Why welding runs on paperwork
You cannot inspect quality into a weld after the arc stops. Most of what decides whether a welded joint will carry its load — fusion, mechanical properties, freedom from cracking — is settled while the weld is being made, by variables nobody can fully verify afterwards without cutting the joint apart. So the trade controls welds the only way it can: by specifying, in advance, exactly how the joint is to be welded, and by proving that the specification works before production starts.
That is the whole purpose of the procedure system. For a given application, weld quality is assured by two things together: a specified welding procedure, and a welder qualified to carry it out[S1]. The documents in this sheet — WPS, WPAR/PQR (WPQR in current ISO wording) and the welder qualification test — are the three corners of that system. They are often talked about as one pile of paperwork; they are not. Each answers a different question:
- WPS — how must this joint be welded?
- WPAR / PQR / WPQR — what is the evidence that welding it that way works?
- WQT / WPQ — can this person weld it that way?
The WPS: the sheet the welder works to
The Welding Procedure Specification is the key document. It sets out the welding variables to be used so that the joint achieves the specified weld quality and mechanical properties[S1]: parent material, welding process, consumable and shielding gas, joint design and preparation, welding position, current and voltage ranges, travel and interpass details, preheat where required. A production welder does not work from the qualification records — those sit in the file. The welder works from the WPS, or from work instructions written out of it[S1].
A WPS on its own, however, is only a claim. What makes it more than a claim is the record standing behind it.
Qualifying a procedure: pWPS to WPQR
The most common route to a qualified procedure is a procedure test, described for steels in BS EN ISO 15614-1 and for aluminium and its alloys in 15614-2[S1]. The sequence matters, so it is worth walking in order.
- The manufacturer drafts a preliminary welding procedure specification (pWPS) — the intended variables, not yet backed by evidence.
- One of the manufacturer’s competent welders welds a test piece to the pWPS.
- The test piece is examined and tested: non-destructive examination and mechanical tests, as the standard requires.
- How the weld was made and how it performed are written up as the welding procedure approval record — WPAR in the BS EN usage TWI describes, PQR under ASME IX, WPQR in the wording of current ISO 15614 editions[S1].
- If the examiner or examining body accepts the record, it is used to finalise one or more WPSs, and those WPSs become the basis of the work instructions given to production welders[S1].
FIG. 1 · Procedure qualification route (BS EN ISO 15614)
Two details in that flow are easy to miss and worth fixing. First, the WPAR/PQR is a record, not a specification — it describes one weld that was actually made and tested. The WPS is derived from it and may cover a range of work. Second, the welder who makes a satisfactory procedure test piece does not walk away empty-handed: that same test also qualifies them for the appropriate range under the relevant welder standard — BS EN ISO 9606, ASME IX or AWS D1.1[S1].
Essential variables: what invalidates a procedure
Both the European and the American systems define essential variables — conditions which, if changed, may affect weld quality or mechanical properties. Change any of them and the qualification no longer stands: a new approval test is required[S1]. The precise list belongs to the relevant standard, but it typically includes the material type, the welding process, the thickness range and, in some cases, the welding position[S1].
This is the discipline that gives the paperwork its teeth. A WPS is not a general licence to weld; it is qualified evidence for a bounded envelope of material, process, thickness and position. Step outside the envelope — thicker plate, a different process, a new material group — and the evidence no longer applies, however similar the job looks from the bench.
Routes that do not need a new test weld
The conventional procedure test is the most common route, and application standards often make it mandatory[S1]. But BS EN ISO recognises alternatives, each with its own standard and its own limits of application regarding processes, materials and consumables[S1]:
- BS EN ISO 15610 — qualification based on tested welding consumables;
- BS EN ISO 15611 — qualification based on previous welding experience, where the manufacturer can document that the joint type has been welded satisfactorily before;
- BS EN ISO 15612 — adoption of a standard welding procedure;
- BS EN ISO 15613 — qualification based on a pre-production welding test.
Where the application standard does not force the test route, the contracting parties can agree one of these alternatives[S1]. On the American side, ASME IX requires a procedure qualification test, while AWS D1.1 permits pre-qualified procedures within the limits the specification details[S1].
Qualifying the welder: WQT and WPQ
A qualified procedure says nothing about the person holding the torch. The welder qualification test exists to demonstrate that a welder has the skill to produce a satisfactory weld under the conditions used in production, as set out in the approved WPS or work instruction[S1]. In BS EN ISO 9606 language this is the welder approval or qualification test (often abbreviated WQT); ASME IX calls the resulting document a welder performance qualification (WPQ).
Welder qualification has its own essential variables — material type, welding process, joint type, dimensions, welding position — which must be specified in the test[S1]. Because the test piece is representative of the joint to be welded rather than of one particular contract, the qualification is independent of the type of construction, and its range extends beyond the exact test conditions to joints the standard considers easier to weld[S1]. In BS EN ISO 9606 the certificate is issued under the sole responsibility of the examiner or examining body[S1] — not the employer, and certainly not a website.
Keeping a welder qualification alive
A welder qualification is not permanent. TWI’s summary of BS EN ISO 9606 says continuity is confirmed at six-month intervals — by the employer, welding coordinator, examiner or examining body — while the welder continues working within the certificate’s range. It then describes three routes for prolonging the qualification[S1]:
- retesting every three years; or
- testing, every two years, two welds made during the final six months of the validity period by radiographic, ultrasonic or destructive methods, with the results recorded; or
- maintaining continuous validity while the welder works for the same manufacturer, the manufacturer’s quality programme is verified to ISO 3834-2 or 3834-3, and documented production welds of acceptable quality confirm position, weld type and backing conditions.
American standards carry similar requirements with different ranges of approval. TWI notes that, since the 2015 edition, ASME IX has included a non-mandatory appendix describing conditions under which welders and welding operators qualified to ISO 9606-1 and ISO 14732 can also be certified to Section IX[S1].
Welding operators and mechanised work
Mechanised and automatic welding splits the human role in two. The people who set up and adjust the equipment — welding operators and weld setters — need qualification when the contract or application standard requires it, under BS EN ISO 14732. The people who merely run it, loading and unloading a robot cell or operating a resistance welding machine, do not[S1].
Operator qualification can be based on a welding procedure test to ISO 15614, a pre-production test to ISO 15613, a test piece to ISO 9606, or a production test — supplemented in each case by a functional test appropriate to the welding unit[S1]. TWI’s summary gives the operator retest route as every six years and the production-evidence route as every three years[S1]. Under ASME IX, operators of both mechanised and automatic equipment require qualification, with their own essential variables[S1].
Terminology register
| Term | Standard home | What it is |
|---|---|---|
| WPS | BS EN ISO 15614 · ASME IX | Welding procedure specification — the variables production welding must follow. |
| pWPS | BS EN ISO 15614 | Preliminary WPS — the draft used for the procedure test, before qualification. |
| WPAR | BS EN usage (as in TWI’s description of BS EN ISO 15614) | Welding procedure approval record — the evidence record behind a WPS. |
| WPQR | Current EN ISO 15614 editions | Welding procedure qualification record — the same record under its current ISO name. |
| PQR | ASME IX | Procedure qualification record — the American equivalent of the WPAR/WPQR. |
| WQT | BS EN ISO 9606 context | Welder qualification test — qualifies the person, not the procedure. |
| WPQ | ASME IX | Welder performance qualification — the ASME document recording a welder’s test. |
Older British practice also used BS EN 288 terminology before the ISO 15614 series superseded it; you will still meet WPAR on long-lived documentation for that reason.
What this sheet is not
This sheet is procedure literacy, not procedure qualification. The Weld Fab does not draft, review, qualify or approve welding procedures, does not test or certify welders, and is not an examiner or examining body. Those roles belong to the manufacturer, the examiner or examining body, and the application standard for your work — nothing on this desk can stand in for any of them[S1].
What the desk can do is help you plan around the paperwork: read the joint geometry a WPS specifies with the groove weld sheet, estimate consumables for a specified joint with the weld volume & filler metal calculator, and see how every figure is produced on the methodology sheet.