Abstract: In order to analyze the failure mechanism of the leakage of the the first economizer tube, the metallurgical structure,mechanical properties, fracture morphology and Energy Dispersion Spectrum(EDS) composition analysis of the tube were examined. The results show that the erosion of the economizer tube wall by high speed fly ash is the main cause of the frequent leakage of the first economizer tube.

Key words: economizer tube, leakage, erosion