Effect of assembly misalignment and weld crack on the maximum pressure of pipeline in-service repair

Abstract The influence of assembly misalignment and welding crack on the maximum pressure in pipeline repair was investigated using numerical simulation methods in this work. The result indicated that the pipeline doesn’t need to be depressurized when welding misalignment is less than or equal to 5mm for the calculated X70 and X80 pipelines. Besides, when the specifications of X80 pipe was 1219×22 mm, the crack depth to pipe diameter was 0.20~0.40, the crack depth to crack length was 0.20~0.80, and the repair pressure level was the highest, with a range of 8.2~11.4 MPa. The maximum repair pressure was distributed with a range of 7.1~9.5 MPa when the thickness of the pipe decreased to 18.4 mm. The pipeline maximum repair pressure increased with the increase in pipe wall thickness. The maximum repair pressure was up to 14 MPa when the pipeline specification was Φ1016-26.2.