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.
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.