Working Principle of Centrifugal Pumps


Centrifugal fire pump is a pump that transports liquid by the centrifugal force generated when the impeller rotates. The impeller is installed in the pump casing and fastened on the pump shaft, which is directly driven by the motor. The liquid enters the pump through the bottom valve and the suction pipe, and is discharged through the liquid discharge port on the pump casing.

Centrifugal fire Pump

What are the main components of a centrifugal pump?

1. Impeller
The function of the impeller is to directly transmit the mechanical energy of the prime mover to the liquid to increase the static pressure energy and kinetic energy of the liquid. There are generally three types of impellers: open type, semi-closed type and closed type. There are two liquid suction methods: single suction and double suction, and 6~12 backward curved blades.
When purchasing a centrifugal pump, impeller selection is critical. The open impeller has no cover plate on both sides of the blade, which is simple to manufacture and easy to clean. It is suitable for conveying materials containing a large amount of suspended solids; the semi-closed impeller has no cover plate on the suction side and a cover plate on the other side. It is suitable for conveying materials that are easy to settle or contain particles; the closed impeller has front and rear cover plates on both sides of the impeller blade, which has high efficiency and is suitable for conveying clean liquid without impurities.
2. Pump casing
The function of the pump casing is to seal the impeller in a certain space, so that the liquid can be sucked in and pressed out by the action of the impeller. The pump casing is mostly made into a volute, so it is also called a volute. As the cross-sectional area of the flow channel gradually expands, the high-speed liquid thrown from around the impeller gradually reduces the flow velocity, so that part of the kinetic energy can be effectively converted into static pressure energy. The pump casing not only collects the liquid thrown off by the impeller, but also serves as an energy conversion device.
3. Shaft seal device
The function of the shaft seal device is to prevent the liquid in the pump casing from leaking out along the shaft or the outside air from leaking into the pump casing. There are two kinds of commonly used shaft sealing devices: packing seal and mechanical seal; the packing generally uses asbestos rope soaked in oil or coated with graphite. the

How does a centrifugal pump work?

Before the centrifugal pump starts, the pump casing is filled with the liquid to be transported → after the start, the impeller is driven by the shaft to rotate at a high speed, and 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 get energy, leave the outer edge of the impeller at high speed and enter the volute pump casing → in the volute, the liquid decelerates due to the gradual expansion of the flow channel, and converts part of the kinetic energy into static pressure energy → finally flows into the discharge pipe at a higher pressure , sent to the place where it is needed.
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