Failure Analysis of Heat Exchanger Tubes

This research aimed to investigate the causes of tube failures in a shell-and-tube heat exchanger at an oil and gas plant. The shell side of this heat exchanger (reboiler) is used to heat cooling water, while the tube side is used to generate process vapor. The tube material was made of SA 213 TP 317LM (UNS 31725), and tube sheet material was SA 240 TP 317LM (UNS 31725). This heat exchanger had failed its 91 tubes against 2998 tubes after just over 1.8 years in service. Eddy current testing was carried out on 100% of tubes during the turnaround and found 91 tubes with wall thickness loss between 10 and 54%. A failure investigation was carried out on the leaked tubes by pulling one tube and examined for visual examination and a chemical composition test (PMI testing) to see if the material used met the standard specification. The preliminary cause of the tube failure is change in the tube material grade, and the actual tube material is SA 213 TP 304L instead of the required SA 213 TP 317LM. Poor quality control from the inspection department has resulted in the tubes failing to meet the required standards specification of the heat exchanger. As a significant corrective or remedial action, heat exchanger tubes must be changed to SA 213 TP 317LM based on the requirement after performing 100% ECT.