Inputs
How it is calculated
- System A of ISO 2553 is used (dual reference line, one continuous and one dashed). A symbol on the continuous line refers to the arrow side, one below the dashed line to the other side; for symmetrical welds the dashed line is omitted.
- Cross-section dimensions (a or z for fillets, s for butt welds) are written to the left of the symbol, the weld length to the right; for intermittent welds the form is n × l (e). The tail carries the process (EN ISO 4063), the quality level (EN ISO 5817), the position and the filler.
- The most used symbols are covered (fillet, V, I, half V, U), with surface contour, weld all around and field weld. Symbols for plug, spot and seam welds are not included.
An informative tool, not a WPS. A welding procedure is specified, qualified and approved according to the standards in force, by competent personnel. The calculations here are engineering estimates made with published formulas; they do not replace the manufacturer data sheet, the material certificate, the qualified procedure or the design check.
Frequently asked questions
What is the “arrow side”?
The side of the joint the arrow points to. If the symbol is on the continuous line, the weld is made on the arrow side; if it is on the dashed line, on the other side. For a fillet, a symbol only on the “other side” does not authorise a weld on the arrow side.
Which is better for fillets: a or z?
“a” is the throat thickness (the distance from the root to the weld face, the one used in strength design), “z” is the leg. For an equal-leg fillet, a = z / √2 (z = 1.41 · a).
Can I use the symbol on an official drawing?
The symbol is a representation following the principles of ISO 2553. On an official drawing, check the standard in force and the customer’s requirements, and the process and quality level must match the qualified procedure.
Sources and method
The formulas, tables and verification examples come from public sources, listed below. The standards themselves are paid documents and are not reproduced: I cite the formulas and values published by these sources and, where sources differ, I say so.
- TWI/Wikipedia: symbols and conventions used in welding documentation (ISO 2553, ISO 4063)
- TWI: Welding consumables, part 3 (EN ISO 2560 and AWS A5.1)