Problem of lage air-leakage rate in air preheater of boilers for 2×300 MW units in Huaneng Yushe Power Plant has resulted from the following causes:unsmooth jamming of the rotor;severe worn-out of the sealing strips;frequent replacement of said sealing strips;poor reliability of the automatic control system for air-leakage etc.Through analysis

it is believed that the air-leakage is mainly resulted from heat distortion of the rotor.Regarding to this

the air preheaters of said two units have been retrofitted with flexible contact sealings.After retrofitting

the air-leakage rate of air preheater has decreased from above 20% to 3%~5%

having remarkable effectiveness.