User Documentation

52714570000/01/12-2020
Scope and denitions
DevicetypeA(simplesubsystem):
The failure modes of all constituent components are
well dened and the behaviour under fault condi-
tions can be completely determined.
FMEDA(FailureMode,E󰀨ectsandDiagnostic
Analysis):
Systematic way to identify and evaluate the e󰀨ects
of di󰀨erent component failure modes, to determine
what could eliminate or reduce the chance of failure,
and to document a system in consideration.
Failureratesλ:
λ
SD
Total failure rate for safe detected failures
λ
SU
Total failure rate for safe undetected failures
λ
DD
Total failure rate for dangerous detected fail-
ures
λ
DU
Total failure rate for dangerous undetected
failures
MTTF(MeanTimeToFailure):
Mean time between two failures. MTTF is a basic
measure of reliability for non-repairable systems.
Proof-testinterval(T
proof
):
Interval between periodic tests performed to detect
failures in a safety-related system.
EnergisedToSafe(ETS):
Safety-related switch-on