International Electrotechnical Commission

Functional safety – Safety instrumented systems for the process industry sector – Part 3: Guidance for the determination of the required safety integrity levels - Edition 2.0
 N 61511-3

Annotation

This part of IEC 61511 provides information on:

– the underlying concepts of risk and the relationship of risk to safety integrity (see Clause A.4);

– the determination of tolerable risk (see Annex K);

– a number of different methods that enable the safety integrity level (SIL) for the safety instrumented functions (SIF) to be determined (see Annexes B through K);

– the impact of multiple safety systems on calculations determining the ability to achieve the desired risk reduction (see Annex J). In particular, this part of IEC 61511:

a) applies when functional safety is achieved using one or more SIF for the protection of either personnel, the general public, or the environment;

b) may be applied in non-safety applications such as asset protection;

c) illustrates typical hazard and risk assessment methods that may be carried out to define the safety functional requirements and SIL of each SIF;

d) illustrates techniques/measures available for determining the required SIL;

e) provides a framework for establishing SIL but does not specify the SIL required for specific applications;

f) does not give examples of determining the requirements for other methods of risk reduction.