In building construction, prequalified welding procedures initiate the system of Welding Procedure Specifications (WPS) qualification and are usually substantiated further with standard qualification and mock-up tests. Prequalified welds must pass the initial testing in order for construction to proceed, while failing the tests requires the engineers to modify and repair their materials before they can continue with the project.
A prequalified weld conforms to technical qualities required by necessary welding requirements as stipulated by structural codes. Some institutions and standards that can approve prequalified welds include the American Welding Society (AWS), Submerged or Shielded Metal Arc Welding (SMAW) standards, and the Canadian Standards Association (CSA).
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Steps and Required Information
To apply for prequalification, a supply contractor must first signify a request for a welding inspector from an appropriate agency to scrutinize the welding process. Information required includes the welding equipment's model name and count, equipment serial number with the Quality Control personnel's signature, welding machine settings, cycle time, pertinent data on adjustments during the welding procedure, and temperature input. Along with other documentation, samples of welded materials done on every welding machine specified in the request must be sent to the appointed prequalification office.
Processing of Applications
After a request for prequalification reaches the agency, all pertinent paperwork and samples are checked and reviewed for completeness. Mechanical testing is then performed, which may include tensile tests on several samples to determine malleability at minimum stress, fatigue and cyclical tests and metallurgical tests. After conformity or non-conformity certifications are finalized, they are evaluated alongside the documentation, after which an approval or rejection is given. Specimens with metallurgical deficiencies are subjected to retesting. Approval allows the contractor to be included in the roster of prequalified suppliers.
In the acceptance of prequalified suppliers, the burden of costs, either fixed or variable, falls on the general contractor's responsibility. These costs include material and scrap costs, process and finishing costs, labor and overhead costs plus filler metal expenses.
- Welding: Principles and Applications by Larry F. Jeffus; 2002
- Guide to understanding Welding Procedure Specification (WPS), Procedure Qualification Record (PQR), and Welder Performance Qualification Record (WPQR)
- Go Welding: Procedure Qualification Record (PQR)
- Welding Qualitification and Certification