Welder Certificates That Do Not Match the Joint Being Welded
A contractor must install a 6 in. NPS Sch. 40 (0.280 in. wall) A106 Gr. B flare header. The WPS is backed by a PQR made on 3/8 in. plate: GTAW root with ER70S-2, SMAW fill with E7018 (F-4), no backing, no PWHT, qualified in 2019. The proposed welders hold certificates for 6G on 2 in. NPS Sch. 80 pipe (0.218 in. wall): GTAW root over a consumable backing ring, SMAW fill and cap with E6010 (F-3). Their continuity log shows the last SMAW production weld on 12 March of last year; today is 20 February. The client specification requires a GTAW root without backing on all process lines and E7018 for fill and cap.
1. Which qualification gaps must be closed before any production welding, and why is each one disqualifying rather than a paperwork issue?
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Three independent gaps exist, and each one alone stops the welders.
Filler metal F-number. The certificates cover F-3 (E6010) fill and cap; production uses F-4 (E7018). A change in F-number is an essential variable for welder performance qualification, so the certificates do not extend to E7018.
Backing. The test was run over a consumable backing ring. Deletion of backing is an essential variable for welder performance qualification, so a welder qualified with backing is not qualified to make a no-backing root, which is exactly what the specification demands.
Continuity. The last SMAW production weld was 12 March of last year and today is 20 February, so the welder has not used the process for well over six months. Under QW-322 the qualification has expired regardless of the certificate still sitting in the file.
The procedure side is largely satisfiable: the plate PQR covers 1/16 in. through 3/4 in., which includes 0.280 in., and matches P-1 to P-1, GTAW plus F-4 SMAW, no backing, no PWHT. 6G also covers all positions. The problem is the welders, not the WPS.
2. Design the most economical requalification that closes every gap at once. Justify each choice of coupon and test.
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One coupon can requalify both procedure and performance if it reproduces the production essential variables: P-1 pipe, GTAW root with ER70S-2 and no backing, F-4 fill and cap, 6G, no PWHT.
Wall thickness. Use a coupon with wall of at least 1/2 in. A welder qualified on 1/2 in. or thicker is qualified for unlimited thickness, which future-proofs the crew against thicker work and costs almost nothing extra.
Diameter. Choose a coupon no smaller than the smallest production pipe and no smaller than 2-7/8 in. OD, so the diameter range question under QW-452 never arises.
Position. 6G covers all positions, so one coupon serves every joint on the header.
Tests. For performance: visual plus root and face bend specimens. For the procedure: tension and bend specimens, with impact specimens only if the specification requires them. If the existing WPS already reflects these variables, the welders can be tested against it and only the performance qualification is new; the WPS still needs review against the current edition and the client specification before use.
3. Before the first production weld, what would you verify about the WPS itself and the production controls, beyond the new certificates?
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Verify that the WPS as written matches what the welders were just tested to: same F-numbers, same no-backing root, same position range, same thickness range, and a current edition review against the code and the client specification. Confirm the PQR's range covers production thickness and that no PWHT is required for 0.280 in. A106 Gr. B in this service; if the line is wet sour, hardness controls and a harder look at PWHT may apply even though the code does not require heat treatment at this thickness.
On the floor, check filler metal control (ER70S-2 cleanliness, E7018 from a sealed or properly rebaked holding oven, electrodes returned at shift end), purge and root cleanliness for the no-backing GTAW root, preheat for the ambient conditions, and that each welder's identification is traceable to the joint. Set the first-off inspection: visual and PT on the root before filling, and a dimensional check. Confirm the welder's continuity system will now actually track the six-month clock so the file does not silently expire again.