Analysis on Cracks Extension in Welding Zone in Stainless Steel Pipe Used at High Pressure Decomposer Equipment

ASTM A276 is stainless steel pipe that used at High Pressure Decomposer (HPD) equipment in fertilizer industry. This pipe has 3 mm of thicknessand operated in pressure about 1.7 MPa with temperature 1300C. It has leaking on welding area of Heat affected zone (HAZ) and causes the factory cannot operate. The purpose of this research is to analyze the causes of failure in pipes that have leaked in the weld area. From the study results, the stress intensity factor (KI) value is about 1244 MPa.m1/2, whereas for the fracture toughness (KIC) of the pipe material value is about 499.9 MPa.m1/2. It can be inferred that due to the KI value is higher than the KIC value then crack propagation occurred on the welding zone so that through pipe wall.This was also influenced by the presence of the residual stress and the corrosive fluid flowing in the pipe and then produced Stress Corrosion Cracking.