What does WPS stand for in welding?

WPS stands for Welding Procedure Specification. It is a written document specifying the welding variables (process, filler, base metal, position, parameters) required to produce a code-compliant weld.

Is a WPS legally required?

A WPS is required whenever the governing code (AWS D1.1, ASME IX, API 1104, etc.) is invoked by contract, by AHJ, or by an industry certification like AISC. For prequalified procedures under AWS D1.1 Clause 5, a WPS is still required even though a separate PQR is not.

Typically a Certified Welding Inspector (CWI), welding engineer, or QC manager. AI-assisted tools can draft the narrative, but a qualified human must review and sign.

What's the difference between a WPS and a PQR?

A WPS prescribes how to weld. A PQR (Procedure Qualification Record) documents that a test weld made under the WPS actually met the required mechanical properties. Prequalified WPSs under AWS D1.1 Clause 5 don't need a project-specific PQR.

What is a Welding Procedure Specification (WPS)?

A Welding Procedure Specification (WPS) is a written document that tells a welder exactly how to make a code-compliant weld. Here's what it contains and why every fab shop needs one.

A Welding Procedure Specification (WPS) is a written instruction document that tells a welder exactly which process, filler metal, base metal, position, joint geometry, and electrical parameters to use to produce a code-compliant weld. It is the contract between the welder and the engineer of record, and it is the first document any third-party inspector or AHJ will ask for.

If you weld to a code — AWS D1.1, ASME Section IX, API 1104, AWS D1.6 — and you do not have a WPS on file for the work you are doing, that work is not compliant.

What a WPS actually contains

A complete AWS D1.1:2025 WPS includes:

Identification: WPS number, revision, date, code edition, scope, supporting PQR reference if any
Process: SMAW, GMAW, FCAW-G, FCAW-S, SAW, GTAW, or a combination
Joint design: groove or fillet, root opening, backing, backgouging, joint sketch
Base metal: specification (e.g., ASTM A36), Group number (Table 6.9 in 2025), thickness range, diameter range
Filler metal: AWS A5.X classification, F-number / A-number, diameter
Position: 1G, 2G, 3G, 4G, 5G, 6G (groove) or 1F–4F (fillet)
Preheat and interpass: minimum preheat, maximum interpass, method of measurement
PWHT: required temperature and hold time, if applicable
Electrical: amperage range, voltage range, travel speed range, transfer mode, polarity
Shielding gas: composition and flow rate (gas-shielded processes)
Technique: stringer vs weave, cleaning between passes, peening rules

The CWI or welding engineer signs and dates each revision.

Why a WPS matters

Three reasons:

Repeatability. Two welders pulling the same WPS off the shelf should produce welds with the same mechanical properties. Without a WPS, every welder makes their own assumptions.
Audit defense. When an AHJ, owner's rep, or AISC auditor asks how you welded a joint, the WPS is the answer. A missing or vague WPS is the single most common deficiency in third-party audits.
Liability. A signed WPS is documentary evidence that the work was performed to a code. In a structural failure investigation, the absence of a WPS shifts the burden of proof onto the contractor.

Prequalified vs qualified WPS

Under AWS D1.1 Clause 5, certain WPS configurations are prequalified — the AWS technical committee has already determined that procedures meeting these limits will produce sound welds, so no project-specific PQR is required. You still write the WPS; you just don't have to qualify it with test welds.

If your WPS falls outside the prequalified limits (unusual filler classification, oversized electrode, joint not in Annex B), you must qualify the procedure with a PQR — a test weld with documented mechanical test results.

Common mistakes that fail review

Listing a single amperage value instead of an acceptable range
Citing AWS D1.1:2020 table numbers in a 2025-edition WPS (the tables renumbered)
Forgetting the joint sketch or backing detail
No signature, no date, no revision history
Listing "ASTM A36 or equivalent" without a Group number

A modern WPS tool catches these before a CWI ever opens the file.