Welding Procedures Testing
Most fabricating codes and standards require qualification and certification of welding and brazing procedures and personnel who perform these tasks. A Welding Procedure Specification (WPS) is a document that provides in detail the required welding conditions for a specific application. WPS’s are either qualified by testing of pre-qualified, which means the WPS is exempt from procedure testing. If the WPS is qualified by producing a representative sample, the procedure qualification test and welding parameters are documented in a Procedure Qualification Record (PQR). The PQR test is tested by either a combination of nondestructive testing and destructive testing or destructive testing alone. The specific requirements for procedure qualification testing or the pre-qualified status are outlined in the specific code, standard or specification for which the production work is being manufactured.
Most industry codes and standards have a list of qualification variables which if changed beyond specified limits, require re-qualification of the welding procedure. Non-essential variables are changed within a WPS that are within the specified ranges allowed by the code or standard and do not require re-qualification.
Pre-qualified welding procedures are permitted by some industry standards and codes. Under this allowance, the employer of fabricator prepares in writing a welding procedure conforming to the specific requirements of that governing code for materials, joint design, welding process, technique, etc. for the application. AWS D1.1 “Structural Welding Code-Steel” has many joint details and welding processes which are classified as prequalified therefore the preparation of the WPS for this application is a much simpler process than qualified by testing.
ASME “Boiler and Pressure Vessel Code” does not allow for the use of pre-qualified welding procedures. Users of this set of industry standards are required to have WPS’s that are qualified by testing. The fabricator can choose from purchasing some WPS’s (Standard Welding Procedure Specifications of SWPS) in lieu of producing a PQR and test sample for the required examinations.
In determining the use, issuance, qualification and other requirements set forth in the large number of welding codes and standards being utilized in the welding industry, it is advised to discuss the testing requirements, sample size, qualification ranges, and other welding requirements for the specific application you are working to with a welding consultant or a testing agency.