The 300MW subcritical feed pump uni

The 300MW subcritical feed pump unit in our plant is typically equipped with 3 sets of motor pump units with capacity of 50%, two for operation and one for standby application. To avoid cavitation of the feed pump, 3 motor pumps are equipped with the forepump. The motor and the corresponding forepump is driven by the same motor, and the forepump connects with the motor directly through the laminated flexible coupler, while the feed pump connects with the motor via hydraulic coupler on the other end of the motor, and the motor pump and the corresponding forepump connects together via laminated flexible coupler. The forepump, the feed pump, the motor as well as the hydraulic coupler are mounted on their own base, which is fixed on the same common concrete foundation. Bearing lubrication of the motor feed pump, the forepump as well as the motor is supplied by the hydraulic coupler lubricating oil system. Each set of the feed pump unit is provided with the inlet strainer of the forepump, the inlet strainer of the feed pump, outlet check valve of the feed pump as well as the minimum discharge recirculation system. The minimum discharge recirculation system consists of one recirculation control valve, 2 recirculation shutoff valves, the differential pressure switch as well as the recirculation decompressor. The signal of the differential pressure switch is sent from the flow orifice plate on the forepump and the feed pump pipeline or the flow nozzle on the feed pump outlet.Section I Forepump of the Feed Pump I. Characteristic parameters of the forepump of the motor feed pump FAID56A centrifugal pump is the forepump of the motor feed pump manufactured for the subcritical 30MW unit of out plant by Shanghai Power Equipment Manufacture Co., Ltd. This pump enjoys a series of characteristics in structure to make it achieve reliable operation and convenient overhaul. The water pump adopts axial end cover split structure, the rotor can be extracted in axial direction, it is unnecessary to dismantle the inlet and outlet pipelines in overhaul, merely dismantling the end cover on the free side can extract the entire pump rotor and check up the pump, achieving convenient overhaul. 2-ends bearing is adopted in the rotor of the water pump to make the rotor operate in a more stable and reliable way. The axial force of the water pump realizes balance via the double suction impeller, and the residual axial force is born by the bi-directional thrust bearing. The bearing adopts the structure that receives self-lubricating or forced lubricating. The characteristic parameters of this pump under different working conditions are shown in Table 6-1.