IEC TR 61508-0:2005
(Main)Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 0: Functional safety and IEC 61508 (see Functional Safety and IEC 61508)
Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 0: Functional safety and IEC 61508 (see Functional Safety and IEC 61508)
IEC/TR 61508-0:2005 introduces the concept of functional safety and gives an overview of the IEC 61508 series. This report is to be read in conjunction with the first edition of the IEC 61508 series of standards only!
Sécurité fonctionnelle des systèmes électriques/électroniques/ électroniques programmables relatifs à la sécurité - Partie 0: La sécurité fonctionnelle et la CEI 61508
introduit le concept de sécurité fonctionnelle et donne une vue d'ensemble de la série CEI 61508.
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IEC/TR 61508-0
Edition 1.0 2005-01
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
Functional safety of electrical/electronic/programmable electronic
safety-related systems –
Part 0: Functional safety and IEC 61508
Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques
programmables relatifs à la sécurité –
Partie 0: La sécurité fonctionnelle et la CEI 61508
IEC/TR 61508-0:2005
All rights reserved. Unless otherwise specified, 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 either IEC or
IEC's member National Committee in the country of the requester.
If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,
please contact the address below or your local IEC member National Committee for further information.
Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de la CEI ou du Comité national de la CEI du pays du demandeur.
Si vous avez des questions sur le copyright de la CEI ou si vous désirez obtenir des droits supplémentaires sur cette
publication, utilisez les coordonnées ci-après ou contactez le Comité national de la CEI de votre pays de résidence.
IEC Central Office
3, rue de Varembé
CH-1211 Geneva 20
Switzerland
Email: inmail@iec.ch
Web: www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.
ƒ Catalogue of IEC publications: www.iec.ch/searchpub
The IEC on-line Catalogue enables you to search by a variety of criteria (reference number, text, technical committee,…).
It also gives information on projects, withdrawn and replaced publications.
ƒ IEC Just Published: www.iec.ch/online_news/justpub
Stay up to date on all new IEC publications. Just Published details twice a month all new publications released. Available
on-line and also by email.
ƒ Electropedia: www.electropedia.org
The world's leading online dictionary of electronic and electrical terms containing more than 20 000 terms and definitions
in English and French, with equivalent terms in additional languages. Also known as the International Electrotechnical
Vocabulary online.
ƒ Customer Service Centre: www.iec.ch/webstore/custserv
If you wish to give us your feedback on this publication or need further assistance, please visit the Customer Service
Centre FAQ or contact us:
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A propos de la CEI
La Commission Electrotechnique Internationale (CEI) est la première organisation mondiale qui élabore et publie des
normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.
A propos des publications CEI
Le contenu technique des publications de la CEI est constamment revu. Veuillez vous assurer que vous possédez
l’édition la plus récente, un corrigendum ou amendement peut avoir été publié.
ƒ Catalogue des publications de la CEI: www.iec.ch/searchpub/cur_fut-f.htm
Le Catalogue en-ligne de la CEI vous permet d’effectuer des recherches en utilisant différents critères (numéro de référence,
texte, comité d’études,…). Il donne aussi des informations sur les projets et les publications retirées ou remplacées.
ƒ Just Published CEI: www.iec.ch/online_news/justpub
Restez informé sur les nouvelles publications de la CEI. Just Published détaille deux fois par mois les nouvelles
publications parues. Disponible en-ligne et aussi par email.
ƒ Electropedia: www.electropedia.org
Le premier dictionnaire en ligne au monde de termes électroniques et électriques. Il contient plus de 20 000 termes et
définitions en anglais et en français, ainsi que les termes équivalents dans les langues additionnelles. Egalement appelé
Vocabulaire Electrotechnique International en ligne.
ƒ Service Clients: www.iec.ch/webstore/custserv/custserv_entry-f.htm
Si vous désirez nous donner des commentaires sur cette publication ou si vous avez des questions, visitez le FAQ du
Service clients ou contactez-nous:
Email: csc@iec.ch
Tél.: +41 22 919 02 11
Fax: +41 22 919 03 00
IEC/TR 61508-0
Edition 1.0 2005-01
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
Functional safety of electrical/electronic/programmable electronic
safety-related systems –
Part 0: Functional safety and IEC 61508
Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques
programmables relatifs à la sécurité –
Partie 0: La sécurité fonctionnelle et la CEI 61508
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
Q
CODE PRIX
ICS 13.110; 25.040; 29.020; 35.240.50 ISBN 2-8318-7816-0
TR 61508-0 IEC:2005 –– 2 – 3 – TR 61508-0 © IEC:2005
CONTENTS
FOREWORD.3
INTRODUCTION.5
1 Scope .6
2 Normative references .6
3 Functional safety .7
3.1 What is functional safety? .7
3.2 Safety functions and safety-related systems.7
3.3 Example of functional safety .8
3.4 Challenges in achieving functional safety .8
4 IEC 61508 – Functional safety of E/E/PE safety-related systems .9
4.1 Objectives .9
4.2 E/E/PE safety-related systems .9
4.3 Technical approach .10
4.4 Safety integrity levels .11
4.5 Example of functional safety revisited .11
4.6 Parts framework of IEC 61508 .12
4.7 IEC 61508 as a basis for other standards.14
4.8 IEC 61508 as a stand-alone standard.14
4.9 Further information .15
Annex A (informative) List of frequently asked questions from IEC “functional safety” zone .16
TR 61508-0 © IEC:2005TR 61508-0 IEC:2005 –– 3 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FUNCTIONAL SAFETY OF ELECTRICAL/ELECTRONIC/
PROGRAMMABLE ELECTRONIC SAFETY-RELATED SYSTEMS –
Part 0: Functional safety and IEC 61508
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
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC 61508-0, which is a technical report, has been prepared by subcommittee 65A: System
Aspects, of IEC technical committee 65: Industrial-process measurement and control.
TR 61508-0 IEC:2005 –– 4 – 7 – TR 61508-0 © IEC:2005
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
65A/413/DTR 65A/422/RVC
Full information on the voting for the approval of this technical report 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.
The parts of this publication, IEC 61508, under the general title Functional safety of electrical/
electronic/programmable electronic safety-related systems are listed in 4.6.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result 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.
TR 61508-0 © IEC:2005TR 61508-0 IEC:2005 –– 5 – 9 –
INTRODUCTION
The purpose of this Technical Report is to introduce the concept of functional safety and to
give an overview of the IEC 61508 series of standards.
You should read it if you are:
• wondering whether IEC 61508 applies to you,
• involved in the development of electrical, electronic or programmable electronic systems
which may have safety implications, or
• drafting any other standard where functional safety is a relevant factor.
Clause 3 of this document gives an informal definition of functional safety, describes the
relationship between safety functions, safety integrity and safety-related systems, gives an
example of how functional safety requirements are derived, and lists some of the challenges
in achieving functional safety in electrical, electronic or programmable electronic systems.
Clause 4 gives details of IEC 61508, which provides an approach for achieving functional
safety. The clause describes the standard’s objectives, technical approach and parts
framework. It explains that IEC 61508 can be applied as is to a large range of industrial
applications and yet also provides a basis for many other standards.
TR 61508-0 IEC:2005 –– 6 – 11 – TR 61508-0 © IEC:2005
FUNCTIONAL SAFETY OF ELECTRICAL/ELECTRONIC/
PROGRAMMABLE ELECTRONIC SAFETY-RELATED SYSTEMS –
Part 0: Functional safety and IEC 61508
1 Scope
This Technical Report introduces the concept of functional safety and gives an overview of
the IEC 61508 series.
2 Normative references
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) appl
...
IEC/TR 61508-0
Edition 1.0 2005-01
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
Functional safety of electrical/electronic/programmable electronic
safety-related systems –
Part 0: Functional safety and IEC 61508
Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques
programmables relatifs à la sécurité –
Partie 0: La sécurité fonctionnelle et la CEI 61508
IEC/TR 61508-0:2005
All rights reserved. Unless otherwise specified, 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 either IEC or
IEC's member National Committee in the country of the requester.
If you have any questions about IEC copyright or have an enquiry about obtaining additional rights to this publication,
please contact the address below or your local IEC member National Committee for further information.
Droits de reproduction réservés. Sauf indication contraire, aucune partie de cette publication ne peut être reproduite
ni utilisée sous quelque forme que ce soit et par aucun procédé, électronique ou mécanique, y compris la photocopie
et les microfilms, sans l'accord écrit de la CEI ou du Comité national de la CEI du pays du demandeur.
Si vous avez des questions sur le copyright de la CEI ou si vous désirez obtenir des droits supplémentaires sur cette
publication, utilisez les coordonnées ci-après ou contactez le Comité national de la CEI de votre pays de résidence.
IEC Central Office
3, rue de Varembé
CH-1211 Geneva 20
Switzerland
Email: inmail@iec.ch
Web: www.iec.ch
About the IEC
The International Electrotechnical Commission (IEC) is the leading global organization that prepares and publishes
International Standards for all electrical, electronic and related technologies.
About IEC publications
The technical content of IEC publications is kept under constant review by the IEC. Please make sure that you have the
latest edition, a corrigenda or an amendment might have been published.
ƒ Catalogue of IEC publications: www.iec.ch/searchpub
The IEC on-line Catalogue enables you to search by a variety of criteria (reference number, text, technical committee,…).
It also gives information on projects, withdrawn and replaced publications.
ƒ IEC Just Published: www.iec.ch/online_news/justpub
Stay up to date on all new IEC publications. Just Published details twice a month all new publications released. Available
on-line and also by email.
ƒ Electropedia: www.electropedia.org
The world's leading online dictionary of electronic and electrical terms containing more than 20 000 terms and definitions
in English and French, with equivalent terms in additional languages. Also known as the International Electrotechnical
Vocabulary online.
ƒ Customer Service Centre: www.iec.ch/webstore/custserv
If you wish to give us your feedback on this publication or need further assistance, please visit the Customer Service
Centre FAQ or contact us:
Email: csc@iec.ch
Tel.: +41 22 919 02 11
Fax: +41 22 919 03 00
A propos de la CEI
La Commission Electrotechnique Internationale (CEI) est la première organisation mondiale qui élabore et publie des
normes internationales pour tout ce qui a trait à l'électricité, à l'électronique et aux technologies apparentées.
A propos des publications CEI
Le contenu technique des publications de la CEI est constamment revu. Veuillez vous assurer que vous possédez
l’édition la plus récente, un corrigendum ou amendement peut avoir été publié.
ƒ Catalogue des publications de la CEI: www.iec.ch/searchpub/cur_fut-f.htm
Le Catalogue en-ligne de la CEI vous permet d’effectuer des recherches en utilisant différents critères (numéro de référence,
texte, comité d’études,…). Il donne aussi des informations sur les projets et les publications retirées ou remplacées.
ƒ Just Published CEI: www.iec.ch/online_news/justpub
Restez informé sur les nouvelles publications de la CEI. Just Published détaille deux fois par mois les nouvelles
publications parues. Disponible en-ligne et aussi par email.
ƒ Electropedia: www.electropedia.org
Le premier dictionnaire en ligne au monde de termes électroniques et électriques. Il contient plus de 20 000 termes et
définitions en anglais et en français, ainsi que les termes équivalents dans les langues additionnelles. Egalement appelé
Vocabulaire Electrotechnique International en ligne.
ƒ Service Clients: www.iec.ch/webstore/custserv/custserv_entry-f.htm
Si vous désirez nous donner des commentaires sur cette publication ou si vous avez des questions, visitez le FAQ du
Service clients ou contactez-nous:
Email: csc@iec.ch
Tél.: +41 22 919 02 11
Fax: +41 22 919 03 00
IEC/TR 61508-0
Edition 1.0 2005-01
TECHNICAL
REPORT
RAPPORT
TECHNIQUE
Functional safety of electrical/electronic/programmable electronic
safety-related systems –
Part 0: Functional safety and IEC 61508
Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques
programmables relatifs à la sécurité –
Partie 0: La sécurité fonctionnelle et la CEI 61508
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
Q
CODE PRIX
ICS 13.110; 25.040; 29.020; 35.240.50 ISBN 2-8318-7816-0
TR 61508-0 IEC:2005 –– 2 – 3 – TR 61508-0 © IEC:2005
CONTENTS
FOREWORD.3
INTRODUCTION.5
1 Scope .6
2 Normative references .6
3 Functional safety .7
3.1 What is functional safety? .7
3.2 Safety functions and safety-related systems.7
3.3 Example of functional safety .8
3.4 Challenges in achieving functional safety .8
4 IEC 61508 – Functional safety of E/E/PE safety-related systems .9
4.1 Objectives .9
4.2 E/E/PE safety-related systems .9
4.3 Technical approach .10
4.4 Safety integrity levels .11
4.5 Example of functional safety revisited .11
4.6 Parts framework of IEC 61508 .12
4.7 IEC 61508 as a basis for other standards.14
4.8 IEC 61508 as a stand-alone standard.14
4.9 Further information .15
Annex A (informative) List of frequently asked questions from IEC “functional safety” zone .16
TR 61508-0 © IEC:2005TR 61508-0 IEC:2005 –– 3 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________
FUNCTIONAL SAFETY OF ELECTRICAL/ELECTRONIC/
PROGRAMMABLE ELECTRONIC SAFETY-RELATED SYSTEMS –
Part 0: Functional safety and IEC 61508
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
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
Publication(s)”). Their preparation is entrusted to technical committees; any IEC National Committee interested
in the subject dealt with may participate in this preparatory work. International, governmental and non-
governmental organizations liaising with the IEC also participate in this preparation. IEC collaborates closely
with the International Organization for Standardization (ISO) in accordance with conditions determined by
agreement between the two organizations.
2) The formal decisions or agreements of IEC on technical matters express, as nearly as possible, an international
consensus of opinion on the relevant subjects since each technical committee has representation from all
interested IEC National Committees.
3) IEC Publications have the form of recommendations for international use and are accepted by IEC National
Committees in that sense. While all reasonable efforts are made to ensure that the technical content of IEC
Publications is accurate, IEC cannot be held responsible for the way in which they are used or for any
misinterpretation by any end user.
4) In order to promote international uniformity, IEC National Committees undertake to apply IEC Publications
transparently to the maximum extent possible in their national and regional publications. Any divergence
between any IEC Publication and the corresponding national or regional publication shall be clearly indicated in
the latter.
5) IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with an IEC Publication.
6) All users should ensure that they have the latest edition of this publication.
7) No liability shall attach to IEC or its directors, employees, servants or agents including individual experts and
members of its technical committees and IEC National Committees for any personal injury, property damage or
other damage of any nature whatsoever, whether direct or indirect, or for costs (including legal fees) and
expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
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.
The main task of IEC technical committees is to prepare International Standards. However, a
technical committee may propose the publication of a technical report when it has collected
data of a different kind from that which is normally published as an International Standard, for
example "state of the art".
IEC 61508-0, which is a technical report, has been prepared by subcommittee 65A: System
Aspects, of IEC technical committee 65: Industrial-process measurement and control.
TR 61508-0 IEC:2005 –– 4 – 7 – TR 61508-0 © IEC:2005
The text of this technical report is based on the following documents:
Enquiry draft Report on voting
65A/413/DTR 65A/422/RVC
Full information on the voting for the approval of this technical report 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.
The parts of this publication, IEC 61508, under the general title Functional safety of electrical/
electronic/programmable electronic safety-related systems are listed in 4.6.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result 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.
TR 61508-0 © IEC:2005TR 61508-0 IEC:2005 –– 5 – 9 –
INTRODUCTION
The purpose of this Technical Report is to introduce the concept of functional safety and to
give an overview of the IEC 61508 series of standards.
You should read it if you are:
• wondering whether IEC 61508 applies to you,
• involved in the development of electrical, electronic or programmable electronic systems
which may have safety implications, or
• drafting any other standard where functional safety is a relevant factor.
Clause 3 of this document gives an informal definition of functional safety, describes the
relationship between safety functions, safety integrity and safety-related systems, gives an
example of how functional safety requirements are derived, and lists some of the challenges
in achieving functional safety in electrical, electronic or programmable electronic systems.
Clause 4 gives details of IEC 61508, which provides an approach for achieving functional
safety. The clause describes the standard’s objectives, technical approach and parts
framework. It explains that IEC 61508 can be applied as is to a large range of industrial
applications and yet also provides a basis for many other standards.
TR 61508-0 IEC:2005 –– 6 – 11 – TR 61508-0 © IEC:2005
FUNCTIONAL SAFETY OF ELECTRICAL/ELECTRONIC/
PROGRAMMABLE ELECTRONIC SAFETY-RELATED SYSTEMS –
Part 0: Functional safety and IEC 61508
1 Scope
This Technical Report introduces the concept of functional safety and gives an overview of
the IEC 61508 series.
2 Normative references
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) appl
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.