When the motor directly connected feed pump starts, the pump speed rises from zero to rated speed in a short time, and there is no means to control the speed. Especially in the early stage of boiler ignition, the feed water flow is small, and the pump runs under unfavorable conditions of high head and small flow.
Therefore, after the oil pump reaches the rated speed, the recircular valve must be opened immediately, so that the oil pump flow is not less than 30% of the rated flow, and at the same time, pay close attention to the water pressure of the balance chamber. Under normal circumstances, the water pressure of the balance chamber should be equal to or slightly higher than the inlet oil pressure, if the water pressure of the balance plate exceeds the inlet oil pressure more, the balance plate is leaking seriously, and the pump should be stopped for inspection. Feed oil pump driven directly by motor, generally with the main oil pump, and pump rotor coaxial operation. The auxiliary oil pump should be started before the pump starts, and the auxiliary oil pump can be stopped only when the main oil pump runs normally. When stopping the pump, the auxiliary oil pump should be started first, and the pump can be stopped only after the auxiliary oil pump runs normally. When consumed as a backup pump, the auxiliary pump should always run with it.
