Welder Qualification Transferability
A welder qualified on 6 mm (0.24 in) plate in the 3G position with GTAW root and SMAW fill is assigned to weld a 25 mm (0.98 in) nozzle in the 6G position using the same processes. The welder's certificate shows qualification on 6 mm plate, 3G, GTAW/SMAW, dated 14 months ago, with continuous employment documented. The welding coordinator argues the welder is qualified because the processes match and thickness is only a performance variable for the root. Production is behind schedule and wants the welder to start immediately.
1. Determine whether the welder's qualification covers the 25 mm 6G nozzle. Identify each variable that must be checked.
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The welder's qualification must be evaluated against each essential performance variable:
- Position: 3G (vertical up/down on plate) does not qualify 6G (inclined pipe). Position is an essential variable; 6G requires separate qualification or a qualification that includes 6G.
- Thickness: A 6 mm plate qualification typically qualifies a limited thickness range. For many codes, a welder qualified on 6 mm is qualified to weld a maximum thickness related to the test coupon (often 2T for some ranges, but not unlimited). A 25 mm nozzle exceeds the typical range from a 6 mm coupon.
- Process: GTAW and SMAW match, but the qualification must cover the specific process combination and root/fill configuration.
- Continuity: 14 months with documented continuous employment satisfies the typical 6-month continuity requirement, but continuity does not expand the qualified range.
Conclusion: The welder is not qualified for the 25 mm 6G nozzle. The coordinator's argument that thickness is only a root variable is incorrect - thickness and position are both essential performance variables. The welder must be qualified (or have an existing qualification) for 6G and the required thickness before starting.
2. What requalification is required, and can any existing qualification be credited?
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Requalification should cover the actual production conditions:
- Position: 6G test coupon (inclined pipe) is required unless the welder holds another qualification that includes 6G.
- Thickness: The test coupon should be at or near the production thickness, or thick enough to qualify the 25 mm range under the applicable code.
- Process: GTAW root and SMAW fill on the test coupon, matching production.
Credit for existing qualification: The 3G/6 mm qualification cannot be credited toward 6G or 25 mm. However, the welder's documented continuity and prior qualification demonstrate a baseline of skill; the new test can be limited to the variables not already covered, but the test itself must be performed and witnessed.
Interim measure: Until requalification is complete, the welder should not weld the 25 mm 6G nozzle. If schedule pressure is severe, a qualified welder should be assigned, or the nozzle welded in a qualified position if design permits. Production pressure does not justify using an unqualified welder.