SIST EN 61508-6:2011

Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 6: Guidelines on the application of IEC 61508-2 and IEC 61508-3 (IEC 61508-6:2010)

1.1 This part of IEC 61508 contains information and guidelines on IEC 61508-2 and IEC 61508-3.
– Annex A gives a brief overview of the requirements of IEC 61508-2 and IEC 61508-3 and sets out the functional steps in their application.
– Annex B gives an example technique for calculating the probabilities of hardware failure and should be read in conjunction with 7.4.3 and Annex C of IEC 61508-2 and Annex D.
– Annex C gives a worked example of calculating diagnostic coverage and should be read in conjunction with Annex C of IEC 61508-2.
– Annex D gives a methodology for quantifying the effect of hardware-related common cause failures on the probability of failure.
– Annex E gives worked examples of the application of the software safety integrity tables specified in Annex A of IEC 61508-3 for safety integrity levels 2 and 3.
1.2 IEC 61508-1, IEC 61508-2, IEC 61508-3 and IEC 61508-4 are basic safety publications, although this status does not apply in the context of low complexity E/E/PE safety-related systems (see 3.4.3 of IEC 61508-4). As basic safety publications, they are intended for use by technical committees in the preparation of standards in accordance with the principles contained in IEC Guide 104 and ISO/IEC Guide 51. IEC 61508-1, IEC 61508-2, IEC 61508-3 and IEC 61508-4 are also intended for use as stand-alone publications. The horizontal safety function of this international standard does not apply to medical equipment in compliance with the IEC 60601 series.
1.3 One of the responsibilities of a technical committee is, wherever applicable, to make use of basic safety publications in the preparation of its publications. In this context, the requirements, test methods or test conditions of this basic safety publication will not apply unless specifically referred to or included in the publications prepared by those technical committees.
1.4 Figure 1 shows the overall framework of the IEC 61508 series and indicates the role that IEC 61508-6 plays in the achievement of functional safety for E/E/PE safety-related systems.

Funktionale Sicherheit sicherheitsbezogener elektrischer/elektronischer/programmierbarer elektronischer Systeme - Teil 6: Anwendungsrichtlinie für IEC 61508-2 und IEC 61508-3 (IEC 61508-6:2010)

Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques programmables relatifs à la sécurité - Partie 6: Lignes directrices pour l'application de la CEI 61508-2 et de la CEI 61508-3 (CEI 61508-6:2010)

La CEI 61508-6:2010 contient des informations et lignes directrices sur la CEI 61508-2 et la CEI 61508-3. L'Annexe A présente un bref aperçu des exigences de la CEI 61508-2 et de la CEI 61508-3 et établit les étapes fonctionnelles de leur application. L'Annexe B donne une technique servant d'exemple pour le calcul des probabilités de défaillance du matériel; il convient de la lire conjointement au 7.4.3 et à l'Annexe C de la CEI 61508-2, et à l'Annexe D. L'Annexe C donne un exemple élaboré de calcul de la couverture de diagnostic; il convient de la lire conjointement avec l'Annexe C de la CEI 61508-2. L'Annexe D donne une méthodologie de quantification de l'effet des défaillances de cause commune relatives au matériel sur la probabilité de défaillance. L'Annexe E donne des exemples d'application des tableaux d'intégrité de sécurité du logiciel spécifiés dans l'Annexe A de la CEI 61508-3 pour les niveaux 2 et 3 d'intégrité de sécurité. 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.

Funkcijska varnost električnih/elektronskih/elektronsko programirljivih varnostnih sistemov - 6. del: Smernice za uporabo IEC 61508-2 in IEC 61508-3 (IEC 61508-6:2010)

1.1 Ta del IEC 61508 vsebuje informacije in smernice o IEC 61508-2 in IEC 61508-3.
– dodatek A podaja kratek pregled zahtev IEC 61508-2 in IEC 61508-3 ter določa funkcijske stopnje pri njihovi uporabi;
– dodatek B podaja vzorčno tehniko za izračun verjetnosti okvare strojne opreme in se mora brati v povezavi s 7.4.3 in dodatkom C IEC 61508-2 in dodatkom D;
– dodatek C podaja zgled za izračun diagnostične pokritosti in se mora brati v povezavi z dodatkom C IEC 61508-2;
– dodatek D podaja metodologijo za kvantifikacijo učinka pogostih vzrokov okvar, povezanih s strojno opremo, na verjetnost okvare;
– dodatek E podaja zgled za uporabo preglednic celovite varnosti programske opreme, ki jih določa dodatek A IEC 61508-3, za raven celovite varnosti 2 in 3.
1.2 IEC 61508-1, IEC 61508-2, IEC 61508-3 in IEC 61508-4 so osnovne varnostne objave, čeprav ta status ne velja v okviru nezapletenih varnostnih sistemov E/E/PE (glej točko 3.4.3 IEC 61508-4). Kot osnovne varnostne objave so namenjeni temu, da jih uporabljajo tehnični odbori pri pripravi standardov v skladu z načeli, opredeljenimi v Vodilu IEC 104 in Vodilu ISO/IEC 51. IEC 61508-1, IEC 61508-2, IEC 61508-3 in IEC 61508-4 se lahko tudi uporabijo kot samostojne objave. Horizontalno varnostno delovanje tega mednarodnega standarda ne velja za medicinsko opremo v skladu s serijo IEC 60601.
1.3 Ena od odgovornosti tehničnega odbora je, če je primerno, da uporabi temeljne varnostne objave pri pripravi svojih objav. V tem okviru zahteve, preskusne metode ali preskusni pogoji te temeljne varnostne objave ne veljajo, razen če se objave, ki so jih pripravili tehnični odbori, nanje izrecno sklicujejo ali jih vključujejo.
1.4 Slika 1 prikazuje celoten okvir serije IEC 61508 in nakazuje vlogo IEC 61508-6 pri doseganju funkcijske varnosti E/E/PE-varnostnih sistemov.

General Information

• Status: Published
• Publication Date: 11-Apr-2011
• ICS: 25.040.40 - Industrial process measurement and control
• Technical Committee: MOV - Measuring equipment for electromagnetic quantities
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 06-Apr-2011
• Due Date: 11-Jun-2011
• Completion Date: 12-Apr-2011
• Ref Project: EN 61508-6:2010 - Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 6: Guidelines on the application of IEC 61508-2 and IEC 61508-3

Relations

• Replaces: SIST EN 61508-6:2007 - Functional safety of electrical/electronic/programmable electronic safety-related systems -- Part 6: Guidelines on the application of IEC 61508-2 and IEC 61508-3
• Effective Date: 01-May-2011
• Replaces: SIST EN 61508-6:2007 - Functional safety of electrical/electronic/programmable electronic safety-related systems -- Part 6: Guidelines on the application of IEC 61508-2 and IEC 61508-3
• Effective Date: 28-Jan-2023
• Revised: SIST EN 61508-6:2007 - Functional safety of electrical/electronic/programmable electronic safety-related systems -- Part 6: Guidelines on the application of IEC 61508-2 and IEC 61508-3
• Effective Date: 07-May-2013

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 61508-6:2011
01-maj-2011
1DGRPHãþD
SIST EN 61508-6:2007
)XQNFLMVNDYDUQRVWHOHNWULþQLKHOHNWURQVNLKHOHNWURQVNRSURJUDPLUOMLYLKYDUQRVWQLK
VLVWHPRYGHO6PHUQLFH]DXSRUDER,(&LQ,(&,(&

Functional safety of electrical/electronic/programmable electronic safety-related systems
- Part 6: Guidelines on the application of IEC 61508-2 and IEC 61508-3 (IEC 61508-
6:2010)
Funktionale Sicherheit sicherheitsbezogener
elektrischer/elektronischer/programmierbarer elektronischer Systeme - Teil 6:
Anwendungsrichtlinie für IEC 61508-2 und IEC 61508-3 (IEC 61508-6:2010)
Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques
programmables relatifs à la sécurité - Partie 6: Lignes directrices pour l'application de la
CEI 61508-2 et de la CEI 61508-3 (CEI 61508-6:2010)
Ta slovenski standard je istoveten z: EN 61508-6:2010
ICS:
25.040.40 Merjenje in krmiljenje Industrial process
industrijskih postopkov measurement and control
SIST EN 61508-6:2011 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 61508-6:2011

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SIST EN 61508-6:2011

EUROPEAN STANDARD
EN 61508-6

NORME EUROPÉENNE
May 2010
EUROPÄISCHE NORM

ICS 25.040.40 Supersedes EN 61508-6:2001


English version


Functional safety of electrical/electronic/programmable electronic safety-
related systems -
Part 6: Guidelines on the application of IEC 61508-2 and IEC 61508-3
(IEC 61508-6:2010)


Sécurité fonctionnelle des systèmes Funktionale Sicherheit sicherheitsbezogener
électriques/électroniques/électroniques elektrischer/elektronischer/programmierbarer
programmables relatifs à la sécurité - elektronischer Systeme -
Partie 6: Lignes directrices Teil 6: Anwendungsrichtlinie für IEC 61508-2
pour l'application de la CEI 61508-2 und IEC 61508-3
et de la CEI 61508-3 (IEC 61508-6:2010)
(CEI 61508-6:2010)




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 61508-6:2010 E

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SIST EN 61508-6:2011
EN 61508-6:2010 - 2 -
Foreword
The text of document 65A/553/FDIS, future edition 2 of IEC 61508-6, 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 61508-6 on 2010-05-01.
This European Standard supersedes EN 61508-6:2001.
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 61508-6:2010 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.
[4] IEC 61078:2006 NOTE  Harmonized as EN 61078:2006 (not modified).
[5] IEC 61165:2006 NOTE  Harmonized as EN 61165:2006 (not modified).
[16] IEC 61131-3:2003 NOTE  Harmonized as EN 61131-3:2003 (not modified).
[18] IEC 61025:2006 NOTE  Harmonized as EN 61025:2007 (not modified).
[26] IEC 60601 series NOTE  Harmonized in EN 60601 series (partially modified).
[27] IEC 61508-1:2010 NOTE  Harmonized as EN 61508-1:2010 (not modified).
[28] IEC 61508-5:2010 NOTE  Harmonized as EN 61508-5:2010 (not modified).
[29] IEC 61508-7:2010 NOTE  Harmonized as EN 61508-7:2010 (not modified).
__________

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SIST EN 61508-6:2011
- 3 - EN 61508-6:2010
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 61508-2 2010 Functional safety of EN 61508-2 2010
electrical/electronic/programmable electronic
safety-related systems -
Part 2: Requirements for
electrical/electronic/programmable electronic
safety-related systems


IEC 61508-3 2010 Functional safety of EN 61508-3 2010
electrical/electronic/programmable electronic
safety-related systems -
Part 3: Software requirements


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

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SIST EN 61508-6:2011

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SIST EN 61508-6:2011
IEC 61508-6
®
Edition 2.0 2010-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE

Functional safety of electrical/electronic/programmable electronic safety-related
systems –
Part 6: Guidelines on the application of IEC 61508-2 and IEC 61508-3

Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques
programmables relatifs à la sécurité –
Partie 6: Lignes directrices pour l'application de la CEI 61508-2 et de la
CEI 61508-3

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
XE
CODE PRIX
ICS 25.040.40 ISBN 978-2-88910-529-8
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

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SIST EN 61508-6:2011
– 2 – 61508-6 © IEC:2010
CONTENTS
FOREWORD.6
INTRODUCTION.8
1 Scope.10
2 Normative references .12
3 Definitions and abbreviations.12
Annex A (informative) Application of IEC 61508-2 and of IEC 61508-3.13
Annex B (informative) Example of technique for evaluating probabilities of hardware
failure .21
Annex C (informative) Calculation of diagnostic coverage and safe failure fraction –
worked example.76
Annex D (informative) A methodology for quantifying the effect of hardware-related
common cause failures in E/E/PE systems.80
Annex E (informative) Example applications of software safety integrity tables of
IEC 61508-3 .95
Bibliography.110

Figure 1 – Overall framework of the IEC 61508 series .11
Figure A.1 – Application of IEC 61508-2 .17
Figure A.2 – Application of IEC 61508-2 (Figure A.1 continued).18
Figure A.3 – Application of IEC 61508-3 .20
Figure B.1 – Reliability Block Diagram of a whole safety loop .22
Figure B.2 – Example configuration for two sensor channels.26
Figure B.3 – Subsystem structure .29
Figure B.4 – 1oo1 physical block diagram .30
Figure B.5 – 1oo1 reliability block diagram.31
Figure B.6 – 1oo2 physical block diagram .32
Figure B.7 – 1oo2 reliability block diagram.32
Figure B.8 – 2oo2 physical block diagram .33
Figure B.9 – 2oo2 reliability block diagram.33
Figure B.10 – 1oo2D physical block diagram.33
Figure B.11 – 1oo2D reliability block diagram .34
Figure B.12 – 2oo3 physical block diagram .34
Figure B.13 – 2oo3 reliability block diagram.35
Figure B.14 – Architecture of an example for low demand mode of operation.40
Figure B.15 – Architecture of an example for high demand or continuous mode of
operation .49
Figure B.16 – Reliability block diagram of a simple whole loop with sensors organised
into 2oo3 logic .51
Figure B.17 – Simple fault tree equivalent to the reliability block diagram presented on
Figure B.1.52
Figure B.18 – Equivalence fault tree / reliability block diagram.52
Figure B.19 – Instantaneous unavailability U(t) of single periodically tested
components .54
Figure B.20 – Principle of PFD calculations when using fault trees.55
avg

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SIST EN 61508-6:2011
61508-6 © IEC:2010 – 3 –
Figure B.21 – Effect of staggering the tests .56
Figure B.22 – Example of complex testing pattern .56
Figure B.23 – Markov graph modelling the behaviour of a two component system .58
Figure B.24 – Principle of the multiphase Markovian modelling .59
Figure B.25 – Saw-tooth curve obtained by multiphase Markovian approach.60
Figure B.26 – Approximated Markovian model .60
Figure B.27 – Impact of failures due to the demand itself.61
Figure B.28 – Modelling of the impact of test duration.61
Figure B.29 – Multiphase Markovian model with both DD and DU failures.62
Figure B.30 – Changing logic (2oo3 to 1oo2) instead of repairing first failure.63
Figure B.31 – "Reliability" Markov graphs with an absorbing state .63
Figure B.32 – "Availability" Markov graphs without absorbing states .65
Figure B.33 – Petri net for modelling a single periodically tested component.66
Figure B.34 – Petri net to model common cause failure and repair resources.69
Figure B.35 – Using reliability block diagrams to build Petri net and auxiliary Petri net
for PFD and PFH calculations .70
Figure B.36 – Simple Petri net for a single component with revealed failures and
repairs .71
Figure B.37 – Example of functional and dysfunctional modelling with a formal
language.72
Figure B.38 – Uncertainty propagation principle.73
Figure D.1 – Relationship of common cause failures to the failures of individual
channels .82
Figure D.2 – Implementing shock model with fault trees.93

Table B.1 – Terms and their ranges used in this annex (applies to 1oo1, 1oo2, 2oo2,
1oo2D, 1oo3 and 2oo3) .27
Table B.2 – Average probability of failure on demand for a proof test interval of six
months and a mean time to restoration of 8 h .36
Table B.3 – Average probability of failure on demand for a proof test interval of one
year and mean time to restoration of 8 h.37
Table B.4 – Average probability of failure on demand for a proof test interval of two
years and a mean time to restoration of 8 h .38
Table B.5 – Average probability of failure on demand for a proof test interval of
ten years and a mean time to restoration of 8 h .39
Table B.6 – Average probability of failure on demand for the sensor subsystem in the
example for low demand mode of operation (one year proof test interval and
8 h MTTR) .40
Table B.7 – Average probability of failure on demand for the logic subsystem in the
example for low demand mode of operation (one year proof test interval and
8 h MTTR) .41
Table B.8 – Average probability of failure on demand for the final element subsystem
in the example for low demand mode of operation (one year proof test interval and
8 h MTTR) .41
Table B.9 – Example for a non-perfect proof test .42
Table B.10 – Average frequency of a dangerous failure (in high demand or continuous
mode of operation) for a proof test interval of one month and a mean time to
restoration of 8 h .45

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SIST EN 61508-6:2011
– 4 – 61508-6 © IEC:2010
Table B.11 – Average frequency of a dangerous failure (in high demand or continuous
mode of operation) for a proof test interval of three month and a mean time to
restoration of 8 h .46
Table B.12 – Average frequency of a dangerous failure (in high demand or continuous
mode of operation) for a proof test interval of six month and a mean time to restoration
of 8 h .Error! Bookmark not defined.
Table B.13 – Average frequency of a dangerous failure (in high demand or continuous
mode of operation) for a proof test interval of one year and a mean time to restoration
of 8 h .Error! Bookmark not defined.
Table B.14 – Average frequency of a dangerous failure for the sensor subsystem in the
example for high demand or continuous mode of operation (six month proof test
interval and 8 h MTTR) .49
Table B.15 – Average frequency of a dangerous failure for the logic subsystem in the
example for high demand or continuous mode of operation (six month proof test
interval and 8 h MTTR) .50
Table B.16 – Average frequency of a dangerous failure for the final element subsystem
in the example for high demand or continuous mode of operation (six month proof test
interval and 8 h MTTR) .50
Table C.1 – Example calculations for diagnostic coverage and safe failure fraction .78
Table C.2 – Diagnostic coverage and effectiveness for different elements .79
Table D.1 – Scoring programmable electronics or sensors/final elements .88
Table D.2 – Value of Z – programmable electronics .89
Table D.3 – Value of Z – sensors or final elements .89
Table D.4 – Calculation of β or β .90
int D int
Table D.5 – Calculation of β for systems with levels of redundancy greater than 1oo2 .91
Table D.6 – Example values for programmable electronics .92
Table E.1 – Software safety requirements specification .96
Table E.2 – Software design and development – software architecture design .97
Table E.3 – Software design and development – support tools and programming
language.98
Table E.4 – Software design and development – detailed design .99
Table E.5 – Software design and development – software module testing and
integration .100
Table E.6 – Programmable electronics integration (hardware and software). 100
Table E.7 – Software aspects of system safety validation .101
Table E.8 – Modification .101
Table E.9 – Software verification .102
Table E.10 – Functional safety assessment .102
Table E.11 – Software safety requirements specification . 104
Table E.12 – Software design and development – software architecture design .104
Table E.13 – Software design and development – support tools and programming
language.105
Table E.14 – Software design and development – detailed design .106
Table E.15 – Software design and development – software module testing and
integration .106
Table E.16 – Programmable electronics integration (hardware and software). 107
Table E.17 – Software aspects of system safety validation . 108
Table E.18 – Modification .108

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SIST EN 61508-6:2011
61508-6 © IEC:2010 – 5 –
Table E.19 – Software verification .109
Table E.20 – Functional safety assessment .109

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SIST EN 61508-6:2011
– 6 – 61508-6 © IEC:2010
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

FUNCTIONAL SAFETY OF ELECTRICAL/ELECTRONIC/
PROGRAMMABLE ELECTRONIC SAFETY-RELATED SYSTEMS –

Part 6: Guidelines on the application
of IEC 61508-2 and IEC 61508-3


FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
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8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61508-6 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 2000. 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.

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SIST EN 61508-6:2011
61508-6 © IEC:2010 – 7 –
The text of this standard is based on the following documents:
FDIS Report on voting
65A/553/FDIS 65A/577/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
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

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SIST EN 61508-6:2011
– 8 – 61508-6 © IEC:2010
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) are 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 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 been 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.
In most situations, safety is achieved by a number of systems which rely on many
technologies (for example mechanical, hydraulic, p
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