Back or backing weld symbol
Also called Backing run, Sealing run, Back weld
A back weld is a pass made on the far side of a groove weld, after the groove is welded. A backing weld is the same pass made first. The symbol is the same; the welding sequence goes in the tail or a note.
What the back or backing weld symbol means
A back weld is a pass made on the far side of a groove weld, after the groove is welded. A backing weld is the same pass made first. The symbol is the same; the welding sequence goes in the tail or a note.
AWS A2.4 and ISO symbols
Backing run (back weld). An open half circle on the other side of the groove symbol, here on the dashed line.
ISO SVGWhere you see it
Full-penetration butt welds welded from both sides, often after back gouging the root.
What is written next to it
On the welding symbol, the back or backing weld carries the height of the back weld where it is specified.
How it is inspected
Inspection of a back or backing weld usually covers the back gouged root before the back weld is made, then the same tests as the groove weld. Each inspection is recorded against the weld, so the joint can be signed off with its evidence. See the ITR guide.
Related symbols
Frequently asked questions
What does the back or backing weld symbol look like?
On AWS A2.4 drawings: An open half circle on the side opposite the groove symbol. A filled half circle means melt-through instead. In ISO 2553: An open half circle on the other side of the groove symbol, here on the dashed line.
Is the back or backing weld symbol the same in ISO and AWS?
No. An open half circle on the other side of the groove symbol, here on the dashed line.
Where is a back or backing weld used?
Full-penetration butt welds welded from both sides, often after back gouging the root.
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