What a WPS Is, and Why You Should Ask to See One
Three documents govern whether a weld on your part was made by someone competent, using a method that has been proven to work. Buyers ask about certificates on the wall far more often than they ask about these, and these are the ones that actually decide the weld.
The WPS
A Welding Procedure Specification is the recipe. For a given joint it states:
- The welding process, for example GMAW, FCAW, GTAW or SAW
- The parent material group and thickness range
- The joint design and preparation
- The welding position
- The filler metal classification and size
- Shielding gas or flux
- Current, voltage and travel speed ranges
- Preheat and interpass temperature
- Post-weld heat treatment where required
- The number and arrangement of passes
A welder working to a WPS is not improvising. The document says what to do and it is the same document every time the joint is made, which is what makes the part repeatable.
The PQR
A Procedure Qualification Record is the proof behind the WPS. A test coupon is welded using the procedure, then destructively tested: tensile tests, bend tests, impact tests where toughness matters, macro examination and hardness surveys depending on the standard.
If the coupon passes, the procedure is qualified, and the PQR records exactly what was welded and what the results were.
A WPS without a supporting PQR is an unqualified procedure. Under most codes that means it is a piece of paper with no standing, with one important exception: AWS D1.1 has prequalified joint configurations that can be used without a PQR when every condition is met. That is a legitimate route, not a shortcut, and a shop using it should be able to say which prequalified configuration applies.
The welder qualification
The procedure being sound does not mean the person running the arc can execute it. A Welder Qualification Test Record, sometimes called a WQR or WPQ, records a test weld by an individual and the result.
The critical concept is range. A qualification does not say “this welder can weld”. It says this welder is qualified within ranges of:
- Process
- Material group
- Thickness, usually a band derived from the test piece thickness
- Position, and a test in a harder position qualifies easier ones
- Joint type, typically plate or pipe, fillet or groove
- Backing or no backing
This is why “our welders are certified” answers nothing. The question is whether they are qualified in the ranges your part needs.
Continuity and expiry
Qualifications are not permanent. Standards require evidence that the welder has been working with the process, usually within a recent period, and the certificate needs periodic endorsement or re-testing.
A certificate that expired two years ago is a record that a welder passed a test once. Ask for current ones.
The three questions to ask
Put these in the RFQ or in the supplier assessment. They take a competent shop under a minute.
1. Do you hold a qualified procedure that covers this material, this thickness and this joint in the positions this part needs?
If the answer is “we will qualify one”, that is legitimate and it is a cost and a schedule item. Qualifying a new procedure means a test coupon, destructive testing and a lab. Know about it at quote time.
2. Can you send the WPS and PQR numbers with the quote?
Not the full documents necessarily, just the references. A shop that has them will list them. A shop that cannot is telling you something useful.
3. Which welders will run this job and are their qualifications current and in range?
On a serious part, ask for the records with the first article.
Where this connects to the rest of the drawing
The WPS controls how the weld is made. The ISO 5817 quality level controls whether the finished weld is acceptable. The inspection method controls how anyone finds out. The code ties the three together.
A drawing that names a quality level but no code, with no procedure requirement, leaves the shop to fill in two of the three. Most will fill them in sensibly. The ones that do not are the ones you find out about later.
What we do with this
We ask every shop at registration which processes it runs, what procedures it holds and what its welders are qualified for, and we match requests against that rather than against a general claim. We do not qualify procedures, we do not certify welders and we hold nothing ourselves. Verification before a purchase order stays with you.
Send your RFQ and we will match it with shops whose qualifications cover your joint.
Frequently asked questions
What is the difference between a WPS and a PQR?
A WPS is the instruction: how to make this weld, with which process, consumable, current, preheat and technique. A PQR is the evidence: a record of a test weld made to those settings and the mechanical test results that proved it works. The WPS is supported by the PQR.
Does a qualified welder cover every job in the shop?
No. A welder qualification covers ranges, typically process, material group, thickness range, position and joint type. A welder qualified on 10 mm plate in the flat position is not automatically qualified for 40 mm plate overhead.
Do welder qualifications expire?
They have validity periods and continuity requirements, and the details depend on the standard. Typically the welder must have been using the process within a recent period and the certificate must be endorsed or re-tested. Ask for current certificates, not certificates.
Need a quote for this part?
Send the drawing. We match you with up to 3 shops that weld and machine it in house, and we reply within 24 business hours.
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