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Concluding Comments
•
The inability to fully test a safety instrumented function will have adverse
effects on the risk reduction it provides if incorrect assumptions on the
proof test coverage have been made. The tolerable risk target may not be
met.
•
PFD
avg
contribution of devices and subsystems should be considered when
allocating effort to optimising proof testing.
•
The user and the designer of the safety instrumented function should
address jointly the means by which it will be maintained throughout its life
…….taking into account a realistic proof test coverage.