SIST EN 61508-1:2011

Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 1: General requirements (IEC 61508-1:2010)

1.1 This International Standard covers those aspects to be considered when electrical/electronic/programmable electronic (E/E/PE) systems are used to carry out safety functions. A major objective of this standard is to facilitate the development of product and application sector international standards by the technical committees responsible for the product or application sector. This will allow all the relevant factors, associated with the product or application, to be fully taken into account and thereby meet the specific needs of users of the product and the application sector. A second objective of this standard is to enable the development of E/E/PE safety-related systems where product or application sector international standards do not exist.
1.2 In particular, this standard
a) applies to safety-related systems when one or more of such systems incorporates electrical/electronic/programmable electronic elements;
NOTE 1 In the context of low complexity E/E/PE safety-related systems, certain requirements specified in this standard may be unnecessary, and exemption from compliance with such  requirements is possible (see 4.2, and the definition of a low complexity E/E/PE safety-related system in 3.4.3 of IEC 61508-4).
NOTE 2 Although a person can form part of a safety-related system (see 3.4.1 of IEC 61508-4), human factor requirements related to the design of E/E/PE safety-related systems are not considered in detail in this standard.
b) is generically-based and applicable to all E/E/PE safety-related systems irrespective of the
application;
c) covers the achievement of a tolerable risk through the application of E/E/PE safety-related systems, but does not cover hazards arising from the E/E/PE equipment itself (for example electric shock);
d) applies to all types of E/E/PE safety-related systems, including protection systems and control systems;
e) does not cover E/E/PE systems where
– a single E/E/PE system is capable on its own of meeting the tolerable risk, and
– the required safety integrity of the safety functions of the single E/E/PE system is less than that specified for safety integrity level 1 (the lowest safety integrity level in this
standard).
f) is mainly concerned with the E/E/PE safety-related systems whose failure could have an impact on the safety of persons and/or the environment; however, it is recognized that the consequences of failure could also have serious economic implications and in such cases this standard could be used to specify any E/E/PE system used for the protection of equipment or product;
NOTE 3 See 3.1.1 of IEC 61508-4.
g) considers E/E/PE safety-related systems and other risk reduction measures, in order that
the safety requirements specification for the E/E/PE safety-related systems can be determined in a systematic, risk-based manner;
h) uses an overall safety lifecycle model as the technical framework for dealing systematically
with the activities necessary for ensuring the functional safety of the E/E/PE safety-related
systems;
NOTE 4 Although the overall safety lifecycle is primarily concerned with E/E/PE safety-related systems, it could also provide a technical framework for considering any safety-related system  irrespective of the technology of that system (for example mechanical, hydraulic or pneumatic).
i) does not specify the safety integrity levels required for sector applications (which must be based on detailed information and knowledge of the sector application). The technical committees responsible for the specific application sectors shall specify, where appropriate, the safety integrity levels in the application sector standards;
j) provides general requirements for E/E/PE safety-related systems where no product or application sector international standards exist;
(...)

Funktionale Sicherheit sicherheitsbezogener elektrischer/elektronischer/programmierbarer elektronischer Systeme -Teil 1: Allgemeine Anforderungen (IEC 61508-1:2010)

Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques programmables relatifs à la sécurité - Partie 1: Prescriptions générales (CEI 61508-1:2010)

La CEI 61508-1:2010 traite des aspects à prendre en considération lors de l'utilisation de systèmes électriques/électroniques/électroniques programmables (E/E/PE) pour exécuter des fonctions de sécurité. L'un des objectifs majeurs de la présente norme est de permettre l'élaboration par les comités d'études qui en sont responsables de normes internationales de produit et d'application sectorielle. Cela permet de prendre pleinement en compte l'ensemble des facteurs pertinents associés au produit ou à l'application, et donc de répondre aux besoins spécifiques des utilisateurs du produit et du secteur d'application concernés. Un second objectif de la présente norme est de permettre le développement de systèmes E/E/PE relatifs à la sécurité en l'absence de normes internationales de produit ou d'application sectorielle. 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 - 1. del: Splošne zahteve (IEC 61508-1:2010)

1.1 Ta mednarodni standard zajema vidike, ki se morajo upoštevati, ko se za izvajanje varnostnih funkcij uporabljajo  električni/elektronski/programirljivi elektronski(E/E/PE) sistemi. Glavni cilj tega standarda je tehničnim odborom, odgovornim za proizvod ali aplikacijski sektor, omogočiti razvoj mednarodnih standardov za proizvode in aplikacijske sektorje. To omogoča, da se v celoti upoštevajo vsi pomembni dejavniki, povezani s proizvodom ali aplikacijo, in se tako zadovoljijo specifične potrebe uporabnikov proizvodov in aplikacijskega sektorja. Drug cilj tega standarda je omogočiti razvoj varnostnih sistemov E/E/PE, za katere mednarodni standardi za proizvode ali aplikacijske sektorje ne obstajajo.
1.2 Ta standard še zlasti
a) velja za varnostne sisteme, pri katerih eden ali več od takih sistemov vključuje električne/elektronske/elektronsko programirljive elemente;
OPOMBA 1: V okviru nezapletenih varnostnih sistemov E/E/EP obstajajo nekatere zahteve, opredeljene v tem standardu, lahko nepotrebne, in mogoče je izvzetje od izpolnjevanja takih zahtev (glej točko 4.2 in opredelitev nezapletenih varnostnih sistemov E/E/PE v točki 3.4.3 IEC 61508-4).
OPOMBA 2: Čeprav oseba lahko tvori del varnostnega sistema (glej točko 3.4.1 IEC 61508-4), zahtev za človeške dejavnike, povezane s projektiranjem varnostnih sistemov E/E/PE, ta standard ne obravnava podrobno.
b) je narejen generično in velja za vse E/E/PE-varnostne sisteme, ne glede na aplikacijo;
c) zajema doseganje sprejemljivega tveganja z uporabo varnostnih sistemov E/E/PE, vendar ne zajema nevarnosti, ki izhajajo iz same opreme E/E/PE (na primer elektrošoka);
d) velja za vse vrste varnostnih sistemov E/E/PE, vključno z zaščitnimi in nadzornimi sistemi;
e) ne zajema sistemov E/E/PE, pri katerih
– en sam sistem E/E/PE samostojno dosega sprejemljivo tveganje in
– zahtevana varnostna celovitost varnostnih funkcij enojnega sistema E/E/PE je nižja od varnostne celovitosti, opredeljene za varnostno celovitost stopnje 1 (najnižje stopnje varnostne celovitosti v tem standardu).
f) v glavnem obravnava varnostne sisteme E/E/PE, pri katerih bi okvara lahko vplivala na varnost oseb in/ali okolja, vendar pa se priznava, da bi imele posledice okvare lahko resne ekonomske posledice in v takih primerih standard lahko določil sistem E/E/PE, ki se uporabi za zaščito opreme ali proizvoda;
OPOMBA 3 Glej točko 3.1.1 IEC 61508-4.
g) obravnava varnostne sisteme E/E/PE in druge ukrepe za zmanjševanje tveganja, da
se specifikacije varnostnih zahtev za varnostne sisteme E/E/PE lahko določijo sistematično, kar izhaja iz tveganja;
h) kot tehnični okvir za sistematično obravnavo aktivnosti, potrebnih za zagotavljanje funkcijske varnosti varnostnih sistemov E/E/PE, uporablja celovit model varnostnega cikla;
OPOMBA 4: Čeprav celovit model varnostnega cikla obravnava predvsem varnostne sisteme E/E/PE, lahko zagotavlja tudi tehnični okvir za obravnavo vseh varnostnih sistemov, ne glede na njihovo tehnologijo (na primer mehanskih, hidravličnih ali pnevmatskih).
i) ne določa stopenj varnostne celovitosti, potrebnih za sektorske aplikacije (ki morajo temeljiti na podrobnih informacijah in poznavanju sektorske aplikacije). Tehnični odbori, odgovorni za določen aplikacijski sektor, po potrebi opredelijo stopnje varnostne celovitosti v standardih za aplikacijski sektor;
j) zagotavlja splošne zahteve za varnostne sisteme E/E/PE, za katere ne obstaja mednarodni standard za proizvod ali aplikacijski sektor;
k) zahteva, da se med analizo nevarnosti in tveganja obravnavajo zlonamerna in nepooblaščena dejanja. Obseg analize vključuje vse pomembne faze varnostnega cikla;

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 61508-1:2010 - Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 1: General requirements

Relations

• Replaces: SIST EN 61508-1:2007 - Functional safety of electrical/electronic/programmable electronic safety-related systems -- Part 1: General requirements
• Effective Date: 01-May-2011
• Revised: SIST EN 61508-1:2007 - Functional safety of electrical/electronic/programmable electronic safety-related systems -- Part 1: General requirements
• Effective Date: 07-May-2013
• Replaces: SIST EN 61508-1:2007 - Functional safety of electrical/electronic/programmable electronic safety-related systems -- Part 1: General requirements
• Effective Date: 28-Jan-2023
• Replaces: SIST EN 61508-1:2007 - Functional safety of electrical/electronic/programmable electronic safety-related systems -- Part 1: General requirements
• Effective Date: 07-Jun-2022

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 61508-1:2011
01-maj-2011
1DGRPHãþD
SIST EN 61508-1:2007
)XQNFLMVNDYDUQRVWHOHNWULþQLKHOHNWURQVNLKHOHNWURQVNRSURJUDPLUOMLYLKYDUQRVWQLK
VLVWHPRYGHO6SORãQH]DKWHYH,(&
Functional safety of electrical/electronic/programmable electronic safety-related systems
- Part 1: General requirements (IEC 61508-1:2010)
Funktionale Sicherheit sicherheitsbezogener
elektrischer/elektronischer/programmierbarer elektronischer Systeme -Teil 1: Allgemeine
Anforderungen (IEC 61508-1:2010)
Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques
programmables relatifs à la sécurité - Partie 1: Prescriptions générales (CEI 61508-
1:2010)
Ta slovenski standard je istoveten z: EN 61508-1:2010
ICS:
25.040.40 Merjenje in krmiljenje Industrial process
industrijskih postopkov measurement and control
SIST EN 61508-1:2011 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

---------------------- Page: 1 ----------------------

SIST EN 61508-1:2011

---------------------- Page: 2 ----------------------

SIST EN 61508-1:2011

EUROPEAN STANDARD
EN 61508-1

NORME EUROPÉENNE
May 2010
EUROPÄISCHE NORM

ICS 13.110; 25.040; 29.020 Supersedes EN 61508-1:2001


English version


Functional safety of electrical/electronic/programmable electronic
safety-related systems -
Part 1: General requirements
(IEC 61508-1:2010)


Sécurité fonctionnelle des systèmes Funktionale Sicherheit sicherheitsbezogener
électriques/électroniques/électroniques elektrischer/elektronischer/programmierbarer
programmables relatifs à la sécurité - elektronischer Systeme -Teil 1: Allgemeine
Partie 1: Exigences générales Anforderungen
(CEI 61508-1:2010) (IEC 61508-1:2010)




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 61508-1:2010 E

---------------------- Page: 3 ----------------------

SIST EN 61508-1:2011
EN 61508-1:2010 - 2 -
Foreword
The text of document 65A/548/FDIS, future edition 2 of IEC 61508-1, 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 61508-1 on 2010-05-01.
This European Standard supersedes EN 61508-1:2001.
It has the status of a basic safety publication according to IEC Guide 104.
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 61508-1:2010 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.
[5] IEC 61508-6:2010 NOTE  Harmonized as EN 61508-6:2010 (not modified).
[6] IEC 61508-7:2010 NOTE  Harmonized as EN 61508-7:2010 (not modified).
[10] IEC 60300-3-1:2003 NOTE  Harmonized as EN 60300-3-1:2004 (not modified).
[15] IEC 61326-3-1 NOTE  Harmonized as EN 61326-3-1.
[17] IEC 61355 series NOTE  Harmonized in EN 61355 series (not modified).
[18] IEC 60601 series NOTE  Harmonized in EN 60601 series (partially modified).
[20] IEC 61508-5:2010 NOTE  Harmonized as EN 61508-5:2010 (not modified).
__________

---------------------- Page: 4 ----------------------

SIST EN 61508-1:2011
- 3 - EN 61508-1:2010
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


IEC Guide 104 1997 The preparation of safety publications - -
and the use of basic safety publications
and group safety publications


ISO/IEC Guide 51 1999 Safety aspects - Guidelines - -
for their inclusion in standards

---------------------- Page: 5 ----------------------

SIST EN 61508-1:2011

---------------------- Page: 6 ----------------------

SIST EN 61508-1:2011
IEC 61508-1
®
Edition 2.0 2010-04
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
BASIC SAFETY PUBLICATION
PUBLICATION FONDAMENTALE DE SÉCURITÉ
Functional safety of electrical/electronic/programmable electronic safety-related
systems –
Part 1: General requirements

Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques
programmables relatifs à la sécurité –
Partie 1: Exigences générales


INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
XB
CODE PRIX
ICS 13.110; 25.040; 29.020 ISBN 978-2-88910-524-3
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale

---------------------- Page: 7 ----------------------

SIST EN 61508-1:2011
– 2 – 61508-1 © IEC:2010
CONTENTS
FOREWORD.5
INTRODUCTION.7
1 Scope.9
2 Normative references.12
3 Definitions and abbreviations .12
4 Conformance to this standard .12
5 Documentation .13
5.1 Objectives .13
5.2 Requirements .13
6 Management of functional safety.14
6.1 Objectives .14
6.2 Requirements .14
7 Overall safety lifecycle requirements .17
7.1 General .17
7.1.1 Introduction .17
7.1.2 Objectives and requirements – general .20
7.1.3 Objectives .25
7.1.4 Requirements .25
7.2 Concept.25
7.2.1 Objective .25
7.2.2 Requirements .26
7.3 Overall scope definition .26
7.3.1 Objectives .26
7.3.2 Requirements .26
7.4 Hazard and risk analysis .27
7.4.1 Objectives .27
7.4.2 Requirements .27
7.5 Overall safety requirements .28
7.5.1 Objective .29
7.5.2 Requirements .29
7.6 Overall safety requirements allocation.30
7.6.1 Objectives .30
7.6.2 Requirements .31
7.7 Overall operation and maintenance planning .35
7.7.1 Objective .35
7.7.2 Requirements .35
7.8 Overall safety validation planning.37
7.8.1 Objective .37
7.8.2 Requirements .37
7.9 Overall installation and commissioning planning.38
7.9.1 Objectives .38
7.9.2 Requirements .38
7.10 E/E/PE system safety requirements specification .38
7.10.1 Objective .39
7.10.2 Requirements .39
7.11 E/E/PE safety-related systems – realisation .41

---------------------- Page: 8 ----------------------

SIST EN 61508-1:2011
61508-1 © IEC:2010 – 3 –
7.11.1 Objective .41
7.11.2 Requirements .41
7.12 Other risk reduction measures – specification and realisation.41
7.12.1 Objective .41
7.12.2 Requirements .41
7.13 Overall installation and commissioning.41
7.13.1 Objectives .41
7.13.2 Requirements .42
7.14 Overall safety validation.42
7.14.1 Objective .42
7.14.2 Requirements .42
7.15 Overall operation, maintenance and repair .43
7.15.1 Objective .43
7.15.2 Requirements .43
7.16 Overall modification and retrofit .46
7.16.1 Objective .46
7.16.2 Requirements .47
7.17 Decommissioning or disposal.48
7.17.1 Objective .48
7.17.2 Requirements .48
7.18 Verification .49
7.18.1 Objective .49
7.18.2 Requirements .49
8 Functional safety assessment .50
8.1 Objective .50
8.2 Requirements .50
Annex A (informative) Example of a documentation structure.54
Bibliography .60

Figure 1 – Overall framework of the IEC 61508 series .11
Figure 2 – Overall safety lifecycle .18
Figure 3 – E/E/PE system safety lifecycle (in realisation phase) .19
Figure 4 – Software safety lifecycle (in realisation phase) .19
Figure 5 – Relationship of overall safety lifecycle to the E/E/PE system and software
safety lifecycles.20
Figure 6 – Allocation of overall safety requirements to E/E/PE safety-related systems
and other risk reduction measures.32
Figure 7 – Example of operations and maintenance activities model .45
Figure 8 – Example of operation and maintenance management model .46
Figure 9 – Example of modification procedure model.48
Figure A.1 – Structuring information into document sets for user groups .59

Table 1 – Overall safety lifecycle – overview.21
Table 2 – Safety integrity levels – target failure measures for a safety function operating
in low demand mode of operation .33
Table 3 – Safety integrity levels – target failure measures for a safety function operating
in high demand mode of operation or continuous mode of operation .34

---------------------- Page: 9 ----------------------

SIST EN 61508-1:2011
– 4 – 61508-1 © IEC:2010
Table 4 – Minimum levels of independence of those carrying out functional safety
assessment (overall safety lifecycle phases 1 to 8 and 12 to 16 inclusive (see Figure 2)) .53
Table 5 – Minimum levels of independence of those carrying out functional safety
assessment (overall safety lifecycle phases 9 and 10, including all phases of E/E/PE
system and software safety lifecycles (see Figures 2, 3 and 4)) .53
Table A.1 – Example of a documentation structure for information related to the overall
safety lifecycle .56
Table A.2 – Example of a documentation structure for information related to the E/E/PE
system safety lifecycle.57
Table A.3 – Example of a documentation structure for information related to the
software safety lifecycle .58

---------------------- Page: 10 ----------------------

SIST EN 61508-1:2011
61508-1 © IEC:2010 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
____________

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

Part 1: General requirements


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 itself does not provide any attestation of conformity. Independent certification bodies provide conformity
assessment services and, in some areas, access to IEC marks of conformity. IEC is not responsible for any
services carried out by independent certification bodies.
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.
International Standard IEC 61508-1 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.
It has the status of a basic safety publication according to IEC Guide 104.

---------------------- Page: 11 ----------------------

SIST EN 61508-1:2011
– 6 – 61508-1 © IEC:2010
The text of this standard is based on the following documents:
FDIS Report on voting
65A/548/FDIS 65A/572/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
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.

---------------------- Page: 12 ----------------------

SIST EN 61508-1:2011
61508-1 © IEC:2010 – 7 –
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.
NOTE 1 Examples of product and 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, 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 this
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 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 formulated 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, through design, implementation, operation 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 international 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 within 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 approach 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 requirements 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.

---------------------- Page: 13 ----------------------

SIST EN 61508-1:2011
– 8 – 61508-1 © IEC:2010
– sets target failure measures for safety functions carried out by E/E/PE safety-related
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 average probability of a
–5
dangerous failure on demand of 10 ;
– a high demand or a continuous mode of operation, the lower limit is set at an average
–9 -1
frequency of a dangerous failure of 10 [h ];
NOTE 3 A single E/E/PE safety-related system does not necessarily mean a single-channel architecture.
NOTE 4 It may be possible to achieve designs of
...