Interpretation of Welding Drawings, Symbols, and Specifications
This domain tests reading fabrication and welding documents: drawing views, dimensions, welding symbols, joint details, WPS variables, and specification requirements.
Core rules
- Read the title block, revision, units, scale, notes, bill of materials, and weld map before looking at individual welds. Dimensions govern; do not scale the drawing.
- In AWS-style symbols, the arrow points to the joint. A weld symbol below the reference line is on the arrow side; above the line is on the other side. The tail carries process or specification notes, a circle at the junction means all around, and a flag means field weld.
- A fillet size is the leg length unless the drawing states throat. A groove symbol includes groove type, groove angle, root opening, and size. Intermittent welds show length and pitch.
- The WPS controls essential variables: base-metal specification and grade, thickness range, joint design, filler classification, polarity, current range, shielding gas and flow, preheat, interpass temperature, and postweld heat treatment.
- Specifications may add NDT, dimensional tolerances, cleaning, and documentation requirements that the symbol does not show.
Worked example
A symbol shows a 6 mm fillet, 50 mm long, 100 mm pitch, below the reference line, with a tail reading GTAW and a circle at the junction. The weld is a 6 mm leg fillet on the arrow side, made in 50 mm increments with 100 mm center-to-center pitch, all around the part, welded by GTAW. The 100 mm is pitch, not weld length; the 6 mm is fillet leg size, not throat.
Traps that cost marks
- Reversing arrow-side and other-side symbols.
- Confusing fillet leg with effective throat.
- Ignoring the latest revision or general notes.
- Treating pitch as weld length.
- Assuming a symbol overrides a stricter WPS or specification requirement.