SIST EN 61508-1:2007

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

Covers those aspects to be considered when electrical/electronic/programmable electronic systems (E/E/PESs) are used to carry out safety functions. A major objective of this standard is to facilitate the development of application sector international standards by the technical committees responsible for the application sector. This will allow all the relevant factors, associated with the application, to be fully taken into account and thereby meet the specific needs of the application sector. A dual objective of this standard is to enable the development of electrical/electronic/programmable electronic (E/E/PE) safety-related systems where application sector international standards may nog exist.

Funktionale Sicherheit sicherheitsbezogener elektrischer/elektronischer/programmierbarer elektronischer Systeme -- Teil 1: Allgemeine Anforderungen

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

Présente une approche générique de toutes les activités liées au cycle de vie de sécurité de systèmes électriques / électroniques / électroniques porgrammables (E/E/PES) qui sont utilisés pour réaliser des fonctions de sécurité. Cette approche unifiée a été adoptée afin de développer une politique technique rationelle et cohérente concernant tous les appareils électriques liées à la sécurité. Déstinée à faciliter l'élaboration de normes par secteur d'application. A le statut, d'une publication fondamentale de sécurité conformément au Guide 104.

Funkcijska varnost električnih/elektronskih/programirljivih elektronskih varnostnih sistemov - 1. del: Splošne zahteve (IEC 61508-1:1998 + popravek 1999)

General Information

• Status: Withdrawn
• Publication Date: 31-Dec-2006
• Withdrawal Date: 11-Apr-2011
• ICS: 25.040.40 - Industrial process measurement and control
• Technical Committee: MKP - Industrial-process measurement and control
• Current Stage: 9900 - Withdrawal (Adopted Project)
• Start Date: 11-Apr-2011
• Due Date: 04-May-2011
• Completion Date: 12-Apr-2011
• Ref Project: EN 61508-1:2001 - Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 1: General requirements

Relations

• Revised: SIST EN 61508-1:2011 - Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 1: General requirements (IEC 61508-1:2010)
• Effective Date: 07-May-2013
• Replaced By: SIST EN 61508-1:2011 - Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 1: General requirements (IEC 61508-1:2010)
• Effective Date: 28-Jan-2023
• Replaced By: SIST EN 61508-1:2011 - Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 1: General requirements (IEC 61508-1:2010)
• Effective Date: 07-Jun-2022
• Replaced By: SIST EN 61508-1:2011 - Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 1: General requirements (IEC 61508-1:2010)
• Effective Date: 01-May-2011

Standards Content (Sample)

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EUROPEAN STANDARD EN 61508-1
NORME EUROPÉENNE
EUROPÄISCHE NORM December 2001
ICS 13.110;25.040;29.020;35.240.50
English version
Functional safety of electrical/electronic/programmable electronic
safety-related systems
Part 1: General requirements
(IEC 61508-1:1998 + corrigendum 1999)
Sécurité fonctionnelle des systèmes Funktionale Sicherheit
électriques/électroniques/électroniques sicherheitsbezogener elektrischer/
programmables relatifs à la sécurité elektronischer/programmierbarer
Partie 1: Prescriptions générales elektronischer Systeme
(CEI 61508-1:1998 + corrigendum 1999) Teil 1: Allgemeine Anforderungen
(IEC 61508-1:1998 + Corrigendum 1999)
This European Standard was approved by CENELEC on 2001-07-03. 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, Czech Republic,
Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands,
Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2001 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 61508-1:2001 E

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EN 61508-1:2001 - 2 -
Foreword
The text of the International Standard IEC 61508-1:1998 including its corrigendum May 1999,
prepared by SC 65A, System aspects, of IEC TC 65, Industrial-process measurement and control,
was submitted to the Unique Acceptance Procedure and was approved by CENELEC as EN 61508-1
on 2001-07-03 without any modification.
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) 2002-08-01
– latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2004-08-01
Annexes designated "normative" are part of the body of the standard.
Annexes designated "informative" are given for information only.
In this standard, annex ZA is normative and annexes A, B and C are informative.
Annex ZA has been added by CENELEC.
IEC 61508 is a basic safety publication covering the functional safety of electrical, electronic and
programmable electronic safety-related systems. The scope states:
"This International Standard covers those aspects to be considered when electrical/electronic/
programmable electronic systems (E/E/PESs) are used to carry out safety functions. A major objective
of this standard is to facilitate the development of application sector international standards by the
technical committees responsible for the application sector. This will allow all the relevant factors
associated with the application, to be fully taken into account and thereby meet the specific needs of
the application sector. A dual objective of this standard is to enable the development of
electrical/electronic/programmable electronic (E/E/PE) safety-related systems where application sector
international standards may not exist".
The CENELEC Report R0BT-004, ratified by 103 BT (March 2000) accepts that some IEC standards,
which today are either published or under development, are sector implementations of IEC 61508. For
example:
� IEC 61511, Functional safety - Safety instrumented systems for the process industry sector;
� IEC 62061, Safety of machinery – Functional safety of electrical, electronic and programmable
electronic control systems;
� IEC 61513, Nuclear power plants – Instrumentation and control for systems important to safety –
General requirements for systems.
The railways sector has also developed a set of European Standards (EN 50126; EN 50128 and
prEN 50129).
NOTE  EN 50126 and EN 50128 were based on earlier drafts of IEC 61508. prEN 50129 is based on the principles of the
latest version of IEC 61508.
This list does not preclude other sector implementations of IEC 61508 which could be currently under
development or published within IEC or CENELEC.
__________

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- 3 - EN 61508-1:2001
Endorsement notice
The text of the International Standard IEC 61508-1:1998 including its corrigendum May 1999 was
approved by CENELEC as a European Standard without any modification.
In the official version, for Bibliography, the following note has to be added for the standard indicated:
IEC 61355:1997 NOTE  Harmonized as EN 61355:1997 (not modified).
__________

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EN 61508-1:2001 - 4 -
Annex ZA
(normative)
Normative references to international publications
with their corresponding European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of any
of these publications apply to this European Standard only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies (including
amendments).
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
ISO/IEC Guide 51 1990 Guidelines for the inclusion of safety--
aspects in standards
IEC Guide 104 1997 The preparation of safety publications--
and the use of basic safety publications
and group safety publications
IEC 61508-2 2000 Functional safety of EN 61508-2 2001
electrical/electronic/programmable
electronic safety-related systems
Part 2: Requirements for
electrical/electronic/programmable
electronic safety-related systems
IEC 61508-3 1998 Part 3: Software requirements EN 61508-3 2001
+ corr. April 1999
IEC 61508-4 1998 Part 4: Definitions and abbreviations EN 61508-4 2001
+ corr. April 1999
IEC 61508-5 1998 Part 5: Examples of methods for the EN 61508-5 2001
+ corr. April 1999 determination of safety integrity levels
IEC 61508-6 2000 Part 6: Guidelines on the application of EN 61508-6 2001
IEC 61508-2 and IEC 61508-3
IEC 61508-7 2000 Part 7: Overview of techniques and EN 61508-7 2001
measures

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INTERNATIONAL IEC
STANDARD
61508-1
First edition
1998-12
BASIC SAFETY PUBLICATION
Functional safety of electrical/electronic/
programmable electronic safety-related systems –
Part 1:
General requirements
 IEC 1998 Copyright - all rights reserved
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 the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail]  Web: www.iec.ch
PRICE CODE
XA
Commission Electrotechnique Internationale
International Electrotechnical Commission
Международная Электротехническая Комиссия
For price, see current catalogue

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61508-1 © IEC:1998 – 3 –
CONTENTS
Page
FOREWORD . 7
INTRODUCTION . 11
Clause
1 Scope . 15
2 Normative references . 21
3 Definitions and abbreviations. 21
4 Conformance to this standard. 23
5 Documentation. 23
5.1 Objectives. 23
5.2 Requirements . 25
6 Management of functional safety . 27
6.1 Objectives. 27
6.2 Requirements . 27
7 Overall safety lifecycle requirements . 31
7.1 General. 31
7.2 Concept . 49
7.3 Overall scope definition. 49
7.4 Hazard and risk analysis . 51
7.5 Overall safety requirements. 55
7.6 Safety requirements allocation . 57
7.7 Overall operation and maintenance planning . 69
7.8 Overall safety validation planning . 71
7.9 Overall installation and commissioning planning . 73
7.10 Realisation: E/E/PES. 75
7.11 Realisation: other technology . 75
7.12 Realisation: external risk reduction facilities . 75
7.13 Overall installation and commissioning . 77
7.14 Overall safety validation . 77
7.15 Overall operation, maintenance and repair. 79
7.16 Overall modification and retrofit. 85
7.17 Decommissioning or disposal . 89
7.18 Verification. 91
8 Functional safety assessment. 93
8.1 Objective . 93
8.2 Requirements . 93

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61508-1 © IEC:1998 – 5 –
Annexes
Annex A (informative) Example documentation structure. 99
A.1 General . 99
A.2 Safety lifecycle document structure . 101
A.3 Physical document structure . 107
A.4 List of documents. 111
Annex B (informative) Competence of persons. 113
B.1 Objective . 113
B.2 General considerations . 113
Annex C (informative) Bibliography . 115
Tables
1 Overall safety lifecycle: overview . 39
2 Safety integrity levels: target failure measures for a safety function, allocated to
an E/E/PE safety-related system operating in low demand mode of operation . 65
3 Safety integrity levels: target failure measures for a safety function, allocated to
an E/E/PE safety-related system operating in high demand or continuous mode
of operation.65
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)) . 97
5 Minimum levels of independence of those carrying out functional safety assessment
(overall safety lifecycle phase 9 - includes all phases of E/E/PES and software safety
lifecycles (see figures 2, 3 and 4)) . 97
A.1 Example documentation structure for information related to the overall
safety lifecycle . 103
A.2 Example documentation structure for information related to the E/E/PES
safety lifecycle . 105
A.3 Example documentation structure for information related to the software
safety lifecycle . 107
Figures
1 Overall framework of this standard . 19
2 Overall safety lifecycle. 33
3 E/E/PES safety lifecycle (in realisation phase) . 35
4 Software safety lifecycle (in realisation phase). 35
5 Relationship of overall safety lifecycle to E/E/PES and software safety lifecycles. 37
6 Allocation of safety requirements to the E/E/PE safety-related systems,
other technology safety-related systems and external risk reduction facilities . 63
7 Example operations and maintenance activities model. 83
8 Example operation and maintenance management model. 85
9 Example modification procedure model . 89
A.1 Structuring information into document sets for user groups . 109
A.2 Structuring information for large complex systems and small low
complexity systems . 109

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61508-1 © IEC:1998 – 7 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
––––––––––
FUNCTIONAL SAFETY OF ELECTRICAL/ELECTRONIC/PROGRAMMABLE
ELECTRONIC SAFETY-RELATED SYSTEMS –
Part 1: General requirements
FOREWORD
1) The IEC (International Electrotechnical Commission) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of the 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, the IEC publishes International Standards. 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. The 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 the 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 National Committees.
3) The documents produced have the form of recommendations for international use and are published in the form
of standards, technical reports or guides and they are accepted by the National Committees in that sense.
4) In order to promote international unification, IEC National Committees undertake to apply IEC International
Standards transparently to the maximum extent possible in their national and regional standards. Any
divergence between the IEC Standard and the corresponding national or regional standard shall be clearly
indicated in the latter.
5) The IEC provides no marking procedure to indicate its approval and cannot be rendered responsible for any
equipment declared to be in conformity with one of its standards.
6) Attention is drawn to the possibility that some of the elements of this International Standard may be the subject
of patent rights. The 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 and control.
The text of this standard is based on the following documents:
FDIS Report on voting
65A/264/FDIS 65A/274/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.
Annexes A, B and C are for information only.
It has the status of a basic safety publication in accordance with IEC Guide 104.

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61508-1 © IEC:1998 – 9 –
IEC 61508 consists of the following parts, under the general title Functional safety of
electrical/electronic/programmable electronic safety-related systems:
– Part 1: General requirements
– Part 2: Requirements for electrical/electronic/programmable electronic safety-related
systems
– Part 3: Software requirements
– Part 4: Definitions and abbreviations
– Part 5: Examples of methods for the determination of safety integrity levels
– Part 6: Guidelines on the application of IEC 61508-2 and IEC 61508-3
– Part 7: Overview of techniques and measures
The contents of the corrigendum of April 1999 have been included in this copy.

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

61508-1 © IEC:1998 – 11 –
INTRODUCTION
Systems comprised of electrical and/or electronic components have been used for many years
to perform safety functions in most application sectors. Computer-based systems (generically
referred to as programmable electronic systems (PESs)) 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 components
(electrical/electronic/programmable electronic systems (E/E/PESs)) 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 application sector standards.
In most situations, safety is achieved by a number of protective 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 electrical/electronic/programmable
electronic (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 E/E/PES applications 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 application sector international standards.
This International Standard
– considers all relevant overall, E/E/PES and software safety lifecycle phases (for example,
from initial concept, through design, implementation, operation and maintenance to
decommissioning) when E/E/PESs 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 application sector international standards, dealing with safety-related E/E/PESs, to
be developed; the development of 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;

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61508-1 © IEC:1998 – 13 –
– uses 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;
– adopts a risk-based approach for the determination of the safety integrity level
requirements;
– sets numerical target failure measures for E/E/PE safety-related systems which are linked
to the safety integrity levels;
– sets a lower limit on the target failure measures, in a dangerous mode of failure, that can
be claimed for 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
–5
failure of 10 to perform its design function on demand,
– a high demand or continuous mode of operation, the lower limit is set at a probability of

–9
a dangerous failure of 10 per hour;
NOTE – A single E/E/PE safety-related system does not necessarily mean a single-channel architecture.
– adopts a broad range of principles, techniques and measures to achieve functional safety
for E/E/PE safety-related systems, but does not use the concept of fail safe which may be
of value when the failure modes are well defined and the level of complexity is relatively
low. The concept of fail safe was considered inappropriate because of the full range of
complexity of E/E/PE safety-related systems that are within the scope of the standard.

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61508-1 © IEC:1998 – 15 –
FUNCTIONAL SAFETY OF ELECTRICAL/ELECTRONIC/PROGRAMMABLE
ELECTRONIC SAFETY-RELATED SYSTEMS –
Part 1: General requirements
1 Scope
1.1 This International Standard covers those aspects to be considered when
electrical/electronic/programmable electronic systems (E/E/PESs) are used to carry out safety
functions. A major objective of this standard is to facilitate the development of application
sector international standards by the technical committees responsible for the application
sector. This will allow all the relevant factors, associated with the application, to be fully taken
into account and thereby meet the specific needs of the application sector. A dual objective of
this standard is to enable the development of electrical/electronic/programmable electronic
(E/E/PE) safety-related systems where application sector international standards may 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 devices;
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 3.4.4 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 possible hazards caused by failures of the safety functions to be performed by
E/E/PE safety-related systems, as distinct from hazards arising from the E/E/PE equipment
itself (for example electric shock etc);
d) does not cover E/E/PE systems where
– a single E/E/PE system is capable of providing the necessary risk reduction, and
– the required safety integrity of the E/E/PE system is less than that specified for safety
integrity level 1 (the lowest safety integrity level in this standard).
e) 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 – See 3.1.1 and 7.3.1.2 of IEC 61508-4.

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61508-1 © IEC:1998 – 17 –
f) considers E/E/PE safety-related systems, other technology safety-related systems and
external risk reduction facilities in order that the safety requirements specification for the
E/E/PE safety-related systems can be determined in a systematic, risk-based manner;
g) 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 3 – The early phases of the overall safety lifecycle include, of necessity, consideration of other technology
(as well as the E/E/PE safety-related systems) and external risk reduction facilities, in order that the safety
requirements specification for the E/E/PE safety-related systems can be developed in a systematic, risk-based
manner.
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 the consideration of any safety-related system irrespective of the technology
of that system (for example mechanical, hydraulic or pneumatic).
h) 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;
i) provides general requirements for E/E/PE safety-related systems where no application
sector standards exist;
j) does not cover the precautions that may be necessary to prevent unauthorized persons
damaging, and/or otherwise
...