WPS, pWPS and PQR — what each document is and the order they happen

Three documents, one sequence:

• A pWPS (preliminary Welding Procedure Specification) is the proposal. It is what you intend to weld to, written before anything is proven.
• A PQR — called a WPQR in ISO standards — is the evidence. It records what was actually welded on the test piece and what the testing found.
• A WPS is the approved instruction. It is the document a welder is issued, and it exists only once a qualification record supports it.

The order matters and cannot be reversed: you write a pWPS, weld a test coupon to it, test that coupon, record the outcome in a PQR/WPQR, and only then issue a WPS. A WPS that is not backed by a qualification record is, for code purposes, just a piece of paper.

The pWPS: your proposal, before it is proven

The pWPS holds the parameters you believe will produce an acceptable weld — process, parent material, filler, joint design, positions, preheat, interpass temperature, current and voltage ranges, travel speed, gas and heat input.

Nothing about it is authoritative yet. Its only job is to be specific enough that the test coupon can be welded to it and that a witness can confirm what was done. Many organisations skip writing a proper pWPS and reconstruct it afterwards from the welder's notes, which is exactly how qualification ranges end up not matching the production work they are supposed to cover.

The PQR / WPQR: what actually happened

Where the pWPS says what you intend, the qualification record says what occurred. It captures the as-welded parameters — the real amperage, voltage, travel speed and heat input, not the planned ones — plus the material certificates and consumable batch, and the results of every test performed on the coupon.

The test programme depends on which standard you are qualifying to and what class of work it is for, but typically includes some combination of visual examination, radiographic or ultrasonic testing, transverse tensile tests, bend tests, macro examination and hardness survey, with impact testing where toughness is required.

Two naming conventions cause constant confusion:

• ASME IX calls it a PQR — Procedure Qualification Record.
• ISO 15614 calls it a WPQR — Welding Procedure Qualification Record.

They serve the same purpose. Watch out for one further collision: WPQ in ASME IX is a Welder Performance Qualification, which qualifies a person, not a procedure. WPQR and WPQ are different documents about different things.

The WPS: the instruction that gets issued

The WPS is what reaches the shop floor. It is derived from the qualification record but is not a copy of it — it states ranges the welder must work within, where the record states the single set of values that were tested.

This is where the concept of a qualification range does the work. A coupon welded at one thickness, in one position, on one material group qualifies a defined band around those conditions, and the rules for how wide that band is are set by the standard. It is why a single test can cover a spread of production work — and why it is worth designing the test coupon around the range you want rather than around the easiest weld to make.

Why the chain has to stay linked

Auditors do not check documents in isolation. They pull a weld and walk backwards: which WPS covered it, which qualification record supports that WPS, does the production work sit inside the qualified range, and was the welder certified for it.

The chain breaks in ordinary ways:

• A WPS is revised, but the qualification record behind it is not re-checked, and the revision quietly moves a parameter outside the qualified range.
• The shop floor is working from a printed copy of a superseded revision.
• Production drifts — a thickness or a position creeps outside what the coupon actually covered.
• The qualification record exists, but nobody can find it during the audit.

None of these are exotic. They are what happens when the three documents live in separate files, or separate spreadsheets, maintained by different people.

Practical points

Write the pWPS properly, before welding the coupon. Reconstructing it afterwards is how ranges end up misaligned with production.

Record as-welded values, not intended ones. Heat input in particular is calculated from what was measured. A qualification record carrying the planned figures is not evidence of anything.

Design the coupon around the range you need. Thickness, position and material group choices on the test piece determine how much production work a single qualification covers.

Check the standard edition in force for your contract. Qualification ranges and test requirements differ between editions, and between ISO 15614-1 and ASME IX. Contracts frequently name a specific year.

Keep the revision history. Being able to show which WPS revision was current on the date a weld was made is often the thing that resolves an audit finding.

This article explains general principles. Always work from the edition of the standard named in your contract — clause numbering, qualification ranges and test requirements change between editions.