Causes of Corrosion and Leakage of High-pressure Heater Tubes in a Thermal Power Plant

The high-pressure heater tubes of a 660MW thermal power plant are made of TP304 austenitic stainless steel. After half year operation, the different degree of leakage of three high-pressure heaters occurred. By testing of chemical composition, mechanical properties and intergranular corrosion of high-pressure heater materials, it is shown that the corrosion cracking was not caused by unqualified material. The results of EDS of tube surface and SEM of cracking surface reveal that corrosion fatigue caused leakage of high-pressure heater tubes, due to the high concentration of Cl- in vapor and vibration of equipment during operation.