EN 61508-5:2010

SLOVENSKI STANDARD
01-maj-2011
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Functional safety of electrical/electronic/programmable electronic safety-related systems
- Part 5: Examples of methods for the determination of safety integrity levels (IEC 61508-
5:2010)
Funktionale Sicherheit sicherheitsbezogener
elektrischer/elektronischer/programmierbarer elektronischer Systeme - Teil 5: Beispiele
zur Ermittlung der Stufe der Sicherheitsintegrität (safety integrety level) (IEC 61508-
5:2010)
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 (IEC 61508-5:2010)
Ta slovenski standard je istoveten z: EN 61508-5:2010
ICS:
25.040.40 Merjenje in krmiljenje Industrial process
industrijskih postopkov measurement and control
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EUROPEAN STANDARD
EN 61508-5
NORME EUROPÉENNE
May 2010
EUROPÄISCHE NORM
ICS 25.040.40 Supersedes EN 61508-5:2001

English version
Functional safety of electrical/electronic/programmable electronic safety-
related systems -
Part 5: Examples of methods for the determination of safety integrity
levels
(IEC 61508-5:2010)
Sécurité fonctionnelle des systèmes Funktionale Sicherheit sicherheitsbezogener
électriques/électroniques/électroniques elektrischer/elektronischer/programmierbarer
programmables relatifs à la sécurité - elektronischer Systeme -
Partie 5: Exemples de méthodes Teil 5: Beispiele zur Ermittlung der Stufe
pour la détermination des niveaux der Sicherheitsintegrität (safety integrety
d'intégrité de sécurité level)
(CEI 61508-5:2010) (IEC 61508-5:2010)

This European Standard was approved by CENELEC on 2010-05-01. CENELEC members 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 to 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 the 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 Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Management Centre: Avenue Marnix 17, B - 1000 Brussels

© 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
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-process 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
patent 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 date 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 version, 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] ISO 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 61508-3.
[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.
__________
- 3 - EN 61508-5:2010
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications

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 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 EN 61508-1 2010
electrical/electronic/programmable electronic
safety-related systems -
Part 1: General requirements
IEC 61508-4 2010 Functional safety of EN 61508-4 2010
electrical/electronic/programmable electronic
safety-related systems -
Part 4: Definitions and abbreviations

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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