Why is a welding procedure necessary?
Basically, ALL Welding Standards require that welding is to be performed by a competent welder, using a qualified welding procedure. It is impossible to verify the “internal quality” of a weld by a visual examination only. A weld may look good on the surface, but it could have internal defects that make it unsafe and unacceptable to the welding standard.
So how do you ensure that a weld is going to meet the Standard requirements? By following a qualified Welding Procedure.
A welding procedure has 2 parts:
1. Procedure Qualification Record (PQR).
This is a document that records the ACTUAL parameters that are used to make a sound weld. These parameters are referred to in the Welding Standards as “Essential Variables”, basically anything that could have an effect on the quality of the weld, some of these “Essential Variables” are; welding process, consumable classification, material type, joint design, pre-heat requirements, amperage, voltage, shielding gas, welding position, travel speed etc. Usually a test weld is done under supervision of a Welding Supervisor, who monitors and recorded in real time all Essential Variables required to make the test weld. Once the weld is completed, a visual inspection is carried out to assess the quality of the finished weld. If the weld is acceptable, then it is sent to a laboratory for destructive testing to verify the internal qualities of the weld have complied with the welding standard. The laboratory will then issue a test Report, which is used as evidence that the PQR is now “Qualified” to the relevant standard.
2. Welding Procedure Specification (WPS)
The Welding Procedure Specification is the written instruction given to a welder which provides instructions required to produce a specific type of weld.
The WPS is based on the actual results recorded in the PQR, and the allowable limits from the welding standard are applied to these essential variables. This provides the working range for all essential variables that the welder must follow. If the welder follows the WPS carefully, the end result should be a sound weld with the same proven qualities as the original procedure.