Steam Pipeline Weld Failure Analysis.

Abstract

Failure investigation of 12″(305 mm) high pressure steel welded pipe was carried out in this study using ASTM standards in all mechanical and metallurgical tests. Visual inspections was done immediately after receiving the failed pipe section. The pipe was then cut at approximately the center position of the failed-welded joint showing a circumferential crack at the joint along half of the outer surface periphery of the pipe. Tensile, hardness, chemical and microstructural analyses were performed on samples taken at different orientation of the pipe and the weld. Optical emission spectrometer were used to obtain chemical composition of samples. Microstructure testing of surfaces were prepared using grinding, polishing and etching. SEM was used to study failure at high magnification. Root cause of failure was found to be due to combination of operating conditions, oxidation cyclic stresses, and depletion of chromium in the matrix near grain boundaries, methods to reduce corrosion were discussed.