Risk Analysis and Reduction in the Chemical Process Industry

381 Pages·1998·9.347 MB·English

by  J. M. Santamaría Ramiro, P. A. Braña Aísa (auth.)

Risk Analysis and Reduction in the Chemical Process Industry
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Risk Analysis and Reduction in
the Chemical Process Industry
1. M. Santamarfa Ramiro
Department of Chemical Engineering
University of Zaragoza
Zaragoza, Spain
and
P. A. Brana Afsa
Amylum lberica, SA
Zaragoza, Spain
Translated by J. Hutchinson
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Contents
Foreword ix
Preface xi
1 Introduction and general concepts 1
1.1 Introduction I
1.2 Risks and hazards 4
1.3 Accidents and risk analysis 4
1.3.1 Quantifying the level of risk 6
1.4 Returns on risk analysis 7
1.5 Stages in risk analysis 9
1.5.1 Making decisions in matters of industrial safety 13
1.6 Risk analysis in the training of chemical industry professionals 14
2 Hazard identification techniques 16
2.1 Introduction 16
2.2 Comparative methods of hazard identification 18
2.2.1 Historical record analysis 19
2.3 Risk indices 25
2.3.1 Dow fire and explosion index (F&EI) 26
2.4 Generalized methods of hazard identification 32
2.4.1 HAZard and OPerability (HAZOP) analysis 32
2.4.2 Methodology of HAZOP analysis 36
2.4.3 Application of HAZOP analysis to sequences of operations and
discontinuous processes 38
2.4.4 'What if' analysis 42
2.4.5 Fault tree analysis (FfA) 42
2.4.6 Event tree analysis (ETA) 51
2.4.7 Failure modes and effects analysis (FMEA) 54
2.5 Questions and problems 57
2.6 References 58
3 Consequence analysis: fires and explosions 59
3.1 Introduction 59
3.2 Flammability characteristics 60
3.2.1 Modifications to the flammability limits 64
3.2.2 Minimum oxygen for combustion 65
3.2.3 Flammability diagrams 66
3.2.4 Mixtures of flammable vapours 68
3.2.5 Flammability degree of different materials 68
3.3 Sources of ignition 69
3.4 Explosions 71
vi CONTENTS
3.5 Effects of fires and explosions 73
3.5.1 Confined explosions 76
3.5.2 Unconfined explosions 80
3.5.3 Estimation of the effects of an explosion as a function of the distance 83
3.5.4 Unconfined Vapour Cloud Explosions (UVCE) 85
3.5.5 Flash fires 88
3.5.6 Vessel rupture 89
3.5.7 Pool fires 92
3.5.9 BLEVEs and fireballs 101
3.6 Questions and problems 106
3.7 References 107
4 Consequence analysis: release of hazardous substances 109
4.1 Introduction 109
4.1.1 Sequences of events 110
4.2 Accidental discharge of liquids 114
4.3 Accidental discharge of gases and vapours 115
4.4 Two-phase discharge 117
4.5 Evaporation of a liquid release 119
4.5.1 Evaporation of superheated liquids 119
4.5.2 Evaporation of boiling liquids 122
4.5.3 Evaporation of non-boiling liquids 124
4.6 Dispersion of gases and vapours in the atmosphere 127
4.6.1 Types of emission 127
4.6.2 Atmospheric stability 129
4.6.3 Wind 131
4.6.4 Dispersion models 133
4.6.5 Concentration contours 142
4.6.6 Dispersion of dense emissions 143
4.7 Questions and problems 148
4.8 References 150
5 Vulnerability of persons and installations 152
5.1 Introduction 152
5.2 Probit methodology 153
5.3 Effects of toxic emissions 156
5.3.1 Toxicity indicators 158
5.3.2 Probit equations for toxic exposure 161
5.4 Vulnerability to thermal effects 163
5.4.1 Effects of thermal radiation on people 163
5.4.2 Effects of thermal radiation on buildings and structures 166
5.5 Vulnerability to explosions 167
5.6 Factors that modify the vulnerability of people and installations 171
5.6.1 Evasive actions 173
5.7 Questions and problems 174
5.8 References 175
6 Quantitative risk assessment 176
6.1 Introduction 176
6.2 Equipment reliability 178
6.2.1 Probability distributions 178
6.3 Reliability and availability of protective systems 189
6.3.1 Associations of systems 191
6.3.2 Common cause failures 194
CONTENTS vii
6.4 Use of fault tree analysis in quantitative risk assessment 195
6.4.1 Ranking of minimal cut sets 197
6.5 Human errors and reliability 201
6.6 Consideration of external agents 206
6.7 Uncertainty of data and parameter sensitivity 207
6.8 Acceptability of risk 209
6.8.1 Risks involving only material losses 209
6.8.2 Accidents with a potential for loss of life 210
6.9 Questions and problems 212
6.10 References 213
7 Risk reduction in the design of chemical plants 215
7.1 Introduction 215
7.2 Research and development 215
7.3 Project development 216
7.3.1 Scope definition 216
7.3.2 Process engineering 217
7.3.3 Detailed engineering 218
7.4 Emergency relief systems 231
7.4.1 Terminology 232
7.4.2 Determination of the design scenario 232
7.4.3 Selecting the type of element 238
7.4.4 Pressure relief element design 245
7.4.5 Two-phase flow 255
7.4.6 Runaway reactions 262
7.4.7 Dust explosions 268
7.4.8 Design documentation 272
7.4.9 Vent treatment 272
7.5 Questions and problems 277
7.6 References 280
8 Risk reduction in operation and maintenance 283
8.1 Risk reduction in operation 283
8.1.1 Safety and environmental management systems 283
8.1.2 Control of the safety management system 287
8.1.3 Accident and incident investigation 290
8.1.4 Operating procedures 291
8.2 Risk reduction in maintenance 296
8.2.1 Permits to work 297
8.2.2 Maintenance programmes 303
8.2.3 Control of modifications 303
8.3 Human resources management 305
8.3.1 Human error 306
8.3.2 Education and training 307
8.3.3 Communication 310
8.4 Questions and problems 311
8.5 References 312
9 Emergency planning 314
9.1 Introduction 314
9.2 The EU Seveso 2 Directive 315
9.3 Internal emergency plan 317
9.3.1 The preparation of an emergency plan 317
9.3.2 Development and editing stages 318
9.3.3 Elements of an emergency plan 320
viii CONTENTS
9.4 External emergency plan 328
9.4.1 Communication and co-ordination of the emergency 328
9.4.2 Community right-to-know 330
9.5 Transport of hazardous materials 332
9.6 Questions and problems 335
9.7 References 335
10 Legislation, standards and design codes 337
10.1 EC legislation 337
10.2 Spanish legislation 338
10.3 USA legislation 339
10.4 Design codes and regulations 340
10.5 Institutions 341
10.6 Internet sites 342
10.7 References 342
Appendix: Some cases of industrial accidents 343
AI Explosions caused by runaway reactions: the accident in the Union Carbide
facilities at Seadrift, Texas, 1991 343
A 1.1 Installation characteristics 343
A 1.2 Chronology 343
A 1.3 Causes of the accident 344
A 1.4 Design and safety considerations 344
A 1.5 Conclusions 346
A.2 Accidents originating with operations of loading and unloading of containers:
the accident in the EMPAK facilities, Deer Park, Texas, 1988 347
A2.1 Installation characteristics 347
A2.2 Chronology 347
A2.3 Causes of the accident 348
A2.4 Safety considerations and conclusions 349
A3 Destruction of process and storage containers by vacuum: various cases 350
A3.1 Case 1 350
A3.2 Case 2 351
A3.3 Case 3 353
A4 Unconfined vapour cloud explosions. The case of the Nypro plant at
Flixborough (United Kingdom) 353
A4.1 Installation characteristics 353
A4.2 Chronology of the accident 355
A4.3 Analysis of the causes of the accident 356
A5 Toxic emissions caused by runaway reactions: the accidents of Seveso (Italy)
and Bhopal (India) 358
A5.! The dioxin emission at Seveso (1976) 358
AS.2 The escape of methyl isocyanate (MIC) at Bhopal (1984) 360
A6 References 364
Index 365
Foreword
As President of the Spanish Chemical Industry Federation (FEIQUE) and on behalf
of the chemical sector I wish to express my satisfaction at the publication of a
book as interesting and as useful as the one written by Jesus M. Santamaria Ramiro
and Pedro A. Braiia Afsa.
The chemical industry, which has always occupied a prominent position in
defence of the safety of its workers, its products and its instalIations and the
environment, takes great pleasure in welcoming a book which will undoubtedly
contribute to the growth of a safety culture from the university lecture rooms in
which our young chemists and engineers are shaped.
The book arrives at a very opportune moment, since, whilst any effort in this
area has always been justified it is even more so now, when risk analysis is receiving
a new impetus as a consequence of the growing number of EC regulations which
aim to increase the levels of safety in industrial activities.
It is also satisfying to observe that many of the techniques and procedures
gathered together and developed in this book were developed in the chemical
industry, and are due to the efforts of its workers. Nowadays, these risk analysis
techniques are being applied to other industrial sectors, effectively helping in the
protection of human life and of property.
The book covers a wide range of methodologies applicable to very diverse
situations. It takes a very practical approach and each chapter is completed with
an extensive bibliography, making it even more useful. It will therefore be an
appropriate tool for work, as much for those university students who wish to
study in depth the techniques involved in risk analysis in the chemical industry, as
for the professionals of our industry responsible for the minimization of these
risks.
Lastly, I would like to emphasize the collaboration between a university
professor and a process engineer from our industry, which has produced such an
important book. My most effusive congratulations to the authors.
Juan Jose Nava Cano
President of FEIQUE
Preface
During the past 30 years, environmental topics have moved up on the list of
society's concerns. At the same time the term 'environmental impact' has extended
its traditional meaning, principally referring to the contamination/pollution of air,
water and soil, to include other aspects. Thus, nowadays, in the forums of
environmental debate, subjects ranging from the adequate use of raw materials to
landscape alterations caused by a new road are discussed.
Within this extensive environmental concept, a special sensitivity has developed,
in view of the possibility of industrial accidents which, because of their magnitude,
are capable of causing significant damage to people, property or the environment.
This concern, which in the past was principally associated with the nuclear industry,
today also includes the chemical industry, even more so after the Flixborough,
Seveso and Bhopal accidents.
The quality of life which society now perceives is not only identified with the
amount of products and services available, but also with the safety of the industries
which produce them. Companies have responded, in general, to the demands of
society, which has given rise to the appearance of environmental and safety
management programmes which are gradually extending to the majority of the
chemical industry. Without a doubt, legislative pressure has contributed to this
tendency, but it is only fair to acknowledge there has also been an important
change in mentality on the part of industry.
Any programme of action designed to improve the safety level of a particular
process should start by carrying out a diagnosis from the beginning, identifying
the most problematic areas and evaluating the available alternatives. It is extremely
difficult to carry out this task using experience and intuition alone without the
help of a tool capable of examining the complex safety problems encountered in
a chemical plant. Risk analysis is the discipline which responds to this need,
combining a number of techniques to produce a quantitative estimation of the
risks involved in a given process.
The reason for the text presented here is the desire to contribute new material,
dealing with risk analysis and reduction in a unified way, i.e. trying to integrate
the different techniques involved using a global approach. Although this book
was originally conceived to serve as a text book for chemical engineering
students, we believe that it may also be useful to industrial engineering and
chemistry students, as well as to the professionals working in the chemical
industry.