Learning from Accidents This book has been written to remember the dead and injured and to warn the living Learning from Accidents Third edition Trevor Kletz OBE, DSc, FEng, FRSC, FIChemE OXFORD AUCKLAND BOSTON JOHANNESBURG MELBOURNE NEW DELHI Butterworth-Heinemann An imprint of Gulf Professional Publishing Linacre House, Jordan Hill, Oxford OX2 8DP 225 Wildwood Avenue, Woburn, MA 01801-2041 A division of Reed Educational and Professional Publishing Ltd A member of the Reed Elsevier plc group First published as Learning from Accidents in Industry 1988 Reprinted 1990 Second edition 1994 Third edition 2001 © Trevor Kletz 2001 All rights reserved. No part of this publication may be reproduced in any material form (including photocopying or storing in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright holder except in accordance with the provisions of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London, England W1P 0LP. Applications for the copyright holder’s written permission to reproduce any part of this publication should be addressed to the publishers British Library Cataloguing in Publication Data Kletz, Trevor A. Learning from accidents. – 3rd ed. 1. Industrial accidents 2. Industrial accidents – Investigations 3. Chemical industry – Accidents I. Title 363.1'165 Library of Congress Cataloguing in Publication Data Kletz, Trevor A. Learning from accidents/Trevor Kletz. – 3rd ed. p. cm. Includes bibliographical references and index. ISBN 0 7506 4883 X 1. Chemical industry – Accidents. 2. Industrial accidents. 3. Industrial accidents – Investigation. HD7269.C45 K43 2001 363.11'65–dc21 2001035380 ISBN 0 7506 4883 X For information on all Butterworth-Heinemann publications visit our website at www.bh.com Composition by Scribe Design, Gillingham, Kent Printed and bound in Great Britain by Biddles of Guildford and Kings Lynn Forethoughts vii Preface ix Acknowledgements xii Introduction 1 1 Two simple incidents 13 2 Protective system failure 22 3 Poor procedures and poor management 32 4 A gas leak and explosion – The hazards of insularity 40 5 A liquid leak and fire and the hazards of amateurism 52 6 A tank explosion – The hazards of optional extras 63 7 Another tank explosion – The hazards of modification and ignorance 73 8 Flixborough 83 9 Seveso 103 10 Bhopal 110 11 Three Mile Island 122 12 Chernobyl 135 13 Aberfan 146 14 Missing recommendations 155 15 Three weeks in a works 162 16 Pipe failures 179 17 Piper Alpha 196 18 The King’s Cross underground railway station fire 207 19 Clapham Junction – Every sort of human error 216 20 Herald of Free Enterprise 226 21 Some aviation accidents 234 22 Invisible hazards 253 23 Signals passed at danger 259 24 Longford: the hazards of following fashions 267 25 The Gresford Colliery explosion 275 26 Green intention, red result 281 27 Looking beyond violations 291 Contents 28 Keeping an open mind 297 29 Secondhand software: the Therac story 303 30 Conclusions 308 Appendix 1 325 Appendix 2 328 Appendix 3 335 Afterthought 336 Index 337 vi Contents It is the success of engineering which holds back the growth of engineering knowledge, and its failures which provide the seeds for its future development. D. I. Blockley and J. R. Henderson, Proc. Inst. Civ. Eng. Part 1, Vol. 68, Nov. 1980, p. 719. What has happened before will happen again. What has been done before will be done again. There is nothing new in the whole world. Ecclesiastes, 1, 9 (Good News Bible). What worries me is that I may not have seen the past here – perhaps I have seen the future. Elie Wiesel Below, distant, the roaring courtiers rise to their feet – less shocked than irate. Salome has dropped the seventh veil and they’ve discovered there are eight. Danny Abse, Way out in the Centre. . . . But if so great desire Moves you to hear the tale of our disasters Briefly recalled However I may shudder at the memory And shrink again in grief, let me begin. Virgil, The Aeneid. I realised that there is no rocket science in this. Improving safety can be quite simplistic if we go back to basics and not overcomplicate the processes we use. Comment made by a supervisor after I had described some accidents. Forethoughts [...]... continue to do so, without prompting Introduction 7 Most of the recommendations described in this book were made during the original investigation but others only came to light when the accidents were later selected for discussion in the way I have just described In the book the presentations differ a little from chapter to chapter, to avoid monotony and to suit the varying complexity of the accounts... If protective equipment has been neglected, will it help to install more protective equipment? (see Chapter 6) 10 Precept or story? Western culture, derived from the Greeks, teaches us that stories are trivial light-hearted stuff, suitable for women and children and for occasional relaxation but not to be compared with abstract statements of principles The highest truths are non-narrative and timeless... is no need for me to spell it out If we have not always prevented accidents in the past this is due to lack of knowledge, not lack of desire 1 Finding the facts This book is not primarily concerned with the collection of information about accidents but with the further consideration of facts already collected Those interested in the collection of information should consult a book by the Center for... killed many people or caused substantial damage They thus include, at one extreme, accidents like Chernobyl and Bhopal that shook the world and at the other extreme accidents that, by good fortune, injured no one and caused little damage The first edition discussed accidents which had occurred mainly in the chemical industry, but later editions cover a wider range The book should therefore interest all... been carried out when the plants were being designed so that modifications, to plant design or working methods, could have been made before the accidents occurred, rather than after Samuel Coleridge described history as a lantern on the stern, illuminating the hazards the ship has passed through rather than those that lie ahead It is better to see the hazards afterwards than not see them at all, as... than those closely involved to see the wider issues and the relevance of the incident to other plants It is difficult to see the shape of the forest when we are in the middle of it Introduction 3 (2) Try not to disturb evidence that may be useful to experts who may be called in later If equipment has to be moved, for example, to make the plant safe, then photograph it first In the UK a member of the... those at the bottom of the diagrams If we are constructing defences in depth we should make sure that the outer defences are sound as well as the inner ones Protective measures should come at the bottom of the accident chain and not just at the top In many of the accidents described later there was too much dependence on the last lines of defence, the protective measures at the top of the accident chain... is the opening of the connecting valve The development of the accident is determined by a number of parameters: the contact probability (the probability that all the necessary input factors are present), the contact efficiency (the fraction of the driving force which reaches the target) and the contact time The model indicates a number of ways in which the probability or severity of the accident may... all those concerned with the investigation of accidents, of whatever sort, and all those who work in industry, whether in design, operations or loss prevention I am not suggesting that the immediate causes of an accident are any less important than the underlying causes All must be considered if we wish to prevent further accidents, as the examples will show But putting the immediate causes right will... vessel rotated anti-clockwise and the contents shovelled out (Figure 1.5) One day the lid fell off and hit the man who was emptying the vessel Fortunately his injuries were not serious Figure 1.3 The mixing vessel in use Figure 1.4 The lid is opened 18 Learning from Accidents Figure 1.5 The vessel is rotated so that the contents can be removed It was then found that the welds between the lid and its hinges . concerned with the collection of information about accidents but with the further consideration of facts already collected. Those interested in the collection of information should consult a book. problems, do not know the best way to act, lack training but do not realise it, put off jobs until tomorrow and do not do everything that they intend to do as quickly as they intend to do it. There are,. investigation but others only came to light when the accidents were later selected for discussion in the way I have just described. In the book the presentations differ a little from chapter to