The Gas Switch and the Thick Production Joint

Production cannot continue as written. The first deficiency is the shielding gas: for gas-shielded FCAW, shielding gas composition is an essential variable in procedure qualification. Changing from 75% Ar/25% CO2 to 100% CO2 changes arc characteristics, penetration, and diffusible-hydrogen behavior, so the existing PQR and WPS do not cover the production weld. The second deficiency is thickness: the PQR qualifies base metal from 1/16 to 1/2 in., but production is 1 in.; the WPS is outside its qualified range. The third is welder qualification: the WPQ covers 1/8 to 3/4 in., but production is 1 in.; the welder is outside the qualified range. A fourth issue is that no preheat is specified for a 1-in. restrained moment connection; that may or may not be required by the qualified procedure, but the WPS must state it. The argument that FCAW is FCAW ignores the qualification system: the WPS is a controlled document, and the gas and thickness are not interchangeable without qualification.

The contractor has two technical paths. One is to return to the qualified 75% Ar/25% CO2 gas and use a WPS that covers 1-in. thickness, which still requires a new PQR or an existing qualified PQR with a qualified thickness range that includes 1 in. The other is to qualify a new procedure with 100% CO2 on a coupon thick enough to cover 1 in.; the PQR must record the actual gas, wire feed speed, voltage, travel speed, preheat, interpass, and joint design. A new WPS is then issued from that PQR. The welder must be requalified on a test coupon whose thickness qualifies the production range, or the contractor must show an existing WPQ whose stated range includes 1 in. The completed production welds made outside the qualified WPS are nonconforming until evaluated by the engineer and examined by the required NDT; they cannot be accepted on appearance. The inspector should require an NCR, a revised WPS, and welder qualification records before the third weld resumes.

I would stop the third weld, have the welder secure the joint, and segregate the two completed joints with a hold tag. I would record the WPS number, PQR number, welder ID, gas cylinder label, flow rate, wire lot, joint location, and the time of the stop. I would photograph the gas regulator and cylinder label and obtain the contractor's gas change order or verbal instruction in writing. I would issue a nonconformance report citing the unqualified gas, thickness exceedance, and welder range exceedance, and route it to the contractor's QC manager and the engineer. I would not permit retest or repair welding on the two completed joints until the engineer defines the disposition. I would also verify that the third joint is not partially welded in a way that creates a crack-sensitive condition; if it is, the contractor should follow an approved interruption procedure. The daily report should state exactly what was observed, not merely that the WPS was not followed.