Proper design of equipment, procedures and the work environment can greatly reduce the probability of human error. Designing and maintaining operating procedures is a challenge for batch systems because of the multiplicity of procedures for each piece of equipment, and the variety of operations within

6.1. Introduction

127

each procedure. It is essential to obtain operator input, from both experienced and inexperienced operators, while developing or revising procedures. Information on preventing human error and writing effecting operating procedures can be found in other CCPS publications (CCPS G-15, G-22, G-29, G-32). There are also several CCPS books that deal with safe design of equipment (CCPS G-11, G-13, G-23, G-30, G-39, G-41). To be able to systematically identify opportunities for reducing human error, it is useful to ask the question, “What is human error?” One definition is that human error is an inappropriate or undesirable human decision or behavior that reduces, or has the potential for reducing safety or system performance (Rasmusssen 1979). There is a tendency to view errors as “operator errors.” However, the error may result from inadequate management, design, or maintenance of the system. This broader view which encompasses the whole system can help provide opportunities for instituting measures to reduce the likelihood of errors. A number of error classification schemes have been developed over the years. These schemes can help provide a systematic framework for looking at error. Two schemes for classification of human errors are outlined in this section. Swain and Guttman (1983) presented a simple framework for error classification. They classified errors as: • Errors of omission involve failure to do something. For example, failure to clean out the reactor before charging. • Errors of commission involve performing an act incorrectly. For example, charging wrong materials to the reactor. • Sequence errors refer to situations when a person performs a task , or an individual step in a task, out of sequence. For example, charging the reactor before starting the cooling water flow. • Timing errors occur when a person fails to perform an action within the allotted time, either performing too fast or too slowly. For example, this may include charging a reactor too quickly or too slowly. Another common approach is to use an information-processing model to classify human errors. The classification models the information processing which occurs when a person operates and controls complex systems such as processing plants. One such classification (Rouse and Rouse, 1983) identifies six steps in information processing. Exhibit 6.1 lists the six steps, and provides some examples of errors that can occur at each of these steps. Applying the information-processing model to each of the operator tasks can provide insights into the potential for human error and also suggest solutions for preventing errors.

128

6. OPERATIONS AND PROCEDURES

Exhibit 6.1. Six Steps in the Information Processing Model 1. Observation of system state • Improper readings • Incorrect interpretation of correct readings • Incorrect readings of appropriate state variables • Failure to observe sufficient number of variables • Observation of inappropriate state variables • Failure to observe any state variables 2. Choice of hypothesis • Hypothesis unable to explain the values of the state variables observed • Hypothesis does not functionally relate to the variables observed 3. Testing of hypothesis • Stopped before reaching a conclusion • Reached wrong conclusion • Considered and discarded correct conclusion • Did not test hypothesis 4. Choice of goal • Insufficient specification of goal • Incorrect goal chosen • Goal not chosen 5. Choice of procedure • Procedure would not fully achieve goal • Procedure would achieve incorrect goal • Procedure unnecessary for achieving goal • Procedure not chosen 6. Execution of procedure • Required step omitted • Unnecessary repetition of required step • Unnecessary step added • Steps executed in wrong order • Step executed too early or too late • Control in wrong position or range • Stopped before procedure complete • Inappropriate step executed

129

6.2. Case Studies

Exhibit 6.2. Human Errors in Continuous and Batch Processes Information Processing Step

Continuous

Batch

Observation of System State Improper reading or erroneous interpretation of correct readings

The readings which are considered correct are constant

Readings which are considered correct may change

Incorrect readings of appropriate state variables

State variables which are considered appropriate are constant

State variables which are considered appropriate may change within the batch and batch-to-batch

Failure to observe a sufficient number of variables

The number of variables which are considered sufficient is constant

The number of variables which are considered sufficient may change

Execution of Procedure Required step omitted or executed in wrong order

Fewer procedural steps

Many procedural steps

Unnecessary step added

Procedures remain relatively constant allowing greater familiarity of the operator

Procedures vary from product to product and may be changed frequently for a given product depending on quality needs.

Control settings do not change

Control settings may be purposefully changed for different phases of batches, different batches or similar batches

Steps executed too early or too late Unrelated inappropriate step executed Control in the wrong position

The potential for a wide range of human errors is greater in batch processes than in continuous processes. Some examples can be found in the categories of errors in Exhibit 6.2.

6.2. Case Studies Initiator Overcharging Incident In a multiprocess train building, an operator was running several batch polymerization reactions. One of these was a copolymerization process involving two monomers, an initiator and an organic solvent. Several of the other processes

130

6. OPERATIONS AND PROCEDURES

were having problems, and the operator was very busy and was not logging in the steps in the batch sheet as the steps were completed. At shift change the operator verbally told the relief operator what process steps remained. The relief operator tested for, and detected unreacted monomer in the copolmerization process. In an attempt to complete the reaction, the relief operator added additional initiator to the reactor; a runaway reaction promptly occurred. No injuries occurred but the rapid emission of the organic solvent overpowered the incinerator, causing it to shut down and resulted in a release to the environment. After the incident, an investigation team determined that the first operator had not added the initiator when required earlier in the process. When the relief operator added the initiator, the entire monomer mass was in the reactor and the reaction was too energetic for the cooling system to handle. Errors by both operators contributed to the runaway. Both operators were performing many tasks. The initiator should have been added much earlier in the process when much smaller quantities of monomer were present. There was also no procedure to require supervision review if residual monomers were detected. The lesson learned was that operators need thorough training and need to be made aware of significant hazardous scenarios that could develop. Operating procedures must be written to clearly identify safety issues. Supervisors must be contacted when process conditions deviate from normal. Proper time and procedures must be maintained to transmit information at shift change.

Reactant Stratification Incident A chemical company produced ortho-nitroanisole, a pigment precursor, by adding caustic and methanol to an agitated mixture of ortho-nitrochlorobenzene in a batch reactor with a volume of 36 m3. The normal process is conducted isothermally at a pressure of 8 bar. The temperature is kept at 90°C during the reaction by cooling. The reactants are normally added over a three hour period with agitation and reaction temperature held constant for an additional 2 hours, also under agitation, to ensure completion. One day the operator failed to start the agitator during the caustic/methanol addition step. Stratification of the reactants delayed the exothermic chemical reaction and no heat was generated, causing the reactor to cool down. In order to re-establish the normal reaction temperature the operator replaced the cooling medium with a heating source (steam). Once the operator realized that the agitator had not been turned on, he started the agitator. The sudden mixing of large amounts of reactants under heating, instead of cooling, caused a runaway reaction. Once the pressure reached 16 bar pressure safety devices were actuated, the temperature at that point had reached 160°C,

6.4. Process Safety Practices

131

and material was released to the environment. Most of the material released solidified initially at the ambient temperature of –2°C but turned later into a yellow-brownish sticky paste. The paste contained amounts of ortho-nitroanisole, a suspected carcinogen. The release caused the intervention of the local authorities and necessitated an extensive cleanup of third party properties adjacent to the chemical facility and included roofs, streets, cars, ships moored in the local river, playgrounds, etc. (Kepplinger and Hartung, 1995).

6.3. Key Issues Safety issues in batch reaction systems relating to human errors and procedures are presented in Table 6. The table is meant to be illustrative but not comprehensive. Listed below are operator related safety issues that are more prevelant in batch operations. Keep in mind, however, that human error consists of more facets than operator error alone. • • • • • •

Operator overload and fatigue Inadequate/improper procedures Inadequate training Frequent process changes More direct involvement by operator in processes Diversity of batch operations aggravate all of above

6.4. Process Safety Practices Listed below are several good practices aimed at minimizing operator-induced process incidents. • Training – Newly assigned people – Equipment modification – Process modification – Periodic refresher training – Process-specific training prior to each compaign for existing processes • Written operating procedures • Procedures addressing all process phases • Procedures for equipment, recipes and emergency • Operator involvement in writing procedures • Periodic review of procedures • Formal management of procedure changes • Adequate staffing levels

132

6. OPERATIONS AND PROCEDURES

Table 6: Operations and Procedures

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

Observation 1.

2.

Multiple batches oper- • Provide displays that clearly indicate which ated simultaneously. readings go with which batch and equipment Operator observes • Do not overload operator information about • Develop and use step-by-step check-off process from wrong procedure display. Misoperation leading to undesired incident.

CCPS G-15

Labeling/color scheme conventions different between plants/countries, leading to mischarging.

• Use conventions prevalent in the country of use

CCPS G-15

• Do not use color coding as the sole solution

CCPS G-29

• Provide adequate labeling

CCPS G-32

For example:

• Verify raw materials before use

• Labels on containers

• Bench scale test critical raw materials prior to use

• Color coding of switches

CCPS G-22 CCPS G-29 CCPS G-32

CCPS G-22

• Color coding of gas bottles • Metric/English units • Labeling of shutdown system • Color coding of pipes 3.

4.

Emergency switch operation not understood or clear to the operator. Equipment works differently in different operating locations.

• Provide clear labeling

Emergency shutdown systems/valves not readily accessible.

• Relocate valves or operating device

CCPS G-15

• Provide a consistent control layout and operation across bays, where possible • Make emergency switches easily accessible • Provide clear guidelines for operators when to use emergency switches

• Provide remote operation capability where necessary • Provide detailed written emergency procedures

CCPS G-32

Table 6: Operations and Procedures

133

Potential Solutions and Control Mechanisms

Additional Resources

Trade name used to identify chemical leads to confusion about identity of chemical species. Potential for using wrong material and/or operator exposure.

• Use clear and unambiguous labeling scheme

CCPS G-15

• Ensure verification of chemical identity by second operator or supervisor

CCPS G-29

Many different grades and concentrations of the same material used. Potential for using wrong grade of material and/or operator exposure.

• Minimize number of different grades of material

CCPS G-15

• Use clear and unambiguous labeling scheme

CCPS G-29

• Provide operator training

CCPS G-32

No. Concern/Issue Observation 5.

6.

• Use bar-coding • Use dedicated staging areas • Bench scale testing prior to use

CCPS G-22

• Ensure verification of chemical identity by second operator or supervisor • Use bar-coding • Use dedicated staging areas • Bench scale testing prior to use • Develop procedure for dealing with deviations from normal

7.

Mislabeling/inconsis• Provide a clear and unambiguous labeling tent labeling of materischeme als. Potential for using • Provide operator training wrong material. • Use certificate of analysis where hazardous materials are involved

CCPS G-15

• Test each lot of chemicals prior to use in production (functional or acceptance test) • Develop procedure for dealing with deviations from normal 8.

Warning signs, labels, • Use a language and terminology easily under- CCPS G-15 MSDS, procedure, etc. stood by operators written in language • Use universally accepted symbols not understood by • Verify that the operators understand all peroperators. tinent warning signs, labels, MSDS and instructions

134

6. OPERATIONS AND PROCEDURES

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Ensure verification by second operator or supervisor

CCPS G-15

Observation 9.

Miscounting number of charged containers.

CCPS G-32

• Sign off on each package unit/partial package unit • Ensure correct amount is on-hand before starting • Develop procedure for dealing with deviations from normal Choice/Testing of hypothesis 10.

Batches run infrequently. This may result in less operator familiarity with processing steps, hazards and troubleshooting.

• Provide detailed operating procedures for each process

CCPS G-32

• Use the detailed operating procedures to train operators • Review process steps and hazards associated with process with operators before start of campaign • Provide refresher training • Develop a procedure for dealing with infrequent batches • Provide back-up coverage by technical staff

Choice of goal/procedure 11.

Wrong material or amount charged to reactor.

• Develop procedure for dealing with deviations from normal • Provide clear labeling of materials • Provide operating procedures • Ensure verification by second operator • Use dissimilar packaging for different chemicals • Bench scale test prior to use, where necessary • Use bar-coding of materials • Use dedicated and separate staging areas • Provide separate storage areas for incompatible materials See also Section 4.1, Charging and Transferring and Table 4.6

CCPS G-32

Table 6: Operations and Procedures

No. Concern/Issue

Potential Solutions and Control Mechanisms

135 Additional Resources

Choice of goal/procedure 12.

“Reference Procedures” used to supplement main operating procedures. Operator selects wrong one or forgets to use reference procedures, etc.

• Update procedures more frequently

CCPS G-32

• Incorporate critical procedures into the master document • Provide training using the operating procedures • Use batch sheets • Review process steps with each operator prior to start of infrequently run campaigns

13.

Operating practice dif- • Investigate the reason for the deviation, and ferent from written correct the procedure or practice as procedures may lead appropriate to an incident. • Enforce adherence to operating procedures

CCPS G-32 CMA 1990

• Audit and periodically review operating procedures • Involve experienced operators in development of procedures • Provide peridoic training on procedures • Provide variance control mechanisms for procedure deviation • Automate critical process steps Execution of Procedure 14.

15.

Operating procedures written in language not understood by operators (confusing, technical jargon).

• Write all procedures in simple, direct language

CCPS G-32

• Involve experienced and inexperienced operators in writing/review of procedures

• Ensure that communications (verbal and Errors due to lack of communication during writen) are sufficent to ensure safe transition shift change leading to of operating responsibility at shift change an incident. • Document sign-off steps • Communication in writing check off, provide and enforce written change of shift logs • Use batch logs to document unusual deviations • Verification of status of equipment by incoming shift • Do not start certain steps unless it can be finished during the shift or require shift to stay late to finish the step • Provide comprehensive training • Automate process steps

CCPS G-15 CMA 1990

136

6. OPERATIONS AND PROCEDURES

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Provide clear indication of process being run

CCPS G-15

Execution of Procedure 16.

17.

Running multiple processes in same equipment or same process in multiple equipment may result in human error leading to an incident.

• Display process name on panel • Provide signs in control room • Provide status lights

• Sign off of critical steps (double checking)

CCPS G-15

• Install permissive interlocks to ensure key steps are done in proper order

CCPS G-32

• Omits steps • Repeats steps

• Automate process steps

Operator makes a sequential error

• Executes in wrong order Ergonomics 18.

Operator has difficulty • Relocate/redesign the gauges so that operator CCPS G-15 reading certain gauges, can read them easily ISA RP 60.3 meters, or recordings. • Ergonomic design of displays Nimmo 1995 • Avoid instruments that have minimum and maximum readings at same position on scale • Design instruments to read normal conditions at mid- range • Standardize gauges as deemed appropriate • Train operators to understand the units that are displayed • Have operators assist in design of displays

19.

Procedures and instru- • Standardize on commonly accepted units and CCPS G-32 keep them consistent ments have different units. • Provide conversion charts and look-up tables • Provide change control to ensure devices and procedures are synchronized • Update procedures to include appropriate unit conversion data

20.

Ambient lighting affects color. Color blind operators.

• Don’t rely solely on color to distinguish. Augment color with other means of identification.

Table 6: Operations and Procedures

No. Concern/Issue

Potential Solutions and Control Mechanisms

137 Additional Resources

Ergonomics 21.

Physical stress induced • Where possible design process and/or restructure job/tasks to reduce need for perby Personal Protection sonal protection equipment (PPE) Equipment (PPE). • Train personel in proper use of PPE

NFPA 1991 NFPA 1992 NFPA 1993

• Limit time operator spends on task requiring use of uncomfortable PPE • Maintain PPE in good working condition Operator Exposure 22.

Sampling needs vary with the batch being run. Use of same equipment/procedure may lead to operator exposure. Frequency of manual sampling is much higher than in continuous plants.

• Develop and implement sampling procedures Lovelace 1979 tailored to the need of the batch being run NFPA 1991 • Use special equipment for sampling, where NFPA 1992 necessary, for meeting the special needs of NFPA 1993 different batches (e.g., hot/toxic) • Monitor operator while sampling highly toxic materials • Provide comprehensive training • Proper selection of personal protection equipment (PPE) • Install inline sensors/analysis • Use sample boxes; sample from line instead of opening hatches • Sample recirculation lines to minimize line purge

23.

Emission of toxic, flammable, corrosive, or hot material when equipment is opened for cleaning/maintenance. Possibility for operator exposure.

• Develop, formalize and implement cleaning procedures • Develop, formalize and implement decontamination procedures • Clean in place • Purge vessel prior to opening • Develop, formalize and implement vessel entry procedures, tag out / lock out procedures, blanking procedures, and line breaking procedures • Ensure use of personal protective equipment (PPE) • Provide adequate ventilation

CCPS G-29 API Std. 2015

138

6. OPERATIONS AND PROCEDURES

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Use barrier technology (closed system airlocks, charging vessels, etc.)

CCPS G-29

Operator Exposure 24.

Emission of toxic, flammable, corrosive or hot material when equipment is opened for charging. Possibility for operator exposure.

• Where needed and practical, install remote operation to remove operator from hazard zone • Provide local exhaust ventilation connected to a disposal system (vent condenser, adsorber, scrubber or thermal oxidizers) • Train operator to shut down operation in response to hazardous vapor detection • Use inherently safer materials • Cool vessel contents and depressurize before opening • Proper use of personal protection equipment (PPE)

25.

Degradation of personal protection equipment (PPE) between uses.

• Implement program for cleaning, storage and repair of personal protection equipment (PPE) • Implement periodic inspection of personal protection equipment (PPE)

NFPA 1991 NFPA 1992 NFPA 1993

General 26.

Use of portable equipment and temporary connections for processing. There is a possibility of operator error in making connections. This may lead to hazardous release, ignition or explosion (see also Chapter 4).

• Use dedicated connections and fittings

CCPS G-15

• Implement management of change for modification/alteration of system/procedures

CCPS G-29

• Replace hose/fitting consistent with expected service life • Provide verification by second operator/supervisor prior to making connection, where necessary • Pressure test connections prior to service • Provide manual bonding and grounding • Analyze hazards before using portable/temporary equipment • Implement safe procedure for installation/hook-up • Use double securement of quick connects • Minimize use of flexible hoses • Use of coded/unique connections

CCPS G-32

Table 6: Operations and Procedures

No. Concern/Issue

139

Potential Solutions and Control Mechanisms

Additional Resources

• Develop, formalize and implement vessel entry procedures, tag out/lock out procedures, blanking procedures, cleaning procedures, and line breaking procedures, assembly and disassembly procedures

API Std. 2015

General 27.

Routine disassembly/assembly of equipment. Possibility of incorrect assembly. Possibility of isolation devices not properly removed prior to start-up. Possible loss of containment.

CCPS G-15 CCPS G-29 CCPS G-32

• Pressure test equipment prior to each use or change of service • Provide procedures to verify change of service • Provide interlock procedures to verify safety before opening • Develop and implement proper maintenance procedures • Select equipment for easy assembly/ disassembly • Provide correct tools for assembly/ disassembly • Use second person verification, where necessary • Use self sealing coupling (“dry-break,” “dripless”) • Routinely replace gaskets when changing filters etc. • Perform operational testing using nonhazardous materials (water) before startup • Use checklists

28.

29.

Frequent handling of hazardous materials, or working with hazardous processes may bring complacency.

• Provide refresher training/awareness of hazards

CCPS G-15

Lack of discipline in following procedures/ logging changes. Potential for miscommunication of status.

• Investigate the reason for the deviation, and correct the procedure or practice as appropriate

CCPS G-15

• Enforce adherence to operating procedures • Perform exit interviews of people transferring/leaving • Conduct anonymous surveys to evaluate safety culture • Audit periodically

CCPS G-22

CCPS G-22

140

6. OPERATIONS AND PROCEDURES

No. Concern/Issue

Potential Solutions and Control Mechanisms

Additional Resources

• Provide more frequent training/refresher training

CCPS G-15

• Schedule training near start of process

CCPS G-29

• Obtain operator input in determining training frequency

CCPS G-32

General 30.

Wide variety of tasks performed by a batch operator requires a high level of training.

CCPS G-22

• Train operators in “error recovery” and “what-if” 31.

32.

33.

Keeping operating procedures current is a challenge because there may be numerous procedures per piece of equipment, and they change with the process.

• Provide sufficient resources to develop/main- CCPS G-32 tain procedures • Implement management of change procedure • Periodically review procedures • Solicit operator input in developing procedures • Conduct internal audits

Operator control/ manipulation of process is frequent. Operator duties are demanding. Vigilance is needed as processing conditions change with time.

• Provide detailed operating procedures

CCPS G-32

• Provide scheduled training

Meister 1987

Operators working on processes with which they have no prior experience.

• Involve operator in Process Hazard Analysis of new process

CCPS G-15

• Perform operating procedures analysis

CCPS G-29

• Conduct technical staff review with operators before each campaign

CCPS G-32

• Perform job design/task analysis (do not overload operator)

• Ensure adequate training • Provide technical staff coverage during first run of new process or infrequent campaigns • Use “Buddy System” pairing experienced/inexperienced personnel • Perform operational testing using nonhazardous materials before startup

CCPS G-22

Table 6: Operations and Procedures

No. Concern/Issue

141

Potential Solutions and Control Mechanisms

Additional Resources

• Provide formal procedures for dealing with ‘off-spec’ batches, partially reacted batches

CCPS G-30

General 34.

Need for reworking, blending, or disposing of partially reacted or “off-spec” batches.

CCPS G-32

• Provide on-call technical assistance/support to operators • Understand chemistry and potential consequences of producing ‘off-spec’ products/waste materials, etc. • Efforts should be make to reduce the production of off-spec material

35.

Avoid written and verbal linguistic confusion. Example 1: the English pronunciation of “benzene” sounds like “benzyne” in Dutch, consequently a verbal instruction to add “benzene” to a process in distress could have dire consequences. Example 2: glyceroltrinitrate is the correct chemical name for what is commonly known as “nitroglycerine.”

• Ensure materials are unequivocally identified CCPS G-32 and that there is a common linguistics understanding at a site, especially among people with different native tongues

References

ACGIH 1986. Industrial Ventilation—A Manual of Recommended Practice, 19th ed. American Conference of Governmental Hygienists, Cincinnati, Ohio. AGA. Manual of Petroleum Measurement Standards. Chapter 14—Natural Gas Fluids Measurement, Section 3: Orifice Metering of Natural Gas and Other Related Hydrocarbon Fluids. AGA Report No. 3. (ANSI/API 2530, 1985 and GPA 8185, 1985). American Gas Association, Cleveland, Ohio. AGA XK0775. Purging Principles and Practices. AGA Cat XK0775. American Gas Association, Cleveland, Ohio. AIChE 1972. Pilot Plant Safety Manual, AIChE, New York, NY. API Publ 327, Aboveground Storage Tank Standards: A Tutorial, September 1994. API Publ 334, A Guide to Leak Detection for Aboveground Storage Tanks, September 1995. API Publ 340, Liquid Release Prevention and Detection Measures for Aboveground Storage Facilities, October 1997. API Publ 761, Model Risk Management Plan Guidance for Exploration and Production Facilities—Guidance for Complying with EPA’s RMP Rule (40 Code of Federal Regulations 68), 2nd ed., August 1997 API Publ 937, Evaluation of Design Criteria for Storage Tanks with Frangible Roof Joints, First ed., April 1996. API Publ 2009, Safe Welding and Cutting Practices in Refineries, Gasoline Plants, and Petrochemical Plants, 6th ed., September 1995 API Publ 2021A, Interim Study—Prevention and Suppression of Fires in Large Aboveground Atmospheric Storage Tanks, 1st ed., July 1998 API Publ 2026, Safe Access/Egress Involving Floating Roofs of Storage Tanks in Petroleum Service, 2nd ed., April 1998. API Publ 2027, Ignition Hazards Involved in Abrasive Blasting of Atmospheric Storage Tanks in Hydrocarbon Service, 2nd ed., July 1988. API Publ 2028, Flame Arresters in Piping Systems, 2nd ed., December 1991. API Publ 2201, Procedures for Welding or Hot Tapping on Equipment in Service, 4th ed., September 1995. 143

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API Std 653, Tank Inspection, Repair, Alteration, and Reconstruction, 2nd ed., December 1995. API Std 2000, Venting Atmospheric and Low-Pressure Storage Tanks: Nonrefrigerated and Refrigerated, 4th ed., September 1992 (ANSI/API Std 2000-1992). API Std 2015, Safe Entry and Cleaning of Petroleum Storage Tanks, Planning and Managing Tank Entry from Decommissioning Through Recommissioning, 5th ed., May 1994. API Std 2510, Design and Construction of Liquefied Petroleum Gas Installations (LPG), 7th ed., May 1995 (ANSI/API Std 2510-1996) API Std 2530. 1985. Orifice Monitoring of Natural Gas and Other Related Hydrocarbons. American Petroleum Institute, Washington, DC. ASME. Boiler and Pressure Vessel Code, Sections I and VIII. American Society of Mechanical Engineers. ASME. 1971. Fluid Meters, 6th ed., American Society of Mechanical Engineers, New York. ASTM 1986. American Society of Testing and Materials Committee D-34 , Proposal-168, Proposed Guide for Estimating the Incompatibility of Selected Hazardous Wastes Based on Binary Chemical Reactions, and included Minority Report. ASTM E 1226. Standard Test Method for Pressure and Rate of Pressure Rise for Combustible Dusts. Balls, B. W., A. B. Rentcome, and J. A. Wilkenson. 1987. Specification and Design of Safety Systems for the Process Industries, 8th International System Safety Conference, New Orleans, LA. Bartknecht, W., Dust Explosions Course, Prevention, Protection, Springer Verlag Berlin, Heidelberg, New York, 1989. Bossart, C. J. 1974. Monitoring and Control of Combustible Gas Concentration Below the Lower Explosive Limit. 20th Analysis Instrumentation Symposium. May 1974. Instrument Society of America, Pittsburgh, Pennsylvania. Brandt, D., W. George, C. Hathaway, and N. McClintock. 1992. An Engineer’s Guide to Plant Layout. Part 2. The Impact of Codes, Standards and Regulations. Chemical Engineering, 99(4), 89–94. Britton, L. G., 1999. Avoiding static ignition hazards in chemical operations, American Institute of Chemical Engineers, Center for Chemical Process Safety. New York. BS 5958. Code of Practice for Control of Undesirable Static Electricity. BSI, U.K. BS 5345. General Recommendations—Code of Practice for Selection, Installation and Maintenance of Electrical Apparatus for Use in Potentially Explosive Atmospheres. BSI, U.K. CCPS G-1. 1992. Guidelines for Hazard Evaluation Procedures, Second Edition with Worked Examples. American Institute of Chemical Engineers, Center for Chemical Process Safety. New York. CCPS G-2. 1987. Guidelines for Use of Vapor Cloud Dispersion Models. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York.

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CCPS G-3. 1988. Guidelines for Safe Storage and Handling of High Toxic Hazard Materials. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-4. 1988. Guidelines for Vapor Release Mitigation. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-6. 1989. Guidelines for Chemical Process Quantitative Risk Analysis. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-7. Process Equipment Reliability Database. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-8. Guidelines for Technical Management of Chemical Process. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-9. Guidelines for Evaluating the Characteristics of Vapor Cloud Explosions, Flash Fires, and BLEVEs. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-10. 1992. Plant Guidelines for Technical Management of Chemical Process Safety and a video, Process Safety for Plant Personnel, based on these Guidelines. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-11. 1998. Guidelines for Pressure Relief and Emergency Handling Systems. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-12. 1993. Guidelines for Safe Automation of Chemical Processes. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-13. Guidelines for Chemical Reactivity Evaluation and Applications to Process Design. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-15. Guidelines for Preventing Human Error in Process Safety. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-19. Guidelines for Investigating Chemical Process Incidents. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-20. Guidelines for Auditing Process Safety Management Systems. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-21. Tools for Making Acute Risk Decisions with Chemical Process Safety Applications. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-22. Guidelines for Process Safety Fundamentals for General Plant Operations. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-23. Guidelines for Engineering Design for Process Safety. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-24. Guidelines for Postrelease Mitigation Technology in the Chemical Process Industries. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York.

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CCPS G-25. Guidelines for Implementing Process Safety Management Systems. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-26. Guidelines for Evaluation Process Plant Buildings for External Explosions and Fires. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-27. Guidelines for Process Safety Documentation. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-28. Guidelines for Chemical Transportation Risk Analysis. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-29. Guidelines for Safe Process Operations and Maintenance. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-30. Guidelines for Storage and Handling of Reactive Materials. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-31. Guidelines for Technical Planning for On-Site Emergencies. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-32. Guidelines for Writing Effective Operating & Maintenance Procedures. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-33. Guidelines for Safe Warehousing of Chemicals. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-34. Contractor and Client Relations to Assure Process Safety. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-35. Concentration Fluctuations and Averaging Time in Vapor Clouds. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-36. Expert Systems in Process Safety. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-37. Understanding Atmospheric Dispersion of Accidental Releases. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-38. Guidelines for Integrating Process Safety Management, Environment, Safety, Health, and Quality. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-39. Guidelines for Design Solutions for Process Equipment Failures. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-41. Inherently Safer Processes: A Life Cycle Approach. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-51. 1998. Understanding Quantitative Risk Assessment. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-55. Guidelines for Performance Measures for Continuous Improvement of Process Safety Management Systems. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York. CCPS G-56. 1998. Guidelines for Improving Plant Reliability through Data Collection and Analysis. American Institute of Chemical Engineers, Center for Chemical Process Safety, New York.

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Index Index terms

Links

B Batch control activities, instrumentation/control systems

110

Batch distillation columns, equipment safety

40

Batch pharmaceutical reactor, equipment safety case study

43

Batch reaction process safety

73

1

approach to

3

chemistry

7

See also Chemistry equipment

35

See also Equipment equipment configuration

27

See also Equipment configuration instrumentation/control systems

109

See also Instrumentation/control systems operations and procedures

125

See also Operations and procedures scope of issues

1

special concerns

2

C Centrifuges, equipment safety

38

64

41

76

See also Equipment safety (summary tables) Change management. See Management of change Charging equipment, equipment safety See also Equipment safety (summary tables) Chemical compatibility, reactivity hazards screening

22

Chemical composition, summary table

15

This page has been reformatted by Knovel to provide easier navigation.

167

168

Index terms Chemical identification, summary table Chemistry

Links 14 7

case study

8

overview

7

process safety practices

9

reactivity hazards screening

21

experimental analysis

24

experimental screening

23

problem context

21

theoretical screening

21

summary table

11

chemical composition

15

chemical identification

14

chemistry/process chemistry selection

11

contamination

19

off-spec product/intermediate raw material

20

runaway reaction

16

waste minimization

20

Chemistry/process chemistry selection, summary table

11

Choice of goal/procedure, operations and procedures, summary table

134

Choice/testing of hypothesis, operations and procedures, summary table

134

Containment loss equipment safety (summary tables) centrifuges

66

drumming equipment

91

filters

103

general

53

reactors and vessels

63

transferring and charging equipment

81

instrumentation/control systems, summary table Contamination, chemistry, summary table

This page has been reformatted by Knovel to provide easier navigation.

115 19

169

Index terms

Links

Corrosion equipment safety (summary tables) centrifuges

66

drumming equipment

92

milling equipment

98

transferring and charging equipment

79

instrumentation/control systems, summary table

115

D Drains, equipment safety

40

75

Drumming equipment, equipment safety

41

90

See also Equipment safety (summary tables) Dryer fire and explosion, equipment safety case study

44

Dryers, equipment safety

39

E Equipment configuration

27

case studies

28

importance of

27

issues in

29

practices in

29

summary table

30

fire/explosion

31

general

33

ignition sources

31

operator exposure

33

shared systems

30

Equipment-related control, instrumentation/ control systems Equipment safety

111 35

batch distillation and evaporators

40

case studies

43

batch pharmaceutical reactor This page has been reformatted by Knovel to provide easier navigation.

43

70

170

Index terms

Links

Equipment safety (Continued) pharmaceutical powder dryer fire and explosion

44

runaway reaction

44

centrifuges

38

charging and transferring equipment

41

drumming equipment

41

dryers

39

filters

42

issues

45

milling equipment

42

overview

35

practices

45

process vents and drains

40

reactors and vessels

36

storage and warehousing summary tables

105 48

See also Equipment safety (summary tables) Equipment safety (summary tables)

48

batch distillation and evaporation

73

centrifuges

64

containment loss

66

corrosion

66

fires/explosions

68

general

68

high temperature

65

ignition sources

67

operator exposure

68

overpressure

64

runaway reaction

65

underpressure

65

drumming equipment

90

containment loss

91

This page has been reformatted by Knovel to provide easier navigation.

171

Index terms

Links

Equipment safety (summary tables) (Continued) corrosion

92

fires/explosions

95

high temperature

94

ignition sources

94

low temperature

95

operator exposure

95

overpressure

90

runaway reaction

93

underpressure

92

dryers

70

filters

100

containment loss

103

fires/explosions

101

high temperature

100

ignition sources

102

operator exposure

104

overpressure

100

runaway reaction

101

general

48

containment loss

53

fire/explosion

49

management of change

52

operator exposure

52

overpressure

48

underpressure

48

milling equipment

96

corrosion

98

fires/explosions

98

general

99

high temperature

96

ignition sources

98

This page has been reformatted by Knovel to provide easier navigation.

172

Index terms

Links

Equipment safety (summary tables) (Continued) low temperature

97

management of change

99

operator exposure

99

overpressure

96

runaway reaction

97

underpressure

96

process vents and drains

75

reactors and vessels

54

containment loss

63

high temperature

55

low temperature

60

mixing

60

overpressure

54

runaway reaction

61

underpressure

55

transferring and charging equipment

76

containment loss

81

corrosion

79

fires/explosions

84

general

76

high temperature

79

low temperature

79

operator exposure

88

overpressure

76

runaway reaction

80

underpressure

79

Ergonomics, operations and procedures, summary table

136

Error. See Operations and procedures Evaporators, equipment safety Execution of procedure, operations and procedures, summary table Experimental analysis, reactivity hazards screening This page has been reformatted by Knovel to provide easier navigation.

40 135 24

73

173

Index terms

Links

Explosions equipment configuration, summary table

31

equipment safety (summary tables) centrifuges

68

drumming equipment filters

95 101

general

49

milling equipment

98

transferring and charging equipment

84

powder dryer fire and explosion, case study

44

Explosion testing, reactivity hazards screening

24

F Filters, equipment safety

42

See also Equipment safety (summary tables) Fires equipment configuration, summary table

31

equipment safety (summary tables) centrifuges

68

drumming equipment

95

filters

101

general

49

milling equipment

98

transferring and charging equipment

84

G Goal/procedure, choice of, operations and procedures, summary table

134

H High temperature, equipment safety (summary tables) centrifuges

65

drumming equipment

94

filters

100 This page has been reformatted by Knovel to provide easier navigation.

100

174

Index terms

Links

High temperature, equipment safety (summary tables) (Continued) milling equipment

96

reactors and vessels

55

transferring and charging equipment

79

Hypothesis, choice/testing of, operations and procedures, summary table

134

I Ignition sources equipment configuration, summary table

31

equipment safety (summary tables) centrifuges

67

drumming equipment filters

94 102

milling equipment instrumentation/control systems, summary table

98 116

Information management, instrumentation/ control systems

109

Information processing model, operations and procedures

128

Instrumentation/control systems

109

batch control activities

109

case study

112

equipment-related control

111

information management

109

issues

113

overview

109

process management

111

process safety practices

114

production scheduling

111

recipe management

111

safety interlocking

111

summary table

115

containment loss

115

corrosion

115

general

116

This page has been reformatted by Knovel to provide easier navigation.

111

111

111

175

Index terms

Links

Instrumentation/control systems (Continued) ignition sources Intermediate raw material, off-spec product and, chemistry, summary table

116 20

L Loss of containment. See Containment loss Low temperature, equipment safety (summary tables) drumming equipment

95

milling equipment

97

reactors and vessels

60

transferring and charging equipment

79

M Management of change, equipment safety (summary tables) general

52

milling equipment

99

Mechanical sensitivity, reactivity hazards screening

24

Milling equipment, equipment safety

42

See also Equipment safety (summary tables) Mixing, equipment safety (summary tables), reactors and vessels

60

O Observation, operations and procedures, summary table Off-spec product, intermediate raw material and, chemistry, summary table Operations and procedures

132 20 125

case studies

129

information processing model

128

issues

131

overview

125

process safety practices

131

summary table

132

choice of goal/procedure This page has been reformatted by Knovel to provide easier navigation.

134

96

176

Index terms

Links

Operations and procedures (Continued) choice/testing of hypothesis

134

ergonomics

136

general

138

observation

132

operator exposure

137

procedure execution

135

Operator exposure equipment configuration, summary table

33

equipment safety (summary tables) centrifuges

68

drumming equipment

95

filters

104

general

52

milling equipment

99

transferring and charging equipment

88

operations and procedures, summary table

137

Overpressure, equipment safety (summary tables) centrifuges

64

drumming equipment

90

filters

100

general

48

milling equipment

96

reactors and vessels

54

transferring and charging equipment

76

P Pharmaceutical powder dryer fire and explosion, equipment safety case study

44

Pharmaceutical reactor, equipment safety case study

43

Powder dryer fire and explosion, equipment safety case study

44

Procedure execution, operations and procedures, summary table This page has been reformatted by Knovel to provide easier navigation.

135

177

Index terms Process management, instrumentation/control systems

Links 111

Process safety. See Batch reaction process safety Process vents, equipment safety Production scheduling, instrumentation/control systems

40

75

111

R Reaction process safety. See Batch reaction process safety Reactivity hazards screening

21

experimental analysis

24

experimental screening

23

problem context

21

theoretical screening

21

Reactors, vessels and equipment safety

36

See also Equipment safety (summary tables) Recipe management, instrumentation/control systems

111

Runaway reaction chemistry, summary table

16

equipment safety case study

44

equipment safety (summary tables) centrifuges

65

drumming equipment

93

filters

101

milling equipment

97

reactors and vessels

61

transferring and charging equipment

80

S Safety interlocking, instrumentation/control systems

111

Scheduling, production, instrumentation/control systems

111

Self-reactivity hazards, reactivity hazards screening

24

Seveso runaway reaction, equipment safety case study

44

Shared systems, equipment configuration, summary table

30

This page has been reformatted by Knovel to provide easier navigation.

54

178

Index terms Storage and warehousing, equipment safety Storage vessels, reactors and, equipment safety

Links 105 36

54

See also Equipment safety (summary tables)

T Temperature high, equipment safety (summary tables) centrifuges drumming equipment filters

65 94 100

milling equipment

96

reactors and vessels

55

transferring and charging equipment

79

low, equipment safety (summary tables) drumming equipment

95

milling equipment

97

reactors and vessels

60

transferring and charging equipment

79

Theoretical screening, reactivity hazards screening

21

Thermal sensitivity, reactivity hazards screening

24

Thermophysical properties, reactivity hazards screening

23

Training. See Operations and procedures Transferring equipment, equipment safety

41

See also Equipment safety (summary tables)

U Underpressure, equipment safety (summary tables) centrifuges

65

drumming equipment

92

general

48

milling equipment

96

reactors and vessels

55

transferring and charging equipment

79

This page has been reformatted by Knovel to provide easier navigation.

76

179

Index terms

Links

V Vents. See Process vents Vessels, reactors and, equipment safety

36

See also Equipment safety (summary tables)

W Warehousing, equipment safety Waste minimization, chemistry, summary table

This page has been reformatted by Knovel to provide easier navigation.

105 20

54