A WPS (Welding Procedure Specification) is the document that describes how a weld is to be made. It tells the welder which process, which base material, which consumable, which current and voltage range and which preheat to use. The aim is that the same weld is made to the same quality every time.
The difference between pWPS, WPQR and WPS
These three documents appear in order:
- pWPS (preliminary welding procedure specification): The draft the engineer prepares saying "this is how we will make this weld." It has not been tested yet.
- WPQR (welding procedure qualification record, called PQR in ASME and AWS): A test piece is welded according to the pWPS, then destructive and nondestructive tests are carried out. The results are written into this record and an inspection body approves it.
- WPS: The final procedure used in production, based on the approved WPQR. It cannot go outside the ranges covered by the WPQR.
In short: the pWPS is the draft, the WPQR is the evidence, the WPS is the instruction used in production.
Related reading: AWS D17.1 explained · Weld records on Gulf oil & gas projects · What do ISO 5817 quality levels B, C and D mean?
The most common mistakes when preparing a WPS
- Going outside the scope of the WPQR
- Writing the preheat without calculating it
- Not controlling heat input
- Not keeping the document up to date
- Not matching it with the welder qualification
Which of these is in your records?
Most of these mistakes slip past when records are read by eye one at a time, and auditors look for them first. The real question is which one sits in your own files. Upload your WPS and WPQR documents to NTB SpecPro and quickly see which points may carry risk, the likely reason and a suggestion.
Preparing a WPS faster
In most companies preparing a WPS is paperwork that takes hours. Transferring ranges from the WPQR one by one, doing the calculations and comparing against welder qualifications is open to error.
The NTB SpecPro welding module makes this easier: it derives a WPS from a WPQR, prepares a pWPS draft, flags out-of-range values and tracks the expiry of welder qualifications. Final checking and approval always stay with the authorized welding engineer.
Free tool: Welding heat input calculator · Carbon equivalent calculator (CE, CET, Pcm)
Prepared by NTB SpecPro process quality engineering; reviewed by an engineer holding the International Welding Engineer (IWE) qualification. Questions: info@ntbspecpro.com
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