AWS Certified Welding Inspector — FundamentalsWelding SymbolsMedium
A welding drawing specifies a backing bar for a groove weld. Which supplementary symbol would be used to indicate that the backing bar should be removed after welding?
- AMelt-through symbol
- BRemovable backing symbol
- CSpacer symbol
- DConsumable insert symbol
Show answer & explanationAnswer & explanation
Correct answer: B. Removable backing symbol
The removable backing symbol is a rectangle placed below the reference line (for arrow side) or above (for other side) with a square or 'R' inside, specifically indicating that the backing should be removed after welding.
Why the other options are wrong
- A. The melt-through symbol indicates complete joint penetration from one side, not backing removal.
- C. The spacer symbol indicates a non-consumable element used to maintain root opening, not a backing that needs removal.
- D. The consumable insert symbol indicates a pre-placed filler metal that becomes part of the weld, not a removable backing.
Removable Backing Symbol
A supplementary welding symbol that specifies the use of a backing material during welding, with the explicit instruction that this backing material must be removed after the welding operation is complete.
- Represented by a rectangle with a specific notation (e.g., 'R' or a square).
- Placed on the reference line, typically opposite to the weld symbol.
- Crucial for applications where backing material would interfere with service or future operations.
Memory trick: Backing is a block, removable has 'R', spacer is a gap-maker.