WPS vs PQR vs WPQ

A weld is a metallurgical event you cannot fully inspect from the outside. Two welds that look identical can have completely different mechanical properties depending on the process, the filler, the heat input and the heat treatment. Because you cannot see soundness, the industry proves it on paper instead — by qualifying the procedure by destructive test, and qualifying the welder against that procedure.

That is the entire logic behind WPS, PQR and WPQ. They are not bureaucracy for its own sake; they are the substitute for being able to x-ray every weld's grain structure. Understanding how they fit together is the difference between a welding chapter that sails through review and one that gets bounced.

The order they are created in matters: you draft a procedure, prove it with a test (PQR), finalise the WPS, and then qualify welders against it. The next sections take each in turn.

A Welding Procedure Specification is the written, qualified instruction a welder follows at the bench. It specifies the welding process (e.g. GTAW, SMAW, GMAW), the base material group and thickness range, the filler metal, the joint design, position, preheat and interpass temperature, post-weld heat treatment, shielding gas, and the electrical parameters (current, voltage, travel speed).

Before it is qualified, it is called a preliminary WPS (pWPS) — a proposed recipe. It only becomes a true WPS once a PQR has proven it works.

A Procedure Qualification Record is the objective evidence behind a WPS. A test coupon is welded strictly to the pWPS, recording the actual parameters used. The coupon is then subjected to destructive testing — tensile tests, guided bend tests, and, where notch toughness is required, Charpy impact tests, plus macro examination and hardness surveys.

The PQR records what was actually done and the results obtained. If the coupon passes, the procedure is qualified — but only within the ranges allowed by its essential variables. Change an essential variable beyond its range (different material group, thickness outside the qualified band, added or removed PWHT) and you need a new PQR. Non-essential variables can be changed by simply revising the WPS.

A Welder Performance Qualification (WPQ, sometimes WPQR or "welder qualification test certificate") proves that a named individual has the manual skill to deposit sound weld metal following a WPS. The welder welds a test coupon, which is then examined — typically by bend test or radiography — and the result is recorded against that welder's name and stamp number.

A WPQ is always tied to ranges: the position, thickness, diameter and process the welder is qualified for. A welder qualified on 6G pipe, for instance, covers a wide range of positions; one qualified only in the flat position does not. The WPQ has a validity period and must be kept current.

The dependency chain runs in one direction:

1. Draft a pWPS — the proposed recipe.
2. Weld and test a coupon → PQR — prove the recipe produces sound metal.
3. Finalise the WPS — now a qualified procedure, supported by its PQR(s).
4. Qualify welders against the WPS → WPQ — prove each person can follow it.
5. Production welding — qualified welders follow qualified WPSs; each weld is logged on a weld map.

Break any link and production welding is not properly qualified: a WPS with no PQR, a welder with no current WPQ, or a weld made to a procedure outside its qualified range will all be flagged on review.

The same logic appears under different code families. The most common are:

• ASME BPVC Section IX — the US/international code covering WPS, PQR and welder/operator performance qualification in one document. Essential variables are listed in the QW tables.
• ISO 15614-1 — European/international procedure qualification (the PQR equivalent is the WPQR — Welding Procedure Qualification Record).
• ISO 9606-1 — European/international welder qualification (the WPQ equivalent).
• AWS D1.1 — structural steel welding in the US.

A note on terminology: under ISO, "WPQR" usually means the procedure qualification record (what ASME calls a PQR) — not the welder qualification. It is a frequent source of confusion on multi-code projects, so always check which standard a document is written to.

In the welding chapter of a Manufacturing Record Book, these documents appear together: the qualified WPSs used on the job, the PQRs that support them, the WPQ certificates for every welder involved, and a weld map linking each weld number to a welder, a WPS and its NDT result. That last link matters — a reviewer cross-checks the weld map against the NDT reports to confirm every joint was both qualified and examined. Material traceability closes the loop, back to the EN 10204 material certificates.