Failure analysis of spiral finned tube on the economizer

This article describes the results of an investigation about the failure of spiral finned tube on a newly designed and retrofitted low pressure economizer in a 300 MW pulverized-coal-fired power plant. In order to find out the failure causes and to suggest preventive measures, phase compositions and macrostructure of the tube metal surface were investigated by X-Ray Diffraction and Scanning Electron Microscope equipped with energy dispersive X-Ray spectroscopy micro-analysis. The results show that the failure was principally owing to comprehensive multiphase erosion, an interaction of the fly ash wearing, flue gas washing and sulfurous acid corrosion. Recommendations are given to minimize such failures.

► Sulfates, nitrates and non-soluble oxide are the main compositions of the deposits.
► The failure is principally owing to comprehensive multiphase erosion.
► Dilute H2SO3, H2SO4 and HNO3 and local uneven flue gas flow should be avoided to aggravating erosion heavily.