When exida conducts an FMEDA for a mechanical final element, such as an actuator, valve, or solenoid, the two most frequent questions when interpreting the tables are:
- Why is the partial valve stroke test (PVST) converting DUs to DDs while the full stroke test has a defined proof test coverage?
- Why is proof test coverage less in the “with PVST” column?
This whitepaper will answer those questions by explaining the difference between a diagnostic test and a proof test, and the proof test coverage calculation when a diagnostic is or is not present.