Welder Performance Test on a Different Joint
A welder holds a performance qualification for GMAW spray transfer on 10 mm plate in the flat position with a single-V butt joint and backing. The company now needs him to weld a 6 mm thick, single-sided, open-root butt joint in the vertical-up position without backing on a pressure-retaining component. The welder has 12 years of experience and passed his original test two years ago. The production engineer argues that because the welder is experienced and the material is the same, no new test is needed.
1. Evaluate whether the existing welder qualification covers the new production joint.
Read the worked answer
The existing qualification does not cover the new joint. Performance qualification is specific to essential variables including base metal thickness range, joint type, backing, position, and process. The original test was on 10 mm plate with backing in the flat position; the new joint is 6 mm, open-root, without backing, in the vertical-up position. Removing backing changes the test from a backed to an open-root condition, which is a distinct qualification. Vertical-up is a different position that requires separate qualification. Thickness also matters: a qualification on 10 mm plate may cover a limited range, and the 6 mm production thickness may or may not fall within it depending on the code's thickness rules, but the position and backing changes alone require a new test. Experience does not substitute for a qualification test. The welder must be tested on the new joint configuration and position, and the test must be witnessed and documented.
2. Describe the test coupon and acceptance criteria the welder should complete.
Read the worked answer
The welder should weld a test coupon matching the production essential variables: 6 mm thick, single-V open-root butt joint without backing, in the vertical-up position, using the same process and filler. The coupon should be long enough to provide the required test specimens. After welding, perform visual inspection for undercut, overlap, and root condition, then bend tests: root bend and face bend, or side bends for thinner sections, depending on the code. Acceptance criteria typically require no crack or defect exceeding the code limit in the bend specimen, and visual acceptance with no unacceptable undercut or incomplete fusion. Radiography may be required if the code specifies it for the joint type. Document the test on a qualification record with the welder's name, process, position, thickness, joint type, and test date, and have it signed by the examiner. The qualification then covers the range of thickness and positions the code allows.