6 Safety Manual
37
Lambda Dangerous Undetect:
λ
DU
Rate of undetected dangerous failures per hour
Lambda Safe:
λ
S
Rate of safe failures per hour
Lambda Safe Detect:
λ
SD
Rate of detected safe failures per hour
Lambda Safe Undetect:
λ
SU
Rate of undetected safe failures per hour
BPCS Basic process control system
DC Diagnostic coverage
FIT Failure in time (1x10
-9
per h)
HFT Hardware failure tolerance
PFD Probability of failure on demand
PFD
avg
Probability of failure on demand average
PFH Probability of dangerous failure per hour
MooN Architecture with M from N channels
MTBF Mean time between failures
MTTR Mean time to restoration (mean time between discovery of the fault and repair of the
system)
MRT Mean repair time (mean time to repair the system)
SFF Safe failure fraction
SIL Safety integrity level
SC Systematic capability
PTC Proof test coverage (diagnostic coverage during repeat test)
T
i
Proof Test intervall
Name Description
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