Is it necessary to close the outlet valve when the centrifugal pump starts operating?

When the centrifugal pump is started, there is no water in the pipeline at the outlet of the pump, so there is no pipeline resistance or lifting height resistance. After the start of the centrifugal pump, the centrifugal pump head is very low, the flow is large, then the pump motor (shaft power) output is large (according to the pump performance curve), it is easy to overload, which will make the pump motor and line damaged, So it should close the outlet valve when start operating the pump, to make the pump work normally.

First. Two points must be guaranteed before starting the centrifugal pump:

1. Fill the pump shell with water for the purpose of forming a vacuum;

2. It is necessary to close the valve on the outlet pipe, so that the water pump does not have a running flow, which can reduce the motor starting current and facilitate the smooth start of the water pump. With the smooth start of the water pump, the gate valve should be opened slowly and timely.

The Suction of water of centrifugal pump is by centrifugal force impeller line into the vacuum, therefore, when the centrifugal pump starts, it must close the valve at the outlet first, and filling water. When the water level exceeds the impeller, the gas in the centrifugal pump can be discharged, and the pump can be started. After starting, the impeller surrounding line into a vacuum, water upward suction, it can be opened by itself, and suction the water out. Therefore, it is necessary to close the outlet valve first.

Second. About the centrifugal pump

Centrifugal pump is a vane pump, depending on the rotating impeller in the process of rotation, because of the interaction between the blade and the liquid, the blade will transfer mechanical kinetic energy to the liquid, so that the pressure of the liquid can be strengthened, to achieve the purpose of conveying liquid. Centrifugal pump working has the following characteristics:

1. Usually it has no self-priming ability, it needs to fill the pump with liquid or vacuum the pipe line before it begins to work.

2. The centrifugal pump is started when the outlet pipeline valve is closed, and the vortex pump and axial flow pump are started when the valve is fully open, so as to reduce the starting power.

3. Centrifugal pump has a rated value at a certain speed produced by the head. Working point flow and shaft power depend on the condition of the device system connected to the pump (position difference, pressure difference and line loss). The head is converted with the flow.

4. Smooth operation, continuous delivery, no pulsation of flow and pressure.

Before starting the pump, the pump shell is filled with the liquid to be delivered; After starting, the impeller is driven by the axis of high-speed rotation, the liquid between the blades must also rotate. Under the action of centrifugal force, the liquid is thrown from the center of the impeller to the outer edge and energy is obtained.

In the volute, the liquid slows down due to the gradual expansion of the flow passage, it converts some kinetic energy into static pressure energy, and then flows into the out pipe at a higher pressure to the required place. When liquid from the center of the impeller into the outer edge, a certain vacuum is created in the center of the impeller row, because the tank liquid side pressure is higher than the pump inlet pressure, the liquid will be pressed into the impeller continuously. So as long as the impeller keeps rotating, the liquid will be continuously sucked in and discharged out.

For more technicial knowledge you can contact Kelly:

Kelly - International Trade Pumps Engineer

Anhui Tenglong Pump And Valve Manufacturing Co., Ltd.(TEFLOW)

No. 30 fortune east road, Jingkai district Jing County, Xuancheng City, Anhui Province, China

Web:www.teflowpump.com

Tel:+86-15156345852

WeChat: 15156345852

Whatsapp :+86 15156345852

Skype: live:liuqin1991123456

Mail: [email protected]

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