The principle and structure of the centrifugal pump

Principle of centrifugal pump

When the centrifugal pump is working, the liquid fills the pump casing and the impeller rotates at high speed. The liquid generates high speed under the action of centrifugal force. The high-speed liquid passes through the gradually expanding pump casing channel, and the dynamic pressure head is converted into static pressure head.

Before the centrifugal pump is started, the liquid gains energy under the action of inertial centrifugal force by relying on the high-speed rotating impeller to increase the pressure. Before the pump is working, the pump body and the water inlet pipe must be filled with pump to prevent cavitation. When the impeller rotates rapidly, the blades cause the medium to rotate quickly. The rotating medium flies out of the impeller under the action of centrifugal force. After the water in the pump is thrown out, a vacuum area is formed in the center of the impeller. On the one hand, the liquid is continuously sucked in, and on the other hand, a certain amount of energy is continuously given to the sucked liquid to discharge the liquid.

(1) According to the liquid suction method

Single-suction pump: the liquid enters from one side of the impeller.

Double-suction pump: the liquid enters from both sides of the impeller.

(2) According to the number of impellers

Single-stage pump: only one impeller is installed on the pump shaft.

Multistage pump: The pump shaft is equipped with two or more impellers in series.

(3) Classification by use

Water pump, corrosion-resistant pump, oil pump, impurity pump.

Structure of centrifugal pump

The main components are pump casing, pump cover, pump body, impeller, sealing ring, pump shaft, machine

seal or stuffing box, coupling, bearing, etc.

(1) Centrifugal pump rotor

The rotor refers to the rotating part of the centrifugal pump, including impeller, pump shaft, sleeve, bearing and other components.

(2) Impeller

The impeller is the working part of the centrifugal pump. It relies on its high-speed rotation to do work on the liquid to achieve liquid transportation. It is an important part of the centrifugal pump.

(3) Pump shaft

The main function of the pump shaft of the centrifugal pump is to transmit power and support the impeller to maintain normal operation in the working position. One end of it is connected to the motor shaft through a coupling, and the other end supports the impeller for rotation. The shaft is equipped with bearings, axial seals and other components.

(4) Bearing

The bearing supports the weight of the rotor and the bearing capacity. Rolling bearings are mostly used in centrifugal pumps. Bearings are generally lubricated with grease and lubricating oil.

(5) Bushing

The function of the bushing is to protect the pump shaft and convert the friction between the packing and the pump shaft into the friction between the packing and the bushing. Therefore, the bushing is a wear-prone part of the centrifugal pump.

(6) Sealing ring

The high-pressure liquid flowing out of the impeller returns to the suction port of the impeller through the gap between the rotating impeller and the fixed pump casing, which is called internal leakage. In order to reduce internal leakage and protect the pump casing, a removable sealing ring is installed on the casing corresponding to the impeller inlet.

(7) Packing seal

The packing seal refers to a device that relies on the contact between the outer cylindrical surface of the packing and the shaft (sleeve) to achieve sealing. It consists of a stuffing box (also known as a stuffing box), packing, a liquid seal ring, a packing gland and stud bolts.

(8) Mechanical seal

The mechanical seal device has the advantages of good sealing performance, compact size, long service life and low power consumption. In recent years, it has been widely used in chemical production.

The structure and working principle of the sealing device, which relies on the end faces of the static ring and the dynamic ring to fit each other and rotate relative to each other, is called a mechanical seal, also known as an end face seal.