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Robin Clark 2010-10-30 17:51:32 +01:00
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fmmd_concept/fmmd_concept.tex
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@ -7,7 +7,7 @@
\abstract{ \abstract{
This paper proposes a methodology for This paper proposes a methodology for
creating failure mode models of safety critical systems, which creating failure mode models of safety critical systems, which
have a common notation has a common notation
for mechanical, electronic and software domains and apply an for mechanical, electronic and software domains and apply an
incremental and rigorous approach. incremental and rigorous approach.
@ -328,10 +328,14 @@ give a value for the `safety level' for the equipment in a given environment.
%%-• The operational profile (environmental stress factors). %%-• The operational profile (environmental stress factors).
This uses MTFF and other statisical models to determine the probability of This uses MTFF and other statisical models to determine the probability of
failures occurring. A component failure mode, given its MTTF failures occurring.
%
A component failure mode, given its MTTF
the probability of detecting the fault and its safety relevant validation time $\tau$, the probability of detecting the fault and its safety relevant validation time $\tau$,
contributes a simple risk factor that is summed contributes a simple risk factor that is summed
in to give a final risk result. Thus a statistical in to give a final risk result.
%
Thus a statistical
model can be implemented on a spreadsheet, where each component model can be implemented on a spreadsheet, where each component
has a calculated risk, a fault detection time (if any), an estimated risk importance has a calculated risk, a fault detection time (if any), an estimated risk importance
and other factors such as de-rating and environmental stress. and other factors such as de-rating and environmental stress.