Leakage occurred many times at the tail heated tubes in heat recovery steam generator(HRSG)of a power plant.Thus

much analysis were performed

such as crack morphology observation

corrosion product analysis

corrosive element measurement and tube wall temperature field FEM calculation.The results show that

the cracks have the stress corrosion cracking(SCC) characteristics and the corrosion type is intergranular fracture SCC.During a certain period of unit startup and shutdown for peaking operation

the low temperature of feed water or flue gas causes the tube outer wall temperature decreases to lower than the flue gas dew point

so the flue gas dews and the SCC solution emerges on outer wall of the tube.The CO2solution is considered as the dominant component resulting in SCC.