Life Prediction of Boiler Tubes in Corrosive Environments

Abstract

Boiler tubes of coal-fired thermal power plants, subjected to prolonged exposure at elevated temperature & pressure, continue to loose their load bearing capacity due to accumulation of several damages. The corrosion damages at the inner and outer surfaces of the tubes are responsible for reduction in tube wall thickness. The microstructural damages, on the other hand, are responshile for reduction in the high temperature strength of the material. In this paper a case study on "Failure of a Superheater Tube of a 500 MW Boiler" has been presented to identify the major factors responsible for failure. A method was developed to estimate the maximum service temperature,the tube had experienced. from the kinetics of oxide scale growth at the tube surfaces. Considering the influences of both corrosion and microstructural damages the life of boiler tube was predicted over a range of wall thickness, thinning rate, operating temperature and pressure.