Lees' Process Safety Essentials: Hazard Identification, Assessment and Control

By Sam Mannan

Lees' Process Safety Essentials is a single-volume digest presenting the critical, practical content from Lees' Loss Prevention for day-to-day use and reference. It is portable, authoritative, affordable, and accessible — ideal for those on the move, students, and individuals without access to the full three volumes of Lees'.

This book provides a convenient summary of the main content of Lees', primarily drawn from the hazard identification, assessment, and control content of volumes one and two. Users can access Essentials for day-to-day reference on topics including plant location and layout; human factors and human error; fire, explosion and toxic release; engineering for sustainable development; and much more. This handy volume is a valuable reference, both for students or early-career professionals who may not need the full scope of Lees', and for more experienced professionals needing quick, convenient access to information.

• Boils down the essence of Lees'—the process safety encyclopedia trusted worldwide for over 30 years
• Provides safety professionals with the core information they need to understand the most common safety and loss prevention challenges
• Covers the latest standards and presents information, including recent incidents such as Texas City and Buncefield

• Language: English
• Publisher: Elsevier Science
• Release date: Nov 12, 2013
• ISBN: 9780080962306

Sam Mannan

M. Sam Mannan, PhD, PE, CSP, is a chemical engineering professor and director of the Mary Kay O’Connor Process Safety Center at Texas A&M University. He is an internationally recognized expert on process safety and risk assessment. His research interests include hazard assessment and risk analysis, flammable and toxic gas cloud dispersion modeling, inherently safer design, reactive chemicals and run¬away reactions, aerosols, and abnormal situation management.

Book preview

Lees' Process Safety Essentials

Hazard Identification, Assessment and Control

Sam Mannan

Table of Contents

Cover image

Title page

Copyright

Foreword

Chapter 1. Introduction

1.1 Management Leadership

1.2 Industrial Safety and Loss Trends

1.3 Safety and Environmental Concerns

1.4 Historical Development of Loss Prevention

1.5 Loss Prevention Essentials

1.6 Environment and Sustainable Development

1.7 Responsible Care

1.8 Academic and Research Activities

1.9 Overview

References

Chapter 2. Incidents and Loss Statistics

2.1 The Incident Process

2.2 Injury Statistics

2.3 Major Disasters

2.4 Major Process Hazards

2.5 Major Hazard Control

2.6 Fire and Explosion Loss

2.7 Causes of Loss

2.8 Trend of Injuries and Losses

2.9 Economics of Loss Prevention

2.10 Insurance of Process Plant

2.11 Property Insurance

2.12 Individual Insurance

2.13 Business Interruption Insurance

2.14 Other Insurance Aspects

References

Chapter 3. Legislation, Law, and Standards

3.1 US Legislation

3.2 US Regulatory Agencies

3.3 Codes and Standards

3.4 Occupational Safety and Health Act 1970

3.5 US Environmental Legislation

3.6 US Toxic Substances Legislation

3.7 US Accidental Chemical Release Legislation

3.8 US Transport Legislation

3.9 US Security Legislation

3.10 US Developing Legislation

3.11 EU Legislations

3.12 US Chemical Safety Board

3.13 The Risk Management Program

3.14 The Process Safety Management Program

References

Chapter 4. Management Systems

4.1 Management Attitude

4.2 Management Commitment and Leadership

4.3 Management Organization and Competent People

4.4 Systems and Procedures

4.5 Project Safety Reviews

4.6 Management of Change

4.7 Standards and Codes of Practice

4.8 Pressure Systems

4.9 Major Hazards

4.10 Total Quality Management

4.11 Safety Management and Safety Policy

4.12 Organization

4.13 Planning

4.14 Measurement

4.15 Control

4.16 Audit System and Audit

4.17 Safety Management Systems

4.18 Process Safety Management

4.19 CCPS Management Guidelines

4.20 Safety Culture

4.21 Safety Organization

4.22 Safety Policy Statement

4.23 Safety Representatives and Safety Committees

4.24 Safety Adviser

4.25 Safety Training

4.26 Safety Communication

4.27 Safety Auditing

4.28 Management Procedure to Implement Required Changes to Establish Proper Safety

4.29 Need for Process Safety Metrics

4.30 Different Types of Metrics

4.31 Choosing Useful Metrics

4.32 Implementing the Selected Metrics

4.33 Future Efforts for Generating Industry-Wide Metrics

4.34 Conclusion

References

Chapter 5. Reliability

5.1 Reliability Engineering

5.2 Equipment Maintenance

5.3 Management of Changes and Modifications

Acronyms

Notation

References

Chapter 6. Hazard Identification

6.1 Safety Audits

6.2 Management System Audits

6.3 Checklists

6.4 Materials Properties

6.5 Pilot Plants

6.6 Hazard Indices

6.7 Hazard Studies

6.8 What-If Analysis

6.9 Event Tree and Fault Tree Analysis

6.10 Bow-Tie Method

6.11 Preliminary Hazard Analysis

6.12 Screening Analysis Techniques

6.13 Hazard and Operability Studies

6.14 Failure Modes, Effects and Criticality Analysis

6.15 Sneak Analysis

6.16 Computer HAZOP

6.17 Human Error Analysis

6.18 Scenario Development

6.19 Consequence Modeling

6.20 Process Safety Review System

6.21 Choice of Method

6.22 Filtering and Follow-Up

6.23 Safety Review Systems

6.24 Hazard Ranking Methods

6.25 Hazard Warning Analysis

6.26 Plant Safety Audits

6.27 Other Methods

6.28 Quality Assurance

6.29 Quality Assurance: Completeness

6.30 Quality Assurance: QUASA

6.31 Standards

Notation

References

Chapter 7. Plant Siting and Layout

7.1 Plant Siting

7.2 Plant Layout

7.3 Layout Generation

7.4 Layout Techniques and Aids

7.5 Layout Planning and Development

7.6 Site Layout Features

7.7 Plot Layout Considerations

7.8 Equipment Layout

7.9 Separation Distances

7.10 Hazardous Area Classification

7.11 Hazard Assessment

7.12 Hazard Models

7.13 Fire Protection

7.14 Effluents

7.15 Blast-Resistant Structures

7.16 Control Buildings

7.17 Toxics Protection

7.18 Modular Plants

References

Chapter 8. Process Design

8.1 Process Design

8.2 Integration of Safety into the Process Design

8.3 Pressure Systems

8.4 Control System Design

Acronyms

References

Chapter 9. Human Factors and Human Error

9.1 Concept of Human Factors

9.2 Role of the Process Operator

9.3 Allocation of Function

9.4 Human Information Processing

9.5 Case Studies in Human Error

9.6 Definition of Human Error

9.7 Human Factors Approaches to Assessing Human Error

9.8 Quantitative Human Reliability Analysis (HRA)

9.9 Human Reliability Assessment Methods

9.10 Human Factors Approaches to Mitigating Human Error

9.11 Alarm Systems

9.12 Fault Administration

9.13 Malfunction Detection

9.14 Training

9.15 CCPS Guidelines for Preventing Human Error in Process Safety

Notation

References

Chapter 10. Safety Culture

10.1 Introduction of Safety Culture

10.2 Developments in Safety Culture

10.3 Evaluating and Implementing Safety Culture

10.4 Conclusion

References

Chapter 11. Emission, Dispersion, and Toxic Release

11.1 Emission

11.2 Two-Phase Flow

11.3 Vessel Depressurization

11.4 Pressure Relief Valves

11.5 Vessel Rupture

11.6 Pipeline Rupture

11.7 Vaporization

11.8 Dispersion

11.9 Dispersion Modeling

11.10 Passive Dispersion

11.11 Passive Dispersion: Models

11.12 Dispersion of Jets and Plumes

11.13 Dense Gas Dispersion

11.14 Dispersion of Dense Gas: Source Terms

11.15 Dispersion of Dense Gas: SLAB and FEM3

11.16 Dispersion of Dense Gas: DEGADIS

11.17 Dispersion of Dense Gas: Field Trials

11.18 Dispersion of Dense Gas: Particular Gases

11.18.1 Propane

11.19 Dispersion of Dense Gas: Plumes from Elevated Sources

11.20 Concentration and Concentration Fluctuations

11.21 Toxic Gas Clouds

11.22 Dispersion over Short Distances

11.23 Hazard Ranges for Dispersion

11.24 Source and Dispersion Modeling: CCPS Guidelines

11.25 Vapor Release Mitigation: Containment and Barriers

11.26 Vapor Cloud Mitigation: CCPS Guidelines

11.27 Fugitive Emissions

11.28 Classification of Models

11.29 Toxic Effects

11.30 Toxic Substances

11.31 Toxicity Assessment

11.32 Control of Toxic Hazard: Regulatory Controls

11.33 Hygiene Standards

11.34 Hygiene Standards: Occupational Exposure Limits

11.35 Dusts

11.36 Metals

11.37 Emergency Exposure Limits

11.38 Gas Toxicity

11.39 Plant Design for Toxic Substances

11.40 Toxic Gas Detection

11.41 Toxic Release Response

11.42 Toxic Release Risk

11.43 Hazard Assessment Methodology

References

Chapter 12. Fire

12.1 Fire

12.2 Flammability of Gases and Vapors

12.3 Flammability of Aerosols

12.4 Ignition

12.5 Fire in Process Plant

12.6 Effects of Fire: Damages and Injuries

12.7 Fire Protection of Process Plant

12.8 Fire Protection Applications

12.9 Fire Hazard

References

Chapter 13. Explosion

13.1 Explosions

13.2 Detonation

13.3 Explosion Energy

13.4 Deflagration Inside Plant

13.5 Detonation Inside Vessels and Pipes

13.6 Explosions in Closed Vessels

13.7 Explosions in Buildings and Large Enclosures

13.8 Explosion Prevention and Protection

13.9 Explosion Venting of Vessels

13.10 Explosion Venting of Ducts and Pipes

13.11 Explosion Relief of Buildings

13.12 Venting of Reactors

13.13 Venting of Reactors and Vessels: DIERS

13.14 Venting of Reactors and Vessels: Vent Flow

13.15 Venting of Reactors and Vessels: Vent Sizing

13.16 Venting of Reactors and Vessels: Leung Model

13.17 Venting of Reactors and Vessels: ICI Scheme

13.18 Venting of Reactors: Relief Disposal

13.19 Venting of Storage Vessels

13.20 Explosive Shock in Air

13.21 Condensed Phase Explosions

13.22 Vessel Burst Explosions

13.23 Vapor Cloud Explosions

13.24 Boiling Liquid Expanding Vapor Explosions

13.25 Explosions in Process Plant

13.26 Effects of Explosions

13.27 Explosion Damage to Structures

13.28 Explosion Damage to Housing

13.29 Explosion Damage by Missiles

13.30 Explosion

13.31 Explosion Injury

13.32 Dust Explosions

13.33 Explosion Hazard

13.34 Hazard Range of Explosions

References

Chapter 14. Plant Commissioning and Inspection

14.1 Plant Commissioning

14.2 Plant Inspection

14.3 Pressure Vessel Inspection

14.4 Pressure Piping Systems Inspection

References

Chapter 15. Plant Operation

15.1 Inherently Safer Design to Prevent or Minimize Operator Errors

15.2 Operating Discipline

15.3 Best Operating Practices

15.4 Operating Procedures and Instructions

15.5 Emergency Procedures

15.6 Handover and Permit Systems

15.7 Operator Training and Functions

15.8 Operation, Maintenance, and Modification

15.9 Start-Up and Shut-Down

15.10 Operation of Storage

15.11 Sampling

15.12 Trip Systems

15.13 Identification Measures

15.14 Exposure of Personnel

15.15 Security

Acronyms

References

Chapter 16. Storage and Transport

16.1 General Considerations for Storage

16.2 Storage Tanks and Vessels

16.3 Selection of Materials for Storage Tanks

16.4 Storage Layout

16.5 Venting and Relief

16.6 Fire Prevention and Protection

16.7 Transport Hazards

16.8 Size of Units for Transport

16.9 Transport Containers

16.10 Road Transport

16.11 Road Network and Vehicles

16.12 Waterway Transport

16.13 Pipeline Transport

16.14 Marine Transport: Shipping

16.15 Tank Farms

References

Chapter 17. Emergency Planning

17.1 Introduction

17.2 On-Site Emergency Planning

17.3 Resources and Capabilities

17.4 Developing an Emergency Plan

17.5 Training

17.6 Essential Functions and Nominated Personnel

17.7 Declaration and Communication of the Emergency

17.8 Evacuation

17.9 Cooperation and Drills

17.10 Public Relations

17.11 Off-Site Emergency Planning

17.12 Transport Emergency Planning

17.13 Emergency Planning for Disasters

17.14 Spectators

17.15 Recovery

17.16 Regulations and Standards

References

Chapter 18. Personal Safety

18.1 Human Factors

18.2 Occupational Health

18.3 Generation of Contaminants

18.4 COSHH Regulations 1988

18.5 Dust Hazards

18.6 Local Exhaust Ventilation

18.7 Skin Disease

18.8 Physico-chemical Hazards

18.9 Ionizing Radiation Hazards

18.10 Non-ionizing Radiation

18.11 Machinery Hazards

18.12 Electricity Hazards

18.13 Personal Protective Equipment

18.14 Rescue and First Aid

18.15 Ergonomics

18.16 Noise

References

Chapter 19. Accident Research and Investigation

19.1 Accident Research

19.2 General Incident Investigation Concepts

19.3 Evidence Issues

19.4 The Investigation Team

19.5 Identifying Root Causes

19.6 Reports

19.7 Databases

References

Chapter 20. Computer Aids and Expert Systems

20.1 Knowledge Representation

20.2 Structured Knowledge

20.3 Problem-Solving, Games, and Vision

20.4 Learning

20.5 Neural Networks

20.6 Graphs, Trees, and Networks

20.7 Databases, Bibliographies, and Indexes

20.8 Process Safety with Design and Optimization

20.9 Expert Systems

20.10 Qualitative Modeling

20.11 Engineering Design

20.12 Fault Propagation

20.13 Hazard Identification and Risk Evaluation

20.14 Fault Tree Analysis

20.15 Operating Procedure Synthesis

20.16 Process Monitoring

20.17 Advisory System

20.18 Information Feedback

20.19 Education and Teaching Aids

Acronyms

References

Chapter 21. Inherently Safer Design

21.1 Introduction

21.2 Definitions

21.3 History of Inherently Safer Design

21.4 Strategies for Process Risk Management

21.5 Inherently Safer Design Strategies

21.6 Inherently Safer Design Conflicts

21.7 Measuring Inherent Safety Characteristics of a Process

21.8 Inherently Safer Design and the Process Life Cycle

21.9 Implementing Inherently Safer Design

21.10 Inherent Safety and Chemical Plant Security

References

Chapter 22. Reactive Chemicals

22.1 Background

22.2 Strategies for Identifying and Characterizing Reactive Hazards

22.3 Identification of Reactive Hazards Scenarios

22.4 Reactive Hazards Risk Assessment

22.5 Batch Reactors: Basic Design

22.6 Likelihood Assessment

22.7 Prevention Measures

22.8 Mitigation Measures

22.9 Chemical Security

References

Chapter 23. Benchmarking in the Process Industry

23.1 Introduction

23.2 Benchmarking Outline

23.3 Possible Barriers and Resolutions for Benchmarking

23.4 Examples of Benchmarking Activities

References

Chapter 24. Liquefied Natural Gas

24.1 LNG Properties and Supply Chain

24.2 LNG Hazards

24.3 LNG Hazard Assessment

24.4 Safety Measures in LNG Facility

References

Chapter 25. Sustainable Development

25.1 Sustainable Development Concepts

25.2 Sustainable Development Principles for Engineering

25.3 Sustainability Measurement

25.4 Analytical Tools: LCA

References

Chapter 26. Case Histories

26.1 Introduction

26.2 Flixborough

26.3 Seveso

26.4 Mexico City

26.5 Bhopal

26.6 Pasadena

26.7 Canvey Reports

26.8 Rijnmond Report

26.9 San Carlos De La Rapita Disaster

26.10 Piper Alpha

26.11 Three Mile Island

26.12 Chernobyl

26.13 Hurricanes Katrina and Rita

26.14 BP America Refinery Explosion, Texas City, Texas, USA

26.15 Buncefield

26.16 Space Shuttle Columbia Disaster

26.17 Deepwater Horizon

Acronyms

References

Chapter 27. Laboratories and Pilot Plants

27.1 Laboratories

27.2 Pilot Plants

Acronyms

References

Chapter 28. Earthquakes

28.1 Earthquake Geophysics

28.2 Earthquake Characterization

28.3 Earthquake Effects

28.4 Earthquake Incidents

28.5 Earthquake Damage

28.6 Ground Motion Characterization

28.7 Ground, Soils, and Foundations

28.8 Earthquake-Resistant Design

28.9 Earthquake Design Codes

28.10 Dynamic Analysis of Structures

28.11 Seismicity Assessment and Earthquake Prediction

28.12 Design Basis Earthquake

28.13 Nuclear Installations

28.14 Process Installations

References

Chapter 29. Offshore Process Safety

29.1 North Sea Offshore Regulatory Administration

29.2 Gulf of Mexico Offshore Regulatory Administration

29.3 Offshore Process Safety Management

29.4 Offshore Incidents

29.5 Inherently Safer Design

29.6 Offshore Emergency Planning

29.7 Offshore Event Data

References

Chapter 30. Nuclear Energy and Safety

30.1 Regulation and Control of Nuclear Industry

30.2 Nuclear Reactors

30.3 Nuclear Waste Treatment

30.4 Nuclear System Reliability

30.5 Nuclear Hazard Assessment

30.6 Nuclear Reactor Operation

30.7 Nuclear Incident Reporting

30.8 Nuclear Incidents

30.9 Rasmussen Report

References

Index

Copyright

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Foreword

Hans Pasman

St. Julian’s, Malta, Spring 2013

Instigated by the tragic industrial accidents of his time, Professor Frank Lees, while writing and editing with passion the first edition of Loss Prevention in the Process Industries in the late 1970s, would never have anticipated that his brainchild would almost quadruple in number of pages. Lees was fully committed to process safety. And having the vision that it would become a discipline of its own, he was determined to create a compendium on loss prevention theory, safety concepts, hazard analysis methods, data, and case histories that was complete. But it all further developed, and Lees’ renewal in 1996 and Mannan’s continuations in 2004 and 2012 have been indispensable, because the field has expanded and intensified greatly.

That growth process still continues, since threats change in nature, challenges posed by technology, scale and intensity of operations, the business, the way we are organized, it all grows and changes. Competition and finite resources force us to scrutinize investments, also those in safety measures, but at the same time the risk of mishap can be disastrous to victims and also to the company that caused it. So, we need better guidance about what to do and more certainty that what we do will be right. In that respect, it is unfortunate that due to economic pressures in quite a number of countries, education in process safety, certainly on the academic level, is diminishing or disappearing. Experience learns that process safety concepts and methods look often rather simple from the outside but appear to require a host of background information and knowledge for successful application. Despite the electronic features of searching and linking in the fourth edition, the nearly 4000 pages may have the effect of missing the wood for the forest, or if on a search may induce the feeling of looking for a needle in a haystack, which both may produce rather frustrating results. Therefore, it has been an insightful initiative of Professor Sam Mannan to work with his crew of Ph.D. students and a team of enthusiastic reviewers on a trimmed down, skinny edition of only 500 pages in 30 chapters!

I hope this book of essentials will contribute much to foster process safety, to guide us to deeper knowledge, and to lay the basis for further developments. Nature is complex, to enable accurate prediction, physics, certainly in its details, is often hard to describe, the spectrum of technology is immensely wide and growing, the result of human action almost impossible to predict reliably, yet we are expected to determine process risks that may occur far less than once in a million years with an accuracy that satisfies CEOs and lawyers. Good success, and don’t think this book will be the end!

Chapter 1

Introduction

This chapter provides a basic introduction to the subject of process safety and the major concepts. Several overarching ideas and trends are introduced which will be elaborated upon in later chapters. The paramount importance of effective management and leadership is introduced. This chapter also presents a brief history of process safety and process safety regulations as well as a summary and discussion of several major trends in the process industries, including the trend toward larger, more integrated facilities. The commonalities between process safety and environmental protection are also discussed.

Keywords

Process safety; loss prevention; environmental quality; sustainability; process safety trend

Chapter Outline

1.1 Management Leadership

1.2 Industrial Safety and Loss Trends

1.3 Safety and Environmental Concerns

1.4 Historical Development of Loss Prevention

1.5 Loss Prevention Essentials

1.6 Environment and Sustainable Development

1.7 Responsible Care

1.8 Academic and Research Activities

1.9 Overview

References

Over the last four decades, there has developed in the process industries a distinctive approach to hazards and failures that cause loss of life and property. This approach is commonly called loss prevention. It involves putting much greater emphasis on technological measures to control hazards and on trying to get things right at the beginning. An understanding of loss prevention requires some appreciation of its historical development against a background of heightened public awareness of safety, and environmental problems, of its relation to traditional safety and also to a number of other developments.

1.1 Management Leadership

By the mid-1960s, it was becoming increasingly clear that there were considerable differences in the performance of companies in terms of occupational safety. These disparities could be attributed only to differences in management. There appeared at this time a number of reports on safety in chemical plants arising from studies by the British chemical industry of the safety performance in the US industry, where certain US companies appeared to have achieved an impressive record. These reports included Safety and Management by the Association of British Chemical Manufacturers (ABCM) (1964, p. 3), Safe and Sound and Safety Audits by the British Chemical Industry Safety Council (BCISC) (1969, p. 9; 1973, p. 12). The companies concerned attributed their success entirely to good management, and this theme was reflected in the reports.

1.2 Industrial Safety and Loss Trends

Around 1970, it became increasingly recognized that there was a worldwide trend for losses, due to incidents, to rise more rapidly than gross national product (GNP).

This may be illustrated by the situation in the United Kingdom. The first half of this century saw a falling trend in personal incidents in British factories, but about 1960, this fall bottomed out. Over the next decade, very little progress was made; in fact there was some regression. Figure 1.1 shows the number of fatal incidents and the total number of incidents in factories over the period 1961–1974. The Robens Committee on Health and Safety at Work, commenting on these trends in 1972, suggested that part of the reason was perhaps the increasingly complex technology employed by industry (Robens, 1972).

Figure 1.1 (a) Fatalities and (b) total accidents in factories in the United Kingdom, 1961–1974. Source: Courtesy of the Health and Safety Executive; Robens (1972); HM Chief Inspector of Factories (1974).

Another important index is that of fire loss. The estimated fire damage loss in factories and elsewhere in the United Kingdom for the period 1964–1974 is shown in Figure 1.2.

Figure 1.2 Total fire losses in the United Kingdom, 1967–1974. Source: Courtesy of the British Insurance Association; British Insurance Association (1975).

1.3 Safety and Environmental Concerns

There was also at this time growing public awareness and concern regarding the threat to people and to the environment from industrial activities, particularly those in which the process industries are engaged. Taking the United Kingdom as an illustration, the massive vapor cloud explosion at Flixborough in 1974 highlighted the problem of major hazards. This led to the setting up of the Advisory Committee on Major Hazards (ACMH) that sat from 1975 to 1983 and to the introduction of legislation to control major hazard installations. Likewise, there was a continuous flow of legislation to tighten up both on emissions from industrial installations and on exposure of workers to noxious substances at those installations.

Similarly, in the United States, the Bhopal incident as well as other highly publicized tragedies (Flixborough, 1974; Seveso, 1976; Three Mile Island, 1979; Cubato, February 1984; Mexico City, November 1984; Houston, 1989) caused widespread public concerns about major incidents in US chemical plants that might disastrously affect the public. Not only was the public’s confidence in the chemical industry shaken, but also the chemical industry itself questioned whether its provisions for protection against major accidental releases were adequate. The recognition of the chemical industry’s need for technical advances led to a number of initiatives. For example, in 1985, the Chemical Manufacturers Association (CMA—now known as the ACC, the American Chemistry Council) published its guidelines on Process Safety Management, and the American Institute of Chemical Engineers (AIChE) created the Center for Chemical Process Safety (CCPS) with significant financial support by industry. Over the next several years, many other centers such as the National Institute for Chemical Safety, the National Environmental Law Center, and the Mary Kay O’Connor Process Safety Center also came into existence. During this same period, the United States Environmental Protection Agency (USEPA) and the Occupational Safety and Health Administration (OSHA) of the United States Department of Labor started several technical initiatives aimed at gathering information about major accident risks.

It is against this background, therefore, that the particular problems of the process industries should be viewed. The chemical, oil, and petrochemical industries handle hazardous substances and have always had to devote considerable effort to safety. This effort is directed both to the safe design and operation of the installations and to the personal safety of the people who work on them. However, there was a growing appreciation in these industries that the technological dimension of safety was becoming more important.

1.4 Historical Development of Loss Prevention

The 1960s saw the start of developments that have resulted in great changes in the chemical, oil, and petrochemical industries. A number of factors were involved in these changes. Process operating conditions such as pressure and temperature became more severe. The energy stored in the process increased and represented a greater hazard. Problems in areas such as materials of construction and process control became more taxing. At the same time, plants grew in size, typically by a factor of about 10, and were often single stream. As a result they contained huge items of equipment, such as compressors and distillation columns. Storage, both of raw materials and products and of intermediates, was drastically reduced. There was a high degree of interlinking with other plants through the exchange of by-products.

The operation of such plants is relatively difficult. Whereas previously chemical plants were small and could be started up and shut-down with comparative ease, the start-up and shut-down of a large, single-stream plant on an integrated site is a much more complex and expensive matter. These factors resulted in an increased potential for loss—both human and economic. Such loss may occur in various ways. The most obvious is the major incident, usually arising from loss of containment and taking the form of a serious fire, explosion, or toxic release. But loss due to such situations as delays in commissioning and downtime in operating is also important.

The chemical and oil industries have always paid much attention to safety and have a relatively good record in this respect. In the United Kingdom, for example, the fatal accident rate for the chemical industry has been about equal to that for industry generally, which in view of the nature of the industry may be regarded as reasonable. However, the increasing scale and technology of modern plants caused the chemical industry to re-examine its approach to the problem of safety and loss. If the historical development of this concern in the United Kingdom is considered, there are several problem areas that can be seen, in retrospect, to have given particular impetus to the development of loss prevention.

One of these is the problem of operating a process under extreme conditions and close to the limits of safety. This is usually possible only through the provision of relatively sophisticated instrumentation. About the mid-1960s, several such systems were developed. One of the most sophisticated, influential, and well documented was the high integrity protective system developed by R.M. Stewart (1971) for the ethylene oxide process. Around that same time, many difficulties were being experienced in the commissioning and operation of large, single-stream plants, such as ethylene and ammonia plants, involving severe financial loss. On the design side, too, there was a major problem in getting value for money in expenditure aimed at improving safety and reducing loss. It was increasingly apparent that a more cost-effective approach was needed.

These developments did not take place in isolation. The social context was also changing and other themes, notably pollution, including effluent and waste disposal and noise, were becoming of increasing concern to the public and the government. In consequence, the industry was obliged to examine the effects of its operations on the public outside the factory fence and, in particular, to analyze more carefully the possible hazards and to reduce emissions and noise. Another matter of concern was the increasing quantities of chemicals transported around the country by road, rail, and pipeline. The industry had to take steps to show that these operations were conducted with due regard to safety. In sum, by the 1970s, these problems became a major preoccupation of senior management. Management’s recognition of the problems and its willingness to assign many senior and capable people as well as other resources to their solution has been fundamental in the development of loss prevention.

The historical development of loss prevention is illustrated by some of the milestones listed in Table 1.1. The impact of events has been different in different countries. Within the industry, loss prevention emerged as a theme of technical meetings which indicated an increasingly sophisticated technological approach. The Institution of Chemical Engineers (IChemE) established a Loss Prevention Panel which operates an information exchange scheme and publishes the Loss Prevention Bulletin. This growing industrial activity was matched in the regulatory sphere. The Robens Committee (1972) emphasized the need for an approach to industrial safety that is more adapted to modern technology and recommended self-regulation by industry as opposed to regulation from outside. This philosophy is embodied in the Health and Safety at Work Act 1974 (HSWA), which provides the framework for such an approach. However, the Act does more than this. It lays a definite statutory requirement on industry to assess its hazards and demonstrate the effectiveness of its safety systems. It is enforced by the Health and Safety Executive (HSE). The General Duty Clause requirements under US regulations enforced by OSHA and USEPA have been interpreted similarly.

Table 1.1

Some Milestones in the Development of Loss Prevention

The disastrous explosion at Flixborough in 1974 has proved to be a watershed event. Taken in conjunction with the Act, it has greatly raised the level of concern for SLP in the industries affected. It also led, as mentioned, to the setting up of the ACMH. The incident at Seveso in 1976 has been equally influential. It had a profound impact in Continental Europe and was the stimulus for the development of the EC Directive on Control of Industrial Major Accident Hazards in 1982. Further disasters such as those at San Carlos, Bhopal and Mexico City, Buncefield, Texas City, and Deepwater Horizon have reinforced these developments.

1.5 Loss Prevention Essentials

The area of concern and the type of approach which goes by the name of loss prevention is a development of safety work. But it is a response to a changing situation and need, and it has certain particular characteristics and emphases. The essential problem which loss prevention addresses is the scale, depth, and pace of technology. In fact, control of such hazards is possible only through effective management. The primary emphasis in loss prevention is, therefore, on the management system. This has always been true, of course, with regard to safety. But high technology systems are particularly demanding in terms of formal management organization, competent persons, systems and procedures, and standards and codes of practice. On top of all of this, there is a growing realization that safety performance is quite often influenced by the safety culture of the company.

The 2003 Columbia shuttle disaster and the following investigation report bring to light some of NASA’s safety culture issues that may have doomed Columbia as well as Challenger. The 2005 BP Refinery Explosion in Texas City reminded the importance of good safety culture again through the consequence of 15 fatalities and a loss of 1.5 billion dollars. The long list of root causes of this disaster includes lack of management of addressing major hazard control, ineffective role and responsibility of organization, lack of reporting and learning from near-misses, and inadequate resources dedicated to prevent major accidents. Most of the root causes concluded that the lack of safety culture leadership caused the failure of many layers of protection.

According to Mannan (2003a), we should pay more attention to safety culture. One school of thought is that safety culture even though a very important issue is not a specific problem of process safety or loss prevention. However, it seems there is a special set of problems that go along with extreme events and the associated risks. Before the event there is great confidence that such a thing could never happen. Afterward there is denial and no cultural change occurs. This may be true of NASA as well as some process companies. What are the attributes of a good safety culture? How do organizations build a good safety culture and maintain it over the life of the organization? How can the safety culture survive changing leaderships, turnovers, budget pressures, early retirements, and other changes? How can we get organizations that do not have a good safety culture make the necessary changes to move toward a good safety culture? These are questions that should be answered.

Mannan (2003a) goes on to describe the investigation of one incident where everyone involved felt that they had done everything they were supposed to do and the incident was just something that was beyond anyone’s control. In fact, a few people in the organization even claimed that if the same set of circumstances were to happen again, the same incident would occur again, possibly with the same consequences. Now, that is a safety culture that needs major overhaul.

Mannan (2003b) states that there are a number of attributes of a good safety culture. It is quite difficult to identify objective characteristics of a good safety culture. However, some known characteristics include:

1. Commitment AND involvement of the highest level personnel.

2. Open communication at all levels of the organization.

3. Everyone’s responsibilities and accountabilities regarding safety are clearly defined and understood.

4. Safety is second nature.

5. Zero tolerance for disregard of management systems, procedures, and technology.

6. Information systems allow all parties access to design, operational, and maintenance data.

As part of a multi-layered approach for a good safety culture, organizations use analysis of trends to spot problems. Trend analysis should be focused on leading as well as trailing metrics (indicators). The metrics are utilized to measure the performance of corporations at all levels. Process safety metrics can provide valuable information about plant operations, maintenance, and human behaviors. Establishing uniform metrics will benefit the comparison between different plants, businesses, and companies. However, the selection of indicators for metrics should be sophisticated because they should provide measurable and accurate performance for safety. The CCPS Guidelines for Process Safety Metrics (CCPS, 2009) recommends different metrics, such as absolute metrics, normalized metrics, and near-miss metrics.

A lagging indicator is a downstream measurement of the outcomes of safety and health efforts. These indicators reflect successes or failures of the system to manage hazards. Examples of lagging indicators include fatalities, injuries, and incidents. A leading indicator is an upstream measure that characterizes the level of success in managing safety systems; measurement of activities toward risk reduction prior to occurrence of incidents. While every effort should be made to measure and track lagging indicators, relying on the lagging indicators to assess safety performance is self-defeating. Thus, it is very important to measure and track leading indicators, particularly for high-risk activities such as space flight. Leading indicators, however, are more difficult to define and measure and vary according to the activity and the mission of the organization. Examples of leading indicators might include:

1. the level of near-miss reporting;

2. effectiveness of incident investigation and corrective action;

3. management of change;

4. emphasis on inherently safer design;

5. effective application of risk assessments;

6. level of deferred maintenance;

7. level of repetitive maintenance;

8. number and severity of faults detected by inspection, testing, and audits;

9. number and nature of unresolved safety issues;

10. participation in continuing education and symposia;

11. employee morale, level of expertise.

Thus, loss prevention is characterized by

1. an emphasis on management and management systems, particularly for technology;

2. a concern with hazards arising from technology;

3. a concern with major hazards;

4. a concern for integrity of containment;

5. a systems rather than a trial-and-error approach;

6. techniques for identification of hazards;

7. a quantitative approach to hazards;

8. quantitative assessment of hazards and their evaluation against risk criteria;

9. techniques of reliability engineering;

10. the principle of independence in critical assessments and inspections;

11. planning for emergencies;

12. incident investigation;

13. a critique of traditional practices or existing regulations, standards or codes where these appear outdated by technological change.

The identification of hazards is obviously important, since the battle is often half won if the hazard is recognized. A number of new and effective techniques have been developed for identifying hazards at different stages of a project. These include hazard indices, chemicals screening, hazard and operability studies, and plant safety audits.

Basic to loss prevention is a quantitative approach, which seeks to make a quantitative assessment, however, elementary. This has many parallels with the early development of operational research. This quantitative approach is embodied in the use of quantitative risk assessment (QRA). The assessment produces numerical values of the risk involved. These risks are then evaluated against risk criteria. However, the production of numerical risk values is not the only, or even the most important, aspect. A QRA necessarily involves a thorough examination of the design and operation of the system. It lays bare the underlying assumptions and the conditions that must be met for success and usually reveals possible alternative approaches. It is therefore an aid to decision-making on risk, the value of which goes far beyond the risk numbers obtained.

Reliability engineering is now a well-developed discipline. Loss prevention makes extensive use of the techniques of reliability engineering. It also uses other types of probabilistic calculation that are not usually included in conventional treatments of reliability, such as probabilities of weather conditions or effectiveness of evacuation. Certain aspects of a system may be particularly critical and may require an independent check. Examples are independent assessment of the reliability of protective systems, independent audit of plant safety, and independent inspection of pressure vessels.

Planning for emergencies is a prominent feature of loss prevention work. This includes both works and transport emergencies.

Investigation of incidents plays an important part in loss prevention. Frequently there is some aspect of technology involved. But the recurring theme is the responsibility of management. While a good safety culture varies according to the mission and activities of the organization, one of the attributes of a good safety culture that is a ‘must’ is ‘learning from incidents’. There is no excuse when ‘lessons learned’ from incidents are ignored or not implemented, particularly ‘lessons learned’ from incidents that have occurred in one’s own organization or incidents that are widely publicized. One of root causes of the 2005 Buncefield tank farm explosion is lack of learning culture. After the incident, people claimed that cold gasoline had never resulted in a vapor cloud explosion. But actually some similar incidents had already been stated in a review of past incidents (Kletz, 1986). The ignorance of past incidents and lack of learning ability can directly lead to the inadequate hazard identification and risk assessment.

Both 2005 Texas City and Buncefield incidents saw the need to perform facility siting studies in permanent and portable occupied buildings. Facility siting evaluates the effects of an incident on the plant area and also the influence to surrounding community. The effects include loss of life, loss of damage, business interruption, and environment as well. Adequate separation between process plants, between equipment and control room, and between tanks and site boundary should be provided by risk assessment. CCPS Guidelines for Facility Siting and layout (CCPS, 2003) gives the most conservative guidance. API 752 and 753 provide guidance to control hazards associated with both permanent and temporary occupied buildings siting problems. In the research area, consequence modeling and optimization methods are currently investigated and have been recommended to find the optimized siting.

The 2010 Deepwater Horizon blowout, which is the largest oil spill incident in the history of America, gained worldwide attention and revealed a series of management and technical gaps in the field of offshore drilling process. The loss of 11 lives and the short-term and long-term environmental impacts have brought the world a big lesson. The trade-off between safety and production, management of change in drilling procedures, planning for emergencies, lessons learned from similar near-misses, and design of blowout preventer system are the main topics that should be improved. The loss prevention approach takes a critical view of existing regulations, standards, rules, or traditional practices where these appear to be outdated by changing technology. Illustrations are criticisms of incident reporting requirements and of requirements for protection of pressure vessels. These developments taken as a whole do constitute a new approach and it is this which characterizes the loss prevention.

Another concept that is gaining increasing prominence is that of safety-critical systems. These are the systems critical to the safe operation of some larger system, whether this is a nuclear power station or a vehicle. In a modern aircraft, particularly of the fly-by-wire type, the computer system is safety critical.

It might perhaps be inferred from the foregoing that the problems which have received special emphasis in loss prevention are regarded somehow as more important than the aspects, particularly personal incidents, with which traditionally safety work in the process industries has been largely concerned. Nothing could be further from the truth. It cannot be too strongly emphasized that mundane incidents are responsible for many more injuries and deaths than those arising from high technology.

1.6 Environment and Sustainable Development

Another major concern of the process industries is the protection of the environment. Developments in environmental protection (EP) have run in parallel with those in SLP. These two aspects of process plant design and operation have much in common and there has been a tendency to assign the same person responsibilities for both. There are some situations where there is a potential conflict between the two, where the safest option has the potential for acute or chronic environmental damage. This can effect decisions regarding equipment venting, flaring, bleeding of dangerous process impurities, leak control of toxic and flammable streams, using halons and other chemicals in fire suppression systems.

Europe and the United States have seen a growing awareness of the need for environmental protection since the 1960s, which led to a growing number of regulations and laws, mostly in the 1970s, 1980s, and early 1990s. In the United States, these laws include the Control of Pollution Act (1974), Air Pollution Control Act (1975), Comprehensive Environmental Resource Conservation and Liability Act (1980), Superfund Amendments and Reauthorization Act (1986), Water Act (1989), Environmental Protection Act (1990), Clean Air Act (1963), and the various amendments to these laws. In Europe, various European Commission Directives play a role in setting pollution control standards for the European Union. There are also advisory bodies on pollution including the Royal Commission on Environmental Pollution (RCEP). The Environmental Protection Agency in the US also provides guidance.

Engineers have the responsibility of adhering to the professional codes and standards, obeying pertinent legislation, fulfilling their job descriptions and terms of employment, and utilizing the information gained through their formal education. All of these responsibilities must be satisfied.

Common elements in an environmental protection plan include use of inherently safer and cleaner design, reduction of intermediate storage, identification, assessment and modeling of hazards, control of fugitive emissions, assessment of environmental impact, and communication with the public. Environmental protection should take a total life cycle approach and consider the final environmental fate of chemicals and wastes produced as well as the chemical capacity of the environment. The different requirements and concerns with regard to liquid, solid, or gaseous pollutants, hazardous vs non-hazardous wastes, reactive vs inert wastes, and different means of disposal, like incineration vs landfill, must all be considered. Environmental monitoring, emergency response planning, spill containment and control, and post-spill clean-up procedures and plans should also be in place, with the facility and responsible parties ready to implement the response and clean-up plans.

The control and management of noxious or unpleasant odors can also be a significant concern depending on odor thresholds, regulations pertaining to odors, and the extent of the impact on the surrounding community. There are a number of methods available for treating air contaminated with odors. Accounts are given by Valentin (1990) and A.M. Martin et al. (1992).

Good environmental protection programs, hand in hand with good safety and loss prevention programs, have been shown to produce cost savings, particularly through reduction in waste generation and clean-up costs. Costs and savings may be computed at a national or company level.

To accomplish the balance between environmental, economic, and social pressures, the concept of sustainable development has been developed in the last two decades. Continuous effort of improving disciplines, technologies, and government strategies toward creating sustainable processes and products has been made, especially for the evaluation of sustainability and life cycle analysis. The tenet of sustainability has been studied a lot in the past decade.

1.7 Responsible Care

In a number of countries, the chemical industry has responded to safety, health, and environmental concerns with the Responsible Care initiative, which was developed in the early 1980s by the Canadian Chemical Producers Association and was then taken up in 1988 in the United States by the ACC, in 1989 in the United Kingdom by the Chemical Industries Association (CIA), and elsewhere.

Companies participating in Responsible Care commit themselves to achieving certain standards in terms of safety, health, and environment. Guidance is given in Responsible Care (CIA, 1992 RC53) and Responsible Care Management Systems (CIA, 1992 RC51). As stated earlier, in 1973, the IChemE created a Loss Prevention Panel. The Institution itself publishes a range of monographs and books on SLP and the panel publishes the Loss Prevention Bulletin and a range of aids for teaching and training. In 1985, the AlChE formed the CCPS. The Center publishes a series of guidelines on SLP issues.

At the European level, the European Process Safety Centre (EPSC) was set up in 1992 to disseminate information on safety matters, including legislation, research and development, and education and training (EPSC, 1993).

1.8 Academic and Research Activities

Over the years, academic and research activities aimed at process SLP have ebbed and flowed. However, lately these activities are becoming more formalized. Engineering departments in various universities throughout the world have begun to realize the importance of the subject and the significant role they can play in educating the students and the solution of industry problems through fundamental research. Many universities in the United States, United Kingdom, elsewhere in Europe, Japan, Korea, China, and other countries now offer specialized courses, certificate programs, and degree programs on process SLP. In some universities, for example Texas A&M University and University of South Carolina, process safety courses instead of being optional electives are now part of the required core curriculum. University professors and researchers are also dedicating extensive efforts toward research topics on process SLP. With regard to academic and research activities, the Mary Kay O’Connor Process Safety Center at Texas A&M University is a classic example of a comprehensive academic and research program dedicated to education, research, and service activities on process SLP.

1.9 Overview

The modern approach to the avoidance of injury and loss in the process industries is the outcome of the various developments just described. Central to this approach is leadership by management, starting with senior management, and creation of a safety culture that provides the appropriate environment for reduction of incidents and improvement of safety performance. Such leadership and safety culture are indispensable conditions for success. They are not, however, sufficient conditions. Management must also identify the right objectives.

As far as the process industries are concerned, it is the contribution of loss prevention to handle the technological dimension and to provide methods by which failure is eliminated. In the modern approach to SLP, these themes come together. The ends are the safety of personnel and the avoidance of loss. The means to achieve both these aims is leadership by management, informed by an understanding of the technology and directed towards the elimination of failures of all kinds.

References

1. Association of British Chemical Manufacturers (ABCM), 1964. Safety and management. Report number: 3.

2. British Chemical Industry Safety Council (BCISC), 1969. Safety and sound. Report number: 9.

3. British Chemical Industry Safety Council (BCISC), 1973. Safety audits. Report number: 12.

4. British Insurance Association, 1975. Insurance Facts and Figures 1974, London.

5. Center for Chemical Process Safety (CCPS). Guidelines for Facility Siting and Layout Wiley-AIChE 2003.

6. Center for Chemical Process Safety. Guidelines for Process Safety Metrics New York, NY: CCPS, AIChE; 2009.

7. Chemical Industries Association (CIA), 1992. RC53 Responsible care.

8. Chemical Industries Association (CIA), 1992. RC51 Responsible care management systems.

9. European Process Safety Centre, 1993. Annual Report, Rugby.

10. HM Chief Inspector of Factories, 1974. Annual Report of HM Chief Inspector of Factories 1974. HM Stationery Office, London.

11. Kletz TA. Accident reports and missing recommendations. Loss Prev Saf Promotion. 1986;5:20–21.

12. Mannan, M.S., 2003a. Director’s Corner, Centerline, Mary Kay O’Connor Process Safety Center Newsletter, vol. 7, no. 2, 2003 Summer.

13. Mannan, M.S., 2003b. Director’s Corner, Centerline, Mary Kay O’Connor Process Safety Center Newsletter, vol. 7, no. 1, 2003 Spring.

14. Martin AM, Nolen SL, Gess PS, Baesen TA. Control odors from CPI facilities. Chem Eng Prog. 1992;88(12):53.

15. Robens, L., 1972. Safety and Health at Work. Cmnd 5034, HM Stationery Office, London.

16. Stewart RM. High integrity protective systems. Major Loss Prev. 1971;99.

17. Valentin FHH. Making chemical-process plants odor-free. Chem Eng. 1990;97(1):112.

Chapter 2

Incidents and Loss Statistics

This chapter serves two main purposes: to highlight incident and loss statistics in different parts of the world with emphasis on risk perception and hazard awareness and to review current insurance issues that may arise in the case of incident or loss. Incident models are introduced to analyze root causes of incidents and assist in hazard analysis. In addition, sources for injury statistics data are reviewed and summarized for the United States and United Kingdom. Major hazards are discussed with an emphasis on hazard mitigation and planning from different areas of the world. Lastly, in case of an incident, the insurance practices behind loss and process incidents are reviewed.

Keywords

Incident process; injury statistics; risk perception; risk management; process hazard control; insurance process; causes of loss; economics of loss prevention

Chapter Outline

2.1 The Incident Process

2.1.1 The Houston Model

2.1.2 Other Incident Models

2.2 Injury Statistics

2.2.1 United States of America

2.2.2 United Kingdom

2.3 Major Disasters

2.4 Major Process Hazards

2.4.1 The Inventory

2.4.2 The Energy Factor

2.4.3 The Time Factor

2.4.4 The Intensity – Distance Relationship

2.4.5 The Exposure Factor

2.4.6 The Intensity – Damage and Intensity – Injury Relationships

2.5 Major Hazard Control

2.5.1 Hazard Monitoring

2.5.2 Risk Issues

2.5.3 Risk Perception

2.5.4 Risk Management

2.5.5 Hazard Control Policy

2.5.6 Process Hazard Control: Advisory Committee on Major Hazards

2.5.7 Process Hazard Control: Major Hazards Arrangements

2.5.8 Process Hazard Control: Planning

2.5.9 Process Hazard Control: European Community

2.5.10 Process Hazard Control: USA

2.6 Fire and Explosion Loss

2.7 Causes of Loss

2.8 Trend of Injuries and Losses

2.9 Economics of Loss Prevention

2.9.1 Cost of Losses

2.9.2 Cost of Prevention

2.10 Insurance of Process Plant

2.10.1 The Insurance Process

2.10.2 Insurance Policies

2.10.3 Loss Measures

2.10.4 Insurance Surveyors

2.10.5 Tariff and Non-Tariff Systems

2.10.6 Fire Insurance in the United Kingdom

2.10.7 Business Interruption Insurance

2.10.8 Large, Single-Train Plants

2.10.9 Insurance Market

2.10.10 Insurance Capacity

2.10.11 Insurance Restrictions

2.10.12 Self-Insurance

2.10.13 Vapor Cloud Explosions

2.10.14 Major Disasters

2.11 Property Insurance

2.11.1 Loss Measures

2.11.2 Risk Assessment Methods

2.11.3 Checklists

2.11.4 Hazard Indices

2.11.5 Premium Rating Plans

2.11.6 Estimation of EML

2.11.7 Risk Assessment Approaches

2.12 Individual Insurance

2.13 Business Interruption Insurance

2.14 Other Insurance Aspects

2.14.1 Insurance Credit

2.14.2 Insurance in Design

2.14.3 Insurers’ Advice

2.14.4 Loss Adjusters

2.14.5 Loss Data and Analysis

References 

It is important in industrial processes to limit (and ideally eliminate) process incidents and their effects. For this to occur it is necessary to analyze hazards and identify root causes of incidents, determine the expected frequency of incidents, and have a financial plan to assure that the company can cover any expenses it incurs. These goals can be reached through proper hazard analysis, statistical information from proper sources, and proper insurance plans. These areas are discussed in greater detail throughout this chapter.

2.1 The Incident Process

Although in some reporting schemes the investigator is required to determine the cause of the incident, it frequently appears meaningless to assign a single cause as the incident has arisen from a particular combination of circumstances. Second, it is often found that the incident has been preceded by other incidents that have been ‘near-misses’. These are cases where most but not all of the conditions for the incident were met. A third characteristic of incidents is that when the critical event has occurred, there are wide variations in the consequences. In one case there may be no injury or damage, while in another case that is similar in most respects, there is some key circumstance that results in severe loss of life or property.

It is helpful to model the incident process in order to understand more clearly the factors that contribute to incidents and the steps that can be taken to avoid them. One type of model, discussed by Houston (1971), is the classical one developed by lawyers and insurers who focuses attention on the ‘proximate cause’. It is recognized that many factors contribute to an incident, but for practical, and particularly for legal, purposes, a principal cause is identified. Several incident process models will be discussed to show more details, starting with the Houston model.

2.1.1 The Houston Model

The model given by Houston (1971, 1977) is shown schematically in Figure 2.1. Three input factors are necessary for the incident to occur: (1) target, (2) driving force, and (3) trigger. Principal driving forces are energy and toxins. The target has a threshold intensity θ below which the driving force has no effect. The trigger also has a threshold level θ′ below which it does not operate.

Figure 2.1 Houston model of the accident process. Source: After Houston (1977).

The development of the incident is determined by a number of parameters. The contact probability p is the probability that all the necessary input factors are present. The contact efficiency ε defines the fraction of the driving force that actually reaches the target, and the contact effectiveness η is the ratio of damage done to the target under the actual conditions compared to that done under standard conditions. The contact time t is the duration of the process.

The model indicates a number of ways in which the probability or severity of the incident may be reduced. One of the input factors (target, driving force, or trigger) may be removed. The contact probability may be minimized by preventive action. The contact efficiency and contact effectiveness may be reduced by adaptive reaction.

2.1.2 Other Incident Models

A simple fault tree model that can be constructed for an incident is given in Figure 2.2. An initiating event occurs which constitutes a potential incident, but often only if some enabling event occurs, or has already occurred. An incident occurs that develops into a more severe incident only if mitigation fails.

Figure 2.2 Fault tree model of the accident process.

A more complex fault tree model is that used in the management oversight and risk tree (MORT) developed by Johnson (1980). This tree is the basis of a complete safety system.

The ACSNI model was proposed by the Advisory Committee on the Safety of Nuclear Installations (ACSNI, 1993). The model provides a general framework that can be used to identify latent failures that are likely to lead to critical errors.

The Bellamy and Geyer model emphasizes the broader, socio-technical background to incidents and was developed by Bellamy and Geyer (1991).

Another approach is that discussed by Kletz (1988), who has developed a model oriented to incident investigation. The model is based essentially on the sequence of decisions and actions that lead up to an incident and shows against each step the recommendations arising from the investigation.

2.2 Injury Statistics

2.2.1 United States of America

In the United States, many federal agencies gather information about the chemical industry. These federal databases, some of which have received information for over three decades, may provide the information needed to develop trends of chemical-related incidents.

Six US federal databases provide information about incidents and incident statistics related to chemical safety at fixed facilities. They are as follows:

1. National Response Center’s (NRC) Incident Reporting Information System (IRIS)

2. EPA’s Risk Management Program (RMP) Rule’s 5-year Accident History Database

3. EPA’s Accidental Release Information Program (ARIP) Database

4. Bureau of Labor Statistics’ (BLS) Databases for the US Occupational Safety and Health Administration (OSHA)

5. US Centers for Disease Control and Prevention’s (CDC) Wide-ranging On-line Data for Epidemiological Reporting (WONDER)

6. US Department of Health and Human Services’ Agency for Toxic Substances and Disease Registry’s (ATSDR) Hazardous Substances Emergency Events Surveillance (HSEES) Database.

2.2.2 United Kingdom

In the United Kingdom, the definition of a major injury changed with the introduction of the Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 1985 (RIDDOR). The Health and Safety Statistics 1990–1991 (HSE, 1992) show that in 1990–1991 there were 572 fatalities reported under RIDDOR, of which 346 were to employees, 87 to the self-employed, and 139 to members of the public. The fatal injury incidence rate for employees was 1.6 per 100,000 workers.

2.3 Major Disasters

It is appropriate at this point briefly to consider major disasters. A list of the worst disasters in certain principal categories, both for the world as a whole and for the United Kingdom, is given in Table 2.1.

Table 2.1

Some of the Worst Non-Industrial and Industrial Disasters Worldwide

aThe Guinness Book of Records states: Thirty one was the official Soviet total of immediate deaths. On April 25, 1991 Vladimir Shovkoshitny stated in the Ukrainian Parliament that 7000 clean-up workers had already died from radiation. The estimate for the eventual death toll has been put as high as 75,000 by Dr Robert Gale, a US bone transplant specialist.

bThe Guinness Book of Records states: There were no deaths as a direct result of the fire, but the number of cancer deaths which might be attributed to it was estimated by the National Radiological Protection Board in 1989 to be 100.

Source: Material from Guinness Book of Records, copyright © reproduced by permission of the publishers.

Those that are of primary concern in the present context are fire, explosion, and toxic release. The explosion at Halifax which killed 1963 people was that of a ship carrying explosives. The Chilwell explosion, in which 134 people died, was in an explosives factory. The toxic gas release at Bhopal, where the death toll was some 2500, was an escape of methyl isocyanate from a storage tank.

2.4 Major Process Hazards

The major hazards with which the chemical industry is concerned are fire, explosion, and toxic release. Of these three, fire is the most common but, as shown later, explosion is particularly significant in terms of fatalities and loss. As already mentioned, in the United Kingdom, the explosion at Flixborough killed 28 people, while offshore 167 men died in the explosion and fire on the Piper Alpha oil platform. Toxic release has perhaps the greatest potential to kill a large number of people. Large toxic releases are very rare but, as Bhopal indicates, the death toll can be very high. There have been no major toxic release disasters in the United Kingdom.

The problem of avoiding major hazards is essentially that of avoiding loss of containment. This includes not only preventing an escape of materials from leaks, etc., but also avoidance of an explosion inside the plant vessels and pipework. Some factors that determine the scale of the hazard are as follows:

2.4.1 The Inventory

The most fundamental factor that determines the scale of the hazard is the inventory of the hazardous material. The larger the inventory of material, the greater the potential loss.

2.4.2 The Energy Factor

For an inventory of hazardous material to explode inside the plant or to disperse in the form of a flammable or toxic vapor cloud, there must be energy. In most cases, this energy is stored in the material itself as the energy either of chemical reaction or of material state.

2.4.3 The Time Factor

Another fundamental factor is the development of the hazard in time. The time factor affects both the rate of release and the warning time.

2.4.4 The Intensity–Distance Relationship

An important characteristic of the hazard is the distance over which it may cause injury and/or damage. In general, fire has the shortest potential range, then explosion, and then toxic release, but this statement needs considerable qualification. The range of a fireball is appreciable, and the range of a fire or an explosion from a vapor cloud is much extended if the cloud drifts away from its source.

2.4.5 The Exposure Factor

A factor