Lamtec F200K2 IR-1, Safety Manual

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6
1 General Information
1.4 Terms and Definitions
For further explanations of terms and definitions see IEC 61508-4 (or DIN EN 61508-4).
DC Diagnostic coverage
DC
AVG
Average diagnostic coverage
E/E/PE-System Electrical/electronic/programmable electronic system
EUC Equipment under control
FIT Failure In Time in 10
-9
1/h
FMEDA Failure Mode, Effects, and Diagnostics Analysis
λ
s
Probability of safe failure (detected and undetected)
λ
d
Probability of dangerous failure
λ
dd
Probability of dangerous detected failure
λ
du
Probability of dangerous undetected failure
λ
no effect,
λ
don’t care
Probability of failures with no effect (not used in SFF calculation)
HFT Hardware fault tolerance
MooN M out of N channel architecture
MTBF Mean time between failures
MTTR Mean time to repair
MTTF Mean time to failure
PFD Probability of dangerous failure on demand (Low Demand mode)
PFD
AVG
Average probability of dangerous failure on demand
PFH Average frequency of a dangerous failure per hour (Continuous mode)
PTC Proof Test Coverage, proportion of detectable unsafe failures
SFF Safe failure fraction
SIF Safety instrumented function
SIS Safety instrumented system
SIL Safety integrity level
SIL AC Safety integrity level architectural constraint
SC Systematic Capability
T
1
Proof test interval
T
2
Diagnostic test interval
T
2 IBD
Interval between demands of the safety function