Safety evaluation of girth weld defect of a river bottom crossing pipeline

Girth weld defect and bending strain are found in the river crossing section of a long-distance oil pipeline through the triaxial MFL and inertial mapping internal detection, so safety evaluation is required. The structural integrity evaluation method in the British standard BS 7910-2005 is used to evaluate the acceptability of girth weld defect under the combined load of internal pressure and the bending stress. Besides, the sensitivity analyses are carried out on the parameters including the bending stress, fracture toughness, defect depth, residual stress, defect length and internal pressure involved in the evaluation, and the influence of each parameter on the evaluation results is discussed. The result shows that under the current conditions, the defect is acceptable and no repair is required temporarily. Based on the results of integrity evaluation and sensitivity analysis, this paper gives reasonable suggestions on the running and monitoring of the pipeline. The evaluation method and its conclusion can be used as a reference to solve the problems of other similar projects.