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Acronyms & Terms Glossary

Safety Integrity Level (SIL) Calculations

A calculation performed to determine the Probability of Failure on Demand (PFD) of a required SIF. SIL calcs are based on failure rate data for the SIF components (i.e., sensors, logic solvers, and control elements) and accounts for factors such as test frequency, redundancy, voting arrangements, etc. The Risk Reduction Factor (RRF) is simply the inverse of PFD (RRF = 1/PFD) and is used to establish the associated SIL rating required to reduce the hazard risk to an acceptable risk tolerance level.

Over-specification of devices to be used in a SIF is not uncommon because it is a SAFETY Instrumented Function. However, over-specification does not necessarily improve safety significantly and can reduce the resources available for overall safety. aeSolutions can help you identify the best devices to use in SIFs and assist you in the purchasing process.

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