The Reason For Starting The Centrifugal Oil Pump After Closing The Outlet Valve

Dec 15, 2024

Centrifugal oil pumps are generally driven by electric motors, and before starting the pump, the pump body and suction pipeline are filled with liquid. When the impeller rotates at high speed, it drives the liquid between the blades to rotate together. Due to the centrifugal force, the liquid is thrown from the center of the impeller to the outer edge of the impeller (the flow velocity can increase to 15-25m/s), and the kinetic energy also increases accordingly. When the liquid enters the pump casing, due to the gradual expansion of the flow channel in the volute shaped pump casing, the liquid flow velocity gradually decreases, and a part of the kinetic energy is converted into static pressure energy, so the liquid flows out along the discharge outlet at a higher pressure. At the same time, a certain vacuum is formed at the center of the impeller due to the liquid being thrown out, and the pressure Pa at the liquid level is higher than that at the center of the impeller. Therefore, the liquid in the suction pipeline enters the pump under the pressure difference. The impeller keeps rotating, and the liquid is continuously sucked in and squeezed out. Due to the fact that centrifugal oil pumps can transport liquids mainly by the action of centrifugal force, they are called centrifugal oil pumps. So, what are the reasons for starting a centrifugal oil pump after closing the outlet valve?
Due to the fact that the rotor speed of the electric motor increases from slow to fast during the start-up phase and reaches the rated value, its stator current decreases from high to low and reaches normal current. The starting current of an electric motor can generally reach 4-7 times the rated working current value. In order to ensure safe operation, it is necessary to try to start the motor under light load conditions. After entering normal operation, Botaibang will increase the load to the rated value. When starting the pump, the flow power is determined to be around 1/3, which can avoid the occurrence of maximum current. Therefore, centrifugal oil pumps are started with valves closed. After the standby speed stabilizes, open the valve for as short a time as possible, generally no more than 3-5 minutes, otherwise the friction and heating inside the pump will cause damage to the pump components.