IEC INTERNATIONAL STANDARD 61025 Second edition 2006-12 Fault tree analysis (FTA) This English-language version is derived from the original bilingual publication by leaving out all French-language pages. Missing page numbers correspond to the French- languagepages. IEC Referencenumber IEC 61025:2006(E) Publication numbering As from 1 January 1997 all IEC publications are issued with a designation in the 60000 series.For example,IEC 34-1is now referred to as IEC 60034-1. Consolidated editions The IEc is now publishing consolidated versions of its publications. For example, edition numbers 1.0, 1.1 and 1.2 refer, respectively,to the base publication, the amendments 1 and 2. FurtherinformationonIECpublications The technical content of IEC publications is kept under constant review by the IEC, thus ensuring that the content reflects current technology. Information relating to this.publication, including its.validity, is available in the IEc Catalogue of publications (see below) in addition to new editions, amendments and corrigenda. information on the subjects under consideration and work in progress undertaken by the technical committee which has prepared this publication, as well as the list of publications issued, is also available from the following: IEc Web Site (www.iec.ch) Catalogueof IEC publications The on-line catalogue on the IEC web site (www.iec.ch/searchpub) enables you to search by a variety of criteria including text searches, technical committees and date of publication. On-line information is also available on recently issued publications, withdrawn and replaced publications, as well as corrigenda. IECJustPublished This summary of recently issued publications (www.iec.ch/online news/ justpub) is also available by email. Please contact the Customer Service Centre (see below) for further information Customer Service Centre If you have any questions regarding this publication or need further assistance. please contactthe Customer Service Centre: Email: [email protected] Tel: +41 22 919 02 11 Fax: +41229190300 IEC INTERNATIONAL STANDARD 61025 Second edition 2006-12 Fault tree analysis (FTA) @ IEC 2006Copyright -all rights reserved No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher. Intemational Electrotechnical Commission, 3, rue de Varembe, PO Box 131, CH-1211 Geneva 20, Switzerland Telephone: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: [email protected] Web: www.iec.ch IEC Commission Electrotechnigue Internationale International Electrotechnical Commission MexayHapoAHaSnekTpoTexHwyeckasKoMwCcMg 61025@IEC:2006 3 CONTENTS FOREWORD INTRODUCTION. Scope 13 2 Normative references. .13 3 Terms and definitions .13 4 Symbols 19 General. 21 5 5.1 Fault tree description and structure 21 .23 5.2 Objectives. 5.3 Applications.. 23 5.4 Combinations with other reliability analysis techniques .25 Development and evaluation. .29 6.1 General considerations.. 6.2 Required system information .35 6.3 Fault tree graphical description and structure .37 Faulttree development and evaluation 7 ..39 7.1 General. .39 7.2 Scope of analysis. .39 7.3 Systemfamiliarization ...39 7.4 Fault tree development... 7.5 Fault tree construction. .41 7.6 Failure rates in fault tree analysis. .75 8 Identification and labelling inafault tree .75 9 Report 77 AnnexA(informative)Symbols. .81 Annex B(informative)Detailed procedure for disjointing. .95 Bibliography... 103 Figure 1 -Explanation of terms used in fault tree analyses.. 19 Figure 2-Fault tree representation of a series structure .45 Figure3-Fault tree representation of parallel,active redundancy Figure 4 - En example of fault tree showing different gate types.. ..51 Figure5-Rectangulargateand eventsrepresentation. ...53 Figure 6-An example fault tree containing a repeated and a transfer event . ....55 Figure7-Example showingcommon cause considerations in