Vega VEGAFLEX 80 series - 9 Appendix B: Term Definitions

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9 Appendix B: Term denitions
VEGAFLEX 80 series • Two-wire 4 … 20 mA/HART
42960-EN-170410
9 AppendixB:Termdenitions
SIL Safety Integrity Level (SIL1, SIL2, SIL3, SIL4)
SC Systematic Capability (SC1, SC2, SC3, SC4)
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 Failure Mode, Eects and Diagnostics Analysis
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
Rate for failure, who causes a low output current (≤ 3.6 mA)
λ
AD
Rate for diagnostic failure (detected)
λ
AU
Rate for diagnostic failure (undetected)
DC Diagnostic Coverage
PTC Proof Test Coverage (Diagnostic coverage for manual proof tests)
T1 Proof Test Interval
LT Useful Life Time
MTBF Mean Time Between Failure
MTTF Mean Time To Failure
MTTR Mean Time To Restoration (Ed.2)
MRT Mean Repair Time
MTTF
d
Mean Time To dangerous Failure (ISO 13849-1)
PL Performance Level (ISO 13849-1)
Abbreviations