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Test Parameters for Weld Procedure Qualification

Blog | July 27th, 2018

Like a mechanically-slanted skills portfolio, engineering services use weld procedure qualifications to provide proof of designated jointing techniques. Instead of print and photographs, however, the procedures are carried out on a qualification plate. After all, the managers who are developing an expensive structural investment aren’t about to take the word of a welding company, even if that service can show off pages of endorsements. No, they want qualification-based tests.

What’s a Weld Qualification Plate? 

Furnished with a list of project specs, the weld procedure undergoes its proving stage. Just like the portfolio example mentioned above, the policy is intended to consolidate a series of promoted skills and to clearly demonstrate a degree of service competence. Delivered in a tangible form, the plate is larger than a sample, plus it contains a set number of demonstrable welding techniques. These examples include destructive and non-destructive test routines.

WPQ Governance: Test Parameters 

Administering the procedural operations, the work incorporates a Break Test. Here, a weld sample is exposed to destructive forces until it fractures. Then, upon viewing the fracture face, the sample is assessed. The exposed face reveals potential weld discontinuities and flaws that would otherwise remain concealed. Next, fusion flaws and porosity issues are one thing, but what about the weld joint’s ductility? This test parameter is explored by carrying out a Bend Examination. The plate is deformed until it meets a required bend radius. Workpieces can be bent at an angle to the weld axis, along the weld root, or along any other required weld face. From here, the ductility of the piece is examined and certain bend-related flaws are exposed. Liner fusion defects are highlighted by this test.

Macroscopic and Hardness Testing 

The above tests utilize destructive machine tools to bend and break the tests pieces. With Macroscopic Testing, the process is still intended to damage the weld, but there are no material deformations taking place. This time, small segments of the weld are polished. Alternatively, the material is exposed to an acid etching compound. The goal is to create a clear cross-sectional view of the weld’s internal structure. Transitional heat zones are easy to assess when acids and polishing mediums create this “cutaway” view. As for Hardness Testing, an indentation assessment is likely here, but then there are abrasion tests and plastic deformation experiments to carry out before the Weld Procedure Qualification process can conclude.

Sample plates, qualification plates, or test workpieces, the test specs and parameters destructively torture those discrete trial segments. Then there’s always room for an additional series of non-destructive weld assessment procedures, all before the weld procedure can be qualified.

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