Fisher ED Safety Manual page 3

SIL Safety Manual
D103401X012
Acronyms
FMEDA: Failure Modes, Effects and Diagnostic Analysis
HFT: Hardware Fault Tolerance
MOC: Management of Change. These are specific procedures often done when performing any work activities in
compliance with government regulatory authorities.
PFD : Average Probability of Failure on Demand
AVG
SFF: Safe Failure Fraction, the fraction of the overall failure rate of a device that results in either a safe fault or a
diagnosed unsafe fault.
SIF: Safety Instrumented Function, a set of equipment intended to reduce the risk due to a specific hazard (a safety
loop).
SIL: Safety Integrity Level, discrete level (one out of a possible four) for specifying the safety integrity requirements of
the safety functions to be allocated to the E/E/PE safety­related systems where Safety Integrity Level 4 has the highest
level of safety integrity and Safety Integrity Level 1 has the lowest.
SIS: Safety Instrumented System — Implementation of one or more Safety Instrumented Functions. A SIS is composed
of any combination of sensor(s), logic solver(s), and final element(s).
ED, ES, ET, EZ, HP, HPA Valves w/ 657/667 Actuator
November 2011
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