ABSTRACT
Safety Integrity Level (SIL) The Safety Integrity Level (SIL) is a measure of reliability of the Safety Instrumented System (SIS) in a process. SIS consists one or more Safety Instrumented Function(s) (SIFs) which are a combination of the sensor, logic solver and final control elements. SIS is for responding to an emergency situation when a process demand occurs, which mayor may not be hazardous. However, process safety may be jeopardized if a SIS fails to respond fully or partially to potentially hazardous or disruptive situations. These SIS failures are measured in terms of Probability of Fail on Demand (PFD) that determines the safety integrity level (SIL) of the SIS. The following table shows the relationship between safety integrity level (SIL) and PFD value.
