Definition(s)
Safety Integrity Level
Discrete integrity level of a safety instrumented function in a safety instrumented system.
- NOTE: SILs are categorized in terms of probability of failure; see Annex E.
Source: API STD 521, Pressure-relieving and Depressuring Systems, Sixth Edition, January 2014. Global Standards
Safety-Integrity Level (SIL)
Discrete integrity level of a safety instrumented function in a safety instrumented system. NOTE SILs are categorized in terms of probability of failure; see Annex E.
Source: API STD 521, Pressure-relieving and Depressuring Systems, Fifth Edition, January 2007 (Addendum May 2008). Global Standards
Safety-Integrity Level (SIL)
discrete level (one out of four) for specifying the safety integrity requirements of the safety instrumented
functions to be allocated to the safety instrumented systems
Note 1 to entry: Safety integrity level 4 is related to the highest level of safety integrity; safety integrity level 1
has the lowest.
Note 2 to entry: The safety integrity level is a requirement about a safety instrumented function. The higher
the safety integrity level, the higher the probability that the required safety instrumented function (SIF) will be
carried out upon a real demand.
Note 3 to entry: This term differs from the definition in IEC 61508–4[2] t o r eflect d ifferences i n p rocess sector terminology.
Source: ISO/TR 12489:2013(E), Global Standards