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GB/T 20438.5-2017 (GB/T20438.5-2017)

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GB/T 20438.5-2017
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 25.040
N 10
GB/T 20438.5-2017 / IEC 61508-5:2010
Replacing GB/T 20438.5-2006
Functional safety of electrical / electronic /
programmable electronic safety-related systems - Part
5: Examples of methods for the determination of
safety integrity levels
(IEC 61508-5:2010, IDT)
ISSUED ON: DECEMBER 29, 2017
IMPLEMENTED ON: JULY 01, 2018
Issued by: General Administration of Quality Supervision, Inspection and
Quarantine;
Standardization Administration of the People's Republic of
China.
Table of Contents
Foreword ... 3 
Introduction ... 5 
1 Scope ... 8 
2 Normative references ... 10 
3 Definitions and abbreviations ... 10 
Annex A (informative) Risk and safety integrity - General concepts ... 11 
Annex B (informative) Selection of methods for determining safety integrity level
requirements ... 26 
Annex C (informative) ALARP and tolerable risk concepts ... 30 
Annex D (informative) Determination of safety integrity levels - A quantitative
method ... 34 
Annex E (informative) Determination of safety integrity levels - Risk graph
methods ... 37 
Annex F (informative) Semi-quantitative method using layer of protection
analysis (LOPA) ... 45 
Annex G (informative) Determination of safety integrity levels - A qualitative
method - hazardous event severity matrix ... 52 
Bibliography ... 54 
Foreword
GB/T 20438 "Functional safety of electrical/electronic/programmable electronic
safety-related systems" consists of the following seven parts:
- 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 GB/T 20438.2 and GB/T 20438.3;
- Part 7: Overview of techniques and measures.
This Part is Part 5 of GB/T 20438.
This Part was drafted in accordance with the rules given in GB/T 1.1-2009.
This Part replaces GB/T 20438.5-2006 "Functional safety of
electrical/electronic/programmable electronic safety-related systems - Part 5:
Examples of methods for the determination of safety integrity levels". Compared
with GB/T 20438.5-2006, the main technical changes in this Part are as follows:
- add the selection of methods for determining safety integrity level
requirements (see Annex B);
- add the risk analysis method: semi-quantitative method of protection layer
analysis (LOPA) (see Annex F).
This Part uses translation method to identically adopt IEC 61508-5:2010
"Functional safety of electrical/electronic/programmable electronic safety-
related systems - Part 5: Examples of methods for the determination of safety
integrity levels".
This Part was proposed by China Machinery Industry Federation.
This Part shall be under the jurisdiction of National Technical Committee on
National Industrial Process Measurement Control and Automation of
Standardization Administration of China (SAC/TC 124).
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 GB/T 20438 provides information on
- the underlying 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 to be determined (see Annexes C, D, E, F
and G).
The method selected will depend upon the application sector and the specific
circumstances under consideration. Annexes C, D, E, F and G illustrate
quantitative and qualitative approaches and have been simplified in order to
illustrate the underlying principles. These annexes have been included 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, and E, see
references [5] and [8] in the Bibliography. See also reference [6] in the Bibliography for a
description of an additional approach.
1.2 GB/T 20438.1, GB/T 20438.2, GB/T 20438.3 and GB/T 20438.4 are basic
safety publications, although this status does not apply in the context of low
complexity E/E/PE safety-related systems (see 3.4.3 of GB/T 20438.4-2017).
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. GB/T 20438.1, GB/T 20438.2, GB/T
20438.3 and GB/T 20438.4 are also intended for use as stand-alone
publications. The horizontal safety function of this international standard does
not apply to medical equipment in compliance with the IEC 60601 series.
1.3 One of the responsibilities of a technical committee is, wherever applicable,
to make use of basic safety publications in the preparation of its publications.
In this context, the requirements, test methods or test conditions of this basic
......
 
Source: Above contents are excerpted from the PDF -- translated/reviewed by: www.chinesestandard.net / Wayne Zheng et al.