Introduction To Centrifugal Pump

Introduction To Centrifugal Pump

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Structure of centrifugal pump
Pump casing
Pump casing includes two types: axial split type and radial split type. Most casings of single stage pumps are volute. Radial split casings of multistage pumps are usually ring casings and round casings.
The inner chamber of volute pump casing is generally spiral fluid passage, which is used to collect the liquid thrown out from impeller, and lead the liquid to the diffusion tube towards the outlet of pump. Pump casing withstands all working pressures and heat loads of liquid.
Impeller
Impeller is the only part to do work. Pump does work on on the liquid by impellers. Impeller can be classified into three types: closed type, open type and semi-open type. The closed impeller is made up of blade, front cover plate and rear cover plate. The semi-open impeller is made up of blade and rear cover plate. The open impeller is only made up of vane. The efficiency of closed impeller is relatively higher, while the efficiency of the open impeller is relatively lower.
Seal ring
The function of seal ring is against inner leakage and external leakage. The seal ring made of wear-resistant materials is mounted on the front and rear cover plate and pump casing. The seal ring can be replaced after wearing down.
Shaft and bearing
One end of pump shaft is used for fixing impeller, the other end is used for installing coupling. Based on pump size, bearing can adopt rolling bearing and plain bearing.
Shaft seal
Shaft seal generally includes mechanical seal and packing seal. The pump is generally designed that can be installed with not only packing seal, but also mechanical seal.

Working principle of centrifugal pump
Centrifugal pump mainly is composed of impeller, shaft, casing, shaft seal and seal ring, etc. Generally speaking, the pump casing needs to be filled with liquids before starting. When pump shaft and impeller rotate, driven by prime motor, liquids move in a circle and at same time are thrown out from impeller centre under the action of centrifugal force. So the liquids obtain pressure energy and velocity energy form impeller. Partial velocity energy is converted into static pressure energy when liquids flow towards liquid outlet via volute. After liquids are thrown out from impeller, impeller centre shall be low-pressure area, which has pressure difference with the pressure of the inhaled liquid surface. Therefore, liquids are continuously inhaled and discharged with a certain pressure.

Performance parameters of centrifugal pump
1. Flow Rate Q of centrifugal pump
Flow rate refers to the volume of liquid discharged from pump outlet per unit time. The unit is m3/h or m3/s.
2. Pump Head H of centrifugal pump
Pump head refers to the energy that obtained from the unit liquid flows through pumps. The pump head can be expressed by H. The unit is m, i.e. liquid column height.
3. Speed n of centrifugal pump
Speed refers to the number of revolution for pump shaft per unit time. The speed can be expressed by n. The unit is r/min.
4. Power of centrifugal pump
a. Effective power P
Effective power refers to the effective energy per unit time obtained by the liquid transported by pump. The effective power also is known as output power.
Pu=pgQH/1000(KW)
where,
Qthe pump flow rate, m /s ;
Hthe pump head, m;
Pmedium density, kg/m ;
Gacceleration of gravity, g=9.81m/s .
b. Shaft power Pa
Shaft power Pa refers to power which is passed to shaft from prime mover per unit time. The shaft power also is known as input power. The unit is W or KW.
5. Power of centrifugal pump
Power refers to the ratio of effective pump power to shaft power. That is,
=Pu/Pa

Spare components of centrifugal pump
The spare components of centrifugal pump include impeller, ring, shaft, shaft sleeve, shaft seal (mechanical seal and packing seal), bearing, oil seal for bearing box (framework seal) and quick-wear components of coupling (elastic block, pin rubber ring and diaphragm, etc.). Bearing, mechanical seal (packing seal), seal ring and shaft also belong to wear-quick components.

About the Author:
China-ogpe.com (http://www.china-ogpe.com) is a professional B2B Website, which focus exclusively on providing you with detailed product and trade information in the field of oil, gas and petrochemical equipment made in China.



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