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1、AS 61508.51999 IEC 61508-5:1998 Australian Standard Functional safety of electrical/ electronic/programmable electronic safety-related systems Part 5: Examples of methods for the determination of safety integrity levels Accessed by UNIVERSITY OF SOUTH AUSTRALIA on 12 Jun 2008 This Australian Standar
2、d was prepared by Committee IT/6, Information Technology for Industrial Automation and Integration. It was approved on behalf of the Council of Standards Australia on 14 July 1999 and published on 5 August 1999. The following interests are represented on Committee IT/6: Australian Association of Con
3、sulting Engineers Australian Electrical and Electronic Manufacturers Association Australian Information Industry Association CSIRO Centre for Planning and Design CSIRO Manufacturing Science and Technology Department of Defence (Australia) Department of Industry Science and Resources (Commonwealth) F
4、ederal Chamber of Automotive Industries Institution of Engineers Australia Monash University New South Wales TAFE Commission RMIT University The Royal Australian Institute of Architects University of Melbourne Review of Australian Standards. To keep abreast of progress in industry, Australian Standa
5、rds are subject to periodic review and are kept up to date by the issue of amendments or new editions as necessary. It is important therefore that Standards users ensure that they are in possession of the latest edition, and any amendments thereto. Full details of all Australian Standards and relate
6、d publications will be found in the Standards Australia Catalogue of Publications; this information is supplemented each month by the magazine The Australian Standard, which subscribing members receive, and which gives details of new publications, new editions and amendments, and of withdrawn Standa
7、rds. Suggestions for improvements to Australian Standards, addressed to the head office of Standards Australia, are welcomed. Notification of any inaccuracy or ambiguity found in an Australian Standard should be made without delay in order that the matter may be investigated and appropriate action t
8、aken. This Standard was issued in draft form for comment as DR 99168. Accessed by UNIVERSITY OF SOUTH AUSTRALIA on 12 Jun 2008 AS 61508.51999 Australian Standard Functional safety of electrical/ electronic/programmable electronic safety-related systems Part 5: Examples of methods for the determinati
9、on of safety integrity levels First published as AS 61508.51999. Published by Standards Australia (Standards Association of Australia) 1 The Crescent, Homebush NSW 2140 ISBN 0 7337 2876 6 Accessed by UNIVERSITY OF SOUTH AUSTRALIA on 12 Jun 2008 ii PREFACE This Standard was prepared by the Standards
10、Australia Committee IT/6, Information Technology for Industrial Automation and Integration. This Standard is identical with and has been reproduced from IEC 61508-5:1998, Functional safety of electrical/electronic/ programmable electronic safety-related systems, Part 5: Examples of methods for the d
11、etermination of safety integrity levels. The objective of this Standard is to provide designers of electrical/electronic/programmable electronic devices used in safety-related applications with the concepts and relationship of risk to safety integrity together with methods of determining safety inte
12、grity levels. A reference to an International Standard identified in the normative references clause (Clause 2) by strikethrough (example) is replaced by a reference to the Australian Standards listed immediately thereafter and identified by shading (example). Where the struck-through referenced doc
13、ument and the referenced Australian Standard are identical, this is indicated in parenthesis after the title of the latter. The term informative has been used in this Standard to define the application of the annex to which it applies. An informative annex is only for information and guidance. As th
14、is Standard is reproduced from an International Standard, the following applies: (a)Its number does not appear on each page of text and its identity is shown only on the cover and title page. (b)In the source text this part of IEC 61508 should read this Australian Standard, and this International St
15、andard should read this series of Standards. (c)A full point should be substituted for a comma when referring to a decimal marker. Copyright STANDARDS AUSTRALIA Users of Standards are reminded that copyright subsists in all Standards Australia publications and software. Except where the Copyright Ac
16、t allows and except where provided for below no publications or software produced by Standards Australia may be reproduced, stored in a retrieval system in any form or transmitted by any means without prior permission in writing from Standards Australia. Permission may be conditional on an appropria
17、te royalty payment. Requests for permission and information on commercial software royalties should be directed to the head office of Standards Australia. Standards Australia will permit up to 10 percent of the technical content pages of a Standard to be copied for use exclusively in-house by purcha
18、sers of the Standard without payment of a royalty or advice to Standards Australia. Standards Australia will also permit the inclusion of its copyright material in computer software programs for no royalty payment provided such programs are used exclusively in-house by the creators of the programs.
19、Care should be taken to ensure that material used is from the current edition of the Standard and that it is updated whenever the Standard is amended or revised. The number and date of the Standard should therefore be clearly identified. The use of material in print form or in computer software prog
20、rams to be used commercially, with or without payment, or in commercial contracts is subject to the payment of a royalty. This policy may be varied by Standards Australia at any time. Accessed by UNIVERSITY OF SOUTH AUSTRALIA on 12 Jun 2008 iii CONTENTS Page 1Scope. 1 2Normative references. 3 3Defin
21、itions and abbreviations 3 Annexes ARisk and safety integrityGeneral concepts. 4 BALARP and tolerable risk concepts.10 CDetermination of safety integrity levels: a quantitative method.13 DDetermination of safety integrity levelsA qualitative method: risk graph .16 EDetermination of safety integrity
22、levelsA qualitative method: hazardous event severity matrix21 FBibliography.23 Figures 1Overall framework of this standard 2 A.1Risk reduction: general concepts 7 A.2Risk and safety integrity concepts. 7 A.3Allocation of safety requirements to the E/E/PE safety-related systems, other technology safe
23、ty-related systems and external risk reduction facilities 9 B.1Tolerable risk and ALARP .11 C.1Safety integrity allocation: example for safety-related protection system 15 D.1Risk graph: general scheme 18 D.2Risk graph: example (illustrates general principles only).19 E.1Hazardous event severity mat
24、rix: example (illustrates general principles only)22 Tables B.1Risk classification of accidents 12 B.2Interpretation of risk classes12 D.1Example data relating to example risk graph (figure D.2)20 Accessed by UNIVERSITY OF SOUTH AUSTRALIA on 12 Jun 2008 iv INTRODUCTION Systems comprised of electrica
25、l 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,
26、 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 those decisions. This International Standard sets out a generic approach
27、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 rat
28、ional 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 exam
29、ple 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 tot
30、al combination of safety-related systems. Therefore, while this International Standard is concerned with electrical/elec- tronic/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.
31、 It is recognised 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.
32、This 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, implementati
33、on, 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 sta
34、ndards, dealing with safety-related E/E/PESs, to be developed; the development of application sector international standards, within the framework of this International Standard, should lead to a high level of consistency (for example, of underlying principles, terminology etc.) both within applicat
35、ion 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; uses safety integrity levels for specify
36、ing 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
37、linked to the safety integrity levels; Accessed by UNIVERSITY OF SOUTH AUSTRALIA on 12 Jun 2008 v 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 de
38、mand mode of operation, the lower limit is set at an average probability of failure of 105to perform its design function on demand; a high demand or continuous mode of operation, the lower limit is set at a probability of a dangerous failure of 109per hour; NOTE A single E/E/PE safety-related system
39、 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
40、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. Accessed by UNIVERSITY OF SOUTH AUSTRALIA on 12 Jun 2008 vi NOTES Accessed by UNIVERSITY OF SOUTH
41、 AUSTRALIA on 12 Jun 2008 COPYRIGHT 1 STANDARDS AUSTRALIA Functional safety of electrical/electronic/programmable electronic safety- related systems Part 5: Examples of methods for the determination of safety integrity levels 1 Scope 1.1 This part of IEC 61508 provides information on the underlying
42、concepts of risk and the relationship of risk to safety integrity (see annex A); a number of methods that will enable the safety integrity levels for the E/E/PE safety-related systems, other technology safety-related systems and external risk reduction facilities to be determined (see annexes B, C,
43、D and E). 1.2 The method selected will depend upon the application sector and the specific circumstances under consideration. Annexes B, C, D and E illustrate quantitative and qualitative approaches and have been simplified in order to illustrate the underlying principles. These annexes have been in
44、cluded to illustrate the general principles of a number of methods but do not provide a definitive account. Those intending to apply the methods indicated in these annexes should consult the source material referenced. NOTE For more information on the approaches illustrated in annexes B, D and E, se
45、e references 4, 2 and 3 respectively in annex F. See also reference 5 in annex F for a description of an additional approach. 1.3 Parts 1, 2, 3 and 4 of this standard are basic safety publications, although this status does not apply in the context of low complexity E/E/PE safety-related systems (se
46、e 3.4.4 of IEC 61508-4). As basic safety publications, they are intended for use by technical committees in the preparation of standards in accordance with the principles contained in IEC Guide 104 and ISO/IEC Guide 51. One of the responsibilities of a technical committee is, wherever applicable, to
47、 make use of basic safety publications in the preparation of its own publications. IEC 61508 is also intended for use as a stand- alone standard. NOTE In the USA and Canada, until the proposed process sector implementation of IEC 61508 (i.e. IEC 61511) is published as an international standard in th
48、e USA and Canada, existing national process safety standards based on IEC 61508 (i.e. ANSI/ISA S84.01-1996) can be applied to the process sector instead of IEC 61508. 1.4 Figure 1 shows the overall framework for parts 1 to 7 of IEC 61508 and indicates the role that IEC 61508-5 plays in the achieveme
49、nt of functional safety for E/E/PE safety- related systems. Accessed by UNIVERSITY OF SOUTH AUSTRALIA on 12 Jun 2008 COPYRIGHT 2 Guidelines for the application of parts 2 and 3 Overview of techniques and measures PART 7 PART 6 Risk based approaches to the development of the safety integrity requirements PART 5 7.6 Realisation phase for E/E/PE safety- related systems Realisation phase for safety-related software PART 3PART 2 Allocation of the safety requirements to the E/E/PE safety-related systems Development of the overall safety requi
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