How Welding Procedures Are Qualified

In a previous article we talked about how to determine the best type of welding, and what variables to consider, whether essential or non-essential, internal or external to the welding procedure.
The following phase will be to produce the necessary documents certifying that each single welding is up to the its required standard. This preliminary work tends to be intense and very detailed, but it's necessary in order to certify the quality of the final work, which is one of Cividac's strengths.

The Welding Procedure Specification (WPS)

The document with all the details of the parameters of the welding is called Welding Procedure Specification (WPS), and summarises all the procedures that welders will have to adopt. The final purpose of the WPS is to guarantee that the welding adheres to known standards of proven quality.
The list of such parameters is very detailed and includes all factors affecting the welding. In the previous article, we mentioned the two most important ones: the material to weld and the welding technique to adopt. In fact, the list is much longer and includes for example: 
  • • Electricity and voltage 
  • • The type of electrode
  • • Working temperatures
  • • Welding speed
  • • Post-welding trEatment
  • • The type of protective gas
  • • Thickness and shape of the part to weld

The importance of testing

Each combination of variables in the WPS corresponds to a "Procedure Qualification Test" (PQR), whose purpose is to qualify welding the welding procedures beforehand.
These tests can also be non-destructive, such as radiography, or other mechanical tests to determine the resilience of the material in different conditions, such different levels of pressure or temperature.
In the industry we operate (unlike other sectors), pre-qualified welding procedures from third parties don't apply. All qualifications must be carried out by the manufacturer, who retains exclusive ownership.
Such tests however, are always performed in presence of independent organizations, such as SGS, Tuev, Lloyd's Register EMEA, that certify their correctness.