Vega VEGASWING 66 Safety Manual - 9 Appendixb-Termdefinitions
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9AppendixB-Termdefinitions
VEGASWING 66 • Two-wire (8/16 mA)
45309-EN-130722
9 AppendixB-Termdefinitions
SIL
Safety Integrity Level
HFT
Hardware Fault Tolerance
SFF
Safe Failure Fraction
PFD
AVG
Average Probability of dangerous Failure on Demand
PFH
Average frequency of a dangerous failure per hour (Ed.2)
FMEDA FailureMode,EffectsandDiagnosticsAnalysis
FIT
Failure In Time (1 FIT = 1 failure/10
9
h)
λ
SD
Rate for safe detected failure
λ
SU
Rate for safe undetected failure
λ
S
λ
S
=λ
SD
+λ
SU
λ
DD
Rate for dangerous detected failure
λ
DU
Rate for dangerous undetected failure
λ
H
Rate for failure, who causes a high output current (> 21 mA)
λ
L
Rateforfailure,whocausesalowoutputcurrent(≤3.6mA)
λ
AD
Rate for diagnostic failure (detected)
λ
AU
Rate for diagnostic failure (undetected)
DC
Diagnostic Coverage
PTC
Proof Test Coverage
T1
Proof Test Interval
LT
Life Time
MTBF
Mean Time Between Failure
MTTF
Mean Time To Failure
MTTR
Mean Time To Restoration (Ed.2)
MTTF
d
Mean Time To dangerous Failure (ISO 13849-1)
PL
Performance Level (ISO 13849-1)
Abbreviations