Welding quality control plays an important practical role in the safe operation of oil and gas pipelines. Especially for high grade pipelines, dimensional control of welding defects is the bottleneck problem in pipeline construction. During the important construction welding process, pore defects are one of the most unavoidable welding problems. To evaluate the applicability of standards specifying pore dimensions, non-linear finite element analysis models of circumferential pipeline weld seams with pore defects were modeled by considering the real structure of the welding seam and the softening of the heat affected zone. Based on the conventional strength theory for pipeline engineering design, three loading conditions of stress analysis are defined. The stress analyses are investigated based on the flow stress failure criterion. The results showed that the effect of the location along the wall thickness of the pipe is not so significant, and compared with X80 grade line pipe, the tolerance of pore defect size in X90 grade line pipe is stricter. A 3 mm pore diameter is acceptable for X80 and X90 circumferential pipeline weld seams.
