Welding Procedure Qualification and Traceability Gap
During a pressure-piping inspection, the inspector finds that a spool of 6-inch carbon steel pipe (ASTM A106 Grade B, Sch 40) was welded using a WPS that references a PQR qualified on 4-inch pipe of the same grade and schedule. The WPS covers the joint design and filler, but the PQR is dated 2019 and the welder's qualification certificate expired four months ago. The line is in hydrocarbon service and will be hydrotested at 1.5 times design pressure. The contractor says the pipe is 'the same material, so the qualification carries over'.
1. Assess whether the WPS/PQR and welder qualification are acceptable under typical pressure-piping code requirements.
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Two separate questions must be answered.
Procedure qualification (PQR/WPS): Under ASME B31.3 / Section IX, procedure qualification is based on essential variables. Pipe diameter is an essential variable for procedure qualification only in specific cases; for groove welds on pipe, a PQR on 4-inch NPS generally qualifies diameters from 2-inch NPS upward (the qualified range extends to larger sizes), so a 4-inch PQR can support a 6-inch WPS provided all other essential variables match: material specification (A106 Gr B is the same P-number), thickness range, filler classification, position, preheat, and PWHT. The WPS must state the qualified ranges. 'Same material' is not a sufficient argument - the PQR must be checked against the WPS for every essential variable.
Welder qualification: The welder's certificate expired four months ago. Under Section IX, welder performance qualification must be maintained; an expired qualification means the welder was not qualified when the welds were made. Those welds cannot be accepted on the basis of the welder's qualification.
Conclusion: the WPS may be supportable if the essential variables match, but the welder qualification failure is a nonconformity that must be resolved.
2. Recommend the actions needed before the line can be hydrotested and accepted.
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- Verify the WPS/PQR - compare every essential variable in the WPS against the PQR; if any essential variable is outside the qualified range, requalify the procedure.
- Resolve welder qualification - the welder must be requalified. Since the welds were made while the certificate was expired, the welds are of unknown quality and must be treated as suspect.
- Inspect the suspect welds - perform volumetric examination (radiographic or ultrasonic) on the welds made by the unqualified welder, in addition to any code-required sampling. If examination is acceptable, the welds may be accepted with documented justification; if not, repair or replace.
- Traceability - confirm the pipe and filler certificates match the WPS and that heat numbers are recorded.
- Hydrotest - only after the above are closed, hydrotest at 1.5 × design pressure with calibrated gauges, correct hold time, and recorded results.
All actions and results must be documented in the inspection record; acceptance cannot rest on verbal assurance.