A Valid WPQ That Does Not Cover the Joint
Your shop runs six FCAW welders on nights fabricating three A709 Gr. 50 plate girders. Flange-to-web joints are 1 in thick, CJP, single-V with steel backing; the WPS requires FCAW-G, 150 °F minimum preheat, 350 °F maximum interpass, 3G position, and 100% UT. The schedule allows nine working days. Only two of the six welders hold qualifications covering 1 in material. Welder R.A. has a current, continuously employed WPQ for FCAW-G, but the qualified thickness range on the certificate is 1/16 in to 3/4 in; he has spent the past year on 1/4 in stiffeners and his UT reject rate is the lowest in the shop. On night two the two qualified welders are still on girder two and girder three has not been started. The foreman proposes putting R.A. on the 1 in joints because his welds never fail UT.
1. May R.A. weld the 1 in flange-to-web joints tonight? State your decision and the actions you take in the next 24 hours.
Read the worked answer
Decision: no.
The WPQ is valid, but its qualified thickness range stops at 3/4 in. Thickness range is an essential variable for welder performance qualification, so a 1 in CJP joint is outside the scope of his qualification no matter how good his UT history is. Test results are evidence about the past, not an extension of a range; no supervisor is authorised to widen a range by judgement.
Next 24 hours:
- Tell the foreman directly and in front of the crew that R.A. stays off the 1 in joints; record the instruction. Keep him on stiffeners and fit-up. Tack welds that will be consumed by the final weld must be made by a qualified welder or removed.
- Move one of the two qualified welders onto girder three root passes tonight, and check both certificates for continuity (no long gap since last use of the process).
- Raise the requalification request tonight so the coupon can be welded on day shift day 3, off the critical path.
- Notify QC and the project manager in writing that the schedule is at risk, so the slip is a managed decision rather than a discovery in week two.
2. If R.A. is requalified, specify the coupon and test, and list what you verify before he strikes an arc on production.
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Coupon and test
- Thickness at least equal to the thickest production joint (1 in), so the resulting qualified range covers the work.
- Same process (FCAW-G), same position as production (3G), and same backing condition, welded to the qualified WPS preheat and interpass.
- Specimen set required by the governing code for that coupon thickness (root and face bends, or side bends for a thick coupon), tested by the approved lab, with results recorded.
Before production
- Signed WPQ on file showing process, position and a thickness range that includes 1 in, issued against the code the contract invokes.
- The WPS at the workstation, with current, voltage, preheat, interpass and gas flow legible.
- Machine output measured at the stinger under load, not read off the dial.
- Preheat measured with a contact thermometer after each pass, not estimated by hand or torch glow.
- Wire lot and storage condition, gas flow at the nozzle, and a short briefing so he knows the parameters he is accountable for.
3. Assume each girder carries two 20 ft flange-to-web CJP joints, a 1 in single-V with backing consumes about 2.4 lb of weld metal per foot, a qualified welder deposits 4.5 lb/h of arc time, operating factor is 45%, and the crew works one 8 h shift per day. Does the nine-day schedule survive? Support with numbers and state your recommendation.
Read the worked answer
Weld metal required
- Length: 3 girders x 2 joints x 20 ft = 120 ft
- Weight: 120 ft x 2.4 lb/ft = 288 lb
Welder-hours available
- Effective deposition: 4.5 lb/h x 0.45 = 2.03 lb/h per welder
- Hours needed: 288 / 2.03 = 142 welder-hours
- Two qualified welders over 9 days: 2 x 9 x 8 = 144 h
So the schedule is arithmetically possible with about two hours of slack in total. That is no slack at all: one UT reject, one machine fault, or one shift of requalification time on the critical path breaks it.
Recommendation
- Requalify R.A. on day shift while the nights run, so the test does not consume the 144 h.
- Add a third qualified welder or a 4 h Saturday buffer, and say so now while the PM can still move it.
- Flag that repair work is not funded in the plan; the first rejected joint consumes the entire float.