Abstract: Aiming at the wearing, tube rupture and overheating phenomena existing in the external heat exchanger(EHE) of 300-MW CFBB units, mechanisms and reasons of the wearing are analyzed. A series of measures against abrasion and overheating, including the optimization of pipe clip structures and maintenance technologies; the monitoring of outlet steam temperature of EHE tubes, as well as the insulation capacity of high-calorific intensity tubes are proposed. The designed structure of EHE for 600-MW CFBBs is also presented in the paper and the wear proof measures for the 300-MW CFBB units are applied to the 600-MW units, which has improved the reliability of the unit with high efficiency.

Key words: CFBB, EHE, wearing mechanism, wear proof technology