Staggered Intermittent Fillet and a Bevel That Was Not on the Drawing
A fitter is given a drawing for a 6 mm mild-steel bracket. The welding symbol on the reference line shows a 6 mm fillet weld, length 60 mm, pitch 120 mm, on both sides, with the upper and lower symbols offset from each other. The tail references WPS-GMAW-02. A second symbol shows a single-bevel groove weld with a 60° included angle, a 2 mm root gap, arrow side, and a note “backing strip”. A general note reads “interpret per ISO 2553; all dimensions in mm”. The fitter reads the fillet as continuous on both sides, bevels the plate to 45°, butts the parts with no gap and omits the backing strip because “it would be welded over anyway”. He completes the joint and sends it to inspection. The inspector rejects the bracket and asks for a written explanation.
1. Interpret the two welding symbols correctly. State the weld type, size, length, pitch, side and any supplementary requirements.
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Fillet symbol: 6 mm leg length (a = 6), 60 mm weld length, 120 mm pitch, therefore intermittent: 60 mm weld, 60 mm gap, repeated. The symbol appears on both sides of the reference line, so both sides are welded. The two symbols are offset, which means staggered, not chain: the welds on the second side sit in the gaps of the first side. If the symbols had been aligned, it would be chain intermittent.
Groove symbol: single-bevel groove, arrow side, 60° included angle, 2 mm root gap, with a backing strip. The tail references WPS-GMAW-02, so the WPS governs preheat, pass sequence and consumables.
Fitter’s reading: continuous welds on both sides is wrong - it doubles deposited metal and heat input and can distort the bracket. A 45° bevel is not the specified 60° included angle. A zero root gap removes root access. Omitting the backing strip removes the specified root support. All three groove deviations change penetration and are drawing/WPS violations, not preferences.
2. For each deviation - continuous fillet, 45° bevel, zero gap, no backing - explain the consequence and classify it as a drawing-interpretation error or a WPS violation.
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- Continuous instead of staggered intermittent fillet: mainly a drawing-interpretation error. Consequence: extra heat input, distortion, residual stress and unnecessary cost. If distortion is within tolerance, a concession may be possible; otherwise the excess weld must be removed and the correct intermittent pattern applied.
- 45° bevel instead of 60° included angle: drawing/WPS error. A narrower groove reduces root volume and access; with GMAW the arc may not reach the root, giving incomplete penetration and different dilution.
- Zero root gap instead of 2 mm: WPS violation. Without gap the root faces touch and the arc cannot penetrate; likely lack of root fusion or incomplete penetration.
- No backing strip: drawing/WPS violation. The backing strip supports the root pool and helps control penetration; omitting it on a single-bevel joint with a 2 mm gap risks burn-through or an irregular root.
The first two are interpretation failures; the last two are direct non-compliance with the WPS. The groove defects are the serious ones because they are internal and not fixed by surface inspection.
3. Write the corrective action and state what you would record before re-welding is accepted.
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Quarantine the bracket and raise an NCR. Do not simply reweld over the joint: the groove must be cut out or gouged back to sound metal, re-prepared at 60° included angle with a 2 mm gap and the backing strip fitted, then re-welded to WPS-GMAW-02. The continuous fillet should be assessed for distortion; if acceptable, a deviation or concession can be requested, but it should not be ground away blindly.
Before re-welding, verify the fitter has the current drawing revision and has been briefed on symbol reading - particularly staggered versus chain, and arrow-side versus other-side. Record: drawing number and revision, WPS number, fitter and welder ID, NCR number, root cause (misread symbol and “shortcut” bevel), disposition, re-inspection results, and any customer concession. Sign and date the re-inspection record so traceability is complete.