Abstract: In #3 boiler and #4 boiler of Sanhe Power Generation Corporation Limited, the speed of the induced draft fans is adjusted by hydraulic coupling. The temperature of working oil of hydraulic coupling was higher, so the furnace negative pressure control can not realize only by using the hydraulic coupling, and the combining adjustment mode of hydraulic coupling and inlet regulating damper must be adopted. In order to reduce the working oil temperature, the working oil pressure and oil flow hadbeen increased, but this caused larger pipe vibration, and the welding seam was cracked and the joint bolt was broken due to large vibration. Based on research of the operation conditions of hydraulic coupling, the bore diameter of orifice plate in oil tube was adjusted, and the support and suspension of working oil pipeline and the route of pipeline were redesigned. Then the temperature of working oil of hydraulic coupling was fallen, and the pipe vibration was weakened.

Key words: induced draft fan, hydraulic coupling, vibration, loop-closed adjustment