PQR Thickness Range for a 1.25 in. Shell Seam
A Section VIII Div. 1 shop has a groove-weld procedure qualification tested on a 3/8 in. SA-516 Gr 70 plate using GTAW root and SMAW fill. The PQR records P-No. 1 to P-No. 1, A-No. 1, F-No. 6 root and F-No. 4 fill, and passes tensile and bend tests. The production weld is the longitudinal seam of a 1.25 in. SA-516 Gr 70 shell with the same joint design and the same welding process. The shop foreman points out that the WPS is 'P-No. 1 unlimited thickness' because the PQR was qualified with a groove weld and no impact testing was required. The AI is asked to approve the WPS for the 1.25 in. seam before welding begins. The production MDMT is 40°F, so impact testing is not part of the question.
1. Does the 3/8 in. groove-weld PQR qualify the WPS for the 1.25 in. production shell?
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No. Under Section IX QW-451.1, the base-metal thickness range qualified by a groove-weld test coupon depends on the coupon thickness. For a 3/8 in. coupon, the maximum qualified base-metal thickness is 2T, or 3/4 in., not unlimited thickness. The P-No. 1 grouping and the absence of impact testing do not remove the thickness limitation; they affect material grouping and toughness requirements, not the QW-451 range. The production shell is 1.25 in., which exceeds 3/4 in. The shop therefore needs a new PQR on a coupon thick enough to qualify 1.25 in., or a PQR already qualified for that thickness. To qualify 1.25 in. under the 2T rule, the test coupon would need to be at least 5/8 in. thick, and the WPS must be revised to state the correct qualified thickness range. The AI should not approve the WPS for the 1.25 in. seam on the basis of the 3/8 in. PQR.
2. Does the deposited weld-metal thickness matter separately from the base-metal thickness?
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Yes. Section IX evaluates base-metal thickness and weld-metal thickness separately. The 3/8 in. coupon also limits the qualified weld-metal thickness for each process. For the SMAW fill, the deposited weld metal thickness qualified is based on the test coupon; for a 3/8 in. deposit, the upper qualified limit is generally 2t, or 3/4 in., not the full 1.25 in. groove. The GTAW root is qualified for its own deposited thickness range. If the production groove requires more weld metal than the qualified range, the WPS is not supported even if the base-metal range were adequate. The shop should list the qualified thickness ranges for base metal and for each process's weld metal on the WPS. The AI should compare those ranges with the actual production joint, including groove depth and any reinforcement, before allowing welding to begin.
3. The shop offers to impact-test the 3/8 in. coupon and add 'impact tested' to the WPS. Does that cure the thickness problem?
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No. Impact testing may affect the minimum design metal temperature that the procedure can support and may be required for certain services, but it does not expand the QW-451 base-metal or weld-metal thickness ranges. The limitation here is thickness qualification, not toughness qualification. The production MDMT is 40°F and impact testing was not otherwise part of the question, so adding impact tests to the 3/8 in. coupon would not make the WPS qualified for 1.25 in. base metal. The shop still needs a PQR with a sufficiently thick test coupon or an existing PQR that covers 1.25 in. The AI should reject the proposed shortcut and require the WPS to be re-qualified or revised on the basis of a qualifying PQR before the longitudinal seam is welded.