Acceptance criteria lack of penetration 1

[nkvon]

Why acceptance criteria lack of penetration per Asme B31.3, ( normal category ) is 38 mm, I think it is a critical defect. Who could help me explain this case code, Many thanks

 

[weldstan]

For one, the Code refers to circ welds which experience close to 1/2 the stress applied in hoop due to pressure plus any externally applied loads. Another is the adverse metallurgical effect produced by a localized repair.