Experimental Study of Oil and Gas Pressure Vessel Welding Using The Shielded Metal Arc Welding Process

Abstract

Oil and gas pressure vessels operating at a pressure of 100 psi or higher generally use base materials with a minimum tensile strength of 400 N/mm². The fabrication of these vessels using welding methods must ensure that the weld joint achieves a minimum tensile strength equal to or greater than 400 N/mm² while maintaining good ductility. Experimental study is conducted to evaluate the effectiveness of the Shielded Metal Arc Welding (SMAW) process in meeting these requirements. The investigation aims to determine whether the selected welding parameters could produce weld joints with the necessary tensile strength and ductility. The base metal material specification used is SA 36 with a thickness of 8 mm. The weld joint uses a single V groove type, and the filler metal specification for the SMAW process is A5.1 with an AWS E7018 classification and a wire diameter of 3.2 mm. The welding machine is set with a current range of 90 A - 170 A and a voltage range of 16 volts - 25 volts. A total of six welding specimens were prepared for mechanical testing. Acceptance criteria for the test results are based on ASME Section IX standards. The tensile test results for two weld specimens showed ultimate tensile strengths of 495.98 N/mm² and 497.41 N/mm2. The root and face bend test results showed no open defects exceeding the criteria set by the ASME IX standard. The hardness test results show relatively uniform values. The microscopy examination showed a grain profile predominantly composed of ferrite structures. Based on these results, the SMAW process, when applied with the selected parameters, proves to be a suitable method for welding oil and gas pressure vessels.