KROHNE H250 M9 Safet V1 EN - Manual (Page 4)

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TERMS AND DEFINITIONS
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H250
www.krohne.com 02/2012 - 4000656701 MA H250-M9 SIL R02
Terms and definitions
Terms and definitions
DC
D
Diagnostic Coverage of dangerous failures
FIT Failure In Time (1x10 -9 failures per hour)
FMEDA Failure Modes, Effects and Diagnostic Analysis
HFT Hardware Fault Tolerance
Low demand mode Mode, where the frequency of demand for operation made on a safety-related
system is not greater than one per year and not greater than twice in the proof test
frequency.
PFD
AVG
Average Probability of Failure on Demand
SFF Safe Failure Fraction summarizes the fraction of failure, which lead to a safe state
and the fraction of failures which will be detected by diagnostic measures and lead
to a defined safety action.
SIF Safety Instrumented Function
SIL Safety Integrity Level
Type A component "Non-complex" subsystem (all failure modes are well defined); for details see
7.4.3.1.2 of IEC 61508-2.
Type B component "Complex" subsystem (all failure modes are well defined); for details see 7.4.3.1.2
of IEC 61508-2.
T[Proof] Proof Test Interval
MA_H250_M9_SIL2_R02_en_656701_PRT.book Page 4 Thursday, March 1, 2012 10:26 AM