Podrobnosti návrhu

1.1 This part of IEC 61508 contains information and guidelines on IEC 61508-2 and IEC 61508‑3.

Annex A gives a brief overview of the requirements of IEC 61508-2 and IEC 61508-3 and sets out the functional steps in their application.

Annex B gives an example technique for calculating the probabilities of hardware failure and should be read in conjunction with 7.4.3 and Annex C of IEC 61508-2 and Annex D.

Annex C gives a worked example of calculating diagnostic coverage and should be read in conjunction with Annex C of IEC 61508-2.

Annex D gives a methodology for quantifying the effect of hardware-related common cause failures on the probability of failure.

Annex E gives worked examples of the application of the systematic capability tables specified in Annex A of IEC 61508-3 for safety integrity levels 2 and 3.

Annex F gives examples on how to include failures of the diagnostic function in the calculation of the safety parameters.

Annex G gives guidance on how to estimate the failure rates from field feedback with confidence intervals and specifically in the context of compliance with route 2H requirements in 7.4.4.3.3 of IEC 61508-2 or route 2S requirements as stated in 7.4.9.5 of IEC 61508-2.

Annex H gives guidance on robust safety architecture.

1.2 IEC 61508-1, IEC 61598-2, IEC 61508-3 and IEC 61508-4 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 IEC 61508-4). This document provides further information to complement these basic safety publications.

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 safety publication will not apply unless specifically referred to or included in the publications prepared by those technical committees.

1.4 Figure 1 shows the overall framework of the IEC 61508 series and indicates the role that IEC 61508-6 plays in the achievement of functional safety for E/E/PE safety-related systems.

Figure 1 – Overall framework of the IEC 61508 series