scope:

NEN-IEC 61511-3 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. Annexes B through K 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.