1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationFunctional safety of electrical/electronic/programmable electronic safety related systemsPart 5: Examples of methods for the determination of safety integrity levelsBS EN 61508-5
2、:2010National forewordThis British Standard is the UK implementation of EN 61508-5:2010. It isidentical to IEC 61508-5:2010. It supersedes BS EN 61508-5:2002 which iswithdrawn.The UK participation in its preparation was entrusted by Technical CommitteeGEL/65, Measurement and control, to Subcommittee
3、 GEL/65/1, System considerations.A list of organizations represented on this committee can be obtained onrequest to its secretary.This publication does not purport to include all the necessary provisions of acontract. Users are responsible for its correct application. BSI 2010ISBN 978 0 580 65449 7I
4、CS 13.260; 25.040.40; 29.020Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of the StandardsPolicy and Strategy Committee on 3 Ju 2010.Amendments issued since publicationAmd. No. Date Text affectedBRITISH STANDAR
5、DBS EN 61508-5:2010ne0EUROPEAN STANDARD EN 61508-5 NORME EUROPENNE EUROPISCHE NORM May 2010 CENELEC European Committee for Electrotechnical Standardization Comit Europen de Normalisation Electrotechnique Europisches Komitee fr Elektrotechnische Normung Management Centre: Avenue Marnix 17, B - 1000 B
6、russels 2010 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members. Ref. No. EN 61508-5:2010 E ICS 25.040.40 Supersedes EN 61508-5:2001English version Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 5
7、: Examples of methods for the determination of safety integrity levels (IEC 61508-5:2010) Scurit fonctionnelle des systmes lectriques/lectroniques/lectroniques programmables relatifs la scurit - Partie 5: Exemples de mthodes pour la dtermination des niveaux dintgrit de scurit (CEI 61508-5:2010) Funk
8、tionale Sicherheit sicherheitsbezogener elektrischer/elektronischer/programmierbarer elektronischer Systeme - Teil 5: Beispiele zur Ermittlung der Stufe der Sicherheitsintegritt (safety integrety level) (IEC 61508-5:2010) This European Standard was approved by CENELEC on 2010-05-01. CENELEC members
9、are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application t
10、o the Central Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has t
11、he same status as the official versions. CENELEC members are the national electrotechnical committees of Austria, Belgium, Bulgaria, Croatia, Cyprus, the Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, the Ne
12、therlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. BS EN 61508-5:2010EN 61508-5:2010 - 2 - Foreword The text of document 65A/552/FDIS, future edition 2 of IEC 61508-5, prepared by SC 65A, System aspects, of IEC TC 65, Industrial-proce
13、ss measurement, control and automation, was submitted to the IEC-CENELEC parallel vote and was approved by CENELEC as EN 61508-5 on 2010-05-01. This European Standard supersedes EN 61508-5:2001. Attention is drawn to the possibility that some of the elements of this document may be the subject of pa
14、tent rights. CEN and CENELEC shall not be held responsible for identifying any or all such patent rights. The following dates were fixed: latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 2011-02-01 latest dat
15、e by which the national standards conflicting with the EN have to be withdrawn (dow) 2013-05-01 Annex ZA has been added by CENELEC. _ Endorsement notice The text of the International Standard IEC 61508-5:2010 was approved by CENELEC as a European Standard without any modification. In the official ve
16、rsion, for Bibliography, the following notes have to be added for the standards indicated: 1 IEC 61511 series NOTE Harmonized in EN 61511 series (not modified). 2 IEC 62061 NOTE Harmonized as EN 62061. 3 IEC 61800-5-2 NOTE Harmonized as EN 61800-5-2. 9 ISO/IEC 31010 NOTE Harmonized as EN 31010. 10 I
17、SO 10418:2003 NOTE Harmonized as EN 10418:2003 (not modified). 12 ISO 13849-1:2006 NOTE Harmonized as EN ISO 13849-1:2006 (not modified). 13 IEC 60601 series NOTE Harmonized in EN 60601 series (partially modified). 14 IEC 61508-2 NOTE Harmonized as EN 61508-2. 15 IEC 61508-3 NOTE Harmonized as EN 61
18、508-3. 16 IEC 61508-6 NOTE Harmonized as EN 61508-6. 17 IEC 61508-7 NOTE Harmonized as EN 61508-7. 18 IEC 61511-1 NOTE Harmonized as EN 61511-1. _ BS EN 61508-5:2010- 3 - EN 61508-5:2010 Annex ZA (normative) Normative references to international publications with their corresponding European publica
19、tions The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. NOTE When an international publication has
20、been modified by common modifications, indicated by (mod), the relevant EN/HD applies. Publication Year Title EN/HD Year IEC 61508-1 2010 Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 1: General requirements EN 61508-1 2010 IEC 61508-4 2010 Function
21、al safety of electrical/electronic/programmable electronic safety-related systems - Part 4: Definitions and abbreviations EN 61508-4 2010 BS EN 61508-5:2010 2 61508-5 IEC:2010 CONTENTS INTRODUCTION.5 1 Scope.7 2 Normative references .9 3 Definitions and abbreviations9 Annex A (informative) Risk and
22、safety integrity General concepts.10 Annex B (informative) Selection of methods for determining safety integrity level requirements.21 Annex C (informative) ALARP and tolerable risk concepts .24 Annex D (informative) Determination of safety integrity levels A quantitative method 27 Annex E (informat
23、ive) Determination of safety integrity levels Risk graph methods .30 Annex F (informative) Semi-quantitative method using layer of protection analysis (LOPA) .38 Annex G (informative) Determination of safety integrity levels A qualitative method hazardous event severity matrix44 Bibliography46 Figur
24、e 1 Overall framework of the IEC 61508 series 8 Figure A.1 Risk reduction general concepts (low demand mode of operation) .14 Figure A.2 Risk and safety integrity concept 14 Figure A.3 Risk diagram for high demand applications .15 Figure A.4 Risk diagram for continuous mode operation 16 Figure A.5 I
25、llustration of common cause failures (CCFs) of elements in the EUC control system and elements in the E/E/PE safety-related system.17 Figure A.6 Common cause between two E/E/PE safety-related systems 18 Figure A.7 Allocation of safety requirements to the E/E/PE safety-related systems, and other risk
26、 reduction measures 20 Figure C.1 Tolerable risk and ALARP.25 Figure D.1 Safety integrity allocation example for safety-related protection system.29 Figure E.1 Risk Graph: general scheme.33 Figure E.2 Risk graph example (illustrates general principles only) .34 Figure G.1 Hazardous event severity ma
27、trix example (illustrates general principles only) .45 Table C.1 Example of risk classification of accidents .26 Table C.2 Interpretation of risk classes 26 Table E.1 Example of data relating to risk graph (Figure E.2).35 Table E.2 Example of calibration of the general purpose risk graph .36 Table F
28、.1 LOPA report.40 BS EN 61508-5:201061508-5 IEC:2010 5 INTRODUCTION Systems comprised of electrical and/or electronic elements have been used for many years to perform safety functions in most application sectors. Computer-based systems (generically referred to as programmable electronic systems) ar
29、e being used in all application sectors to perform non-safety functions and, increasingly, to perform safety functions. If computer system technology is to be effectively and safely exploited, it is essential that those responsible for making decisions have sufficient guidance on the safety aspects
30、on which to make these decisions. This International Standard sets out a generic approach for all safety lifecycle activities for systems comprised of electrical and/or electronic and/or programmable electronic (E/E/PE) elements that are used to perform safety functions. This unified approach has be
31、en adopted in order that a rational and consistent technical policy be developed for all electrically-based safety-related systems. A major objective is to facilitate the development of product and application sector international standards based on the IEC 61508 series. NOTE 1 Examples of product a
32、nd application sector international standards based on the IEC 61508 series are given in the Bibliography (see references 1, 2 and 3). In most situations, safety is achieved by a number of systems which rely on many technologies (for example mechanical, hydraulic, pneumatic, electrical, electronic,
33、programmable electronic). Any safety strategy must therefore consider not only all the elements within an individual system (for example sensors, controlling devices and actuators) but also all the safety-related systems making up the total combination of safety-related systems. Therefore, while thi
34、s International Standard is concerned with E/E/PE safety-related systems, it may also provide a framework within which safety-related systems based on other technologies may be considered. It is recognized that there is a great variety of applications using E/E/PE safety-related systems in a variety
35、 of application sectors and covering a wide range of complexity, hazard and risk potentials. In any particular application, the required safety measures will be dependent on many factors specific to the application. This International Standard, by being generic, will enable such measures to be formu
36、lated in future product and application sector international standards and in revisions of those that already exist. This International Standard considers all relevant overall, E/E/PE system and software safety lifecycle phases (for example, from initial concept, though design, implementation, opera
37、tion and maintenance to decommissioning) when E/E/PE systems are used to perform safety functions; has been conceived with a rapidly developing technology in mind; the framework is sufficiently robust and comprehensive to cater for future developments; enables product and application sector internat
38、ional standards, dealing with E/E/PE safety-related systems, to be developed; the development of product and application sector international standards, within the framework of this standard, should lead to a high level of consistency (for example, of underlying principles, terminology etc.) both wi
39、thin application sectors and across application sectors; this will have both safety and economic benefits; provides a method for the development of the safety requirements specification necessary to achieve the required functional safety for E/E/PE safety-related systems; adopts a risk-based approac
40、h by which the safety integrity requirements can be determined; introduces safety integrity levels for specifying the target level of safety integrity for the safety functions to be implemented by the E/E/PE safety-related systems; NOTE 2 The standard does not specify the safety integrity level requ
41、irements for any safety function, nor does it mandate how the safety integrity level is determined. Instead it provides a risk-based conceptual framework and example techniques. BS EN 61508-5:2010 6 61508-5 IEC:2010 sets target failure measures for safety functions carried out by E/E/PE safety-relat
42、ed systems, which are linked to the safety integrity levels; sets a lower limit on the target failure measures for a safety function carried out by a single E/E/PE safety-related system. For E/E/PE safety-related systems operating in a low demand mode of operation, the lower limit is set at an avera
43、ge probability of a dangerous failure on demand of 105; a high demand or a continuous mode of operation, the lower limit is set at an average frequency of a dangerous failure of 109h-1; NOTE 3 A single E/E/PE safety-related system does not necessarily mean a single-channel architecture. NOTE 4 It ma
44、y be possible to achieve designs of safety-related systems with lower values for the target safety integrity for non-complex systems, but these limits are considered to represent what can be achieved for relatively complex systems (for example programmable electronic safety-related systems) at the p
45、resent time. sets requirements for the avoidance and control of systematic faults, which are based on experience and judgement from practical experience gained in industry. Even though the probability of occurrence of systematic failures cannot in general be quantified the standard does, however, al
46、low a claim to be made, for a specified safety function, that the target failure measure associated with the safety function can be considered to be achieved if all the requirements in the standard have been met; introduces systematic capability which applies to an element with respect to its confid
47、ence that the systematic safety integrity meets the requirements of the specified safety integrity level; adopts a broad range of principles, techniques and measures to achieve functional safety for E/E/PE safety-related systems, but does not explicitly use the concept of fail safe However, the conc
48、epts of “fail safe” and “inherently safe” principles may be applicable and adoption of such concepts is acceptable providing the requirements of the relevant clauses in the standard are met. BS EN 61508-5:201061508-5 IEC:2010 7 FUNCTIONAL SAFETY OF ELECTRICAL/ELECTRONIC/ PROGRAMMABLE ELECTRONIC SAFE
49、TY-RELATED SYSTEMS Part 5: Examples of methods for the determination of safety integrity levels 1 Scope 1.1 This part of IEC 61508 provides information on the underlying concepts of risk and the relationship of risk to safety integrity (see Annex A); a number of methods that will enable the safety integrity levels for the E/E/PE safety-related systems to be determined (see
