Fracture assessment of pipeline girth weld at low temperature

The results of long-distance oil and gas pipeline failure analysis are important to the industry in order to maintain the reliability and safety of them. Seam welding in these pipes is done with good accuracy at place of work, while girth welding is carried out in the installation site and usually causes the main failure problem. Therefore, the most vulnerable and crucial part of these pipes is the girth welding. Investigating the fracture behavior of girth weld in high-pressure gas pipeline systems at low temperatures is important because these products are hazardous and may lead to explosion, leading to economic losses and environmental pollution. In the present study, the fracture behavior of girth-welded API 5L X65 natural gas transportation pipes was experimentally investigated at low temperatures. The fracture parameters were obtained using Arcan fixture in which all of the in-plane modes including pure tensile mode to pure shear mode can be created by altering the loading angle from 0 degrees to 90 degrees. Finite element analysis was also conducted by ABAQUS finite element software in order to determine geometrical coefficients which are required in calculating the fracture toughness. Results revealed that by decreasing the temperature and increasing the mode II loading contribution, the fracture toughness values were also decreased.