Proof testing and restoration assumptions

Interval and coverage

The proof-test interval controls how long a dangerous undetected failure can remain latent. Proof-test coverage is the fraction of the relevant dangerous failures that the defined test can reveal. A shorter interval cannot compensate for failure modes the procedure never tests.

Diagnostics are different

Online or periodic diagnostics can reveal failures between proof tests. Record the diagnostic interval, coverage and response to a detected fault. A diagnostic claim should include the complete detection path and the action taken when the fault is found.

Partial stroke testing

A partial stroke test can reveal selected final-element failure modes without a full trip. The calculation should apply only the coverage justified for those modes. Full-stroke proof testing is still required for failures not detected by the partial test.

Repair and restoration

Detected failures contribute according to the assumed repair or restoration time. Define when the clock begins, whether the process is protected during repair, how spares and access affect the time, and what maximum duration is controlled by procedure.

Procedure acceptance criteria

• State the initial conditions, permits, bypass controls and required personnel.
• Exercise the complete path or identify every excluded part.
• Measure setpoint, response time, final position and diagnostic indications where applicable.
• Define pass/fail limits and restoration checks.
• Record as-found and as-left condition, failures, repair and retest.
• Feed proof-test findings back into reliability and interval review.