EN 61508-4:2001
(Main)Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 4: Definitions and abbreviations
Functional safety of electrical/electronic/programmable electronic safety-related systems - Part 4: Definitions and abbreviations
Contains the definitions and explanation of terms that are used in parts 1 to 7 of this standard. 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. EN 61508 is also intended as a stand-alone standard. Has the status of a basic safety publication in accordance with IEC Guide 104.
Funktionale Sicherheit sicherheitsbezogener elektrischer/elektronischer/programmierbarer elektronischer Systeme - Teil 4: Begriffe und Abkürzungen
Sécurité fonctionnelle des systèmes électriques/électroniques/électroniques programmables relatifs à la sécurité - Partie 4: Définitions et abréviations
Contient les définitions et explications des termes utilisés dans les parties 1 à 7 de cette norme. Destinées à être utilisées par tous les comités d'études pour la mise au point de leurs normes, conformément aux principes décrits dans le Guide CEI 104 et dans le Guide ISO/CEI 51. La EN 61508 est également prévue pour une utilisation en tant que norme autonome. A le statut, d'une publication fondamentale de sécurité conformément au Guide 104.
Funkcijska varnost električnih/elektronskih/programirljivih elektronskih varnostnih sistemov - 4. del: Definicije in kratice (IEC 61508-4:1998 + popravek 1999)
General Information
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EUROPEAN STANDARD EN 61508-4
NORME EUROPÉENNE
EUROPÄISCHE NORM December 2001
ICS 25.040.40;29.020
English version
Functional safety of electrical/electronic/programmable electronic
safety-related systems
Part 4: Definitions and abbreviations
(IEC 61508-4:1998 + corrigendum 1999)
Sécurité fonctionnelle des systèmes Funktionale Sicherheit
électriques/électroniques/électroniques sicherheitsbezogener elektrischer/
programmables relatifs à la sécurité elektronischer/programmierbarer
Partie 4: Définitions et abréviations elektronischer Systeme
(CEI 61508-4:1998 + corrigendum 1999) Teil 4: Begriffe und Abkürzungen
(IEC 61508-4:1998 + 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 61508-4:2001 E
Foreword
The text of the International Standard IEC 61508-4:1998 including its corrigendum April 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 61508-4
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 annex A is 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.
__________
- 3 - EN 61508-4:2001
Endorsement notice
The text of the International Standard IEC 61508-4:1998 including its corrigendum April 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 61131-3:1993 NOTE Harmonized as EN 61131-3:1993 (not modified).
ISO 9000-3:1991 NOTE Harmonized as EN 29000-3:1993 (not modified).
__________
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
IEC 60050-191 1990 International Electrotechnical --
Vocabulary (IEV) -- Chapter 191:
Dependability and quality of service
IEC 60050-351 1975 Chapter 351: Automatic control - -
IEC 61508-1 1998 Functional safety of EN 61508-1 2001
+ corr. May 1999 electrical/electronic/programmable
electronic safety-related systems
Part 1: General requirements
IEC 61508-2 2000 Part 2: Requirements for EN 61508-2 2001
electrical/electronic/programmable
electronic safety-related systems
IEC 61508-3 1998 Part 3: Software requirements EN 61508-3 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
IEC Guide 104 1997 The preparation of safety publications--
and the use of basic safety publications
and group safety publications
ISO/IEC 2382-14 1998 Data processing - Vocabulary --
Part 14: Reliability, maintainability and
availability
ISO/IEC Guide 51 1990 Guidelines for the inclusion of safety--
aspects in standards
ISO 8402 1994 Quality management and quality EN ISO 8402 1995
assurance - Vocabulary
INTERNATIONAL IEC
STANDARD
61508-4
First edition
1998-12
BASIC SAFETY PUBLICATION
Functional safety of electrical/electronic/
programmable electronic safety-related systems –
Part 4:
Definitions and abbreviations
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: +41 22 919 02 11 Telefax: +41 22 919 03 00 E-mail: inmail@iec.ch Web: www.iec.ch
PRICE CODE
U
Commission Electrotechnique Internationale
International Electrotechnical Commission
Международная Электротехническая Комиссия
For price, see current catalogue
61508-4 © IEC:1998 – 3 –
CONTENTS
Page
FOREWORD . 5
INTRODUCTION . 9
Clause
1 Scope. 13
2 Normative references. 17
3 Definitions and abbreviations. 19
3.1 Safety terms. 19
3.2 Equipment and devices . 21
3.3 Systems: general aspects . 25
3.4 Systems: safety-related aspects . 29
3.5 Safety functions and safety integrity . 31
3.6 Fault, failure and error. 37
3.7 Lifecycle activities. 41
3.8 Confirmation of safety measures . 43
Annex A (informative) Bibliography . 49
Index. 51
Figures
1 Overall framework of this standard . 15
2 Programmable electronic system (PES): structure and terminology. 27
3 Electrical/electronic/programmable electronic system (E/E/PES):
structure and terminology . 27
4 Failure model . 39
Table
1 Abbreviations used in this standard . 19
61508-4 © IEC:1998 – 5 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
_________
FUNCTIONAL SAFETY OF ELECTRICAL/ELECTRONIC/PROGRAMMABLE
ELECTRONIC SAFETY-RELATED SYSTEMS –
Part 4: Definitions and abbreviations
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 61508-4 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/265/FDIS 65A/275/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.
Annex A is for information only.
61508-4 © IEC:1998 – 7 –
IEC 61508 consists of the following parts, under the general title Functional safety of elec-
trical/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 parts 2 and 3
– Part 7: Overview of techniques and measures
This part 4 shall be read in conjunction with all other parts.
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