Estimation method of thermal fatigue life consumption for boiler water wall tubes of thermal power plants

Fatigue damage is a problem in the stable operation of thermal power plants. Especially in coal-fired thermal power plant boilers, grooving corrosion in water wall tubes caused by thermal fatigue combined with sulfide corrosion may occur. Since this grooving corrosion may cause breakage of a water wall tube, various costly repairs are conducted. Some design guidelines for power plants (e.g.: ASME Boiler Pressure Vessel Code Section III SS-NH) propose a method using FEA for evaluating thermal stresses causing fatigue. However, thermal and mechanical boundary conditions are changeable with time and uncertain, and therefore performing FEA for complex boundary conditions is not straightforward. Hence, we propose a method to easily evaluate thermal stresses and fatigue life consumption by monitoring temperature data of an actual water wall tube, without performing FEA. Furthermore, we analyzed the monitoring temperature data of actually taken from a boiler with the proposed method. We also observed the trend of fatigue damage.