Leakage Reason Analysis of a High Temperature Super-Heater in a Circulating Fluidized Bed Boiler

A high temperature super-heater of 15CrMoG steel used in a circulating fluidized bed boiler of a power plant leaked during the hydrostatic test after 22 000 h of service. Macro examination, chemical composition analysis, hardness measurement, metallographic examination, scanning electron microscopy and energy dispersive spectroscopy were conducted for analyzing the leakage causes of the super-heater. And corresponding improvement measures were proposed. The results show that the cooperation of electrochemical corrosion in the pipes of the high-temperature super-heater and flue gas corrosion outside the pipes caused a serious reduction in wall thickness, which eventually led to the leakage of pipes.