What is the maximum allowable undercutting adjacent to the final bead on the outside of the pipe based on visual inspection?

The standard specifies that the maximum allowable undercutting adjacent to the final bead on the outside of the pipe should not exceed 0.031 inches in depth or 12.5% of the pipe wall thickness, whichever is smaller. This criterion is established to ensure the integrity and strength of the welded joint. Undercutting can compromise the retention of the weld and create stress concentrations, which might lead to premature failure or leaks.

By putting a limit on how deep the undercut can be, the standard maintains a balance between allowing some manufacturing imperfections while ensuring that the structural integrity of the weld is not compromised. Ensuring that the undercut adheres to these dimensions helps uphold safety standards within pipeline welding. Therefore, option B properly outlines the allowed limits for undercutting, aligning with the guidelines provided in API 1104.