What is Probability of Failure on Demand means?

Asked by aodai 6 years, 11 months ago | 1 Answers


1 Answer

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michelnr 6 years, 11 months ago
Probability of Failure on Demand or PFD means the probability that a Safety Instrumented Function will fail dangerously, and not be able to perform its safety function when required. IEC 61508/61511 and ISA 84.01 use average PFD as the system metric upon which the achieved SIL for a Safety Instrumented Function is defined. PFD is related to the amount of risk reduction that is provided by a Safety Instrumented Function.