Interpreting Welding Drawings, Symbols, and Specifications
Domain 2 - Interpretation of welding drawings, symbols, and specifications. The exam checks whether you can take a drawing and a WPS and know exactly what weld to make, where, and to what size, without asking the inspector.
Drawing basics
Read the title block (material, units, revision), the projection symbol (third-angle is common in Philippine industry; first-angle appears on imported drawings), and the dimensions that locate the joint. General notes and the weld map often override a symbol, so read both.
Symbol anatomy (AWS A2.4)
A symbol has an arrow, a reference line, and a tail. The tail carries the process or specification, for example GMAW or per WPS-xx. The weld symbol sits on the reference line: below the line means arrow side, above means other side, and symbols on both sides mean weld both sides. Size goes to the left of the symbol (fillet leg or groove depth); length and pitch go to the right, so 50-150 means a 50 mm weld on a 150 mm pitch. Supplementary symbols include the all-around circle, the field-weld flag, and contour/finish marks.
WPS and qualification
A WPS is a written, qualified procedure; the PQR records the test that qualified it; the welder holds a separate performance qualification. Essential variables for GMAW typically include current type and polarity, amperage and voltage ranges, wire feed speed, travel speed, transfer mode, shielding gas composition and flow, electrode classification (for example ER70S-6), preheat and interpass temperature, and joint design. Working outside these ranges without requalification is a nonconformance.
Worked example: A symbol shows 6 to the left, 50-150 to the right, the fillet symbol below the reference line, an all-around circle, and a tail reading WPS-GMAW-01. Meaning: 6 mm fillet legs on the arrow side, intermittent 50 mm welds on 150 mm centres, continuous around the part, welded to that WPS.
Traps: reading fillet size as throat instead of leg; treating the side you can see as the arrow side; ignoring the tail note; assuming a symbol above the line applies below it.