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 provides information on:
- the underlying concepts of risk and the relationship of risk to safety integrity (see Appendix 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 Appendixes B, C, D and E).
1.2 The method selected will depend upon the application sector and the specific circumstances under consideration. Appendixes B, C, D and E illustrate quantitative and qualitative approaches and have been simplified in order to illustrate the underlying principles. These appendixes 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 appendixes shall consult the source material referenced.
Note: For more information on the approaches illustrated in Appendixes B, D and E, see references [4], [2] and [3] respectively in Appendix F. See also reference [5] in Appendix F for a description of an additional approach.
1.3 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 3.4.4 of GB/T 20438.4-2006). 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 make use of basic safety publications in the preparation of its own publications. GB/T 20438 is also intended for use as a stand-alone standard.
1.4 Figure 1 shows the overall framework for GB/T 20438 and indicates the role that this Part plays in the achievement of functional safety for E/E/PE safety-related systems.
2 Normative References
The following normative documents contain provisions which, through reference of this Part of GB/T 20438, constitute provisions of this Part. For dated reference, subsequent amendments to (excluding corrigendum), or revisions of, any of these publications do not apply. However, the parties whose enter into agreement according to this Part are encouraged to research whether the latest editions of these documents apply. For undated references, the latest edition of this part applies.
GB/T 20438.1-2006 Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems - Part 1: General Requirements (IEC 61508-1: 1998, IDT)
GB/T 20438.2-2006 Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems - Part 2: Requirements for Electrical/Electronic/Programmable Electronic Safety-related Systems (IEC 61508-2: 2000, IDT)
GB/T 20438.3-2006 Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems - Part 3: Software Requirements (IEC 61508-3: 1998, IDT)
GB/T 20438.4-2006 Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems - Part 4: Definitions and Abbreviations (IEC 61508-4: 1998, IDT)
GB/T 20438.6-2006 Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems - Part 6: Guidelines on the Application of GB/T 20438.2 and GB/T 20438.3 (IEC 61508-6: 2000, IDT)
GB/T 20438.7-2006 Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems - Part 7: Overview of Techniques and Measures (IEC 61508-7: 2000, IDT)
ISO/IEC Guide 51: 1990 Safety Aspects - Guidelines for their Inclusion in Standards
IEC Guide 104: 1997 The preparation of Safety Publications and the Use of Basic Safety Publications and Group Safety Publications
3 Definitions and Abbreviations
Foreword I
Introduction II
1 Scope
2 Normative References
3 Definitions and Abbreviations
Appendix A (Informative) Risk and Safety Integrity - General Concepts
Appendix B (Informative) As Low As Reasonably Practicable (ALARP) and Tolerable Risk Concepts
Appendix C (Informative) Determination of Safety Integrity Level: a Quantitative Method
Appendix D (Informative) Determination of Safety Integrity Levels - A Qualitative Method: Risk Graph
Appendix E (Informative) Determination of Safety Integrity Levels - A Qualitative Method: Hazardous Event Severity Matrix
Bibliography
