Investigation of overheating of the final super-heater in a 660 MW power plant

Overheating of the final super-heater in a 660 MW power plant after service for 4700 h was investigated. The scanning electron microscopy (SEM) equipped with an energy dispersive spectrometer (EDS) was employed to observe the surface morphology and cross-section of the tube’s steam side and analyze the ingredient of oxide scales. Results show that exfoliation of iron oxides was detected at the steam side of the tube, resulting in the over-heating of the final super-heater. Compressive stresses in the oxide scale generated during the unexpected shutdown of the power plant, which was responsible for the exfoliation of iron oxides. Finally, the growth and exfoliation mechanism of the oxide scale were put forward to conduct the related prevention and control measures.