Components of a Centrifugal Pump
Centrifugal pumps can be broadly categorized into two main groups: the first group is the wet end, which includes parts that determine the hydraulic performance of the pump, such as the impeller and volute. The second group is the mechanical end, which encompasses the internal components like the pump shaft and casing. The primary components of centrifugal pumps are as follows:
Impeller
The impeller is the rotating part of the pump that features a series of blades or vanes that spin to move the fluid through the pump. Its main function is to increase the kinetic energy of the flow, and it is mounted on a shaft that connects to an electric motor. There are several types of impellers, including:
- Open Impeller
This type has blades that are unsupported and open on both sides, making it suitable for pumping fluids that contain solids. Open impellers are generally low-cost and are commonly used in small diameter pumps, albeit with lower efficiency.
- Semi-Open Impeller
This design features blades that are open on one side and closed on the other, allowing its use in medium diameter pumps handling fluids with small amounts of suspended solids.
- Closed Impeller
In this configuration, the blades are enclosed between two discs. Closed impellers are used for pumping clean fluids free of particulates and are typically more expensive, often utilized in large diameter pumps.
Volute
The volute is the casing or shell that encloses the internal components of the pump. Its purpose is to prevent fluid leakage and maintain pressure. The volute is designed to transform the kinetic energy from the impeller’s discharge into pressure energy before the fluid exits into the discharge pipe. Generally, there are three types of volutes used in centrifugal pumps:
- Spiral Volute
This type gradually increases the flow area, resulting in reduced velocity and increased fluid pressure as it passes through the volute.
- Vortex Volute
This design features a circular gap between the impeller and volute to minimize energy loss and is considered more efficient than the spiral volute.
- Volute with Guide Vanes
This type incorporates guide vanes mounted on a ring known as a diffuser, designed to allow the fluid exiting the impeller to enter the guide vanes smoothly, minimizing turbulence. An increase in the area of the guide vanes leads to a reduction in fluid speed and an increase in pressure.
Pump Shaft
The pump shaft serves as the primary component for transmitting mechanical energy. It is responsible for transferring the motion and torque generated by the motor to the impeller.
Suctions Pipe with Foot Valve and Strainer
The suction pipe connects one end to the pump inlet while the other end is submerged in the liquid reservoir. It includes a foot valve that permits fluid flow in one direction, along with a strainer at its bottom end to filter out unwanted particles and prevent pump clogging.
Discharge Pipe
The discharge pipe connects the first end to the pump outlet, while the second end is designed to reach the desired elevation for liquid transfer.
What is a Centrifugal Pump?
A centrifugal pump is a hydraulic machine that converts mechanical energy into hydraulic energy, relying on centrifugal force to act on the fluid, which flows radially outward. It is commonly used to elevate liquids from a lower level to a higher level and is one of the most widely used pump types. The centrifugal pump was invented by French engineer Denis Papin in the 17th century.