Failure analysis of fuel oil return line in gas turbines

In this study the failure analysis of austenitic stainless steel welded joints of fuel oil pipes have been investigated. Microstructure characterizations and fractography were performed on pipes and the crack initiation and fracture mechanism were studied. The results show that the fracture mechanism of pipes was fatigue and due to the early initiation and higher stress concentration in the overlap weld zone the fatigue life has been decreased. In order to increase fatigue life of pipes it is suggested to determine the initial crack created during service by NDT methods. It was recommended to provide additional support brackets in the affected pipe length to prevent the fuel oil return line from vibrating extremely.