Study of Failure Case in Fillet Weldment of Natural Gas Transmission Facility

摘要

A branched pipe joint has been used to perform the pressure control, condition check, purgation, and distribution of the gas in the natural gas transmission facilities. Installation of branch pipes is generally done by the welding work, and as a welding process, there are the weldolet (the butt welding process) and the sockolet (the fillet welding process). During the maintenance working of in-service natural gas pipeline, there was gas leakage in sockolet weldment. The causes of incident were investigated with various tests. From chemical composition analysis, tensile test, hardness test, macro and micro structure analysis and fractography analysis, we found the wrong pipe material, the weld defect and the non-destructive test limitation of fillet weldment as the reasons of weldment failure and gas leakage.