What is the maximum permissible size for a single porosity, skip, or void defect in a butt joint with backing?

What is the maximum permissible size for a single porosity, skip, or void defect in a butt joint with backing?

• A. 6 mm (1/4 inch)
• B. 1.5 mm (1/16 inch)
• C. 3 mm (1/8 inch)
• D. 2 mm (1/16 inch)

Answer: (C)

The key idea is how large a single porosity defect can be in a welded joint that uses backing. Porosity are gas pockets inside the weld, and their size tells you how much of the weld cross-section is compromised. In a butt joint with backing, the backing provides support and helps form a more stable root, so the acceptance criteria allow a slightly larger single defect before the weld must be rejected. A single porosity defect can be as large as 3 mm (about 1/8 inch). If a pore exceeds that size, the weld wouldn’t meet the acceptance standards and would typically require repair. Values smaller than that are allowed only if all other conditions are met, such as the total porosity and distribution along the weld length, but the maximum allowed single defect is 3 mm.

The key idea is how large a single porosity defect can be in a welded joint that uses backing. Porosity are gas pockets inside the weld, and their size tells you how much of the weld cross-section is compromised. In a butt joint with backing, the backing provides support and helps form a more stable root, so the acceptance criteria allow a slightly larger single defect before the weld must be rejected.

A single porosity defect can be as large as 3 mm (about 1/8 inch). If a pore exceeds that size, the weld wouldn’t meet the acceptance standards and would typically require repair. Values smaller than that are allowed only if all other conditions are met, such as the total porosity and distribution along the weld length, but the maximum allowed single defect is 3 mm.