Serious oxidization corrosion phenomenon occurred in high temp. reheater of 670t/h boiler in 200MW unit of Huaneng Huaiyin Power Plant in three years after put into operation. Seriously corrosive tube sections need to be replaced at each routine maintenance after year 1996 (operation in 1993). Defects in thermal calculation method on which boiler design is based were analyzed. Such defects caused the calculated value of gas temp. at furnace outlet and convection Pass being lower. Seriousness of nonuniform h...