WPS and WPQR: welding procedure documentation
How a welding method is determined, tested and approved
On load-bearing and pressure-bearing welding work, you can't just weld as you see fit. The welding method is described in an approved procedure, and that procedure has itself been tested and documented. That system ensures that a joint can be welded uniformly and with a quality that is proven in advance.
§WPS — the welding procedure
A WPS (Welding Procedure Specification) is the instruction the welder works from. It describes all essential aspects for a particular joint: method, base material and material group, thickness and dimension, filler material, shielding gas, joint design, welding position, current and voltage range, any preheat and sequence of passes.
| Document | What it is |
|---|---|
| pWPS | Preliminary procedure to be tested |
| WPQR | Report documenting the approved test |
| WPS | The final, approved instruction to the welder |
§From pWPS to approved procedure
First a preliminary procedure, a pWPS, is written with the parameters expected to be used. Then a test piece is welded according to it and the piece is examined with required tests. If the test passes, it is documented in a WPQR (Welding Procedure Qualification Record), and on that basis the final WPS is issued.
§Validity area
A qualified procedure applies only within a specific area — for example a range of material thicknesses and diameters a material group and one or more welding positions. If you change significantly on these conditions a new qualification may be required. This corresponds to the principle of the welder's own certification but here it's the method itself that has been tested.
§Procedure and welder are linked
There are two things that must be in place: the procedure must be qualified (WPS built on WPQR) and the welder must be qualified to perform it (welder certificate according to the relevant standard). Both are necessary — a good welder without an approved procedure or a good procedure executed by an unqualified welder does not meet requirements.
§The welder's responsibility
For the welder on the floor the system means you must know and follow the WPS that applies to the task — not deviate from it because you 'usually do'. If reality doesn't match the procedure it must go to the welding coordinator not be solved by improvising. That is the core of quality-controlled welding.