The difference between WPS, PQR and WPQ is simple once you see how they fit together: the PQR proves a welding procedure works, the WPS tells the welder how to weld using that proven procedure, and the WPQ proves that a particular welder can actually do it. One is about the procedure, one is about the proof, and one is about the person.
- WPS (Welding Procedure Specification) – the written instructions for making a weld.
- PQR (Procedure Qualification Record) – the record of a test weld and its test results that supports the WPS.
- WPQ (Welder Performance Qualification) – the record that a welder passed a test and is qualified to weld within certain limits.
What is a WPS?
A Welding Procedure Specification (WPS) is the instruction sheet for production welding. It tells the welder and the inspector which process, filler metal, preheat, interpass temperature, current range, travel speed, joint design and post-weld heat treatment to use for a given joint.
Under ASME Section IX, a WPS lists the essential, non-essential and, when notch toughness applies, the supplementary essential variables. The code gives a suggested layout, form QW-482, but any format is acceptable as long as all the required variables are covered.
A WPS is a living document. You can revise its non-essential variables (for example, a different electrode diameter within the same classification) without new testing. You cannot change an essential variable beyond the range of its supporting PQR.
What is a PQR?
A Procedure Qualification Record (PQR) is the evidence behind the WPS. It records the actual variables used to weld a test coupon and the results of the tests on that coupon. The suggested ASME Section IX form is QW-483.
For a groove weld under ASME IX, the usual tests are tension tests and guided bend tests. When the construction code requires impact toughness, Charpy tests are added and the supplementary essential variables come into play.
Two things make a PQR different from a WPS:
- It records what was actually done, not a range. If the coupon was welded at 110 A, the PQR says 110 A.
- It cannot be changed after testing. Only editorial corrections or added information that does not change the test are allowed. If you need different essential variables, you weld and test a new coupon.
The PQR also sets the limits of the WPS. For example, the thickness of the test coupon decides the range of base metal thickness the WPS can cover. A coupon between 10 mm and 19 mm thick qualifies base metal from 1.5 mm up to twice the coupon thickness.
What is a WPQ?
A Welder Performance Qualification (WPQ) is the record that a specific welder, or welding operator for machine and automatic welding, has made an acceptable test weld following a qualified WPS. ASME IX gives suggested forms QW-484A for welders and QW-484B for welding operators. In AWS D1.1 the same document is usually called a WQTR (Welder Qualification Test Record).
The WPQ tests the person, not the procedure. The test weld is checked by bend tests or by radiography or ultrasonic testing, and the record states the ranges the welder is qualified for: process, position, diameter, deposited thickness, filler metal group and backing.
A welder's qualification does not last forever. Under ASME IX, it lapses if the welder has not used that process for six months or more. That is why every project needs a welder continuity log, and why continuity is one of the first things a client auditor checks.
WPS vs PQR vs WPQ: side-by-side comparison
| WPS | PQR | WPQ | |
|---|---|---|---|
| Full form | Welding Procedure Specification | Procedure Qualification Record | Welder Performance Qualification |
| Question it answers | How should this joint be welded? | Does this procedure produce sound welds? | Can this welder make sound welds? |
| Qualifies | The procedure (supported by a PQR) | The procedure | The welder or welding operator |
| Contents | Ranges of variables | Actual values used + test results | Actual test values + ranges qualified |
| ASME IX form | QW-482 | QW-483 | QW-484A / QW-484B |
| Can it be revised? | Yes, within the PQR limits | Editorial changes only | No – a new test for new ranges |
| Validity | As long as the PQR supports it | Does not expire | Lapses after 6 months without welding in that process |
| Used by | Welders and inspectors at the joint | Engineers, auditors, clients | QC team, welder register, auditors |
How the three documents connect
Think of it as a chain. A PQR supports one or more WPSs. Each production joint is welded to a WPS. Each welder who makes that joint must hold a WPQ covering the process, position and size, and must still be within continuity.
On a well-run project, the weld log shows this chain for every joint: joint number, WPS number, root and fill welder IDs, and the inspection and NDT results. If any link is missing, the joint is not traceable.
WPS, PQR and WPQ in AWS D1.1 and ISO
- AWS D1.1 (structural steel): uses WPS, PQR and WQTR. It also allows prequalified WPSs, which can be used without a PQR when every condition of the prequalification clause is met.
- ISO 15614-1 and ISO 9606-1: a pWPS (preliminary WPS) is tested to produce a WPQR (Welding Procedure Qualification Record), and the approved procedure becomes the WPS. Welders are qualified under ISO 9606-1, with their qualification confirmed every six months.
The names change, but the logic is the same in every code: prove the procedure, write the instructions, prove the welder.
Common mistakes on site
- Writing a WPS beyond its PQR. Thickness, P-number, preheat or PWHT ranges that the PQR does not support are a frequent audit finding.
- Treating the PQR as a template. The PQR records one test. Editing it to "match" a new job is not allowed – the job needs a new test.
- Forgetting welder continuity. A welder who has not used the process for six months is not qualified, even if the WPQ looks valid on paper.
- Welder outside the WPQ range. Position, diameter or thickness limits are exceeded on the shop floor when nobody checks the welder register.
- No link in the weld log. Joints without a WPS number or welder ID cannot be traced, and the dossier review stops there.
How to keep WPS, PQR and WPQ under control
- Keep a WPS / PQR register that shows which PQRs support each WPS and the approved ranges.
- Keep a welder register with continuity tracking, so expiring qualifications are flagged before they lapse.
- Record the WPS number and welder IDs for every joint in the weld log.
- Check the WPS and the welder's WPQ at fit-up, not after NDT.
Our Weld Log & Welder Continuity Tracker does points 2 and 3 in one Excel workbook, and our WPS from PQR service prepares WPSs from your qualified PQRs and checks every range.
Frequently asked questions
What is the main difference between WPS and PQR?
A WPS gives the instructions for production welding, with ranges for each variable. A PQR records the actual variables and test results of the qualification weld that supports the WPS.
Can one PQR support more than one WPS?
Yes. One PQR can support several WPSs, and one WPS can be supported by more than one PQR, as long as every essential variable in the WPS is within the qualified range.
Does a WPQ expire?
Under ASME Section IX, a welder's qualification for a process lapses if the welder has not used that process for six months or more. It can also be revoked if there is a specific reason to question the welder's ability.
Is WQTR the same as WPQ?
Yes, in practice. WPQ is the ASME Section IX term and WQTR is the AWS D1.1 term for the welder's qualification test record.
Do I always need a PQR for a WPS?
Under ASME Section IX, yes. AWS D1.1 allows prequalified WPSs without a PQR when all prequalification conditions are met.
This guide is a practical summary. Always work to the current edition of the governing code, the client specification and your approved quality plan.
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