All WPSs start with a PQR. It is a record of the test. It DOES NOT have any ranges. It lists the actual values recorded during the welding of a test piece. It proves the welding process.
Then using the essential variables (ranges) from the relevant code/standard a WPS can be generated from this record of actual values.
PQR is essentially the ‘actual’ method that is used to create and test the welds to ensure they meet all applicable requirements.
The test procedures and final results are documented in the PQR. If the PQR meets the set standards of the welding world, then it will serve as the foundation on which one or more WPSs are drafted.
Even though a PQR eventually leads to a WPS, it is important for welders to have knowledge of both documents. In critical applications and in mechanised and automatic welds welders can refer to the PQR and replicate the actual values used in the test weld, this removes all the variation.
On face value, these documents look very similar but serve completely different purposes.
The best way to think of it is;
- PQR is an office document
- WPS is a workshop document
Both are necessary in most cases. The PQR supports the WPS as evidence of qualification.