Functional Safety of Electrical/Electronic/Programmable Electronic Safety-Related Systems - Part 1: General Requirements
|Publication Date:||1 December 1998|
|ICS Code (Industrial automation systems):||25.040|
|ICS Code (Electrical engineering in general):||29.020|
|ICS Code (Safety of machinery):||13.110|
This International Standard covers those aspects to be considered when electrical/electroni
In particular, this standard
a) applies to safety-related systems when one or more of such systems incorporates electricaI/electroni
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; 1)
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;
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 adversely affecting, the functional safety of E/E/PE safety-related systems.
This part of IEC 61508 specifies the general requirements that are applicable to all parts. Other parts of IEC 61508 concentrate on more specific topics:
- parts 2 and 3 provide additional and specific requirements for E/E/PE safety-related systems (for hardware and software);
- part 4 gives definitions and abbreviations that are used throughout this standard;
- part 5 provides guidelines on the application of part 1 in determining safety integrity levels, by showing example methods;
- part 6 provides guidelines on the application of parts 2 and 3;
- part 7 contains an overview of techniques and measures.
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 (see 3.4.4 of part 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 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 is published as an international standard in the USA and Canada, existing national process safety standards based on IEC 61508 (i.e. ANSI/ISA S84.01-1996) (see reference  in annex C) can be applied to the process sector instead of IEC 61508.
Figure 1 shows the overall framework for parts 1 to 7 of IEC 61508 and indicates the role that IEC 61508-1 plays in the achievement of functional safety for E/E/PE safety-related systems.
1) Applies to French text only.