pWPS vs WPQR vs WPS:
The Difference Explained.
Three records, one chain of proof — the draft you test against, the record that proves it, and the procedure your welders actually follow.
The Short Answer
A pWPS is the proposed procedure you weld a test piece to; the WPQR is the record of that test proving the procedure works; and the WPS is the final, qualified procedure your welders follow in production. They are three stages of the same thing: a draft, its proof, and the approved production version. A WPS is only ever as valid as the WPQR behind it — and that WPQR started life as a pWPS. Get the order straight and the acronym soup clears up fast.
pWPS — the Preliminary Draft
A pWPS (preliminary Welding Procedure Specification) is the first draft — the procedure you think will work, written from experience before anything is proven. It sets out the intended parameters: process, material, joint, position, and the ranges you expect to qualify.
- It is a proposal, not proof. Nothing is qualified yet. The pWPS exists to be tested — a test coupon is welded to it, then examined and destructively tested.
- It carries intended values and expected ranges. The draft records both what you plan to weld at and the qualified range you are aiming to prove, so the test has a clear target.
- Governed by content rules. Under ISO, ISO 15609-1 defines what technical content a welding procedure specification must contain — the pWPS follows the same structure as the WPS it will become.
WPQR — the Qualification Record
A WPQR (Welding Procedure Qualification Record) is the evidence that the pWPS actually produces sound welds. You weld the test piece to the pWPS under witness, run the required examinations and tests, and the WPQR records what was welded, how, the results, and — critically — the ranges those results qualify.
- It is the proof. Where the pWPS proposes, the WPQR confirms. It is the objective test record a WPS leans on.
- It qualifies a range, not a single point. Under ISO 15614-1, a single WPQR qualifies a band of production conditions — a range of thicknesses, diameters and related variables — so one qualification test can support several production procedures.
- One WPQR, many WPS. Because it qualifies a range, one WPQR commonly underwrites multiple WPSs, each written to sit inside the qualified band.
- "WPQR" or "PQR"? They are the same record under different codes: WPQR is the ISO term, PQR (Procedure Qualification Record) is the ASME term. We default to WPQR because we are EU-first.
WPS — the Production Procedure
A WPS (Welding Procedure Specification) is the finished, qualified procedure a welder follows on the floor. Its ranges are written to fall inside what the WPQR qualified, so every instruction on it is backed by test evidence.
- It instructs; the WPQR proves. The WPS tells the welder exactly how to make the weld; the WPQR is the record standing behind those instructions.
- It must stay inside the qualified range. A WPS cannot specify conditions the supporting WPQR did not qualify — if production needs to go outside the band, you need further qualification.
- It is traceable to its proof. A well-run system links each WPS back to the WPQR (and originating pWPS) behind it, so an auditor can follow the chain from production instruction to test evidence in one step.
How They Fit Together
Read in order, the three records are simply draft → proof → production:
- 1. pWPS — you propose a procedure and weld a test piece to it.
- 2. WPQR — you test that piece; the record proves the procedure and fixes the qualified ranges.
- 3. WPS — you write the production procedure inside those ranges, and welders follow it.
Standards split the job cleanly: under ISO, ISO 15609 governs the content of the specification (the pWPS and WPS), while ISO 15614 governs the tests that qualify it (the WPQR) and the range of approval those tests grant.
Where the Two Codes Genuinely Differ
The three-record idea exists in both code families, but there is one real, load-bearing difference beyond the names — worth knowing if you work to both.
- The names. ISO calls the qualification record a WPQR; ASME calls it a PQR. Both mean the same document. ISO welding-procedure qualification lives in the 15607 / 15609 / 15614 family; ASME's lives in Section IX.
- Where the range of approval lives — the key difference. Under ISO, the WPQR carries the range of approval, and the WPS must stay within the scope the WPQR defines. Under ASME, the PQR records only what was actually tested, and the WPS is where the ranges are stated. Same evidence, but the qualified ranges are documented in a different place — a genuine trap when reading records across codes.
- Terminology overlap. Watch "WPQR": in ISO it is the procedure record, but in ASME the same letters are sometimes used for a welder's performance qualification record. Context decides which one is meant.
Software that assumes a single code hides these differences until they bite. Elenchon keeps traceability records for both standards and defaults to ISO terminology by design.
Draft, Proof and Production — Linked
Elenchon runs the whole chain in one place: define a preliminary WPS, capture the real WPQR parameters on the shop floor, import those values back to set the qualified ranges, and export a finalized WPS — every WPS traceable to the WPQR evidence behind it. It is the full WPS, WPQR and WPQ qualification workflow on an on-premise appliance you own. For the welder side of qualification, read the companion guide: what welder qualification management software does.