A welding procedure specification, usually called a WPS, is the written instruction for making one type of weld. It names the welding process, the steel, the joint, the consumables and the settings, so that every welder produces the same result. When you buy fabricated steel, the WPS list is one of the first documents to ask for.
What a welding procedure specification contains
A WPS records the variables that affect the quality of a weld. Typical entries are:
- The welding process, such as submerged arc or gas-shielded flux-cored welding, described in this overview of welding processes
- The parent material group and the range of thickness it covers
- The joint type, the groove shape and the welding position
- The filler metal or wire and the flux or shielding gas
- Preheat and interpass temperature limits where they apply
- The range of current, voltage and travel speed
The document is short, but each line closes a possible source of variation. A weld made outside the stated ranges is no longer covered by the procedure.
How a procedure is qualified
A WPS is not just written. It is proven by making a test weld and testing it, and the result is recorded in a procedure qualification record. The tests depend on the standard and the joint, and may include visual checks, non-destructive testing and mechanical tests. Welder qualification is a separate step: it shows that a person can follow the procedure.
Where the WPS sits in a quality system
A quality system for welding places the procedure inside a wider routine. Contract review, personnel, consumable control, inspection and records all connect to it. Our explanation of EN ISO 3834-2 welding certification shows how those elements fit together, and our guide to bolted and welded connections explains where welds are used and where bolts are the better choice.
What to ask a fabricator
- A list of the welding procedure specifications that cover your joints
- The qualification records behind each one
- The welders and the coordinators assigned to your package
- How a change of material, thickness or process is approved
- The inspection plan, including non-destructive testing and the acceptance criteria
If you compare each steel structure fabrication company on these points, differences between suppliers become clear very quickly. A supplier that can show the list in a few minutes usually has the system in place.
How Truong Thinh applies this
At Truong Thinh, the quality control department inspects dimensions and welds to AWS D1.1 before delivery. Our welding quality certificate, EN ISO 3834-2:2021, covers welding processes 136 and 121 and parent material groups 1.1 and 1.2, as shown on our certified quality page. The welding scope is repeated in the technical specifications. Treat the project specification as the governing document, and use the WPS list to confirm that our procedures cover your joints.
If you need to agree welding requirements for a steel package, send the drawings and the specification, and discuss your structural design requirements with our engineering team.
Frequently Asked Questions
Is a WPS the same as a welder qualification?
No. A WPS describes how a weld is made. A welder qualification shows that a welder can make sound welds following a procedure. Both are needed.
Does every weld need its own WPS?
Not every weld. One WPS covers a range of joints within its limits, such as a material group, a thickness range and a position. Welds outside the range need another procedure.
Who approves the WPS on a project?
The project specification decides. Some projects require the engineer or the client to review the procedures before fabrication, others accept the fabricator’s qualified procedures.
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