Seam Weld Symbol
How to read a seam weld symbol — the circle with a horizontal line through its center. Width, length, pitch, and why the process designation in the tail is mandatory.
Seam Weld Symbol Dimensions
Per AWS A2.4 §12, seam weld symbols follow the same general dimension rules as spot welds, with added length and pitch for intermittent seam welds.
Where Each Dimension Goes
Width (weld size) — to the LEFT of the symbol. This is the width of the seam weld nugget or bead.
Length — to the RIGHT. For continuous seam welds, length is the total weld length. For intermittent, it appears as part of the length-pitch format.
Pitch — to the RIGHT, in length-pitch format (e.g. 2-4 means 2-inch weld segments at 4-inch center-to-center spacing).
Number of seam welds — in parentheses.
Process — REQUIRED in the tail. Per A2.4 §12.1.3, the welding process must be specified: RSEW, GTAW, GMAW, etc.
Three Placement Options
Below reference line — arrow side. The seam weld is on the side the arrow points to.
Above reference line — other side.
Centered on reference line — no side significance. Used for RSEW and EBW where the weld forms between members regardless of which side faces the electrode.
Resistance vs Arc Seam Welding
The same seam weld symbol represents fundamentally different processes. The tail designation determines which one.
| Feature | Resistance Seam (RSEW) | Arc Seam (GTAW/GMAW) |
|---|---|---|
| Equipment | Rotating wheel electrodes | Standard arc welding torch |
| Side significance | None — center on ref line | Yes — arrow/other side |
| Material range | Thin sheet (typically <3mm) | Wider range, thicker material |
| D1.1 scope | Outside D1.1 scope | Arc process rules apply |
| Applications | Automotive, tanks, leak-tight joints | Less common in structural work |