What is the difference between SIF and SIS concepts in LOPA?
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What is the difference between Safety Instrumented Function (SIF) and Safety Instrumented System (SIS)? Why is the term SIF used in LOPA instead of the more well-known term SIS? ? At the same time
SIF stands for Safety Instrumented Function, which is a safety function circuit – a control circuit designed for a specific scenario within a SIS safety instrumented system. Generally, what is analyzed in Lopa relates to calculations for a single scenario, so basically only SIF is discussed. However, when considering Utilities, the possibility of a complete SIS failure should be taken into account.