It is a semi quantitative method for assessment of adequacy of protection layers used to determine the performance requirements for Safety Instrumented System (SIS).
Safety Integrity Level (SIL) Determination study is carried out to establish the level of risk reduction required for Safety Instrumented System (SIS) to reduce risks from identified process hazards (including explosion, toxic exposure, loss of containment, etc.) to as low as reasonably practicable (ALARP).
The functional output of SIL Determination study is to assign each Safety Instrumented Function (SIF) a performance target or SIL which can then dictate the design of SIF to be installed with regards to its reliability.
SIL will determine through the analysis the potential hazardous scenarios the level of reliability the SIF must achieve to meet the required residual risk level. Following this procedure will ensure compliance of the SIF assessed with IEC 61508 and 61511 standards.
SIL determination study will serve as a basis of design and specification of all SIS and associated SIF. Design of SIS and associated SIF for assigned SIL levels will be confirmed through SIL verification study as required by IEC 61511 and 61508.