IEC 61508-5:2010
(Main)Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 5: Examples of methods for the determination of safety integrity levels (see Functional Safety and IEC 61508)
Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 5: Examples of methods for the determination of safety integrity levels (see Functional Safety and IEC 61508)
IEC 61508-5:2010 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 Annexes C, D, E, F and G). The method selected will depend upon the application sector and the specific circumstances under consideration. Annexes C, D, E, F and G illustrate quantitative and qualitative approaches and have been simplified in order to illustrate the underlying principles. These annexes have been included to illustrate the general principles of a number of methods but do not provide a definitive account. Those intending to apply the methods indicated in these annexes should consult the source material referenced. This second edition cancels and replaces the first edition published in 1998. This edition constitutes a technical revision. It has been subject to a thorough review and incorporates many comments received at the various revision stages.
NEW! Also available: IEC Standards+ 61508:2010, containing all parts, together with a commented Redline version. Changes made in this 2nd edition are highlighted and commented by a leading world expert.
This publication is of high relevance for Smart Grid.
Sécurité fonctionnelle des systèmes électriques / électroniques / électroniques programmables relatifs à la sécurité - Partie 5: Exemples de méthodes pour la détermination des niveaux d'intégrité de sécurité
La CEI 61508-5:2010 fournit des informations sur les concepts sous-jacents à la notion de risque et les liens entre le risque et l'intégrité de sécurité (voir Annexe A), un certain nombre de méthodes qui permettent de déterminer les niveaux d'intégrité de sécurité des systèmes E/E/PE relatifs à la sécurité (voir Annexes B, C, D et E). La méthode retenue dépend du secteur d'application et des conditions spécifiques à prendre en considération. Les Annexes C, D, E, F et G illustrent les approches quantitatives et qualitatives et ont été simplifiées dans le but d'illustrer les principes sous-jacents. Ces annexes ont été incluses pour illustrer les principes généraux d'un certain nombre de méthodes mais ne fournissent pas une interprétation figée. Il convient que les personnes souhaitant appliquer les méthodes indiquées dans ces annexes consultent les sources documentaires référencées. Cette deuxième édition annule et remplace la première édition publiée en 1998 dont elle constitue une révision technique. Elle a fait l'objet d'une révision approfondie et intègre de nombreux commentaires reçus lors des différentes phases de révision.
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IEC 61508-5 ®
Edition 2.0 2010-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Functional safety of electrical/electronic/programmable electronic safety-related
systems –
Part 5: Examples of methods for the determination of safety integrity levels
Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques
programmables relatifs à la sécurité –
Partie 5: Exemples de méthodes pour la détermination des niveaux d'intégrité
de sécurité
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IEC 61508-5 ®
Edition 2.0 2010-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Functional safety of electrical/electronic/programmable electronic safety-related
systems –
Part 5: Examples of methods for the determination of safety integrity levels
Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques
programmables relatifs à la sécurité –
Partie 5: Exemples de méthodes pour la détermination des niveaux d'intégrité
de sécurité
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
X
CODE PRIX
ICS 25.040.40 ISBN 978-2-88910-528-1
– 2 – 61508-5 © IEC:2010
CONTENTS
FOREWORD.3
INTRODUCTION.5
1 Scope.7
2 Normative references .9
3 Definitions and abbreviations.9
Annex A (informative) Risk and 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 (informative) 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 matrix.44
Bibliography.46
Figure 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 – Illustration 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 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 matrix – example (illustrates general principles
only) .
Table C.1 – Example of risk classification of accidents .
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.1 – LOPA report .40
61508-5 © IEC:2010 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FUNCTIONAL SAFETY OF ELECTRICAL/ELECTRONIC/
PROGRAMMABLE ELECTRONIC SAFETY-RELATED SYSTEMS –
Part 5: Examples of methods for the determination
of safety integrity levels
FOREWORD
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International Standard IEC 61508-5 has been prepared by subcommittee 65A: System
aspects, of IEC technical committee 65: Industrial-process measurement, control and
automation.
This second edition cancels and replaces the first edition published in 1998. This edition
constitutes a technical revision.
This edition has been subject to a thorough review and incorporates many comments received
at the various revision stages.
– 4 – 61508-5 © IEC:2010
The text of this standard is based on the following documents:
FDIS Report on voting
65A/552/FDIS 65A/576/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2
A list of all parts of the IEC 61508 series, published under the general title Functional safety
of electrical / electronic / programmable electronic safety-related systems, can be found on
the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the stability date indicated on the IEC web site under "http://webstore.iec.ch" in the data
related to the specific publication. At this date, the publication will be
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