Column Splice in Cold Wind: Preheat and Welder Qualification
A W12x106 column splice with 1-in.-thick flanges is being completed with a CJP groove weld using E70T-1 FCAW. The approved WPS requires 150°F preheat, 300°F maximum interpass, and protection from wind. Ambient is 36°F with a 12-mph crosswind; the steel has condensation on it. The welder's qualification coupon was 3/8-in. plate in the 3G position, and his continuity record shows no welding for seven months. He says A992 is "pretty forgiving" and wants to start the root pass without preheat, then "let the next passes heat it up." The inspector is not scheduled until the next day, and the splice is on the critical path.
1. Should the root pass proceed under these conditions? Explain the technical reasons.
Read the worked answer
No. The approved WPS requires 150°F preheat, and the welder cannot substitute the heat of later passes for the preheat. Preheat slows cooling, helps drive off moisture, and reduces the risk of hydrogen-assisted cracking in a thick, highly restrained CJP splice. At 36°F ambient, the steel will pull heat out of the joint quickly, so preheat must be applied and verified before the root pass, and interpass temperature must be maintained between 150°F and 300°F. Condensation on the steel is another stop condition: welding on a damp surface can introduce hydrogen and porosity.
The 12-mph crosswind is a direct problem for gas-shielded FCAW because it can blow away shielding gas and produce porosity and incomplete fusion. The joint must be sheltered, or the process changed under an approved procedure. The weld area should be heated, dried, and checked with a contact pyrometer before welding. The inspector should be notified before the root pass, not after the splice is complete, because this is a hold point on a critical structural weld.
2. Is the welder qualified for this splice? Address both the test coupon and the continuity record.
Read the worked answer
No on both counts. A qualification test on 3/8-in. plate does not qualify a welder for a 1-in. groove weld. Performance qualification rules limit the thickness range based on the test coupon thickness; qualifying on thin plate and then welding thick, restrained column flanges is outside that range. The welder must be qualified on a coupon thick enough to cover the production thickness, in the position and configuration required, under the applicable welding code.
Separately, the continuity record shows seven months without welding. Most structural welding codes require requalification when a welder has not used a qualified process for a defined period, commonly six months. Even if the thickness issue were resolved, the lapsed continuity would still stop the work. The supervisor should pull the welder from the splice until both the thickness qualification and the continuity requirement are satisfied. Letting the welder start and then "seeing how it looks" is not acceptable for a CJP column splice.
3. If the welder has already placed a root pass, what should happen next?
Read the worked answer
Stop the work and treat the pass as nonconforming. Do not cover it with subsequent passes. Notify the inspector and the engineer, document the conditions, and evaluate the deposited weld. Depending on the joint and the engineer's direction, the root may need to be removed by grinding or air-carbon-arc gouging under an approved procedure, followed by surface inspection of the excavated area before re-welding. The joint should be re-prepared, preheated to the WPS requirement, sheltered from wind, and welded by a welder qualified for the thickness and process.
The completed splice then needs the inspection required for a CJP groove weld, which may include visual, penetrant, and ultrasonic testing per the project's inspection plan. Record the nonconformance, the welder's qualification status, the repair method, and the final test results. If the welder was not qualified when the pass was made, the engineer may require testing of any other welds made during the same period, because the problem is not limited to this one splice.