First Out

Specification and lifecycle

Writing a proof test procedure that achieves its coverage

The structure of a good procedure, device-specific steps that matter for coverage, and how records feed back into the next verification.

2 min read · First Out AI knowledge library

A proof test procedure is where the verification's assumptions meet reality. If the procedure does not reveal the failures the calculation assumed, the function is worse than its report says.

Structure

  1. Scope and basis: the function, interval and coverage per subsystem taken from the verification.
  2. Safety and prerequisites: permits, operations informed, bypass method and compensating measures, test equipment and its calibration, competence, estimated duration.
  3. As-found checks: active bypasses and alarms, program version, visual inspection, comparison of redundant channels.
  4. Subsystem tests: sensors, logic, final elements, each with acceptance criteria.
  5. Complete function test: from field input to final elements, with timing.
  6. Restoration: reset, removal of all bypasses and test connections, as-left record.
  7. Test record: every step with acceptance, as found, as left, pass or fail, initials.
  8. Failures found: reported and fed back into the failure data.

Steps that decide coverage

  • Transmitters: apply the real process variable at the sensor where practicable (pressure at the manifold, level by raising the level), not only a signal at the electronics. Check impulse lines.
  • Switches: actuate by moving the process element, not by shorting the contact.
  • Valves: full stroke from the logic solver, stroke time, solenoid venting, spring return; leak test where tight shut-off is part of the function.
  • Motor trips: confirm each contactor or breaker in the trip path opens.
  • Logic: voting, time delays, degraded modes, program version and checksum.

Acceptance criteria

Write numbers: trip within ± x % of setpoint, stroke time ≤ y s, leakage ≤ z. "Satisfactory" is not an acceptance criterion.

Feedback

Failures found at proof tests are the most relevant failure data you will ever have. Record failure mode, cause and repair, and review them at each periodic assessment of the SIF.

In First Out AI

The proof test draft is generated per function with device-type specific steps (transmitters, radar, temperature, flame scanners, switches, valves, motor-operated valves, motor trips, logic solver), acceptance criteria from the specification and a test record table. Download it as Word.

Written for First Out AI as engineering guidance. It supports engineering work and does not replace it; check every value against your standards, certificates and company rules with a competent functional safety engineer.