Witnessing acceptance tests: who signs, what is recorded

1. What the witness is responsible for

A witnessed test involves two separate roles. The performer sets up the valve, applies the pressure and records the readings. The witness watches, checks and signs.

A witness signature says one thing clearly. This person saw this test, on this valve, under the conditions written in the record. It does not say the witness performed the test. Nor does it make the witness responsible for the valve's later behaviour. Keeping those roles separate is what makes the record trustworthy.

The witness also has the standing to stop a test. If the medium, the pressure or the method departs from the agreed procedure, the witness should pause and record the deviation before the test continues.

2. Who signs, and for whom

Signature authority should be settled before the test day, in the purchase order or the contract. Common signatories include:

1. An engineer or inspector representing the owner or the buyer of the valve.
2. A third-party inspection body engaged by either party under the contract.
3. The manufacturer's quality representative, signing on behalf of the maker.
4. A contractor supervisor, when the test forms part of installed plant work.

The performer of the test signs the same record, typically on a separate line. Two signatures, two roles, one document.

On a live plant, the permit system adds its own layer. The permit names who may be present. The witness named in the contract should be one of them. Agreeing this in advance avoids a wasted visit.

3. What a complete record contains

A witnessed test is only as strong as its record. A complete record should carry:

1. Valve identity: tag number, serial number, size, class and manufacturer.
2. Test date, location and the procedure or standard applied, cited by name.
3. The acceptance criterion agreed before the test, written in plain terms.
4. The test medium, the pressures applied and the holding times used.
5. The instruments used, with their calibration status or reference.
6. The observed result, recorded as a reading, not as a judgement.
7. Any deviation, its cause, and how it was handled.
8. Names, roles, dates and signatures of performer and witness.

Readings and observations are evidence. Conclusions belong in a separate summary. For what a fuller evidence file looks like in practice, see reading a valve survey report.

4. Factory acceptance and field verification

API 598 covers seat leakage testing and ISO 5208 defines leakage classes. Both are factory acceptance references. A witnessed factory test proves the valve met its criterion on the day of manufacture. It says nothing about seat condition after years in service.

In the field, the confirming test for a passing valve is a seat-leak test under agreed conditions. Common forms include pressure decay across the closed valve, double block and bleed monitoring, or a witnessed leak test.

Sound, flow indication and bubbles are screening evidence. They suggest a leak or its absence. They do not confirm one. Name the confirming test in the record, and the argument ends there.

5. Disputes a witnessed record settles

Most test disputes have the same shape: each side remembers a different test. Common causes include:

• A criterion agreed verbally and never written down.
• A gauge of unknown calibration status.
• A test medium that differed from the agreed procedure.
• A missing serial number, which leaves the tested valve in doubt.

A witnessed record closes each gap. The criterion is written before the test, and the instruments are identified. The signatures then fix what was seen.

The record also supports honest endings. When a valve still fails a witnessed test after treatment, the endpoint is repair or replacement. See when a trial fails for that path, and photographs and video as evidence for what to capture on the day.

6. Arranging a witnessed field test

If you are evaluating an online valve maintenance provider, make witnessing part of the trial. Ask the provider to state, before the job, what will be measured and against what criterion. Then send your own witness, or an inspector you trust, and have them sign.

We work to that discipline. Our teams welcome a client witness wherever fittings, valve design and site rules allow the job. They record before and after readings, such as torque before and after, supported by photographs. Working across the Middle East, Asia and Africa, they are used to client inspectors. A valve survey is often the first step. Choosing an online valve maintenance provider sets out the wider questions to ask.