What is a WPS? Welding procedure specification, PQR and WPQ explained

What is a WPS?

A welding procedure specification (WPS) is the written instruction for making a particular weld. It lists the welding variables — process, materials, filler metal, gas, position, joint design, current, voltage, travel speed, preheat and so on — so that every welder who follows it produces a weld with the same, proven quality.

The important word is proven. A WPS is not just a good recipe; it has to be backed by evidence that welds made within its ranges meet the requirements of the job. In ISO terms (ISO 15607) the WPS is qualified by one of several methods; under ASME Section IX it is supported by one or more procedure qualification records. Before qualification, the draft is called a preliminary WPS (pWPS).

The content of a WPS for arc welding is specified in ISO 15609-1. ASME Section IX lists the variables per welding process and offers a suggested form (QW-482); AWS D1.1 has its own WPS form and additionally allows prequalified WPSs that may be used without a procedure test when all of the code’s prequalification conditions are met.

What a WPS contains

Forms differ between standards and companies, but a WPS for arc welding typically covers these groups of information:

• Identification — manufacturer, WPS number and revision, the supporting PQR/WPQR number(s), applicable standard.
• Process — welding process(es), for example 111 (MMA/SMAW), 135 (MAG/GMAW) or 141 (TIG/GTAW) in ISO 4063 numbering, and the mode of metal transfer where relevant.
• Joint — joint type, a sketch of the joint preparation and the weld build-up (sequence of runs), backing and back gouging.
• Parent material — material designation or group, thickness range and outside diameter range.
• Filler metal and gases — designation, make and size of consumables, shielding and backing gas.
• Position — welding position(s) and, for pipes, the direction of welding.
• Electrical parameters — type of current and polarity, current, voltage and travel speed ranges per run, and heat input where required.
• Thermal cycle — preheat temperature, maximum interpass temperature and any post-weld heat treatment.
• Technique — stringer or weave beads, single or multiple electrodes, cleaning between runs.

Every one of these values must lie within the range qualified by the supporting procedure qualification. That is why writing a WPS starts with finding the right PQR.

WPS vs PQR vs WPQ

The three documents answer three different questions. Confusing them is one of the most common findings in welding audits.

PQR or WPQR?

Both names describe the same idea: the record of a successful procedure test. PQR (procedure qualification record) is used by ASME Section IX and AWS. WPQR (welding procedure qualification record) is the ISO term, for example in ISO 15614-1. Our guide to PQR and WPQR explains the tests in detail.

WPQ, WPQR or welder certificate?

WPQ (welder performance qualification) is the ASME term for the welder’s qualification record; in ISO practice it is the welder qualification certificate to ISO 9606-1. Note the difference to WPQR: the WPQR qualifies the procedure, the WPQ qualifies the person. See our guide to welder qualification.

How the three depend on each other

In practice the documents form a chain that runs from the test laboratory to the shop floor:

1. A pWPS describes the procedure you intend to qualify.
2. A test piece is welded to the pWPS, examined and tested. The results are recorded in the PQR/WPQR.
3. From the PQR/WPQR, one or more WPSs are written for production, each within the qualified ranges.
4. Welders are qualified by a test — their WPQ or welder certificate — for the processes, materials, thicknesses and positions they will weld.
5. In production, a weld is only compliant if the WPS is supported by a valid PQR and the welder holds a valid qualification that covers that WPS.

Break any link and the weld is not traceable: a WPS outside the PQR’s range, a welder whose certificate expired last month, or a PQR nobody can find during the audit. Most of the effort in welding documentation goes into keeping this chain intact as WPSs, PQRs and welders change.

Common mistakes with WPS documents

• Copying the PQR into the WPS. A PQR records the actual values of one test; a WPS gives ranges for production. The WPS should use the ranges the standard allows, not the single test values.
• Ranges outside the qualification. Thickness, diameter, heat input or preheat drifting beyond what the PQR supports — often after several revisions.
• Missing link to the PQR. The WPS does not state which PQR(s) support it, or refers to a superseded one.
• Old revisions in production. The welder works from a printout that was replaced months ago.
• Welders not matched to the WPS. The WPS is correct, but the welder’s certificate does not cover its process, material group or position.

Do this in weldXpert

weldXpert keeps the whole chain in one place. You filter your PQRs by material, thickness or values, pick the one that supports a new WPS and let weldXpert fill the WPS from it — with ISO, ASME IX or AWS D1.1 selectable, heat input calculated and the approval history stored. Welder qualifications are matched to each WPS, and expiry dates are tracked with colour warnings and e-mail reminders.

WPS software →

PQR and WPQR management →

Welder qualification software →