Safety assessment of incomplete penetration defects at the root of girth welds in pipelines

Abstract

The connection between two submarine pipelines is usually made by welding. In the process of welding, the incomplete penetration, incomplete fusion, porosity, cracks and other welding defects are hardly preventable. The incomplete penetration defects at the root of pipeline girth welds can greatly reduce the safety of submarine pipelines and increase the risk of pipeline failure. In this paper, the safety assessment of incomplete penetration defects at the root of pipeline girth welds are studied. Firstly, a novel model of incomplete penetration defects at the root of girth weld pipelines is provided. Then, an analytical solution of the novel model is obtained according to stress function method. Next, the residual strength equation of the incomplete penetration defects at the root of pipeline girth welds is derived based on the analytical solution. In the end, the calculated results of the residual strength equation are verified by finite element method (FEM) and experiment. The results indicate that the calculated values are in good agreement with the FEM and experiment. In addition, the results indicate that the safety assessment method of incomplete penetration defects at the root of pipeline girth welds is feasible. It is beneficial for the safety assessment of pipelines with incomplete penetration defects.