Abstract:This article takes low-pressure bypass valve frequent internal leakage (Siemens imported products from Germany) of 2×660MW supercritical coal-fired unit of a certain company as an example. It is found that the sealing surface of the valve seat and the valve core is damaged through repeatedly disintegration, the main reason is due to the impurities, foreign bodies such as hard metal jamming, however,the system is complicated to cause the dead side of the boiler dead corner to be difficult to completely clean, which has seriously affected the safe and economic operation of the unit. By means of equipping with filters at the entrance of low pressure bypass valve, surface mechanical attrition, enlarging pressure-relief vent, replacing the valve, reforming valve core, the bypass valve reconstruction schemes of comprehensive contrasted, Finally, it is accepted to reforming valve core with feasibility analysis, the implementation effect is obvious. As a result, it is significantly effective to prevent the damage of valve core and valve seat sealing surface, completely solved the problem in low pressure bypass-valve frequent leakage, ensuring the safety and economy of the unit operation, providing a reference to the thermal power unit solution with similar problems.