Guidelines for Process Safety in Batch Reaction Systems

Guidelines for

Process Safety in Batch Reaction Systems

@

INTERSCIENCE AMERICAN INSTITUTE OF CHEMICAL ENGINEERS

CENTER FOR CHEMICAL PROCESS SAFETY

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

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Guidelines for

Process Safety in Batch Reaction Systems

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This book is one of a series of publications available from the Center for Chemical Process Safety. A complete list of titles appears at the end of this book.

Guidelines for

Process Safety in Batch Reaction Systems

@

INTERSCIENCE AMERICAN INSTITUTE OF CHEMICAL ENGINEERS

CENTER FOR CHEMICAL PROCESS SAFETY

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

Copyright 8 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 othenvise 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 responsibilitywhatsoever 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 A1 Noren

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Contents Preface

Acknowledgments Acronyms and Abbreviations

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 2 3

2 Chemistry 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 ExperimentalScreening Conduct ExperimentalAnalysis

7 8 9 9 11 21 21 21 23 25 vii

...

CONTENTS

Vlll

3

.IyIILIAIIRIy

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

4

Equipment ~~

4.1. Introduction Vessels Including Reactorsand 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

27 28 28 28 29 29 30

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

InstrumentationlControl Systems 5.1. Introtluction 5.2. Case Study 5.3. Key Issues 5.4. Process Safety Practices Table 5: InstrumentatiodControl Systems

Operations and Procedures 6.1. Introduction 6.2. Case Studies Initiator OverchargingIncident Reactant StratificationIncident

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

References Glossary

109 112 113 114 115

125 129 129 130 13 1 131 132

143 159

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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 manageiment 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 issueskoncerns, 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

ACKNOWLEXMENTS

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 8z 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

IS0

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

ACRONYMS AND ABBREVIATIONS

xviii THA TLV UBC UEL UFL UL UPS

UT

VCE VDI VDE

voc VSP

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

1 Process Safety in Batch Reaction Systems 2.1. 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. I[n 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 issuedconcerns, ultimately the user needs to make the case for the solutions that provide a balance between risk

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 Use:din 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. Concei:dIssue: 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.

0

0

Figure 1. Typical batch reaction system.

To waste solvent recovery

J

Product

1.3. Approach Uscd 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 vapordgases due to leaks. This chapter presents issues/concerns, and provides potential solutions related to equipment configuration and la.yout 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. InstrumentationlControl 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-spedpartially 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 uninten'ded 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 ii process chemistry or synthesis route that is inherently safer. Perform chemical reactivity testing, including the analytical verification of reactants, catalyst, quenches, 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

Selection of ChemistryProcess Chemistry I.

Raw materials, intermediates, praiducts, by-products, decomposition or unintended products are hazardous. Use of the hazardous materials poses a potential risk to the people and the environment.

Select a process chemistry or synthesis route that is inherently safer (e.g., nontoxic, nonflammable materials, less severe operating condition) Use Process Safety Management techniques to minimize the risk to people, and the environment Select equipment design for high integrity containment .

CCPS G-1 CCPS G-6 CCPS G-10 CCPS G-21 CCPS G-24 CCPS G-25 CCPS G-31 CCPS (2-41

!.

Use of maaerials sensi-

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) Prevent exposure to shock, high temperature or pressure Design for pressure containment Provide adequately designed relief device Use less severe operating conditions

ASME VIlI Div I and II CCPS G-11 CCPS G-13 CCPS G-23 CCPS G-30 CCPS G-41 DIEM NFPA 68 NFPA 69

ChemicaVmaterials that may potentially come in contact are incompatible. Inadvertent contact between two or more chemicals may lead to a hazardous condition.

Use inherently safer chemistry (e.g., when

API RP750 CCPS G-1 CCPS G13 CCPS G-22 CCPS G 3 CCPS E 3 0 CCPS G-32 CCPS G-41 Hendershot

).

tive 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.

phosgene is cooled in a heat exchanger, consider use of an inert oil as the coolant rather than water as heat exchanger tubes may fail) Use chemical interaction matrices to identify 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

1987

Kletz 1991 Lees 1996

12

2. CHEMISTRY

Selection of Chemistry/Process Chemistry ~

l".ll__ll

I.

Ingress of air into reactor containing pyrophoric material. 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 Design system to accommodate deflagration pressure Provide fire and/or deflagration suppression system Provide closed feed system Provide explosion venting

IGA-XK0775 SCPS G-29 qFPA 2001 \JFPA 68 VFPA 69

;.

Water reactivity of chemicals involved in reaction* Of runaway.

Avoid use of water as cooling/heating medium Avoid use of watedsteam for cleaning of reactor Avoid direct water connection to reactor Prevent backflow from scrubber into reactoi 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

SCPS G-13 X P S G-41

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 _ " I

._

I

13

Table 2: Chemistry

Selection of ChemistryProcess Chemistry i.

Raw materials, intermediates, products, by-products and/or undesired byproducts are subject to runaway reactions that produce extreme heat and/or extreme amounts of gaseoudvapor products.

Test suspect materials for undesired properties, (e.g., endothermic compounds, compounds containing oxidizing and reducing group such as ammonium nitrate) Substitute or attenuate hazardous materials (inherently safer alternative) Construct equipment to handle extreme temperatures and or pressures Provide emergency relief systems Provide process monitoring and control systems Provide External Risk Reduction Facility (ERRF)

:cps (3-11 NERS EC 61508

7.

Unknown intermediate / side reaction. Unknown

Test suspect materials to characterize undesired properties Conduct thermal hazards analysis Evaluate methods for controlling runaway reactions (e.g., short stop, inhibitors) Determine consequences of runaway reactions and ensure mitigation techniques are in place

;CPS G-13 MERS

bility for runaway reaction.

5.

Chemicalis for use in the process are selected because they are convenient and not necessarily because they are the most suited. Nonoptirnal system design in terms of safety and economics.

XPS (3-23 Carefully and deliberately select process chemicals and synthesis route :CPS G-41 Emphasize consequences of chemical choices to Research and Design Engineering

14

__-9.

10.

2. CHEMISTRY

Selection of Chemistry/F'rocess Chemistry Process chemistry

Use inherently safer chemistry

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

Consider the consequences of using existing equipment for new processes (e.g., batch size, corrosion, cost) Anticipate future product needs before purchase of equipment Match batch sizes to equipment capabilities

Operating Of the equipment and the relief capability.

Provide equipment with comparable pressure rating for the entire system Implement management of change orocedures

Short development time may in a less than complete knowledge of the hazards.

Allocate enough time for development Use more time-efficient PHA techniques Use administrative controls to decide when to go to full scale production Establish minimum requirements "transfer package" for process knowledge Require development chemist to be present during initial product runs

X P S G-1 X P S G-8 X P S (2-23 ZCPS G-41

API RP 750 CCPS G-1 CCPS (2-10 CCPS G-25

Chemical Identification

11.

Establish procedures for testing and verifica Trade name of process tion of raw materials, including use testing chemical changes or trade name prevents Implement management of change immediate recognition procedures of harmful effects/ inter* Implement operating procedures and action of chemical. training Sometimes different Use consistent internal labeling system vendors use different names for chemicals. Use of incorrect chemicals leads to hazardous conditions.

CCPS G-13 CCPS G-22 NFPA 325M NFPA 401 NFPA 704

15

Table 2: Chemistry

Composition 2.

L3.

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

Change in feed composition. Thiis may happen due to change in suppliers or due to introduction of reworked material. 'Unwanted effect on reaction produ c t ~ by-products. , Varying inhibitor concentrations in monomers from different vendors. Potential for runaway reaction.

Use dedicated feed tank and reactor Implement procedure for double checking reactant identification and quality Implement procedure for double checking addition of correct reactant in correct order Develop operating instructions on the correct or permitted connections between tank! and vessels Color code and label lines Provide dedicated storage areadunloading 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

V1 RP 750 XPS G-13 XPS G-22 X P S G-29 XPS G 3 0

Design for feed variations Obtain certificate of analysis Establish purity limits for each feed Bench scale use testing Sample and analyze feed stocks before addition 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

CCPS G-1 CCPS Ell CCPS E l 3 CCPS G-23 CCPS Y-28 DIERS

2

.... .... ....... .. .....

16

2. CHEMISTRY

Runaway Reaction 14.

Runaway reaction (caused by, e.g., generation of excessive heat during "fast" charging).

Provide automatic or manual addition of diluent, poison, or inhibitor directly to reactor Provide 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 automatidmanual 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

XPS G-11 :CPS G-13 :CPS G-23

>IERS (letz 1991

_ I

15.

Overchargdoverfeed of reactants Possibility of overfilling vessel, or initiating runaway reaction.

Use of dedicated reactant charge tank sized only to hold amount of reactant needed Interlock reactant feed charge ed via feed totalizer or weight comparison in charge tank Provide automatidmanual response to level or other indication of abnormal quantity of vessel contents Monitor reaction initiation and progress during charging Provide batch sequencing interlocks that demand operator action Provide adequately designed relief device

JCPS G-13 X P S G-23

16.

Undercharge/ underfeed of reactants. Possibility of unreacted mixed reactants left at end of batch, leading to a subsequent runaway reaction.

Use dedicated reactant charge tank sized to hold correct amount of reactant needed Interlock reactant feed charge via feed totalizer or weight comparison in charge tank

ZCPS G-11 X P S G-13 X P S G-23

DIERS Provide automatidmanual response to level or other indication of abnormal quantity of Kletz 1991 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 material!

17

Table 2: Chemistry

Runaway Reaction 7.

Overcharge of catalyst or initiator, too much or too fast. Possibility of runaway reaction.

Use dedicated catalyst or initiator charge

XPS G-15 XPS G-23 ZCPS G-29

18.

Undercharge of catalyst. Potential fsor accumulation of reactants and subsequent runaway reaction. Possibility of no reaction resulting in a waste disposal issue.

Use dedicated catalyst charge tank sized to hold only the amount of catalyst needed Implement administrative (procedural) controls for catalyst on the amount or concentration to be added Use staging area for preweighed single catalyst 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

XPS G-11 XPS G-13 X P S G-23

m

__ -_

tank sized to hold only the amount of catalyst needed Limit quantity of catalyst or initiator added by flow totalizer 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

m

-

18

2. CHEMISTRY

Runaway Reaction 1.

20.

Overactive and/or wrong catalyst. Possibility for runaway reaction.

Use dedicated catalyst charge tank sized to

:cps :cps :cps :cps

Establish procedures for testing and verification of catalyst activity and identification including use testing Provide means of detecting reaction completion before proceeding Design reactor and/or downstream system to accommodate maximum expected pressure

X P S GCCPS GCCPS GDlERS Kletz 19'

hold only the amount of catalyst needed Passivate fresh catalyst prior to use or use prediluted catalyst Establish procedures for testing and verification of catalyst activity and identification including use testing. Include procedure to monitor shelf life of catalyst to maintain 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

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.

- .

Provide adequately designed relief device Establish procedure for disposal of unreacted reactant mixture

G-. GGG:CPS GX P S GIIERS

19

Table 2: Chemistry

Runaway Reaction :cps G-11 :CPS G-13 :CPS G-23 )IERS 3etz 1991

21.

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

Provide automatic control of inhibitodinitiator addition Provide analytical verification of inhibitor / initiator effectivenessincluding use testing (including shelf life issues) Avoid conditions for precipitating, or otherwise separating inhibitor from reacting species Design system to accommodate maximum expected pressure and temperature Provide emergency cooling Provide adequately designed relief device

22.

lnsufficientdiluent due to under feled or excessive evaporation ing in insufficient heat sink. possit,ility of runawaY reaction due to high temperature excursion Or high concentfation of reac+ng species

:cPS G-11 Provide automatic control of diluent addition XPS G-23 Select diluent less susceptible to evaporation Install automatidmanual isolation based on detection of unexpected reaction rate Provide emergency cooling Provide adequately designed relief device Monitor liquid level

23.

Incomplete reaction due to insufficient residence time* low Overactive inhibitor etc* Possibility of no tion. Possibility of unexpected reaction in processing steps. Problem of disposing Of unreacted mixture.

Auto/Manual response to low reaction progress Decision not to proceed to next step based on detection of low reactor temperature and/or reactor composition sampling Design reactor or downstream vessel to accommodate maximum expected pressure Provide adequately designed relief device Implement procedure for disposing of unreacted mixture

SCPS G-11 X P S G-13 ZCPS G-15 X P S G-22 CCPS G-23 CCPS G-31 DIEM

Develop written procedures to clean and verify reactor readiness Implement checklist verification Analyze used cleaning solvent

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

Contamination 24.

Chemical reaction due to equipment not being proper'y drained from previous run. Possibibty of unwantedreaction or insufficient desired reaction.

20

2. CHEMISTRY

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 heatingkooling 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 na

react with or inhibit reactor contents Use external heaterkooler (panel coil) Use electrical heating with proper consider ation of maximum possible heating elemeni temperature Use lower pressure heating or cooling medium to avoid flow into reactor in the event of a leak Consider impact of reactor contents leakin] into utility implement procedures for IeaUpressure testing of jacket, coil or heat exchanger prior to operation Provide emergency cooling Transfer reactor contents to dump tank with diluent quench.

X P S G-23

Off-spec producthntermediate raw material i 26.

The raw materials are Off-Wec in generation of excessive waste products.

Implement effective quality ~. control .prograi Employ good operating procedures Provide procedures to safely handle the unplanned waste generation and/or neutral ize off-spec materials.

X P S G-29

Implement strict quality control program Employ good operating procedures Develop effluent handling procedures

X P S G-29 X P S G-32

I

Waste Minimization

27. i

Variation in waste by batch. Feed to downstream waste processing equipment. Possibility of reaction in waste streams, flammable/ toxic hazard.

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.l 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 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

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

matrix

~

-*-

w-

~

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

Themopbysical 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 I5xperimental 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 Negligible to Low

Less exothermic than -1.2 kJ/g (-0.28 kcaVg)

< 700K

Intermediate

-1.2 kJ/g < AHr < -3.0 kJlg (-0.28 kcaVg -z AHr < -0.7kcaVg)

<1600 K

High

More exothermic than -3 kJ/g (-0.7 kcaVg)

> 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

i3

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, C,, 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)

L

t,

I

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

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 Specific heat Vapor pressure of solvent as a function of temperature Gas evolution

Table of data Thermodynamic data Calculations; estimations Differential Thermal Analysis (DTA) / Differential Scanning Calorimetry (DSC) Dewar flask experiments Reaction calorimetry with pressure vessel Thermometryhnanometry APTAC" /ARC" /RSST/VSP

2. What is the potential temperature rise by undesired reactions or thermal decomposi- tion, such as from contaminants, impurities, etc.? What are the: consequences? What is the maximum pressure?

Enthalpy of undesired reaction Specific heat Rate of undesired reaction as a function of temperature

DTA/DSC Dewar flask experiments APTAC" /ARC" /RSST/VSP

3. Is reactant accumulation possible? What are thc consequences?

Steady state concentrations Kinetic data Data from 1 and 2

Reaction calorimetry combined with analysis Potential energy by DSC/DTA VSP / APTAC"

4. What is the safe storage tempera-

Kinetic data

Isothermal Storage Test

ture for shelf life?

**

I ye

,

",,-

This page intentionally left blank

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 l.arger 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 headcold 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 classificationis 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 struaures/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

3. EQUIPMENT CONFIGURATION AND LAYOUT

28

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 (CCPSG-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 pumpinghalve 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 pres'ented 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 daimage limiting construction Provide spill control Install adequate sprinkler protection

30

3. EQUIPMENT CONFIGURATION AND LAYOUT

Table 3: Equipment Configuration and Layout

Shared Systems 1.

2.

Shared vent systems. Possibility of incompatible materials coming together.

Design to avoid incompatible materials present in the same vent system Install deflagration suppression systems Design vent to prevent backflow/accumulation Prescrub vent discharge before transfer to vent header Monitor circulating utility systems for contamination

Shared utility supply systems. Possibility of incompatible materials coming together via contamination of the shared utility system

Design to avoid common utility supply headers and/or systems to processes with incompatible materials Install backflow protection on supply lines Implement mechanical integrity program to prevent contamination of utility systems Monitor circulating utility systems for contamination

ICGIH 1986

X P S G-11 VFPA-69 YFPA-91

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

_ I

API RP 750 CCPS G-11 CCPS (2-22 Kletz 1991 Lees 1996 NFPA-91

3.

Shared equipment (e.g. auxiliary processing "scrubbers"). POSsibility of incompatible materials coming together.

Design to avoid or minimize use of common equipment for incompatible materials Implement proper cleaning procedure between incompatible uses to prevent cross contamination Prescrub or treat process streams before transfer to common equipment

4.

Shared transfer

Avoid the use of incompatible materials in API RP 750 shared transfer systems Klen 1991 Ensure cleaning procedures are followed Lees 1996 NFPA-91

.

31

Table 3: Equipment Configuration and Layout

\

Ignition Sources

0

5.

Ignition of flammable re!iultingin fire or explosion.

Provide safe separation distances Develop appropriate area electrical classification Provide ignition source control Place ignition sources in positive pressure enclosure and buildings Provide adequate ventilation

LPI RP 500 IS 5345 6 5958 4FPA-70 *PA-77

osion 6.

Shared vent systems. Potential for fire travthe shared vent system.

Design vent system to prevent backflow/accumulation Prescrub or treat vent discharge before transfer to the vent header Install detonation and / or deflagration arresters Install deflagration suppression system Provide explosion venting and isolation mechanism Provide vent system inecting or purging Install dedicated vent systems

I3 CFR 154 WPA-69 WPA-91

7.

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

Provide spill control through adequate drainage and curbs or dikes Provide adequate ventilation Wash down systems Minimize possibility of ignition Minimize possibility of spills

API RP 750 CCPS G-22 CCPS G-24 CCPS G-30 Lees 1996 NFPA 69 NFPA-15

Provide segregation storage of incompatible materials Don't put incompatible materials in the same dike Use segregated drainage & sewer systems Wash down systems Minimize possibility of ignition

API RP 750

spills. Possibilin drainage and dikes.

--%r-&nmr

CCPS G-22 CCPS G-22 CCPS (2-24 CCPS G-30 NFPA-328 NFPA-329 "

\

"

I

*

3. EQUIPMENT CONFIGURATIONAND LAYOUT

32

FireExplosion 9.

10.

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

\PI RP 752. Proper location of air intake Provide adequate control room ventilation X P S G-26 system gFPA-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 battled 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 I 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

Batch equipment located indoors. A release of flammabldtoxic 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 Install flammablehoxic detection systems in buildings with alarms to warn building occupants of hazardous accumulations 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

ACGIH 1986 CCPS G-3 CCPS (3-13 CCPS G-26 NFPA-68

33

Table 3: Equipment Configuration and Layout

Operator Exposure 1.

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

Install point source ventilation Install building ventilation Install flammabldtoxic detection systems in buildings with alarms to warn building occupants of hazardous accumulations Use personal protective equipment Provide sufficient bottled air/SCBA Develop emergency response procedures Develop appropriate evacuation plans

,PI 2007

:cPs G-22 XPS (3-32

General

.

.2.

Close proximity of Provide segregated storage feed chemicals for difseparate the processes ferent processes result* Provide unique loading devices ing- in possibility of . using wrong material. See also Chapter 6

XPS G-29 :cps G-3

.3.

Close proximity of process equipment and process areas impedes response and evacuation. Possibility of exposure and/or reduction in efficiency of emergency response.

XPS G-29 :lea 1991 @PA-101 decklenburgh 985

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 auditdinspection 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

3. EQUIP=

34

CONFIGURATIONAND LAYOUT

General

t

14.

Operator access to equipment. There is a greater need to provide 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.

X P S G-23 Provide shortest, most direct and safest route to items requiring most frequent NFPA-101 attention Mecklenburgh Consider ergonomics during layout design 1985

___^__

_ I _ -

15.

API RP 752 Close proximity of Maintain safe separation distances hazardous processes* Consider the need for fire walls, solid Of re'eases floors, etc. in building design and or other hazardous construction conditions in one pro* Provide emergency relief design to vent to ceSSaffecting the safe location neighboring process areas resulting in escalation of the hazard. _ I _

16.

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

Maintain safe separation distances

API RP 750 CCPS G-26 Dow F&EI

i

4 Eauhment 1

.

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 MI 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 iiiventories 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 TransferringEquipment (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 continucius 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 ]mechanicalassists 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, o r uncontrolled reactions occurring after drumming, leading to potential fires or explosions. Special consideration needs to be given to drummed materials that are shocwheat 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 nonconclucting; 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

44

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. I f 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 IUOC). 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 mixindinhibition 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 fimngdconneaiondcoupliigs(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

48

4. EQUIPMENT

Table 4.0: General

Overpressure Blockage of piping, valves or flame arresters due to solid deposition. Potential for system overpressure.

Size piping system to maintain minimum required velocity to avoid deposition If appropriate, eliminate flame arrester or use parallel switchable flame arresters with flow monitoring Monitor flow in line Remove solids from process stream (use knockout pot, filter, etc.) Install insulatiodtracing 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)

2.

Failure of vacuum

Design vessel to accommodate maximum vacuum (full vacuum rating) Provide vacuum relief devicehystem (can be a source of oxygen in vapor space resulting in flammable atmosphere) Provide a vacuum alarm Interlock to inject inert gas Select vacuum source to limit vacuum capability

4PI 2000 X P S G-11 DIERS FMEC 7-59 VFPA 69

Design vessel to accommodate maximum vacuum (full vacuum rating) Use blanketing gas pressure control system to minimize vacuum

4SMG VlII FMEC 7-59

1

resulting in POssibility of vessel

3. t g

iPI 2028 X P S G-1 1 \SME VIll .iptak 1982 Vilday 1991

1.

Uncontrolled condensatiodabsorpOf vapor phase component resulting in vacuum creation inside vessel.

Provide vacuum relief devicehystem 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)

_

NFPA 99C

.

.

49

Table 4.0: General

FirelExplosion '.

Deflagration of vapor caused by air leakage into equipment "Perating under vacuum. Possibility of fire/explosion.

Design vessel to accommodate maximum expected deflagration pressure Provide deflagration pressure relief device/system

Ignition of condensed flammable vapor or solid deposits in ductwork! Possibility of fire,exo~osion.

Design system to prevent condensation in ductwork or buildup of deposits by providing smooth surfaces, elimination of potential points of soliddliquid accumulation. Periodicall; flush and/or steam clean piping/ducts Include cleaning procedure in process write-up 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

JFPA 68 JFPA 69

Provide oxygen analyzer with activation of inert gas addition on detection of high oxygen concentration Provide continuous inert purge to check for leaks before Start-up Operate below the Lower Flammable Limit (LFL) ZCPS G-41 'MEC 7-59 4FPA 69 JFPA 77 JFPA 68

50

4. EQUIPMENT

FireExplosion

7.

I.

hadequate ventilation in ducts due to partial obstructions or closed dampers leading to creation of flammable atmosphere. Possibility of firdexplosion.

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 prescrubberdcondensers to reduce load in duct

:cps G-4 ?FPA 13 JFPA 15 JFPA 1 6 JFPA 68 JFPA 69

Inadequate circulation in equipment causing ~ w d a t i o of n 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

X P S G-41 rlFPA 69

Premature shutdown of fandventilation system immediately following shutdown of heat input (prior to sufficientcoolin& resulting in hot spots and flammable pockets (dryers, carbon beds, and thermal oxidizers). Possibility of subsequent ignition resulting in fire or explosion.

Design where natural circulation is sufficient to \IFPA 69 prevent accumulation of flammables and/or creation of hot spots Design to contain overpressure where practical Provide postventilation interlocks and/or operating procedures to keep fans running for a sufficient time after shutdown of heating system

51

Table 4.0: General

Fire/Explosion

11.

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

Operate below minimum oxygen concentration Maintain good housekeeping Crindhlend 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

?FPA 68 JFPA 69 JFPA 650 JFPA 654

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 firelflammable atmosphere or overpressure in duct system Provide automatic sprinkler systedinerting gas Provide deflagration vents Provide deflagration suppression system Monitor flammable atmospherdfire Provide nitrogen blocks (nitrogen injection to stop flame propagation) or other explosion isolation measures

JFPA 13 JFPA 15 JFPA 16 JFPA 68 rlFPA 69

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

^

-

Maintain good operating and cleaning procedures X P S G-32 X P S G-41 Provide fixed water spray, if appropriate Use inherently safe material, where possible VFPA 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

--

+ ,.-

"-* >

&

La">

I -

52

4. EQUIPMENT _ . “

.

Operator Exposure

2

Emission of toxic, flammable or corrosive vapors

Provide local exhaust ventilation connected to a disposal system (vent condenser, adsorber, scrubber or incinerator)

when equipment is Opened for deanindmaintenance or during charging of hazardous material. Possibility for operator exposure.

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.

14.

15.

-

~

-

-

-

”

”

~

-

-

Equipment used in different processes during its lifecycle. equipment Or existing equipment reused for different use. passibility 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 Design equipment for the entire system to accommodate the maximum expected pressure

Using existing equipment for new process may Overtax existing ancillary units e.g., utilitieddisposav fire protection etc. Possibility of hazardous event.

Ensure that the equipment is able to handle the new process chemistry, and that the demands of the new process on ancillary units are also met Perform process hazards analysis

Use of temporary equipment for processing

:CPS G-41

XX‘S Y-28

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

Perform management of change review

”

.”

I

Implement management of change procedure

CCPS G-1

53

Table 4.0: General

Management of Change

16.

Equipment inspection may provide a poor prediction of equipment due to change of material handled or change in process chemistry over the life of equipment.

Reevaluate and possibly reset inspection intervals when equipment is used for handling different chemistry Perform management of change review

Not "in-kind" replacements (e.g., gaskets, ruI'mre disks, packing, mechanical seals) resulting in failure. Possibility of hazardous release.

Ensure that the replacement satisfies the requirements of duty Implement management of change review process

j

I

18. Cyclic nature of batch process (e.g., stadstop, thermal cycling). Possibility of mechanical wear and tear. Possible loss of containment.

Implement mechanical integrity program Design equipment for easy replacement Consider demand of cycling while designing equipment and controls

19, Available equipment determines the process chemistry selected. Operating 'lose to the safe operating envelope of the equipment and the relief capability.

Procure equipment that can be used in other processes (current or future) without operating close to its operating envelope. Provide equipment with comparable pressure rating for the entire system Match batch sizes to equipment capabilities

20.

Frequent stardstop of equipment may lead to equipment failure.

CPS Y-28

,SHA

910.119

Loss of Containment

1

cps G-22 CPS G-27

Minimize frequent stadstop by proper sizing of equipment (e.g. pump capacity) Implement mechanical integrity program Develop procedure to investigate causes for frequent reset of control Minimize frequent stadstop of equipment <

" - - w e

_*l(rn

54

4. EQUIPMENT

Table 4.1: Reactors and Vessels

Overpressure ~

1.

Overfill, resulting in vessel overpressure.

iPI 2350 Use open vent or overflow line discharged to a safe location B M E 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 uncontrolled Opening Of high pressure system resulting in vessel overpressure.

Ensure that utility connections do not exceed pressure rating of vessel Use incompatible utility couplings to prevent connections of high pressure utilities Use fixed piping and adequate labeling to avoid coupling errors 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

4SME VIII X P S G-11 ZCPS G-41 ISA S84.01

55

Table 4.1: Reactors and Vessels

Ovmressure

.

I.

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

Develop and implement procedure to remove and inspect relief device after suspected operation Perform visual inspection and scheduled replacement of relief devices periodically Provide flow sweep fitting at inlet of relief device Heat tracelinsulate 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

Ignition of flammable atmosphere in vessel vapor space.

Use nonflammable solvents

S M E VlII

,cPs G-11

kPI 2028 Provide ignition source controls (e.g., permanent NFPA 30 groundinghnding, nonsplash filling, etc.) NFPA 68 Store or process material below its flash point NFPA 69 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 devicdsystem maximum deflagration pressure

56

4. L ~ U I I ' M E N I

Underpressure i.

Uncontrolled condensatiodabsorpOf vapor phase component resulting in vacuum creation inside vessel.

Design vessel to accommodate maximum vacuum (full vacuum rating) Use blanketing gas pressure control system to minimize vacuum

IGA XK0775

ISME VIll 'MEC 7-59

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)

I l l _ n

5.

Excessive liquid withdrawal rate in POssib i b of Pulling vacuum.

Design vessel to accommodate maximum vacuum (full vacuum rating) Provide open automatidmanual vent or install a restriction orifice

4SME VlII X P S (2-30 FMEC 7-59

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. Temperaexcursion Outside the safe operating envelope resulting in a runaway reaction.

Install high temperature alarm, and interlock to 4SME VlII activate cooling or shut off feeds at desired X P S G-11 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

57

Table 4.1: Reactors and Vessels

High Temperature

.

Loss of effective cooh3. Temperature excursion outside the safe Operating

SME VlII Provide back-up source of cooling Measure, alarm and/or interlock low coolant :cps G-11 flow, low coolant pressure, high differential tem- :CPS G 4 1 perature between inlet and outlet 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

Reactiodlgnition 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 heatingkooling system to eliminate heat transfer to unwetted surface Heat with sparged steadtempered 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 phax deflagrations Install emergency relief device (ERD) Design system to accommodate maximum expected temperature and pressure

iSME VlII XPS G-11 XPS (2-30 :MEC 7-59 WPA 68 rJFPA 69

58

4. EQUIPMENT

High Temperature

1

is

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 emerzencv relief device

LSME VIII X P S G-11

11.

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

X P S G-11 X P S G-12 X P S G-23 X P S G-36 Fisher 1990

12.

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 CCPS G-23 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

10.

X P S G-22 XI'S G-23

59

Table 4.1: Reactors and Vessels

High Temperature 3.

32s G-11

External fire expoSure resulting in runaway reaction system overpressure.

Fireproof insulation (limits heat input) Slope-away diking with remote impounding of spills

14.

High temperature due to excessive agitator shah work resulting in high reaction rates.

Limit agitator power input and provide proper impeller design Limit shaft speed Monitor shaft speed Provide adequate cooling system Design system to accommodate maximum expected temperature, and pressure

CCPS G-7 CCPS G 2 9 Lees 1996

15.

Hot bearingheals 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

CCPS G 2 2 CCPS G-29 CCPS G-39 CCPS G-41

FMEC 7-44 WPA 1 Locate batch operation outside of affected fire VFPA 11 zone VFPA IS Provide safe separation distances WPA 16 Install fixed fire protection and alarms, water sprays (deluge), and/or foam systems activated by *PA 25 flammable gas, flame, and/or smoke detection WPA 68 devices ?IFPA 69 Install fire safe bottom valves S P A 204 Install fire safe valves on major solvent lines NFPA 704 Install remote shut off of fuel sources OSHA Eliminate points of leakage (flanges, hoses). 1910.119. 106 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

x.."

60

4. EQUIPMENT

Low Temperature 6.

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

:CPS G-23 :CPS G-29 .ees 1996

Monitor temperature Provide adequate heating Design system to accommodate minimum expected temperature Provide freeze protectiodheat tracing

Mixing 7.

Limit agitator power input and provide proper Excessive mixing of reactants or impeller design impurities which Return process to pilot or development to redepromotes sign process to eliminate or minimize this emulsification. problem Poor phase separation in Limit shaft speed problems in subse- Monitor shaft speed Went processing Test for phase separation steps or in downstream eauipment. * Install de-emulsifiers

XPS (3-29 .ees 1996

L8.

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

Design process to work within agitator limitations Design agitator to account for property variations with reaction progress Monitor shaft speed Design system to accommodate maximum expected pressure and temperature Provide emergency relief device

X P S G-29
Incompletely submerged agitator impeller resulting in excessive forces on reactor wall and heads. Possible loss of containment.

Monitor agitator power input Design agitator to be stable during filling and emp tying operation (e.g., stiffer shaft, foot bearing) Install low level shutoff preventing further liquic withdrawal from vessel Install low level alarm with interlock to automal i d l y shutdown the agitator Provide instructions to manually stop agitation predetermined level in vessel

19.

Monitor viscosity Add diluent to reduce viscosity Monitor agitator power input

-_

I

CCPS G-29 Kletz 1991 Lees 1996

61

Table 4.1: Reactors and Vessels

Mixing !O.

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.

Use compatible/mutually soluble materials XPS G-11 Provide agitator monitor (shaft speed, load, etc.) X P S G-23 to alert operators. X P S G-29 Implement procedures to dispose of unreacted Uetz 1991 materials Implement procedure and/or back-up equipment xes 1996 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

Runaway Reaction 21.

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

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 automatidmanual closure of isolation valve(s) in feed line on detection of low or no flow Provide for automatidmanual 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

X P S G-11

X P S G-23

XPS (2-29 Uetz 1991 xes 1996

62

4. EQUIPMENT

Runaway Reaction ~~

2.

Corrosion products lead to catalysis Of unwanted reaction.

Understand process and do not use materials of construction that may lead to problems Use corrosion inhibitor Implement corrosion monitoring and correction program Implement mechanical integrity program Upgrade material of construction or use resistant liner Implement procedure for testing liner with continuity meter Provide emergency dump of reactor contents. Design system to accommodating maximum expected pressure Install emergency relief device (ERD) (UPS

LSME VIll XPS G-7 X P S G-11 X P S G-22 X P S G-29 ZCPS G-56 Clem 1991 xes 1996

G-11)

Ensure that pickling or passivation of the system is complete prior to starting the system :3.

Corrosion of equipment and piping* loss of containment.

Use less corrosive chemistry (inherently safer principles) Consider addition of corrosion inhibitor 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.

ZCPS G-29 X P S G-32 CCPS G-41

63

Table 4.1: Reactors and Vessels

Loss of Containment 24.

Loss of sealing fluid for vessel agitator seal failure and emission of flammable or toxic vapors.

Circulate vessel contents via external, seal-less pump Use double or tandem mechanical seal with inert seal fluid Include requirements for operators to visually check seal fluid reservoir levels on a regular basis 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

X P S G-23

64

4. EQUIPMENT

Table 4.2: Centrifuges

Overpressure 1.

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

Implement routine checks of vent lines for plugging 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.

Blocked liquid effluent line resulting in

Provide level switches for effluent collection vessels 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 Equipmendline-up checks Remove unnecessary valves Seal valves open

.

Clem 1991 .ees 1996

65

Table 4.2: Centrifuges

:

Underpressure 5.

Exhaust system introduces a negative pressure in the centrifuge, can introduce air into resultine in flamiable atmosphere.

-

i

Maintain nonflammable atmosphere (e.g., inert gas purging) Maintain integrity of gaskets and seals Check mating faces for corrosiodunevenness particularly on clad components Use gaskets compatible with materials being processed

\IFPA 69

Hiah Temoerature

6.

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

Provide and maintain an automated inerting system-oxygen concentration or pressure controlled Eliminate leakage sources (fumedair) Use alternative solvents (nonflammable or less flammable) Reduce feed temperature and/or monitor temperature of feed and interlock with feed shutdown

?JFPA 69

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) 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

FMEC 7-59 NFPA 69

1

r

Runaway Reaction L 8.

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

Test material for impactkhock sensitivity and thermal hazards Use alternate (low energy) separation process for shock xnsitivdunstable material

66

4. EQUIPMENT

Runaway Reaction

[ R

9.

Multiple feeds to sing1e two feeds open at once. Incornpatible materials-come in contact, possibly leading to runaway reaction.

Eliminate interconnections Interlock feed valves so only one can be open Install three-way valve Implement appropriate operating procedures and training

CCPS G-15 CCPS G-32

Corrosion 10.

Failure of cladding, substrate to be exposed, leading to corrosion and potential failure.

Implement routine inspections Implement periodic nondestructive testing

CCPS G-7

11.

Inappropriate materials of construction lead to corrosion and potential failure.

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

Dillon 1992

t'

Loss of Containment

i 12.

Solvent/fume leakage from casing joints resulting in loss of containment.

Maintain integrity of gaskets and seals Use gaskets compatible with process materials Check mating faces for corrosiodunevenness, particularly on clad components

13.

Loss of containment during solids discharge.

Use bottom unloading or inverting (basket) machines 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

Loss of Containment 14.

Leakage or failure of flexible connection' between centrifuge and receiving container.

Use materials of construction compatible with process Implement routine inspections, monitoring and preventive maintenance programs Design flexible connections and their attachment methods to accommodate expected process pressures (positive and negative), system movements and vibrations

15.

Lids andlor inspection ports opened while in operation leading to loss of containment, loss of inerting, operator exposure.

Interlock so that it is not possible to operate centrifuge if lids and/or inspection ports are open

Ignition Sources 16.

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

17. Foreign bodies embedded in cake cause headsparks during (plowing out).

Use alternate solvent with reduced static potential Use conductive materials of construction Add antistatic agent to nonpolar solvent Check conductivity prior to feeding 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 inemng Bowl drive shaft requires grounding other than through gear box/bearings (e.g., brushes, slip rings) 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)

3SS958 'MEC 7-59 qFPA 77 'ratt 1997

68 . .

.

.. .... -

4. EQUIPMENT

__

I

Ignition sources

I CCPS G-22

8.

Loose or misplaced internal hardware causes headsparks during plowing out.

Preventative maintenance and oDerator mestart checklist

9.

Loose drive belts generating frictional headstatic electricity.

Preventative maintenance checks, tightness and protection from contaminants Check belt tension

CPS G-29

!O.

Hot running bearings.

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

:CPS G-29

.

FireslExplosions !l. See ignition

sources* these can lead to fire or explosion.

Oxygen monitored inerting system Explosion suppression devices

Operator Exposure

!2.

Operator exposure during solids discharge and removal residual heel.

Use bottom unloading or inverting (basket) machines Design flexible containment around discharge opening Enclose centrifuge in contained room or enclosure Use nitrogen knife to scrape centrifuge

General

23.

Vibration during plowing out-can lead premature equipment failure and a potential ignition ~ u r c see above.

Check plow and linkage for loose compo. nentdwear 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

69

Table 4.2: Centrifuges

General 24.

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

Preventive maintenance and operator checklist inspections Use effective vibration monitodshutdown device

25.

Running unbalanced-vibration due to uneven feeding.

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

26.

External corrosion of high-energy equipment. LOSS of containment and damage due to flying debris.

Implement mechanical integrity program Implement proper selection of material of construction

27.

Continued feed after basket is full. __I

28.

Liquid feed continues after basket of centrifuge stops spinning. ~"

.

Install automatic cut-off (weight activated) Monitor process Interlock feed to bowl rotation

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

70

4. EQUIPMENT

Table 4.3: Dryers

General

1.

2.

P I 2028 LPI RP 750 iossart 1974

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 Bond and ground ducts and equipment Eliminate flammables, wherever possible Use inert atmosphere Design ventilation system to keep flammable concentration below lower flammable limit Install on-line flammable gas detection and activation of inerting system Provide automatic sprinkler protection Install deflagration vents Provide automatic isolation of associated equipment via quick closing valves 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

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

FMEC 7-43 Inert/purge dryer Design ventilation system to handle the peak sol- FMEC 7-59 vent evaporation rate SFPE 1998 Replace flammable solvent (e.g., water based)

X P S G-11 :cps G-22 X P S G-29 X P S G-36 X P S (2-41 ;MEC 7-43 'MEC 7-59 VFPA 13 VFPA 15 VFPA 68 VFPA 69 ;FPE 1998

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 Eliminate flammable solvent (e.g., water-based) Design system to accommodate maximum deflagration pressure, where practical

ACGlH 1986 CCPS G-23 CCPS G-29 CCPS G-39 CCPS G-41

71

Table 4.3: Dryers

General

.

.

Premature shutdown of fandventilation system following shutdown of heat input (prior to sufficient cooling) resulting in hot spots and flammable pockets (dryers, carbon beds, thermal oxidizers). Possibility of subsequent ignition resulting in fire or explosion.

CCPS G-11 CCPS G-23 CCPS G-39 NFPA 68 NFPA 69

Production of fine Operate below minimum oxygen concentration powder during Practice good housekeeping auxiliary processof a * Grindblend under inert atmosphere ing. Provide damage limiting construction dust or dusdhybrid Design system to accommodate maximum deflaexplosion. gration pressure, where practical Maintain inlet temperature of heating medium tc equipment sufficiently below the minimum ignition temperature Eliminate flammable solvent

AGA XK0775 CCPS G-23 CCPS (2-41 Eckhoff 1997 FMEC 7-59 Lees 1996 NFPA 69 NFPA 654 Palmer 1973

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

API RP 750 CCPS G-23 CCPS (2-29 CCPS G-30 CCPS E 4 1 Lees 1996 NFPA 654 NFPA 86 Palmer 1973

~ i.

Design so that natural circulation is sufficient to prevent accumulation of flammables and/or creation of hot spots Design system to accommodate maximum deflagration pressure, where practical Use postventilation interlocks and/or operating procedures to keep fans running for a sufficient time after shutdown of heating systems

-

-

Control temperature of heating media below expected initiation temperature Use isothermal aging tests to monitor stability at desired drying temperature Use inert atmosphere/purge to eliminate combus tion that could serve to initiate bulk thermal decomposition Screen chemicals to be dried for thermal stability Evaluate and design for pressure consequences o thermal decomposition Evaluate potential for solid phase deflagration (Continued on next page)

72

4. EQUIPMENT

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 CO, 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.

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

Use inert atmosphere/purge Evaluate and design for pressure consequences c thermal decomposition Evaluate potential for solid phase deflagration Design system to accommodate the maximum expected deflagration pressure

8.

Material sent to next step too hot from dryer: thermally unstable material leading to violent decomposition

Cool material adequately before emptying from dryer See also Drumming Equipment (Table 4.7)

-

-_.

combustible material leads to firdexplosion in downstream equipment.

JFPA 86 JFPA 654 4FPA 69

Table 4.4: Batch Distillation and Evaporation

73

Table 4.4: Batch Distillation and Evaporation

General

.

!

Consider downstream processing that does not require that the intermediate be stripped to dryness Use vacuum distillation to obtain lower boiling point of solvent to allow lower distillation temperature Consider co-distillation (replace one liquid with another in portionwise distillation) or azeotropic distillation Consider incorporating inert material to act as heat sink 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 heatingkooling medium (e.g.. tempered water in atmospheric loop vs. high pressure steam) Provide redundant independent temperature monitoring instrumentation

iPI RP 750 XPS (3-13 XPS C-23 XPS G-29 XPS G-30 X P S (3-41 :conin 1987 kkhoff 1997 VFPA 36 VFPA 491

Evaluate thermal stability characteristicsof reacRemoval of liquid tion mixture from phase that is an unknown therConduct 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 2 9 CCPS G-30 CCPS Y-28 Cronin 1987

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

74

4. EQUIPMENT

General

13.

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) Monitor pressure drop across condenser Provide “thawing cycle” Provide high pressure interlock to shutdown heating and/or process feed

4PI RP 750 X P S G-10 X P S G-29

4.

Drawing distillate back into the distilling vessel.

Do not use sub-surface inlet to receiver from condenser Use “weep-hole” (siphon break) in sub-surface inlet piping 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 Install check valve in distillate discharge line

4PI RP-7.5 Bossart 1974

5.

Inadequate removal of solvent leading to unwanted reaction in downstream equipment or in subsequent steps.

Sample and analyze prior to proceeding to next step

API RP 750 CCPS G-6 CCPS G-13 CCPS G-27 CCPS G-29

6.

Co-distillation leads to long period of time under heat ing in exceeding the isothermal aging characteristics for a thermally unstable material which leads to thermal decomposition and overpressure of the vessel.

Evaluate isothermal aging characteristics of ther- CCCPS G-1 mally unstable components at the maximum CCPS (2-6 expected utility temperature CCPS G-13 Consider using the same solvent in the next step Cronin 1987 (i.e. eliminate the co-distillation)

CCPS G-10 CCPS G-22 CCPS G-25 CCPS G-27 CCPS G-29 FMEC 7-59

75

Table 4.5: Process Vents and Drains

Table 4.5: Process Vents and Drains

[

General X P S G-11 Design vent lines to prevent low point traps (pockets) X P S (2-22 Provide adequate drainage ZCPS G-23 Design and maintain drainage system for trapped sections of vent lines

1.

Low point traps (pockets) in vent

2.

Prescrubbing Provide subsurface addition to prevent "bypassing" of prescrubber solution (vessel containing scrubber solution Implement pH monitoring to determine useful between vacuum life of scrubbing solution source and batch vessel). ~ i con~ h Consider the thermal effects of reaction mixture centration of transfer to prescrubber Provide agitation, cooling jacket, and temperature off-gases resulting in overpowering control for prescrubber to improve operation Install high temperature interlock on discharge of condenser to shutdown reactor and initiate emergency cooling

3.

Bringing scrubbing solution back into reactor.

Provide vacuum break to prevent siphoning of prescrubber solution back to reactor

4.

Uncontrolled release of flamma-

Route to scrubber, quench, or other control device Install differential pressure or flow monitoring device to indicate flow into/out of vent Use conservation vent to minimize releases Provide flame arrester i d o n vent line Ensure vents relieve to a safe location. If vented to atmosphere, ensure proper classification and controlled access

CCPS G-3 CCPS G-4 CCPS G-11 CCPS G-13 CCPS G-23 CCPS G-29

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 reac-

CCPS (3-13 CCPS G 2 3 CCPS G-30

bles

Or

detrimental vapors from atmospheric vents.

5.

F

Drawing reaction mixture into vacuum system or scrubbing system*

4PI RP 750 ZCPS G-13 CCPS G-22 CCPS (2-23 CCPS G-25 CCPS G-29 CCPS G-41 FMEC 7-43 Hendershot 1987 NFPA 36

76

4. EQUIPMENT

Table 4.6: Transfewing and Charging Equipment

General 1.

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 Provide clear labeling on all lines entering and exiting vessels Provide and require use of personal protective equipment (PPE) Implement appropriate procedures and training

CCPS G-3 CCPS G-10 CCPS G-1.5 CCPS G-20 CCPS (3-22 CCPS G-29 CCPS G-30 CCPS G-32

2.

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

Limit opening of manholes Use localized ventilation (flexible ventilation pick-up close enough to manway/addition port to effectively capture emissions) Lower batch temperature to 20°C below boiling point before opening

ACGIH 1986 API std. 653 API std. 2000 API std. 2015 CCPS G-29 NFPA 328

Overpressure 3.

Overfill resulting in vessel overpressure.

Use sensors/alarm/interlocks (i.e., weight, level sensors) Ensure vessel has room for transfer Install high-high level switch in receiving vessel interlocked to feed and/or emergency dump

API RP 750 CCPS G-3 CCPS G-29 CCPS G-30

4.

Excessive fill rate.

Install flow restriction orifice in fill line Install fill line control with high flow alarm and/or shutdown Provide interlock activated by high pressure or high flow Develop and implement procedures to monitor level and fill rate during transfer and verify that vessel has sufficient free board prior to transfer Provide emergency relief device (ERD) Design vessel to accommodate maximum expected supply pressure

API RP 750 ASME VllI CCPS G- 11 CCPS G-22 CCPS (2-23 CCPS G-29 DIERS

77

Table 4.6: Transferring and Charging Equipment

Overpressure

/j

5.

6.

.

r

8.

Incorrect amounts charged.

Check for improperly labeled partial containers Ensure correct amount is on hand before starting Use control devices (flow, level, etc.) Modify recipe to use whole containers Modify recipe to use whole pallet or container

WI RP 750

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

Design casing to contain decomposition overpressure Provide deadhead protection (hydraulic relief) Use jacketed cooled pumps Avoid the use of positive displacement pump Select pump to minimize heat input Provide high temperaturdpressure alarm and shutdown Provide emergency relief device (ERD)

X P S G-1 X P S G-8 X P S G-11 X P S G-23 'MEC- 1974 x e s 1996 VFPA 496

X P S G-22 X P S G-29

I _ _ _ _ -

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 heat input Install deflagration venting and/or suppression system Eliminate tramp metal in feed to grinder, screw, etc. Eliminate tramp metal generated due to equipment breakage

SCPS G-11 X P S G-28 NFPA 68 NFPA 69 VFPA 654

Pump used for higher than design density fluid service resulting in high discharge pressure.

Design to accommodate for maximum expected pressure Verify suitability of pump for service; replace if necessary

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

Provide emergency relief device (ERD) Provide interlock to shutdown pump on detection of high discharge pressure Ensure management of change procedures are followed Monitor power and install high current utdown

78

4. EQUIPMENT

Overpressure

ll.lll.llll"

9.

Pump deadheaded.

Check for downstream closure Use minimum flow recirculation lines piped back to feed vessel Consider use of internal relief valve as applicable

ZCPS G-11 X P S G-29

10.

Vent system inoperable or plugged.

Check and open vents by scheduled preventive maintenance Monitor flow through vent system; provide steady purge if needed Make sure vent system is sloped to drain to knock-out pot (separator) Perform periodic maintenance and inspection

iGA-X0775 :CPS G-11 :CPS G-22 ZCPS (3-29

11.

Inert gas or other pressure source is open.

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

12.

Adding volatile phase On top Of hot phase (or vice versa) resulting in rapid phase transition and overpressuring of vessel.

Indication and alarm on high temperature Interlock additions valves to vessel temperature Provide adequately sized emergency relief device (ERD)

IPI RP 750 X P S G-11 X P S (2-22 X P S (2-29

13.

Blockage of piping, valves or flame due to build-up of solids. Potential for system overpressure.

Size piping system to maintain minimum required velocity to avoid build-up of solids Eliminate flame arrester or use dual (parallel) flame arresters with on-line switching caoabilities

X P S G-11 X P S (3-54 3IERS FMEC 1974

Remove solids from process stream (knockout pot, filter, cyclone separator, etc.) Provide insulatiodtracing 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

IRI 1990 Lees 1996 VFPA 54 VFPA 69

79

Table 4.6: Transferring and Charging Equipment

Underpressure

J

14.

Low pump head pressure.

Increase pressure at source Verify pump design will achieve needed pressure Check for restrictions in suction and discharge lines

X P S G-23

15.

Failure of vacuum system control resulting in ~ 0 ~ s ' bility of vessel collapse.

Design vessel to accommodate maximum vacuum (full vacuum rating) Install vacuum relief system Provide low pressure alarm and interlock to inert gas supply Selecddesign vacuum source to limit vacuum capability

UME VlII XPSG-23 XPSG-39

High Temperature I

16.

17. I

:

i

I

Temperature control On linedequipment.

Perform periodic maintenance and inspection Install redundant control system

CCPS G-22 CCPSG-29

Line or equipment exposed to direct sun or heat source.

Include hydraulic relief in line Provide adequate insulation for solar protection

CCPSC-11

' i

Clear lines after each use

Low Temperature

1

18.

i 19. i

1 d

!

Cold ambient temperature.

Provide insulation, heating, etc.

TemDerature control failure On lines or equipment.

Check heat tracing Perform periodic maintenance and inspection

CCPS G-29

Corrosion

I

20.

Incorrecdincompatible materials Of

used in transferrindcharging line or equipment.

Review material of construction requirements vs. CCPS (3-23 existing equipment before changing service Use corrosion coupons during piloddevelopment/scale-up

I

80

4. EQUIPMENT

Corrosion !l.

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

Check label versus process requirements Check correct step in operating procedure Label materials, lines pumps and valves Use staging area Check labels against batch sheets Use double check system Set valves to correct flow path Use procedures and training

CCPS G-22 CCPS (2-29 CCPS G-30 Hendershot 1987

Runaway Reaction

22.

Unwanted reaction due to contaminants.

Clean and inspect equipment after each use Design with compatible materials Maintain integrity of the system Design emergency relief system (ERS) for run. away scenario

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

23.

Accumulation of reactive material in Of auxiliary equipment or piping. possibility of runaway reaction.

Design system to accommodate maximum expected pressure Use inherently safer chemistry Implement on-line measurement (e.g., level, tern. perature, composition) and side draw-off of reactive material Eliminate pockets where material could accumulate Design piping and equipment to drain to a safe location Provide emergency relief design (ERD) Provide procedures to clean pipes

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

24.

Incorrect chemicals used.

Label materials, lines, pumps and valves

API RP 750 CCPS G-3 CCPS G-22 CCPS G-30 CCPS G-33

- _ . _ _ ~

usestaging area

Check labels against batch sheets Set valves to correct flow path Use double check system Use procedures and training Use different packaging for different chemicals

81

Table 4.6: Transferring and Charging Equipment

Runawav Reaction

25.

Charging thermally unstable to warm reactor results in decomposition.

Install local indication and alarm on high temperature Provide emergency cooling

:CPS G-23

26.

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

Implement appropriate procedures and training

X P S 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 Install minimum flow recirculation line to heat sink to ensure adequate cooling of the pump Provide interlock to shutdown pump on minimum flow indication Implement procedural controls to avoid operating at too low a flow Provide deadhead protection

X P S G-23 X P S G-29

28.

Transfer path is blocked due to

Verify open and clear transfer path before initiatine; transfer Utilize pressure and flow sensors

X P S G-29

Implement procedure for line breaking Select materials of construction for pipes and gaskets to be compatible with all materials to be transferred Install fireproof/spiral wound gaskets where applicable Install new hose gaskets for each batch connection (Continued on next p g e )

4PI RP 1623 9SME B31.3 ECPS G-22 CCPS G-23 CCPS G-24 CCPS G-29 CCPS G-39

etc. Pressure is built up in system and leaks in piping occur.

29. Release of

toxidflammable material from piping due to leak, flange leak, valve leak, pipe rupture, collision, or improper support.

-

-_^

82

4. EQUIPMENT

Loss of Containment !9.

(Continued)

Maximize use of welded pipe vs. screwed or flanged and minimize use of unnecessary fittings Avoid use of undergroundlhidden 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.

Degradation of hose in leak and release of toxicjflammable material.

Eliminate hose, use hard pipes wherever possible Consider use of higher integrity hose (e.g., metallic braided) Use hoses rated for required maximum system 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 clo sure under fire conditions (Continued on next page)

X P S G-22 X P S G-23 CCPS G-29 Kletz 1991 NFPA 30 NFPA 70

83

Table 4.6: Transferring and Charging Equipment

Loss of Containment 30.

(Continued)

31. Deterioration of pipe/hose lining

Use pipe material of construction which does no

PI RP 1632 ritton 1999 :CPS G-23 :CPS G-29 JFPA 69 JFPA 77

32.

Piping erosion.

Limit fluid velocity

:cane's Fluid :low 4andbook

33.

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

Pressure test connections Provide manual bonding and grounding Analyze hazards before using portable equipmer Evaluate procedure for installatiodhook-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

XPS G-29 4FPA 70

due to attack Of static discharge.

f

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 require lining Use conductive liner to reduce potential for degradation due to static discharge Use thicker liner material Limit liquid velocity to minimize static buildup 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

I

*_"

84

Loss of Containment 14.

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

Follow mechanical integrity program Implement testing of equipment prior to each use or change of service Implement procedures to verify change of

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

X P S G-29 R1 1990
Fire and Explosion 55.

Ignition of condensed flammable vapor or solid deposits in ductwor Wpiping resulting in possibility of fire/explosion.

Design system to prevent condensation Design system with smooth surfaces to minimize buildup of deposits Eliminate potential points of soliddliquid accumulation Implement good housekeeping procedures Provide for drainage of pipindducts (e.g., sloped, low point drains) Eliminate ignition sources within the ductwork Provide adequate bonding and grounding Eliminate flammables or combustibles Use of 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 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

IPI RP 750 2CPS G-11 2CPS (2-22 ZCPS G-23 2CPS (2-24 ZCPS G-29 ZCPS G-41 Lees 1996 VFPA 13 VFPA 15 VFPA 68 VFPA 69

Table 4.6: Transferring and Charging Equipment

85

Fire and Explosion

6. 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., subsurface addition, addition along the wall, etc.) Use "antistat" with nonpolar solvents Ensure that cooling solvent temperature is sufficiently low to operate outside flammable limits Control velocity/turbulence of liquid addition Avoid filters on addition lines close to inlet to reduce turbulence and charge generation Inert vessel and verify safe atmosphere before charging 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 clothinglattire (e.g., conductive shoes with periodic testing) Install permanent bondinglgrounding of equipment system with periodic testing Install fire/deflagration suppression system

LPI RP2003 )S 5958

17. 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) Consider charging solids before solvents Charge solids materials by means of a closed system (e.g., hopper and rotary airlock, screw feeder, double-dump valve system, etc.) Inert vessel and verify safe atmosphere before charging Control humidity in operating area (as humidity increases, static potential decreases) (Continued on next page)

AGA XK0775 API RF' 2003 BS 5958 CCPS (2-22 CCPS G-23 CCPS G-29 CCPS G-32 NFPA 68 (Continued)

---

XPS G-11 GPA 13 rJFPA 68 rJFPA 69 rlFPA 70 rJFPA 77 'ratt 1997

sY -.-.

86

r

4. EQUIPMENT

Fire and Exdosion

37.

(Continued)

Avoid use of nonconductive materials of construaion for both installed equipment and charging containers, funnels, etc. Avoid use of nonconductive liners in charge containers 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 clothindanire (e.g., conductive shoes with periodic testing) Install permanent bondindgrounding of equipment system with testing Install fire/deflagration suppression system

rlFPA 69 JFPA 70 JFPA 77 ’ran 1997

38.

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

Install scalping screen on vessel charge hatch Remove tramp materials prior to charging vessel

X P S G-22 XI’S G-23 X P S G-29

39.

Inert gas not presleading to ereation of flammable atmosphere.

Determine process requirements Implement correct procedures Install vapor space analyzers with alarm

Bossart 1974 X P S G-1 X P S G-22 CCPS G-23 CCPS G-29 CCPS ‘2-32

j

ISA RP 12.13

40.

Incorrect electrical classification for equipment or auxiliary equipment, lighting, etc., possibly leading to unsafe conditions.

Check area classification and verify that electrical equipment is properly rated

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

87

Table 4.6: Transferring and Charging Equipment

Fire and Explosion 41.

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

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

\GA XK0775 X P S (3-23 X P S G-29 FMEC 1997

42.

Vacuum transfer into reactor, drum Or feed tank runs drv. resultinr in air bekg pulled"into vessel, creating flammable atmosphere. Potential for fire/explosion. Also, potential for static charges generation due to misting of liquid at end of transfer.

Install low level interlock on supply vessel to shut down transfer Monitor oxygen level in head space

ZCPS G-23 ZCPS G-29 Fisher 1990 [SA S84.01

43.

Static charge generation due to too rapid transfer out Of drum Or intermediate bulk container (super sack).

Charge solids by means of a closed system (e.g., CCPS G-22 hopper and rotary airlock, screw feeder, double- CCPS G-23 dump valve system, etc.) CCPS G-29 Control rate of solids addition (e.g., size of CCPS G-32 opening in super sack) Procedures and training

44.

Inadequate ventilation in ducts due to partial obstructions or closed dampers leading to creation of flammable atmosphere and 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 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 prescrubberslcondensers to reduce load in duct

ACGIH 1986 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

Operator Exposure CCPS G-3 CCPS (3-22 CCPS G-29 CCPS G-32

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

Follow safe procedures for drum stacking and moving Use lockouthagout procedures

46.

Material released when transfer lines are disconnected.

Blow (purge) system, clean lines, before breaking AGA XK0775 the connection CCPS G-22 ~ i ~useof i hoses ~ i ~ ~ CCPS (2-29 FMEC 1997

47.

Lines are not depressurized before disconnecting.

Follow proper operating instructions Install or use small bleed valves

CCPS (2-22 CCPS G-23 CCPS G-29

48.

Nitrogen pressurization of lines or equipment that are not sealed tight.

Check line integrity and all fittings, couplings, etc. before transfer is started

CCPS G-22 CCPS G-29

Pressurization due plugged transfer lines.

Stop transfer and de-pressurize before breaking line and clearing plug

CCPS G-22 CCPS G-29

50.

Sampling spills.

Wear proper personal protective equipment WE) Follow proper sampling procedures Use safe sampling design

CCPS G-22 CCPS G-23 CCPS G-29 Lovelace 1979

51.

Blowing down lines for 'leaning*

Verify flow path before starting the flow. Blow (purge) lines to safe location which protects the operator and environment Wear proper personal protective equipment (PPE) Follow proper sampling procedures Use safe blow-down design

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

45.

49.

to

"^--.

lll..".."llllll__^.ll"

.-

.

" 1 _ .

~ " - - ~ " ~

89

Table 4.6: Transferring and Charging Equipment

LCGIH 1986 :cPS (3-22 XPS G-23 XPS G-29

from open manway, Operatorignite resulting in flash tire.

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

53.

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

Interlock manway with vessel pressure Design system for closed manual operation

:cPs G-22 XPS G-23 XPS G-29 :isher 1990 SA S84.01

54.

Operator exposure to fumes or inerts.

Charge liquids and solids materials by means of a closed system (e.g., hard piping, hopper and rotary airlock, screw feeder, double-dump valve system, etc.) Provide local ventilation Use proper personnel protective equipment (PPE)

KGIH 1986 X P S (3-22 ZCPS (3-23 ZCPS G-29

55.

Operator comes into contact with agitator through manway.

Implement procedures and training Interlock manway with agitator rotation Install scalping screen on manway

CCPS G-22 CCPS G-23 CCPS (3-29 Fisher 1990 ISA S84.01

56.

Ergonomic issues during charging, handling of heavy and unwieldy containers, potential for personnel injury.

Provide mechanical assists for handling and dumping of containers

CCPS G-23 CCPS G-29

90

4. EQUIPMENT

Table 4.7: Drumming Equipment

Overpressure

I.

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

inspect drum before filling

X P S G-3 X P S (3-15 X P S G-29 ECPS G-30

2.

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

Provide level indicator in feed vessel with aiardinterlock

9GA XK0775 CCPS G-3 ECPS G-15 CCPS (3-22 CCPS G-23 CCPS G-29 FMEC 1997

3.

Use of -pumps - to

transfer material to drum leading to overpressure.

.use

Limit filling rate to not exceed vent rate metering pumps

ACGlH 1986 CCPS G-3 CCPS G-15 CCPS G-22 CCPS G-23 CCPS G-29

4.

Vent bung cap not removed prior to

Vent around feed nozzle through 2”bung opening Select container designed to fail at low pressure Follow proper drum filling procedurekhecklist

ACGiH 1986 CCPS (2-3 CCPS G-22 CCPS (2-23 CCPS (2-29

5.

Vent system inoperable or clogged.

Test system back pressure before use Flow indication or pressure drop indication

ACGlH 1986 CCPS G-3 CCPS G-22 CCPS (2-23 CCPS G-29

Reduce feed rate or redesign vent system

ACGlH 1986 CCPS (2-22 CCPS G-23 CCPS G-29

Overpressure

6.

Vent system not balanced with inlet, or undersized.

91

Table 4.7: Drumming Equipment

Overpressure 7.

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

i

1

i

Store drum at proper temperature Keep drum away from heat source Ensure reaction is complete before drumming Allow adequate freeboard for material Provide adequate sprinkler protection Thermally initiated venting (e.g., melt-out bungs)

X P S G-3 X P S G-15 X P S G-22 X P S G-29

Loss of Containment 8.

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

Drum at proper temperature Keep drum away from heat source Ensure reaction is complete before drumming Allow adequate freeboard for each material

X P S G-3 X P S (3-14 X P S G-22 SCPS G-29

9.

Palletizinghoving drums incorrectlydrum falls and breaks or opens.

Follow proper palletizing and drumming procedures Stretch wrapping/strapping pallets

X P S G-3 X P S G-14 X P S G-22 CCPS G-29

10.

Drum not sealed properly.

Seal containers as directed in operating procedures Use new gaskets Provide correct tools for sealing drums

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

11.

Drum not intactetc-

Inspect drum before use Pressure check drums for leaks

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

12.

Calibrate weighing devices and maintain equipOverfill drum due ment in good working order to operator error or valve failure, Use metering pumps can lead to operator exposure, slip- * Interock fill operation with weighing device pery floors, spread of flammable liauids.

13.

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 AGA XK0775 filters CCPS G-3 Isolate and drain filters CCPS G-14 CCPS G-22 CCPS G-29 FMEC 1997

92

4. EQUIPMENT

Loss of Containment 14.

Leaks in various system cornPonents, hoses, valves, swivel joints in arm, lance, etc.

Periodic replacement of components Pressure test aII lines Ensure proper materials of construction

X P S G-3 X P S G-22 X P S G-29

15.

Lines are not depressurized before checking, changing filters.

Follow operating procedures Install pressure indication instrumentation and vent valves

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

16.

In solid drumming systems, failure of liner allowing powder to blow out of the container.

Check liner position and integrity before filling

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

Underpressure 17.

Thermal contraction vacuum created which can suck air, moisture, etc., into drum creating unwanted reaction; or collame of the drum.

.

Drumming at proper temperatures High integrity walls Store to prevent water accumulation on drum tops

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 (2-29

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

Corrosion 20.

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

Clean system on service changes

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

21.

External corrosion.

Inspect drums before use

CCPS G-3

ccps G-22

CCPS (2-29 22.

Contaminant4 foreign material in drum.

Inspect drum before use

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

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 (3-29

24.

Drum not sealed properly and foreign material enters.

Seal drum per operating procedures Use drum covers

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

25.

Filters are dirty and/or need changingincompatible chemicals, etc.

Increase frequency of filter changes during service changes

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

26.

System not properly*

Increase frequency of cleaning Clean system during service change Visually inspect system

CCPS G-3 CCPS (3-15

ccps G-22

CCPS G-29 27.

Reaction not complete before transfed drumming.

Verify final batch analysis and conditions before drumming

CCPS G-1s CCPS G-22 CCPS (2-29 CCPS (2-30

4. EQUIPMENT

94

Ignition Sources 18.

Incorrect electrical classification for equipment or auxiliary equipment, lighting, etc.

29.

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

.

Check area electrical classification

NFPA 70

See that workers are equipped with static resistant clothing See that workers use nonsparking tools Use subsurface feeds for organic liquids Ground and bond equipment Use of conductive or static dissipative drums and drum liners whenever possible

API RP 2003 CCPS (2-13 CCPS G-22 CCPS G-29 CCPS G-32 NFPA 77 Pratt 1997

High Temperature 30.

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

Follow operating procedures Cool adequately before drumming Don’t seal drums until material has cooled down sufficiently Provide adequate fixed fire protection Insure good ventilation Check heat tracing for excessive heat input

ACGIH 1986 Bossart 1974 CCPS G-1s CCPS G-22 CCPS G-29 CCPS G-30

31.

Density is lower and drum may be overfilled due to high material temperatures.

Verify proper temperatures before drumming. Use volumetric measurement

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

32.

Contact with operator due to spill, over flow, hot drum, etc.

Drum at temperatures low enough to protect operator against thermal injury

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

Seal drums properly Drum at correct temperatures

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

Firflxplosions 33.

Air, water drawn into drum.

95

Table 4.7: Drumming Equipment "

.-___

_..

. ..

Fire/Explosions 34.

Elevated drum temperatures reaching Accelerating Decomposition Temperature (SADTI.

Evaluate thermal stability parameters of material (isothermal aging tests, SADT, etc.) Keep drums away from source of heat Drum and store at required temperature

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

35.

Vapors in vent collection system in flammable range.

Design to be outside the flammable region in the vent system ( N 2 purge, dilution air, etc.) Monitor flammable concentration Monitor oxygen concentration Install flame/detonation arresters

ACGIH 1986 AGA XK0775 API 2028 Bossart 1974 CCPS (2-23 CCPS (2-29 CCPS G-30 FMEC 1987 NFPA 69

Monitor and control temperature in feed system Heat trace and/or insulate lines Use proper line break procedures Use personal protective equipment (PPE) Use proper lockout-tagout and confined space entry procedures

CCPS G-23 CCPS (2-29 Fisher 1990

Design operation to minimize/eliminate dusts or vapors use proper personal protective equipment Ensure proper design of local ventilation

ACGIH 1986 CCPS G-3 CCPS G-22 CCPS (2-23 CCPS G-29

i

Low Temperature

36.

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

Operator Exposure 37.

Dusts from solid filling, vapors from liquid filling.

"

-".

-7.8

-

96

4. EQUIPMENT

Table 4.8: Milling Equipment

Overpressure

.

Pressure build-up downstream of mil1 (risk Of POnent Particularly in gas conveying systems). Internal pressure may also force product out of the mill.

Provide adequate venting and dust filtration on receiving vessel vent Where liquefied gas (nitrogen or COZ ) is used for milling, ensure adequate vent sizing and limit liquefied gas feed-rate to mill

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

Ensure all system components, including flexible connectors are rated for maximum feasible vacuum conditions Ensure adequate pressure control system and back-up (e.g., vacuum relief devices)

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

CCPS G-12 CCPS G-23 CCPS G-29 NFPA 654

Underpressure

!.

Failure of components in subatmospheric pressure conveying operations.

High Temperature 3.

Overfeeding resulting in plugging of mill and subsequent heat buildup.

Limit feed-rate, design for uniform feed-rate (e.g., screw feeder or rotary valve) Measure temperature at strategic points in mill casing to detect and alarm product temperature rise

1.

Heat build-up due to too fine or blocked outlet screen.

Replace screen with one correctly sized and/or clean screen Install pressure indicator downstream and upstream of mill for conveyed systems

“ 1 _ 1 1

CCPS G-12 CCPS G-23 CCPS (2-29

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 Monitor and alarm bearing temperature Ensure proper belt tension

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

97

Table 4.8: Milling Equipment

High Temperature 6.

Heat build up due to plugged discharge line.

Design discharge to avoid bridging, provide reliable instrumentation to detect full receiver (load cells or level probe) Check lines to ensure they are clear before startup Monitor and alarm temperature

XPS G-12 XPS G-23 XPS G-29 XPS G-39

7.

Heat build-up due to loss of cooling.

Monitor and alarm temperature use coolant flow/temperature sensors or product temperature sensors.

XPS (2-12 X P S G-23 X P S G-29

8.

Heat build-up due to running too fast.

Use shaft speed sensor Implement administrative controls on adjustable speed drives

X P S (2-12 X P S G-23 X P S G-29

9.

Nonuniform feedstock variation in 'perating conditions resulting in overheating.

Feedstock should be blended before milling Test feedstock before commencing milling operation (e.g., moisture content)

X P S G-1 X P S G-23 ZCPS G-29

Ensure all materials of construction exposed to low temperatures are suitable (carbon steel, plastics, elastomers in seals, lubricants, etc.) Provide adequate control system to maintain design temperature

CCPS G-29 CCPS G-12 CCPS (2-23 CCPS G-39 Fisher 1990 NFPA 55

Screen for thermal hazards prior to milling material Consider slurry milling prior to product isolation Measure temperature in mill casing and product outlet to monitor for hot spots and interlock to shut system down and if appropriate initiate quenching operation Provide cooling jackets on mill or use cryogenic cooling with liquefied gas such as nitrogen or carbon dioxide

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

Low Temperature

10.

Component failure when cryogenic cooling is used.

Runawav Reaction

B

i 11.

Product in mill exceeds temperature at which thermal runaway is initiated, resulting in explosion. (This condition can also occur in mill feeding equipment such as screw feeders; similar countermeasures are

98

4. EQUIPMENT

Corrosion 12.

Internal corrosion in can Occur if feed is high in corrosives, such as halogens, and is hygroscopic.

Use appropriate materials of construction Maintain dry or inert atmosphere in mill at all times

ZCPS G-1 ZCPS G-23 ZCPS G-39 Percy 1984

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

Ignition Sources 13.

Hot bearings providing a source of ignition.

Avoid by regular preventive maintenance (PM) inspections, lubrication and belt checks Use improved lubrication

14.

Tramp metal reaching mill resulting in frictional heatinglmechanical 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 Use enclosed feed systems, not operator fed system

15.

Static electricity generation both in mill and conveying equipment.

Inert milling system ControVinterlock with oxygen concentration monitoring

Leakage from mill ignited by

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

16.

Ground, bond all electrically conductive components Use conductive materials of construction

CCPS G-12 CCPS G-23 CCPS G-29 CCPS G-32 ISA S84.01 NFPA 654

CCPS G-23 CCPS (2-29 NFPA 13 NFPA 15 NFPA 16

99

Table 4.8: Milling Equipment

Operator Exposure I

17.

Operator exposure to hazardous Or

broken parts during feeding and packaging operations..

18.

Running different products through mill, or change in upstream process, resulting in different feed charac-

Use closed equipment wherever possible (hoppers and intermediate bulk containers (IBCs)). Where product is exposed at transitions or packing operations: use containment devices such as gloveboxes; provide airflow control (laminar flow booths); or as a last resort use the room as containment and provide suitable personal protective equipment for the operators 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

ICGIH 1986 X P S G-3 X P S G-22 X P S G-23 X P S G-29

Develop procedures to characterize feedstock CCPS Y-28 whenever changes have been made and reevaluate milling conditions Implement management of change review procedure Use adequate cleaning procedures

unsuitable milling overheating due to blocked outlet screen.

I

I

General 19.

Thermal decomposition of mate-

20.

Tramp metal from mill causes downstream

Perform thermal and shock hazards analysis prior CCPS G-1 CCPS G-23 Consider milling under different conditions, e.g., CCPS (3-27 slurry milling CCPS G-29 Use liquid nitrogen injection as a coolant CCPS G-41

to milling

Provide screens or magnetic separator on mill outlet

CCPS G-23 CCPS G-29

I P - 3 Sd33 6 f - 3 Sd33

LZ-3 S d 3 3

f2-3 Sd33 1-3S d 3 3

82-AS d 3 3

LZ-3 S d 3 3

fZ-3 SJ33 1-3 S d 3 3

L66I ueJd L6P VddN LL VddN OL 3 3 N 65-L 33Wd 6 2 - 3 Sd33 f Z - 3 Sd33 12-3Sd33 COOZ dX IdV 00s dX IXV

SLLOXX

v3v

101

Table 4.9: Filters

Runaway Reaction I

Unwanted reacdue to 'Ontaminants in equipment _ . or solvent wash.

Label material, lines, pumps and valves Use double check system Check labels against batch sheets Use procedures and training Set valves to correct flow path

V I 750 S T M Pro~osal168 X P S G-1s X P S G-22 X P S G-27 X P S (2-29 X P S G-32 Frurip 1997 iutton 1995

Clean and inspect equipment after each change Segregate incompatible materials

FirJExplosion 5.

Improper cloth or filter media disPOsai may in fire and explosion hazard.

Include proper handling and disposal in operating orocedures Use high temperature filter media Use flame retardant personnel protective equipment Inerdpurge filter with nitrogen

4GA- XK077S X P S (2-22 X P S G-23 CCPS G-29 CCPS G-31 FMEC 1997

6.

Spontaneous combustion of pyrophoric matein the after opening or blowing dry.

Rinse filter with water (or other appropriate solvent) prior to opening Upon opening, immediately transfer cake to safe shipping container while still wet

AGA- XK077S CCPS G-29

7.

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 For closed filters, purge filter with nitrogen prior to opening, cleaning or starting solvent slurry Use nonflammable solvent where ever possible Use alternate closed filtering methods Design internal filter ventilation for excessive flammable vapors Provide adequate building ventilation Install local air exhaust pickup points at filter (e.g., elephant trunks) (Continuedon next page)

ACGIH 1986 AGA- XK077.5 Bossart 1974 CCPS G-22 CCPS (2-23 CCPS G-29 CCPS G-31 ISA RP 12.13 (Continued)

102

4. EQUIPMENT

FireExplosion

7.

(Continued)

-Ignition Sources 8.

Ignition of flarnmable sphere 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.

Provide combustible gas analyzers Provide automatic area sprinkleddeluge protection For filter boxes, interlock filter box ventilation with solvent feed 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

qFPA 13 VFPA 15 ?IFPA 16 VFPA 30

----. Cool and/or rinse filter prior to opening filter Check area electrical classification Control humidity of air in operating area to reduce accumulation of static electricity Use conductive floors Ground the operator with proper clothing (conductive shoes, gloves, etc.) Periodic testing of conductive shoes Implement procedure for manual bonding and grounding of tools to filter box Avoid use of nonconductive materials of construction Use nonsparking tools 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

API RP 2003 API RP SO0 CCPS G-22 CCPS G-23 CCPS G-29 CCPS G-31 CCPS G-32 CCPS G-41 NFPA 498 NFPA 70 NFPA 77 Pram 1997

103

Table 4.9: Filters

Loss of Containment

11.

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

Use alternate filtering methods Provide combustible gas analyzers Provide high level cut-off interlocked with solvent feed Provide level control system on filtrate receivers with bottoms pumps For vacuum transfer of filtrate, alarm on loss of vacuum 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

XPS G-15 :cPS G-22 XPS G-23 XPS G-29 XPS G-3 1 SA RP 12.13 xes 1996

Leakage of flammable or toxic chemical from equipment.

Provide vapor-tight enclosure around filter and run at negative pressure with exhaust fans Implement frequent maintenance of sealing surfaces and clamping systems Use new gaskets where appropriate To protect clamping system, use dissimilar metals to prevent galling on threaded fasteners Check area electrical classification Provide emergency ventilation

VI RP 500

Leakage of flammable or toxic chemical from vacuum filter.

Provide vapor-tight enclosure with adequate lighted viewing window around filter and run at negative pressure with exhaust fans Route solid discharge directly into receiver tank Provide catchment trough and routine maintenance to minimize valveplate leakage Provide overflow/high level shutoff on feed trough Check area electrical classification Provide emergency ventilation Provide adequate fixed fire protection where appropriate

9pI RP 500 CCPS G-22 CCPS (3-23 CCPS G-29 CCPS G-31 CCPS G-39 Lees 1996 NFPA 497

X P S G-22 X P S G-23 X P S G29 ZCPS G-31 X P S (2-39 Lees 1996 NFPA 497

104

4. EQUIPMENT

contaminated material could lead to operator

Design filter box ventilation for excessive flammable vapors Segregate incompatible materials Clean and inspect equipment after each batch Use procedures and training

GGIH 1986 :cps G-3 :cps G-1 XPS G-22 :CPS G-23 XPS (2-29 X P S G-3 1 3bson 1991 -ees 1996 ,ovelace 1979 qFPA 498

13

Operator exposure to toxic vapors during opening and cleaning.

Purge prior to opening or cleaning use appropriate personnel protective equipment Use alternate closed filtering methods Use cleaning methods which don’t require opening the filters Provide adequate building ventilation Provide local air exhaust pickup points at filter (e.g. elephant trunks)

\CGIH 1986 \GA- XK0775 X P S G-3 X P S G-15 ,CPS G-22 X P S G-23 X P S (3-29 X P S G-3 1 9FPA 1993

14

Improper disposal of filter media may result in operator exposure.

Include proper handling and disposal in operating procedures Use appropriate personnel protective equipment Provide local air exhaust pickup points at filter

X P S G-15 X P S (3-22 CCPS G-29 CCPS G-3 1 CCPS G-32 CCPS Y-28

15.

Ergonomic issues in wash-

Use alternate filtering methods Provide ergonomic design, mechanical assist

CCPS (3-15 Sanders 1993

shoveling of filter boxes, moving of portable units e.g. plate and frame

Appendix 4A. Storage and Warehousing

105

Operator Exposure

16.

Manual operation places operator in close proximity to potential hazards.

Use alternate filtering methods

use appropriate personnel protective equipment

Brandt 1992 CCPS G-15 CCPS G-22 CCPSG-31 Mecklenburgh

I

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 drumsbags 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

108

4. EQUIPMENT

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 I’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 o f 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.

3 InstrumentationIControl 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 instrumentatiodcontrol systems, and through human intervention. The human element is discussed in Chapter 6. Proper operation requires a close interaction between the operators and the instrumentatiodcontrol 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 instrumentatiodcontrol 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

MANAGEMENT

1_1 PRODUCTION

MANAGE SITE RECIPES

PROCESS MANAGEMENT

I MANAGEMENT

PROCESS CONTROL T E D

ISAFETY INTERLOCKING

Figure 5.1 Batch control activities (ISA).

INFORMATION MANAGEMENT PROCESS/ PRODUCT

PRODUCTION INFORMATION

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 Ametica'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 . INSTRUMENW~ONlCONTROLSY-S

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 instrumendcontrol systems are presented in Table 5. The table is meant to be illustrative but not comprehensive. Some key issues are presented below:

9

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

5. INSTRUMENTATION/CONTROLSYSTEMS

114

used to pump idout). 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 : InstrumentatiodControl Systems

Table 5: InstrumentationlControl System

Corrosion

!.

Use corrosion resistant material of construction

Verify suitability of instrumentation to service Use multiple voting with plausibility analysis Avoid equipmenthystemssubject to covert (unannounced) faults

‘DWDE 180, Part 1

Corrosion of pneumatic lines, electronics, electrical equipment.

Relocate vulnerable components to a more controlled environment Provide purging for electronics to prevent external corrosion Use corrosion resistant material of construction Implement mechanical integrity program to prevent leaks of corrosive material Use multiple voting with plausibility analysis

IDI/VDE

Avoid use of vulnerable instruments in hazardous service Use instruments of same or higher pressure rating as vessel Provide proper support of small lines

SA S84.01

of

Loss of Containment 1.

:CPS G-12 EC 61508 ISA

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

Leakage from instrumentation or breakage of instruments resulting in Of hazardous material.

Perform regular inspections, testing and maintenance

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 pipedfimng, holding 01 pipingltubing etc.) Provide protective cagedshields to minimize human exposure (e.g., avoid sight glasses) Choose inherently safer instrumentation Locate vulnerable instruments within protective enclosures to prevent accidental breakage

84.01

:180

SA S71.04

116

5. INSTRUMENTATlON/CONTROLSYSTEMS

Ignition Sources 4.

Instrumentation and/or ancillary equipment provide a source of ignition.

Base area electrical classification on range of chemicals used Ensure proper design and selection of instrumentation as per area electrical classification Consider the use of intrinsically safe instrumentation Encapsulate, and seal potential ignition sources Locate instruments in purge4pressurized enclosure Use pneumatidhydraulic system where necessary in hazardous environments Locate instruments away from potential leak sources Provide for proper bonding and grounding

iPI RP 2003 3ritton 1999 h h n 1998 SA S84.01 SA-S12.6 VFPA 70 VFPA 77 VFPA 496 VFPA 497 VDWDE 2180

General 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 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

6.

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

Verify suitability of new instrumentation to service Perform process hazard analyses Perform Management of Change review

CCPS Y-28

7.

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

More development/characterization of chemistry and determination of physical properties Measure diverse parameters (e.g., measure temperature and pressure) Implement functionality testing Perform Thermal Hazards Analysis (THA)

CCPS G-13

I

Table 5: InstrumentatiodControl Systems

117

General

.

1.

10.

11.

Change in service may lead to inappropriate instru. mentation 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 analvsis of process is done to provide proper level of protection Install appropriate instrumentation Perform Management of Change review

XPS G-12 h h n 1998 EC 61508 SA S84.01 3SHA L910.119 XF'S Y-28

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

Design for reliability and availability Take common cause failures into account while evaluating reliability Perform periodic proof testing of systems 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

X P S G-12 ,EC 61508 VDWDE 1180

Same sensor used for BPCS and safety instrumented system. Failure of sensor leads to loss of control system and safety system functionality.

Provide independent sensors for use in BPCS anc CCPS G-12 safety instrumented system with a plausibility IEC 61508 analysis ISA S84.01 Provide appropriate redundancy for risk classification of system

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 redundanddiverse 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

Provide on-line self-diagnostic system

IEC 61508 ISA S84.01

1

I

118

12.

5. INSTRUMENTATION/CONTROLSYSTEMS

Loss of motive power for instruments.

13. Gauges, meters, or recorders are not easily read by

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

JDINDE !180

Relocatehedesign the gauges so that operator can read them easily Provide ergonomic design of displays

X P S G-15 h h n 1998 S A RP 60.3

.

Avoid instruments that have minimum and maxi. mum 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 during transmission.

Of

Select proper material of construction Implement procedures for proper installation, 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

119

Table 5: InstrumentatiodControl Systems

General Minimize the effect of electrical interference by the design, installation and selection of instrumented systems Removehsolate interference sources Periodically test grounding Provide adequate lightning protection Provide signs to indicate areas where use of portable electronic devices are controlled

LPI IU'2003 EC 61508 rlFPA 75 rlFPA 77 *PA 780

16. Process equipment function changes with different steps in process sequence (e.g., same vessel used as feed tank, reactor, crystallizer; pump used to pump idout). 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 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

X P S G-29 X P S G-32

17. BPCS and SIS located closer to the processes than

House logic-solver components of BPCS, and safety instrumented systems (SIS)in a controlled environment Provide clean-air purge Maintain good housekeeping Provide robust systems suitable for environment

NFPA 75 VDVVDE 2180

18.

Use instruments that resist degradation during

VDWDE 2180 VDWDE 3542

IS.

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

continuous 'Ysterns, possibly leading to environmental attack from corrosion, dust, humidity, temperature. etc.

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

idle periods Provide periodic testing Implement preuse verification and calibration Periodically flusWpurge of instruments Provide recirculation during idle periods

s

t

120

5. INSTRUMENTATION/CONTROLSYSTEMS

General

9. Large instrument spans required to address variety of operating conditiondrequirements 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 Use smart instruments that allow quick change of span Use multiple parallel instrumentdcontrol valves of different ranges for the for same service Install instruments that are appropriate for the current operation

SA S84.01

iptak 1982

__I-_-

!O.

Temperature control systems incapable of handling multiple medidduty (e.g., coolindtempered waterheam). 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 heatingkooling media over a wide temperature range without loss of performance Use separate control valves for heatingkooling Use same media for heatingkooling Design for rapid change over of services

iptak 1982

!l.

Calibration unsuitfor procesdstep. Some processes require greater accuracy of measurements.

Calibrate for every batch Check calibration before change of service Purchase and install instrumentation whose resolution is high enough for the most sensitive procesdstep

SA S84.01

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.

iptak 1982

Verifj suitability of sampling frequency for pro- Stephancess dynamics (can vary from process to process) opolous 1984 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

121

Table 5 : InstrumentatiodConaoI Systems

General

*

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

Standardize instrumentation while utilizing diverse measurements or instruments, where necessary 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 operatinglmaintenance procedures)

iptak 1982

24.

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

Eliminate multiple control locations, if possible Provide local hand/off/auto switch to prevent control room operation during field activities with indication of status in control room

ISA RP 60.3

25.

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 Provide training and procedures

26.

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

VDWDE Design system which does not require frequent 2180 changes in tuning parameters 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

changing of software execution and sequencing module such as VESSEL” in a PLC. May

ware on all its applications Implement Management of Change Procedures (MOC)

i 23. i

Proof run process using nonhazardous materials after software change Perform a common mode failure analysis

Gruhn 1998 VDWDE 3542

122

5. INSTRUMENTATION/CONTL SYSTEMS

I

I

General 8.

Operator has to Provide operating procedures /checklists CCPS G-15 Observe the proISA RP 60.3 Provide scheduled operator training cess more freDesign system to minimize frequent changes quently as a result Record and communicate all changes (manual or of nonsteady state operating condiautomatic) tions. This See Cbapter 6 for more details requires more frequent control interventions, leading to an increased potential for human error.

:9.

Common use of manual mode control increases potential for human error.

CCPS (2-12 Minimize use of manual mode control through well designed automatic mode of operation ISA RP 60.3 Ensure that SIS is not disabled when operating in manual mode Provide operating procedures /checklists Provide operator training Log all changes Provide reliable and appropriate measurement of all critical process variables

10.

Manual sampling/ is part Of scheme in a large "lag time" in determining when to proceed and what to do (heatkool, 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

Table 5 : InstrumentatiodControl Systems

123

General 31.

2.

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.

Jimmo 1995 Eliminate unnecessary 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., VisuaUaudible) 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 lmplement 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

Software failure resulting in hazardous event.

ZCPS G-12 Follow strict controls throughout the software life cycle including requirement specifications, IEC 61508 software design, coding, testing, and [SAS84.01 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

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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-spedpartially finished products Conducting maintenance Providing emergency response Process logging, communication 125

126

6. OPERATIONS AND PROCEDURES

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. i

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 (CCPSG-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 Infomation Processing Model _________ _ _ __ ... -. ... __ _ ___ -.. .. . . ... .- ..... . . .. __ . . . .__ .-__ 1. O&eruu:ion ofsystem 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

Hypothesis unable to explain the values of the state variables observed Hypothesis does not functionally relate to the variables observed

Stopped before reaching a conclusion Reached wrong conclusion Considered and discarded correct conclusion Did not test hypothesis 4.

Insufficient specification of goal Incorrect goal chosen Goal not chosen

Procedure would not fully achieve goal Procedure would achieve incorrect goal Procedure unnecessary for achieving goal Procedure not chosen

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 i

-w

----*

I"

Information Processing Step

Continuous

Batch

-

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

Required step omitted or executed in wrong order Unnecessary step added Steps executed early or late Unrelated inappropriate step executed

Fewer procedural steps

Many procedural steps

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 in the wrong position

Control settings do not change

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

~-~~~_..----~

--

.._--*_

-=-=

______xY

-

=

-

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. OPERATIONSAND 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-nitrochloro-

benzene 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 caustidmethano1 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°Cbut 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-specifictraining 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

Observation

.

Multiple batches operated simultaneously. 'perator Observes information about process from wrong display. Misoperation leading to undesired incident.

Provide displays that clearly indicate which readings go with which batch and equipment Do not overload operator

Labelingkolor scheme conventions different between piantdcountries, leading to mischarging.

Use conventions prevalent in the country of use Do not use color coding as the sole solution Provide adequate labeling Verify raw materials before use Bench scale test critical raw materials prior

.

For example: Labels on containers Color coding of switches Color coding of gas bottles MetridEnglish units Labeling of shutdown system Color coding of pipes

Develop and use step-by-step check-off procedure

:CPS G-1.5 ZCPS G-22 X P S G-29 :CPS (3-32

X P S G-1.5 X P S G-22 2CPS G-29 33's G-32

to use

1.

Emergency switch Operation not understood Or 'Iear to the operator. Equipment works differently in different operating locations.

CCPS G-1.5 Provide clear labeling 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

1.

Emergency shutdown not readily accessible.

Relocate valves or operating device Provide remote operation capability where necessary Provide detailed written emergency procedures

CCPS G-32

Table 6: Operations and Procedures

133

Observation

.

I.

’.

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

Use clear and unambiguous labeling scheme Ensure verification of chemical identity by second operator or supervisor Use bar-coding Use dedicated staging areas Bench scale testing prior to use

:CPS G-15 :CPS E 2 9

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

Minimize number of different grades of material Use clear and unambiguous labeling scheme Provide operator training 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

:CPS E l 5 :cPS G-22 :CPS (3-29 XPS G-32

Mislabelinglinconsistent labeling of materi-

Provide a clear and unambiguous labeling scheme

:cps G-1s

materials are involved Test each lot of chemicals prior to use in production (functionalor acceptance test) Develop procedure for dealing with deviations from normal

$.

Warning signs, labels, MSDS, procedure, etc. written in language not understood by operators.

Use a language and terminology easily under stood by operators Use universally accepted symbols Verify that the operators understand all pertinent warning signs, labels, MSDS and instructions

XPS G-15

134

6. OPERATIONS AND PROCEDURES

Observation 9.

~-

Miscounting number of charged containers.

Ensure verification by second operator or supervisor Sign off on each package unidpartial package unit Ensure correct amount is on-hand before starting Develop procedure for dealing with deviations from normal

:cps G-15 :CPS G-32

ChoicJTesting of hypothesis 10.

Batches run infrequently. This may result in less Operator familiarity with processing steps, hazards and troub~eshooting.

Provide detailed operating procedures for each process Use the detailed operating procedures to train operators

:CPS G-32

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 goaVprocedure 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. I , Charging and Transfening and Table 4.6 _ " -"

XPS G-32

Table 6: Operations and Procedures

135

Choice of aoal/procedure 12.

13.

:CPS G-32

"Reference Procedures" used to ment main operating procedures. Operator selects wrong one or forgets to use reference procedures, etc.

Update procedures more frequently Incorporate critical procedures into the master document

Operating practice different from written procedures may lead to an incident.

Investigate the reason for the deviation, and correct the procedure or practice as appropriate Enforce adherence to operating procedures 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

:CpS (2-32 :MA 1990

X P S G-32

Provide training using the operating procedures Use batch sheets Review process steps with each operator prior to start of infrequently run campaigns

Execution of Procedure 14.

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

Write all procedures in simple, direct language Involve experienced and inexperienced operators in writindreview of procedures

15.

Errors due to lack of communication during shift change leading to an incident.

X P S G-15 Ensure that communications (verbal and writen) are sufficent to ensure safe transition Zh4A 1990 of operating responsibility at shift change 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

-

136

6. OPERATIONS AND PROCEDURES

Execution of Procedure .6.

Running multiple proSame equipmentor same process in multiple equipment may result inhuman error leading to an incident.

ceSSeSin

17. Operator makes a sequential error Omits steps Repeats steps Executes in wrong order

Provide clear indication of process being run Display name on panel . . process . Provide signs in control room

:cps c-1s

Provide status lights

Sign off of critical steps (double checking) Install permissive interlocks to ensure key steps are done in proper order Automate process steps

:cps G-1s :CPS C-32

Relocate/redesign the gauges so that operatoi can read them easily Ergonomic design of displays

:CPS G-15 SA RP 60.3 Jimmo 1995

Ergonomics 18.

Operator has difficulty reading certain gauges, meters, Or recordings*

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.

_ 1 1 ” _ 1 1 _ 1 _ _

Procedures and instruments have different units.

Standardize on commonly accepted units anc keep them consistent Provide conversion charts and look-up tabler Provide change control to ensure devices anc 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.

:CPS G-32

Table 6: Operations and Procedures

137

Ergonomics !1.

Physical stress induced by Personal Protection Equipment (PPE).

Where possible design process and/or restructure jobltasks to reduce need for personal protection equipment (PPE) Train personel in proper use of PPE Limit time operator spends on task requiring use of uncomfortable PPE Maintain PPE in good working condition

JFPA 1991 JFPA 1992 qFPA 1993

Operator Exposure !2.

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

Develop and implement sampling procedures tailored to the need of the batch being run Use special equipment for sampling, where necessary, for meeting the special needs of different batches (e.g., hodtoxic) Monitor operator while sampling highly toxic materials Provide comprehensive training Proper selection of personal protection equipment (PPE) Install inline sensordanalysis Use sample boxes; sample from line instead of opening hatches Sample recirculation lines to minimize line Purge

Bvelace 1979 *PA 1991 rJFPA 1992 qFPA 1993

23.

Emission of toxic, flammable, corrosive, Or hot when equipment is opened for cleaninglmaintenance. Possibility for operator exposure.

Develop, formalize and implement cleaning procedures Develop, formalize and implement decontamination procedures

X P S (3-29 4PI Std. 2015

'lean 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

138

6. OPERATIONS AND PROCEDURES

Operator Exposure 14.

!S.

X P S G-29

Emission of toxic, flammable, corrosive Or hot when equipment is Opened for charging. Possibility for operator exposure.

Use barrier technology (closed system airlocks, charging vessels, etc.) Where needed and practical, install remote operation to remove operator from hazard

Degradation of personal protection equipment (PPE) between uses.

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

\IFPA 1991 UFPA 1992 \IFPA 1993

Use dedicated connections and fittings Implement management of change for modificatiodalteration of systedprocedures Replace hose/fitting consistent with expected service life Provide verification by second operatodsupervisor prior to making connection, where necessary Pressure test Connections prior to service Provide manual bonding and grounding

X P S G-15 X P S G-29 X P S G-32

Provide local exhaust ventilation connected to a disoosal svstem (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 WE)

General 16.

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).

Analyze hazards before using portablehemporary equipment Implement safe procedure for installatiodhook-up Use double securement of quick connects Minimize use of flexible hoses Use of codedhnique connections

Table 6: Operations and Procedures

139

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

LPIStd. 2015 XPS G-15 CPS G-29 CPS (2-32

7.

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

!8.

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

Provide refresher trainingawareness of hazards

:CPS G-15 :cps G-22

29.

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 Enforce adherence to operating procedures Perform exit interviews of people transferrindleaving Conduct anonymous surveys to evaluate safety culture Audit periodically

:cps G-15 :cps G-22

6. OPERATIONS AND PROCEDURES

140

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

Provide more frequent traininghefresher training Schedule training near start of process Obtain operator input in determining training frequency Train operators in ''error recovery" and "what-if"

3 1.

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

Provide sufficient resources to develophain- X P S G-32 rain procedures Implement management of change procedurt Periodically review procedures

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

Provide detailed operating procedures Provide scheduled training Perform job desigdtask analysis (do not

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

Involve operator in Process Hazard Analysis of new process Perform operating procedures analysis Conduct technical staff review with operators before each campaign Ensure adequate training Provide technical staff coverage during first run of new process or infrequent campaigns Use "Buddy System" pairing experiencedhnexperienced personnel Perform operational testing using nonhazardous materials before startup

32.

33. 4

X P S (3-15 X P S G-22 ZCPS G-29 :CPS C-32

30.

Solicit operator input in developing procedures Conduct internal audits CCPS G-32 Meister 1987

Overload 'perator)

h_u%

CCPS G-1s CCPS G-22 CCPS G-29 CCPS G-32

Table 6: Operations and Procedures

141

General 4.

Need for reworking, blending, or disposing Of partially reacted Or "off-spec" batches.

Provide formal procedures for dealing with 'off-spec' batches, partially reacted batches Provide on-call technical assistance/support operators

XPS G-30 XPS C-32

Understand chemistry and potential consequences of producing 'off-spec' productdwaste materials, etc. Efforts should be make to reduce the production of off-spec material '5.

Avoid written and verbal linguistic confusion. Example I : 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." Y

.

Ensure materials are unequivocally identified and that there is a common linguistics under. standing at a site, especially among people with different native tongues

:CPS G-32

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NFPA 79: Electrical Standard for Industrial Machinery. National Fire Protection Association, Quincy, MA. NFPA 80A: Recommended Practice for Protection of Buildings from Exterior Fire Exposures. National Fire Protection Association, Quincy, MA. NFPA 86: Standard for Ovens and Furnaces. National Fire Protection Association, Quincy, MA. NFPA 86C: Standard for Industrial Furnaces Using a Special Processing Atmosphere. National Fire Protection Association, Quincy, MA. NFPA 86D: Standard for Industrial Furnaces Using Vacuum as an Atmosphere. National Fire Protection Association, Quincy, MA. NFPA 91: Standard for Exhaust Systems for Air Conveying of Vapors, Gases, Mists, and Noncombustible Particulate Solids. National Fire Protection Association, Quincy, MA. NFPA 92A: Recommended Practice for Smoke-Control Systems. National Fire Protection Association, Quincy, MA. NFPA 99C: Standard on Gas and Vacuum Systems, 1999 ed. National Fire Protection Association, Quincy, MA.NFPA 101: Code for Safety to Life from Fire in Buildings and Structures. National Fire Protection Association, Quincy, MA. NFPA 101A: Guide on Alternative Approaches to Life Safety, 1998 edition. National Fire Protection Association, Quincy, MA. NFPA 110: Standard for Emergency and Standby Power Systems, 1999 edition. National Fire Protection Association, Quincy, MA. NFPA 111: Standard on Stored Electrical Energy Emergency and Standby Power Systems, 1996 edition. National Fire Protection Association, Quincy, MA. NFPA 170: Standard for Fire Safety Symbols, 1996 edition. National Fire Protection Association, Quincy, MA. NFPA 214: Standard on Water-Cooling Towers, 1996 edition. National Fire Protection Association, Quincy, MA. NFPA 220: Standard on Types of Building Construction, 1995 edition. National Fire Protection Association, Quincy, MA. NFPA 221: Standard for Fire Walls and Fire Barrier Walls, 1997 edition. National Fire Protection Association, Quincy, MA. NFPA 23 1: Standard for General Storage, 1998 edition. National Fire Protection Association, Quincy, MA. NFPA 231C: Standard for Rack Storage of Materials, 1998 edition. National Fire Protection Association, Quincy, MA. NFPA 312: Standard for Fire Protection of Vessels during Construction, Repair, and Lay-Up, 1995 edition. National Fire Protection Association, Quincy, MA. NFPA 325: Guide to Fire Hazard Properties of Flammable Liquids, Gases, and Volatile Solids, 1994 edition. National Fire Protection Association, Quincy, MA. NFPA 326: Standard Procedures for the Safe Entry of Underground Storage Tanks, 1993 edition. National Fire Protection Association, Quincy, MA.

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NFPA 327: Standard Procedures for Cleaning or Safeguarding Small Tanks and Containers without Entry, 1993 edition. National Fire Protection Association, Quincy, MA. NFPA 328: Recommended Practice for the Control of Flammable and Combustible Liquids and Gases in Manholes, Sewers, and Similar Underground Structures, 1992 edition. National Fire Protection Association, Quincy, MA. NFPA 385: Standard for Tank Vehicles for Flammable and Combustible Liquids, 1990 edition. National Fire Protection Association, Quincy, MA. NFPA 386: Standard for Portable Shipping Tanks for Flammable and Combustible Liquids, 1990 edition. National Fire Protection Association, Quincy, MA. NFPA 471 : Recommended Practice for Responding to Hazardous Materials Incidents, 1997 edition. National Fire Protection Association, Quincy, MA. NFPA 491: Guide for Hazardous Chemical Reactions, 1997 edition. National Fire Protection Association, Quincy, MA. NFPA 49 1M: Fire Protection Guide on Hazardous Materials. National Fire Protection Association, Quincy, MA. NFPA 495: Explosive Materials Code, 1996 edition. National Fire Protection Association, Quincy, MA. NFPA 496: Standard for Purged and Pressurized Enclosures for Electrical Equipment, 1998 edition. National Fire Protection Association, Quincy, MA. NFPA 497: Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, 1997 edition. National Fire Protection Association, Quincy, MA. NFPA 499: Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas, 1997 edition. National Fire Protection Association, Quincy, MA. NFPA 550: Guide to the Fire Safety Concepts Tree. National Fire Protection Association, Quincy, MA. NFPA 650:Standard for Pneumatic Conveying Systems for Handling Combustible Particulate Solids, 1998 edition. National Fire Protection Association, Quincy, MA. NFPA 654: Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids, 1997 edition. NFPA 704: Standard for the Identification of the Fire Hazards of Materials for Emergency Response. National Fire Protection Association, Quincy, MA. NFPA 750: Standard on Water Mist Fire Protection Systems. National Fire Protection Association, Quincy, MA. NFPA 780: Standard for the Installation of Lightning Protection Systems. National Fire Protection Association, Quincy, MA. NFPA 820: Standard for Fire Protection in Wastewater Treatment and Collection Facilities. National Fire Protection Association, Quincy, MA. NFPA 921: Guide for Fire and Explosion Investigations. National Fire Protection Association, Quincy, MA. NFPA 1600: Recommended Practice for Disaster Management, 1995 edition. National Fire Protection Association, Quincy, MA.

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NFPA 1620: Recommended Practice for Pre-Incident Planning, 1998 edition. National Fire Protection Association, Quincy, MA. NFPA 1670: Standard on Operations and Training for Technical Rescue Incidents, 1999 edition. National Fire Protection Association, Quincy, MA. NFPA 1982: Standard on Personal Alert Safety Systems (PASS), 1998 edition. National Fire Protection Association, Quincy, MA. NFPA 1991: Standard on Vapor-Protective Suits for Hazardous Chemical Emergencies, 1994 edition. National Fire Protection Association, Quincy, MA. NFPA 1992: Standard on Liquid Splash-Protective Suits for Hazardous Chemical Emergencies, 1994 edition. National Fire Protection Association, Quincy, MA. NFPA 1993: Standard on Support Function Protective Clothing for Hazardous Chemical Operations, 1994 edition. National Fire Protection Association, Quincy, MA. Nimmo, I. 1995. Adequately Address Abnormal Operations. Chemical Engineering Pmgress, 91(9), 36-45. Nimmo, I. 1996. Abnormal Situation Management. Process and Control Engineering, 49(5), 8, 1996. Nimmo, I. 1996. Abnormal Situation Management. Instrument Society of America, New Orleans. Opslag van Gevaarlijke Stoffen. 1988. Storage of Hazardous Materials, Comite Europeen des Assurances (in Dutch) . Palmer, K. N. 1973. Dust Explosiorrs and Fires, Chapman and Hall, London. Pedley, J. B., R. D. Naylor, and S. P. Kirby, Thermochemical Data of Organic Compounds, 2nd ed., Chapman and Hall, London, New York. Perry, R. H., P. W. Green, and J. 0. Maloney, 1984. Perry's Chemical Engineers' Handbook. 6th ed. McGraw-Hill, New York. Powell-Price, M. 1997. The Explosion and Fires at the Texaco Refinery, 24 July 1994, Loss Prevention Bulletin 138, pp. 3-10. Pratt, Thomas 1997. "Electrostatic Ignition of Fires and Explosions." Procyk, L.M. 1991. Batch Process Automation. Chemical Engineering, 98(5), 11 1-1 17. Rasmussen, J. 1979. Notes on human error analysis and prediction. In G. Apostalakis and G. Volta (Eds.), Synthesis and Analysis Methods for Safety and Reliability Studies, Plenum, New York. Reid, R.C., J.M. Prausnitz and B.E. Poling 1987, The Properties o f Gases and Liquids, 4th ed., McGraw-Hill, Inc., New York. Rippin, D.W.T.1991. Batch Process Planning. Chemical Engineering, 98(5), 100-107. Rouse, W. and S. Rouse 1983. Analysis and classification of human error. IEEE transactions on Systems, Man, and Cybernetics, SMC-13(4),539-549. RUSSO,T.J., Jr. and A.J. Tortorella 1992. An Engineer's Guide to Plant Layout. Part 3. The Contribution of CAD.Chemical Engineering, 99(4), 97-101. Sanders, M.S. and E.J. McCormick 1993. Human Factors in Engineeringand Design, 7th ed., McGraw Hill, New York, Sanders, R. E., Learning from Case Histories, 2nd edition.

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Glossary Autoignition Temperature (AIT): The autoignition temperature of a substance, whether solid, liquid, or gaseous, is the minimum temperature required to initiate or cause self-sustained combustion, in air, with no other source of ignition. Basic Process Control System (BPCS): The control equipment that is installed to support normal production functions. Boiling Liquid Expanding Vapor Explosion (BLEVE): The explosively rapid vaporization, and corresponding release of energy of a liquid, flammable or otherwise, upon its sudden release from containment under greater-thanatmospheric pressure at a temperature above its boiling point. A BLEVE is often accompanied by a fireball if the suddenly depressurized liquid is flammable and its release results from vessel failure caused by external fire. The energy released during flashing and vaporization may contribute to a shock wave. Bonding: The process of connecting two or more conductive objects together by means of a conductor. Car Seal: A metal or plastic cable used to fix a valve in the open position (car seal open) or closed position (car seal closed). Proper authorization, controlled via administrative procedures, must be obtained before operating the valve. The physical seal should have suitable mechanical strength to prevent unauthorized valve operation. Catastrophic Incident: An incident involving a major uncontrolled emission, fire or explosion that causes significant damage, injuries and/or fatalities onsite and have an outcome effect zone that extends into the surrounding community. Combustible Liquid: A term used to classify certain liquids that will burn on the basis of flash points. The National Fire Protection Association (NFPA) defines a “combustible liquid” as having a flash point of 100°F (37.8”C) or higher. See also, “Flammable Liquid.” Class I1 liquids have flash points at or above 100”F, but below 140°F. Class 111 liquids are subdivided into two subclasses. 159

160

GLOSSARY

Class IIIA: Those having flash points at or above 140°Fbut below 200°F. Class IIIB: Those having flash points at or above 200°F. Common Mode Failure: An event having a single cause with multiple failure effects, which are not consequences of each other. Covert Fault: Faults that can be classified as hidden, concealed, unannounced, undetected, unrevealed, latent, etc. In the case of safety instrumented systems covert faults impair the intended safeguarding function without being apparent to the operator. Covert faults can only be detected by testing or challenging the system. Damage Limiting Construction: Construction of equipment (building) with weak sections to limit the damage to the equipment (building). The weak sections fail early and prevent damage to the rest of the equipment (building). Dead-heading: A blockage on the discharge side of an operating pump which results in the flow reducing to zero and an increase in the discharge pressure. The energy input from the deadheaded pump increases the temperature and pressure of the fluid in the pump. Deflagration: A propagating chemical reaction of a substance in which the reaction front advances into the unreacted substance at less than the sonic velocity in the unreacted material. Where a blast wave is produced that has the potential to cause damage, the term explosive deflugrution may be used. Deflagration to Detonation Transition: A reaction front that starts out with velocities below the speed of sound and subsequently accelerates to velocities higher than the speed of sound in the unreacted material is said to have undergone a Deflagration to Detonation Transition. The possibility of transition is enhanced by confinement/turbulence generators in the path of the reaction front. Detonation: A propagating chemical reaction of a substance in which the reaction front advances into the unreacted substance at equal to or greater than the sonic velocity in the unreacted material. Design Institute for Emergency Relief Systems (DIERS): Institute under the auspices of the American Institute of Chemical Engineers founded to study relief requirements for reactive chemical systems and two-phase flow systems. Distributed Control System (DCS): A system that divides process control functions into specific areas interconnected by communications (normally data highways) to form a single entity. It is characterized by digital controllers, typically administered by central operation interfaces and intermittent scanning of the data highway. Dow Fire and Explosion Index (F&EI): A method (developed by Dow Chemical Company) for ranking the relative fire and explosion risk associated with a

Glossary

161

process. Analysts calculate various hazard and explosion factors using material characteristics and process data. Emergency Relief Device: A device that is designed to open during emergency or abnormal conditions to prevent rise of internal fluid pressure in excess of a specified value. The device also may be designed to prevent excessive internal vacuum. The device may be a pressure relief valve, a nonreclosing pressure relief device, or a vacuum relief valve. Emergency Shutdown Device: A device that is designed to shutdown the system to a safe condition on command from the emergency shutdown system. Emergency Shutdown System: The safety control system that overrides the action of the basic control system and shuts down the process when predetermined conditions are violated. Equipment Reliability: The probability that, when operating under stated environment conditions, process equipment will perform its intended function adequately for a specified exposure period. Explosion: A rapid or sudden release of energy that causes a pressure discontinuity or blast wave. Fail-safe: Design features which provide for the maintenance of safe operating conditions in the event of a malfunction of control devices or an interruption of an energy source (e.g., direction of failure of a control valve on loss of signal). A system is fail-safe if failure of a component, signal, or utility that would create a hazard initiates an action that maintains the system in a safe condition. Failure: An unacceptable differencebetween expected and observed performance. Failure Mode and Effects Analysis (FMEA): A failure identification methodology where the failure modes of a component sub-system are identified. An analysis of these failure modes on the safety of the entire system is performed. Fire Point: The temperature at which a liquid continues to burn when the ignition source is removed. Flame Arrester: A flame arrester is a device permeable to gas flow but impermeable to any flame. It quenches the flame and cools the products sufficiently to prevent reignition at arrester outlet. Arresters are used to prevent a flame propagating into the system from outside (such as via a tank vent) or one part of the system to another (such as through connected piping). Flammability Limits: The minimum and maximum concentrations of combustible material in a homogeneous mixture with gaseous oxidizer that will propagate a flame. flammable Liquid: A "Flammable Liquid" is defined by NFPA as a liquid with a flash point below 100°F (37.8"C).Flammable liquids provide ignitable vapor at room temperatures and must be handled with caution. Precautions

162

GLOSSARY

such as bonding and grounding must be taken. Flammable liquids are Class I liquids and may be subdivided as follows: Class 1A: Those having flash points below 73°F and having a boiling point below 100°F Class 1B: Those having flash points below 73°F and having a boiling point at or above 100°F Class 1C: Those having flash points at or above 73°F and below 100°F Flash Fire: The combustion of a flammable gas or vapor and air mixture in which the flame propagates through the mixture in a manner such that negligible or no damaging overpressure is generated. Flash Point: The lowest temperature at which vapors above a liquid will ignite at a pressure of 760 mm Hg absolute. The temperature at which vapor will burn while in contact with an ignition source, but which will not continue to burn after the ignition source is removed. There are several flash point test methods, and flash points may vary for the same material depending on the method used. Consequently, the test method is indicated when the flash point is given. A closed cup type test is used most frequently for regulatory purposes. The lower the flash point temperature of a liquid, the greater the fire hazard following a release. Froth-over: When water is present or enters a tank containing hot viscous oil, the sudden conversion of water to steam causes a portion of the tank contents to overflow. Fugitive Emissions: Emissions of material from process equipment due to leakage. Grounding: Grounding is a conducting connection between a piece of equipment or electrical circuit and the earth. Hazard: An inherent chemical or physical characteristic that has the potential for causing harm to people, property, or the environment. Hazard Analysis: The identification of undesired events that lead to the materialization of a hazard, the analysis of the mechanisms by which these undesired events could occur and usually the estimation of the consequences. Hazard and Operability Study (HAZOP): A systematic qualitative technique to identify process hazards and potential operating problems using a series of guide words to study process deviations. A HAZOP is used to question every part of a process to discover what deviations from the intention of the design can occur and what their causes and consequences may be. This is done systematically by applying suitable guidewords. This is a systematic detailed review technique, for both batch and continuous plants, which can be applied to new or existing processes to identify hazards.

Glossary

163

Hazardous Material: In a broad sense, any substance or mixture of substances having properties capable of producing adverse effects on health, safety or the environment. These dangers may arise from but are not limited to toxicity, reactivity, instability, or corrosivity. Human Factors: A discipline concerned with designing machines, operations, and work environments so that they match human capabilities, limitations, and needs. Includes any technical work (engineering, procedure writing, worker training, worker selection, etc.) related to the human factor in operator-machine systems. Inert Gas: A noncombustible, nonreactive gas that at sufficient concentrations renders the combustible material in a system incapable of supporting combustion. Inherently Safer: A system is inherently safer if it relies on the chemistry and physics (the quantity, properties and conditions of use of the process materials) rather than on control systems, interlocks, alarms and procedures to prevent incidents. Interlock System: A system that detects out-of-limits or abnormal conditions or improper sequences and either halts further action or starts corrective action. Intrinsically Safe: Equipment and wiring which is incapable of releasing sufficient electrical or thermal energy under normal or abnormal conditions to cause ignition of a specific hazardous atmospheric mixture or hazardous layer. Likelihood: A measure of the expected frequency with which an event occurs. This may be expressed as a frequency (e.g., events per year), a probability of occurrence during a time interval (e.g., annual probability), or a conditional probability (e.g., probability of occurrence, given that a precursor event has occurred). Limiting Oxidant Concentration (LOC): The limiting oxidant concentration (LOC) is that concentration of oxidant, below which a deflagration (flame propagation in the gas, mist, suspended dust, or hybrid mixture) cannot occur. For most hydrocarbons where oxygen is the oxidant and nitrogen is the diluent the LOC is approximately 9 to 11vol% oxygen. The LOC for dusts is dependent on the composition and particle size distribution of the solid. Values of LOC for most organic chemical dusts lie in the range of 10 to 16 ~ 0 1 %oxygen, again where nitrogen is the diluent Minimum Explosible Concentration (MEC): The lowest concentration of combustible dust necessary to produce an explosion. Minimum Ignition Energy (MIE): Initiation of flame propagation in a combustible mixture requires an ignition source of adequate energy and duration to overcome heat losses to the cooler surrounding material. Dust and vapor

164

GLOSSARY

clouds may be readily ignited if exposed to electric discharges that exceed the minimum ignition energy (MIE) for the combustible mixture. Mitigation: Reducing the risk of an accident event sequence by taking protective measures to reduce the likelihood of occurrence of the event, and/or reduce the magnitude of the event and/or minimize the exposure of people or property to the event. Net Positive Suction Head (NPSH): The net static liquid head that must be provided on the suction side of the pump to prevent cavitation. Overt Fault: Fault that can be classified as announced, detected, revealed, etc. Oxidant: Any material that can react with a fuel (gas, dust or mist) to produce combustion. Oxygen in air is the most common oxidant. Plausibility Analysis: A comparison of values for process variables that allows faults in the measurement channels of the safety system to be recognized while the process is still in its normal operating range. Pool Fire: The combustion of material evaporating from a layer of liquid at the base of the fire. Process Safety: A discipline that focuses on the prevention and mitigation of fires, explosions, and accidental chemical releases at process facilities. Excludes classic worker health and safety issues involving working surfaces, ladders, protective equipment, etc. Piping and Instrument Diagram (P&ID): A diagram that shows the details about the piping, vessels, and instrumentation. Process Flow Diagram (PFD): A diagram that shows the material flow from one piece of equipment to the other in a process. It usually provides information about the pressure, temperature, composition, and flow rate of the various streams, heat duties of exchangers, and other such information pertaining to understanding and conceptualizing the process. Process Hazard Analysis (PHA): A structured procedure whereby hazards associated with a process are identified and evaluated. Pressure Relief Valve (PRV): A relief valve is a spring-loaded valve actuated by static pressure upstream of the valve. The valve opens normally in proportion to the pressure increase over opening pressure. A relief valve is normally used with incompressible fluids. Pressure Safety Valve (PSV): A safety valve is a spring loaded valve actuated by static pressure upstream of the valve and characterized by rapid opening or pop action. A safety valve is normally used with compressible fluids. Process Safety System (PSS): A process safety system comprises the design, procedures, and hardware intended to operate and maintain the process safely. Programmable Electronic System (PES): A system based on a computer connected to sensors and/or actuators in a plant for the purpose of control,

Glossary

165

protection or monitoring (includes various types of computers, programmable logic controllers, peripherals, interconnect systems, instrument distributed control system controllers, and other associated equipment). Programmable Logic Controller (PLC): A microcomputer-based solid-state control system which receives inputs from user-supplied control devices such as switches and sensors, implements them in a precise pattern determined by instructions stored in the PLC memory, and provides outputs for control or user-supplied devices such as relays and motor starters. Proof Testing: A run through the process substituting nonhazardous materials (e.g., water) to check for the adequacy of the equipment e.g., heatingkooling load, and to verify procedural steps. Purge Gas: A gas that is continuously or intermittently added to a system to render the atmosphere nonignitable. Quenching: Rapid cooling from an elevated temperature, e.g., severe cooling of the reaction system in a short time (almost instantaneously), “freezes” the status of a reaction and prevents further decomposition or reaction. Reactors: Continuous-flow Stirred Tank Reactor (CSTR): A reaction vessel in which the feed is continuously added, and the products continuously removed. The vessel (tank) is continuously stirred to maintain a uniform concentration within the vessel. Plug Flow Reactor (PFR): A plug flow reactor is a tubular reactor where the feed is continuously introduced at one end and the products continuously removed from the other end. The concentratiodtemperature profile in the reactor varies with position. Batch Reactor: In a batch reactor, the reactants are added to the reactor at the start of the reaction. The reactants are allowed to react in the reactor for a fixed time. No feed is added or product withdrawn during this time. The reaction products are removed at the end of the batch. Semi-Batch Reactor: In a semi-batch reactor, some reactants are added to the reactor at the start of the batch, while others are fed intermittently or continuously during the course of the reaction. Runaway: A thermally unstable reaction system which exhibits an uncontrolled accelerating rate of reaction leading to rapid increases in temperature and pressure. Safety Instrumented System (SIS): The instrumentation, controls, and interlocks provided for safe operation of the process. Safety Layer: A system or subsystem that is considered adequate to protect against a specific hazard. The safety layer is totally independent of any other protective layers cannot be compromised by the failure of another safety layer

166

GLOSSARY

must have acceptable reliability must be approved according to company policy and procedures must meet proper equipment classification may be a noncontrol alternative (i.e., chemical, mechanical) may require diverse hardware and software packages may be an administrative procedure Short-Stop Agent: A material added to a reaction mixture to stop or greatly reduce the reaction rate. This is usually done to prevent a runaway reaction. Upper Flammable Limit (UFL): The highest concentration of a vapor or gas (the highest percentage of the substance in air) that will produce a flash of fire when an ignition source (heat, arc, or flame) is present. See also Lower Flammable Limit. At concentrations higher then the UFL, the mixture is too “rich” to burn. Valve Failure Positions: In the event of instrument air or electrical power failure, valves either Fail Closed (FC), Fail Open (FO), or Fail in the last position (FL). The position of failure must be carefully selected so as to bring the system to, or leave the system in a safe operating state. Vapor Cloud Explosion (VCE): Explosive oxidation of a vapor cloud in a nonconfined space (not in vessels, buildings, etc.). The flame speed may accelerate to high velocities and produce significant blast overpressure. Vapor cloud explosions in plant areas with dense equipment layouts may show acceleration in flame speed and intensification of blast. Vapor Pressure: The pressure exerted by a vapor above its own liquid. The higher the vapor pressure, the easier it is for a liquid to evaporate and fill the work area with vapors which can cause health or fire hazards. Venting: Emergency flow of vessel contents out of a vessel. The pressure is controlled or reduced by venting, thus avoiding a failure of the vessel by overpressurization. The emergency flow can be one-phase or multi-phase, each of which results in different flow characteristics.

Index B Batch control activities, insmmentation/control systems, 110 Batch distillation columns, equipment safety, 40,73-74 Batch pharmaceutical reactor, equipment safety case study, 43-44 Batch reaction process safety, 1-6 approach to, 3-5 chemistry, 7-25. See also Chemistry equipment, 35-108. See also Equipment equipment configuration, 27-34. See a h Equipment configuration instrumentation/controolsystems, 109-123. See also Instrumentation/controrol systems operations and procedures, 125-141. See also Operations and procedures scope of issues, 1-2 special concerns, 2-3

C Centrifuges, equipment safety, 3&39,64-69. See also Equipment safety (summary tables) Change management. See Management of change Charging equipment, equipment safety, 41, 76-89. See also Equipment safety (summary tables) Chemical compatibility, reactivity hazards screening, 22 Chemical composition, summary table, 15 Chemical identification, summary table, 14

Chemistry, 7-25 cw Study, 8-9 overview, 7-8 process safety practices, 9-10 reactivity hazards screening, 21-25 experimental analysis, 24 experimental screening, 23-24 problem context, 21 theoretical screening, 21-23 summary table, 11-20 chemical composition, 15 chemical identification, 14 chemirtrylprawsschemistry selection, 11-14 contamination, 19-20 off-spec product/intermediate raw material, 20 runaway reaction, 16-19 waste minimization, 20 Chemistry/process chemistry selection, summary table, 11-14 Choice of goal/procedure, operations and procedures, summary table, 134-135 Choice/testingof hypothesis, operations and procedures, summary table, 134 Containment loss equipment safety (summary tables) centrifuges, 66-67 drumming equipment, 91-92 filters, 103 general, 53 reactors and vessels, 63 transferring and charging equipment, 81-84 insmmentation/controI systems, summary table, 115 167

168 Contamination, chemistry, summary table, 19-20 Corrosion equipment safety (summary tables) centrifuges, 66 drumming equipment, 92-93 milling equipment, 98 transferring and charging equipment, 79-80 instrumentation/controlsystems, summary table, 115

D Drains, equipment safety, 40-41,75 Drumming equipment, equipment safety, 41, 90-95. See alro Equipment safety (summary tables) Dryer fire and explosion, equipment safety case study, 44-45 Dryers, equipment safety, 394,70-72

E Equipment configuration, 27-34 case studies, 28-29 importance of, 27-28 issues in, 29 practices in, 29 summary table, 30-34 fire/explosion, 31-32 general, 33-34 ignition sources, 31 operator exposure, 33 shared systems, 30 Equipment-related control, instrumentation/control systems, 111 Equipment safety, 35-108 batch distillation and evaporators, 40 case studies, 43-45 batch pharmaceutical reactor, 43-44 pharmaceuticalpowder dryer fire and explosion, 44-45 runaway reaction, 44 cenuifbges, 38-39 charging and transferring equipment, 41 drumming equipment, 41 dryers, 3 9 4 filters, 42-43 issues, 45

INDEX

milling equipment, 42 overview, 35 practices, 45-47 process vents and drains, 40-41 reactors and vessels, 36-38 storage and warehousing, 105-108 summary tables, 48-105. Sce d o Equipment safety (summary tables) Equipment safety (summary tables), 48-105 batch distillation and evaporation, 73-74 centrifuges, 64-69 containment loss, 66-67 corrosion, 66 fires/explosions, 68 general, 68-69 high temperature, 65 ignition sources, 67-68 operator exposure, 68 overpressure, 64 runaway reaction, 65-66 underpressure, 65 drumming equipment, 90-95 containment loss, 91-92 corrosion, 92-93 fires/explosions, 95 high temperature, 94 ignition sources, 94 low temperature, 95 operator exposure, 95 overpressure, 90-91 runaway reaction, 93-94 underpressure, 92 dryers, 70-72 filters, 100-105 containment loss, 103 fires/explosions,101-102 high temperature, 100 ignition sources, 102 operator exposure, 104-105 overpressure, 100 runaway reaction, 101 general, 48-53 containment loss, 53 fire/explosion, 49-5 1 management of change, 52-53 operator exposure, 52 overpressure, 48 underpressure, 48 milling equipment, 96-99 corrosion, 98

Index fires/explosions, 98 general, 99 high temperature, 96-97 ignition sources, 98 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, 54-63 containment loss, 63 high temperature, 55-59 low temperature, 60 mixing, 60-61 overpressure, 54-55 runaway reaction, 61-62 underpressure, 55 transferring and charging equipment, 76-89 containment loss, 81-84 corrosion, 79-80 fires/explosions, 84-87 general, 76 high temperature, 79 low temperature, 79 operator exposure, 88-89 overpressure, 76-78 runaway reaction, 80-81 underpressure, 79 Ergonomics, operations and procedures, summary table, 136-137 Error. Scc Operations and procedures Evaporators, equipment safety, 40,73-74 Execution of procedure, operations and procedures, summary table, 135-136 Experimental analysis, reactivity hazards screening, 24 Explosions equipment configuration, summary table, 31-32 equipment safety (summary tables) centrifuges, 68 drumming equipment, 95 filters, 101-102 general, 49-5 1 milling equipment, 98 transferring -and charging equipment, 84-87 powder dryer fire and explosion, case study, 4445

169 Explosion testing, reactivity hazards screening, 24

F Filters, equipment safety, 4243, 100-105. Scc nlso Equipment safety (summary tables) Fires equipment configuration, summary table, 31-32 equipment safety (summary tables) centrifuges, 68 drumming equipment, 95 filters, 101-102 general, 49-5 1 milling equipment, 98 transfming and chargingequipment, 84-87

G Goal/procedure, choice of, operations and procedures, summary cable, 134-135

H High temperature, equipment safety (summary tables) centrifuges, 65 drumming equipment, 94 filters, 100 milling equipment, 96-97 reactors and vcssels, 55-59 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) centrihges, 67-68 drumming equipment, 94 filters, 102 milling equipment, 98 instrumentation/contl systems, summary table, 116 Information management, insmunentation/control systems, 109,111 Information processing model, operations and procedures, 128

170 Instrumentation/control systems, 109-123 batch control activities, 109, 111 case study, 112-1 13 equipment-related control, 111 information management, 109, 111 issues, 113-1 14 overview, 109 process management, 111 process safety practices, 114 production scheduling, 111 recipe management, 111 safety interlocking, 111 summary table, 115-123 containment loss, 115 corrosion, 115 general, 116-123 ignition sources, 116 Intermediate raw material, off-spec product and, chemistry, summary table, 20

L

Loss of containment. Scc 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, 52-53 milling equipment, 99 Mechanical sensitivity, reactivity hazards screening, 24 Milling equipment, equipment safety, 42, 96-99. Scc nlw Equipment safety (summary tables) Mixing, equipment safety (summary tables), reactors and vessels, 60-61

0 Observation, operations and procedures, summary table, 132-134 Off-spec product, intermediate raw material and, chemistry, summary table, 20

INDEX

Operations and procedures, 125-141 case studies, 12S131 information processing model, 128 issues, 131 overview, 125-129 process safety practices, 131 summary table, 132-141 choice of goal/procedure, 134-135 choice/testing of hypothesis, 134 ergonomics, 136-137 general, 138-141 observation, 132-134 operator exposure, 137-138 procedure execution, 135-136 Operator exposure equipment configuration, summary table, 33 equipment safety (summary tables) centrifuges, 68 drumming equipment, 95 filters, 104-105 general, 52 milling equipment, 99 transferring and charging equipment, 88-89 operations and procedures, summary table, 137-138 Overpressure, equipment safety (summary tables) centrifuges, 64 drumming equipment, 90-91 filters, 100 general, 48 milling equipment, 96 reactors and vessels, 54-55 transferring and charging equipment, 76-78

P Pharmaceutical powder dryer fire and explosion, equipment safety case study, 4445

Pharmaceutical reactor, equipment safety case study, 43-44 Powder dryer fire and explosion, equipment safety case study, 44-45 Procedure execution, operations and procedures, summary table, 135-136 Process management, instrumentation/control systems, 111 Process safety. Scc Batch reaction process safety

171

Index Process vents, equipment safety, 4041,75 Production scheduling, instnunentationfcontrol systems, 111

R Reaction process safety. See Batch reaction process safety Reactivity hazards screening, 21-25 experimental analysis, 24 experimental screening, 23-24 problem context, 21 theoretical screening, 21-23 Reactors, vessels and, equipment safety, 36-38, 54-63. See alro Equipment safety (summary tables) Recipe management, insuumentation/controrol systems, 111 Runaway reaction chemistry, summary table, 16-19 equipment safety case study, 44 equipment safety (summary tables) centrifuges, 65-66 drumming equipment, 93-94 fdters, 101 milling equipment, 97 reactors and vessels, 61-62 transferring and charging equipment, 80-8 1

S Safety interlocking, instnunentation/control systems, 111 Scheduling, production, insuumentationfcontrol systems, 111 Self-reactivityhazards, reactivity hazards screening, 24 Seveso runaway reaction, equipment safety case study, 44 Shared systems, equipment configuration, summary table, 30 Storage and warehousing, equipment safety, 105-1 08 Storage vessels, reactors and, equipment safety, 3638,5443. See alro Equipment safety (summary tables)

T Temperature high, equipment safety (summary tables) centrifuges, 65 drumming equipment, 94 filters, 100 milling equipment, 96-97 reactors and vessels, 55-59 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, 21-23 Thermal sensitivity, reactivity hazards screening, 24 Thermophysical properties, reactivity hazards screening, 23 Training. See Operations and procedures Transferringequipment, equipment safety, 41, 76-89. See alro 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

V Vents. See Process vents Vessels, reactors and, equipment safety, 36-38, Equipment safety (sum54-63. See mary tables)

W Warehousing, equipment safety, 105-108 Waste minimization, chemistry, summary table, 20

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Publications Available from the CENTER FOR CHEMICAL PROCESS SAFETY of the AMERlCAN INSTITUTE OF CHEMICAL ENGINEERS 3 Park Avenue, New York, Ny 10016-5991

CCPS Guidelines Series Guidelines for Process Safety in Batch Reaction Systems Guidelines for Consequence Analysis of Chemical Releases Guidelines for Pressure Relief and Effluent Handling Systems Guidelines for Design Solutions for Process Equipment Failures Guidelines for Safe Warehousing of Chemicals Guidelines for Postrelease Mitigation in the Chemical Process Industry Guidelines for Integrating Process Safety Management, Environment, Safety, Health, and Quality Guidelines for Use of Vapor Cloud Dispersion Models, Second Edition Guidelines for Evaluating Process Plant Buildings for External Explosions and Fires Guidelines for Writing Effective Operations and Maintenance Procedures Guidelines for Chemical Transportation Risk Analysis Guidelines for Safe Storage and Handling of Reactive Materials Guidelines for Technical Planning for On-Site Emergencies Guidelines for Process Safety Documentation Guidelines for Safe Process Operations and Maintenance Guidelines for Process Safety Fundamentals in General Plant Operations Guidelines for Chemical Reactivity Evaluation and Application to Process Design Tools for Making Acute Risk Decisions with Chemical Process Safety Applications Guidelines for Preventing Human Error in Process Safety Guidelines for Evaluating the Characteristics of Vapor Cloud Explosions, Flash Fires, and BLEVEs Guidelines for Implementing Process Safety Management Systems Guidelines for Safe Automation of Chemical Processes Guidelines for Engineering Design for Process Safety Guidelines for Auditing Process Safety Management Systems Guidelines for Investigating Chemical Process Incidents Guidelines for Hazard Evaluation Procedures, Second Edition with Worked Examples Plant Guidelines for Technical Management of Chemical Process Safety, Revised Edition Guidelines for Technical Management of Chemical Process Safety Guidelines for Chemical Process Quantitative Risk Analysis Guidelines for Process Equipment Reliability Data with Data Tables Guidelines for Safe Storage and Handling of High Toxic Hazard Materials Guidelines for Vapor Release Mitigation

CCPS concepts series Avoiding Static Ignition Hazards in Chemical Operations Estimating the Flammable Mass of a Vapor Cloud RELEASE: A Model with Data to Predict Aerosol Rainout in Accidental Releases Local Emergency Planning Committee Guidebook: Understanding the EPA Risk Management Program Rule Inherently Safer Cemical Processes. A Life-Cycle Approach Contractor and Client Relations to Assure Process Safety Understanding Atmospheric Dispersion of Accidental Releases Expert Systems in Process Safety Concentration Fluctuations and Averaging Time in Vapor Clouds

Proceedings and Other Publications Proceedings of the International Conference and Workshop on Modeling the Consequences of Accidental Releases of Hazardous Materials Proceedings of the International Conference and Workshop on Reliability and Risk Management, 1998 Proceedings of the International Conference and Workshop on Risk Analysis in Process Safety, 1997 Proceedings of the International Conference and Workshop on Process Safety Management and Inherently Safer Processes, 1996 Proceedings of the International Conference and Workshop on Modeling and Mitigating the Consequences of Accidental Releases of Hazardous Materials, 1995 Proceedings of the International Symposium and Workshop on Safe Chemical Process Automation, 1994 Proceedings of the International Process Safety Management Conference and Workshop, 1993 Proceedings of the International Conference on Hazard Identification and Risk Analysis, Human Factors, and Human Reliability in Process Safety, 1992 Proceedings of the International Conference and Workshop on Modeling and Mitigating the Consequences of Accidental Releases of Hazardous Materials, 1991 Safety, Health and Loss Prevention in Chemical Processes: Problems for Undergraduate Engineering Curricula

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