Practical Hazops, Trips and Alarms

345 Pages·2004·4.28 MB·English

by  David Macdonald

Practical Hazops, Trips and Alarms
vi Contents
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Malcolm Barnes)
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Practical Power Distribution for Industry (Jan de Kock and Cobus Strauss)
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Practical Telecommunications and Wireless Communications (Edwin Wright and Deon Reynders)
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vi Contents
Practical Hazops, Trips and Alarms
David Macdonald,
BSc (Hons) Inst. Eng., Senior Engineer,
IDC Technologies, Cape Town, South Africa
Series editor: Steve Mackay
AMSTERDAM (cid:127) BOSTON (cid:127) HEIDELBERG (cid:127) LONDON
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Newnes is an imprint of Elsevier
vi Contents
Newnes
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First published 2004

Copyright © 2004, IDC Technologies. All rights reserved

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British Library Cataloguing in Publication Data
Macdonald, D. M
Practical hazops, trips and alarms – (Practical Professional)
1. Machinery – Safety appliances 2. Machinery – Monitoring
I. Title
621.3'0289

Library of Congress Cataloguing in Publication Data
A catalogue record for this book is available from the Library of Congress

ISBN 0 7506 6274 3

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vi Contents
Contents
Preface................................................................................................................viii
1 Introduction to hazard studies...............................................................................1
1.1 Scope and objectives of this chapter.......................................................1
1.2 Introduction to hazards and risk management.........................................1
1.3 Risk assessment....................................................................................10
1.4 Concepts of Alarp and tolerable risk.......................................................15
1.5 Regulatory frameworks and examples from EU and USA......................21
1.6 Methods of identifying hazards...............................................................26
2 Hazard studies at levels 1 and 2 .........................................................................31
2.1 Introduction.............................................................................................31
2.2 Methodologies for hazard study 1...........................................................37
2.3 Process hazard study 2..........................................................................40
2.4 Practical example of hazard 2 application ..............................................53
2.5 Case study.............................................................................................62
2.6 Conclusion on hazard studies 1 and 2....................................................62
3. Risk reduction measures using alarms and trips.................................................65
3.1 Risk reduction measures........................................................................65
3.2 Terminologies and standards for safety systems....................................66
3.3 Equipment under control ........................................................................67
3.4 Protection layers.....................................................................................72
3.5 The role of alarms in safety....................................................................78
3.6 Alarm types and do they qualify as safeguards?....................................81
3.7 Identification and design of safety-related alarms...................................82
3.8 Key design principles for alarms.............................................................87
3.9 SIS, principles of separation...................................................................90
3.10 Simple and complex shutdown sequences, examples............................92
3.11 Conclusions: the role of Hazops in defining alarms and trips..................95
4 Hazop method ....................................................................................................97
4.1 Introduction.............................................................................................97
4.2 Introduction to Hazop.............................................................................98
4.3 Overview of Hazop method....................................................................99
4.4 Points to note on the examination procedure ...................................... 116
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4.5 Practical exercise: continuous process example..................................120
4.6 Hazop for batch processes and sequential operations.........................120
4.7 Hazops for other disciplines.................................................................124
4.8 Conclusions.........................................................................................129
5 Planning and leadership of Hazops ................................................................ 130
5.1 Introduction......................................................................................... 130
5.2 Organizing the Hazop......................................................................... 130
5.3 The team leader and the team............................................................ 132
5.4 Practical exercise: hybrid batch process example............................... 141
6 Specifying safety instrumented systems ......................................................... 143
6.1 Introduction..........................................................................................143
6.2 Risk reduction by instrumented protection...........................................144
6.3 What affects the safety integrity of an instrument trip? ........................149
6.4 Overview of IEC 61508........................................................................150
6.5 Determining the safety integrity............................................................156
6.6 Design essentials to meet SIL targets..................................................159
6.7 Specifying the SIS requirements..........................................................168
6.8 Documenting the SRS.........................................................................174
6.9 Conclusions.........................................................................................179
7 Hazard analysis methods .................................................................................180
7.1 Introduction..........................................................................................180
7.2 Outline of methods...............................................................................181
7.3 Fault tree analysis................................................................................185
7.4 Practical exercise in FTA.....................................................................192
7.5 Conclusions.........................................................................................192
8 Factors in the choice of protection system .......................................................193
8.1 Introduction and objectives..................................................................193
8.2 Equipment selection.............................................................................197
8.3 Key points about sensors and actuators..............................................206
8.4 Guidelines for the application of field devices in the SIS......................209
8.5 IEC 61508 requirements for field devices............................................216
8.6 Technology issues...............................................................................216
8.7 Guidelines for final elements................................................................218
8.8 Summary of technology and applications.............................................224
8.9 Summary of SIL vs cost.......................................................................224
9 Exercise in specifying an SIS from the Hazop .................................................226
9.1 Introduction..........................................................................................226
9.2 Process description..............................................................................226
9.3 Safety requirements specifications ......................................................231
9.4 Conclusion...........................................................................................236
Contents vii
Appendix A: References used in the manual................................................................237
Appendix B: Some websites for safety systems information.........................................239
Appendix C: Notes on national regulations relevant to hazard study and safety
management.............................................................................................242
Appendix D: Software tools for hazard studies.............................................................247
Appendix E: EPA case study of phenol resin hazards..................................................248
Appendix F: Expanded guideword table for continuous processes...............................249
Appendix G: Methods of reporting................................................................................251
Appendix H: Design and calibration of a risk graph......................................................253
Appendix I: Data capture sheet ....................................................................................257
Appendix J: Glossary of terms used in hazard studies and safety-related systems......259
Practical exercises........................................................................................................264
Exercise 1..........................................................................................................264
Exercise 2..........................................................................................................266
Exercise 3..........................................................................................................268
Exercise 4..........................................................................................................275
Exercise 5..........................................................................................................280
Exercise 6..........................................................................................................286
Exercise 7..........................................................................................................288
Exercise 8..........................................................................................................294
Exercise 9..........................................................................................................302
Answers to practical exercises .....................................................................................306
Exercise 1..........................................................................................................306
Exercise 2..........................................................................................................308
Exercise 3..........................................................................................................309
Exercise 4..........................................................................................................314
Exercise 5..........................................................................................................320
Exercise 6..........................................................................................................323
Index.............................................................................................................................325
Preface
Introduction to the book
This introduction maps out the reasons why this book has been prepared and introduces the ideas
behind it. This section also provides a guide to the contents and uses of the manual.
What is the book about?
This book is about some of the critical activities involved in making sure that a manufacturing
process is:
• Safe for people to work with
• Safe against damage to the environment
• Secure against failures that could result in major asset losses in the business.
It concentrates on the application of hazard study methods and the actions that follow from them for
providing protection against hazards. The book seeks to provide training in three basic steps that form
part of the overall risk management framework for industries such as chemicals, oil and gas,
pharmaceuticals and food processing. The steps can be seen in Figure P.1.
Information on the process
Identify hazards Hazard studies
Hazard analysis and
Evaluate risks
risk assessment
Specify risk reduction measures Trips and alarms

Figure P.1
Scope of the book