• These hydraulic machines which convert mechanical energy into hydraulic energy are called pumps.
• This hydraulic energy means in the form of pressure energy.
• If some mechanical energy does convert into pressure energy through means of centrifugal force acting on the fluid, each hydraulic machine is called a centrifugal pump.

Main Parts of a Centrifugal Pump

The following are some main parts of a centrifugal pump

1. Impeller
2. Casing
3. Suction pipe by a foot valve also a strainer
4. Delivery pipe.

Group the main parts of the centrifugal pump shown in Fig.

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• Impeller: This rotating part from a centrifugal pump is called an ‘impeller’. This consists of a series of backwards-curved vanes. This impeller is mounted on a shaft that is connected to this shaft by an electric motor.
• Casing: Some casing of a centrifugal pump is similar to the casing of a reaction turbine. This air-tight passage surrounding the impeller is also designed in such a way that the kinetic energy of that water discharged at this outlet of the impeller is converted into pressure energy before the water leaves the casing and enters the delivery pipe.

Each following three types of casings is generally adopted

1. Volute Casing: Fig. shows the volute casing that surrounds the impeller. This is of a spiral type into which the area of flow increases gradually. This increase in the area of flow decreases the velocity of flow. Some decrease in velocity increases the pressure of some water flowing through the casing. This has been observed that in the case of the volute casing, the efficiency of the pump increases slightly since a large amount of energy is lost due to the formation of eddies into this type of casing.
2. Vortex Casing: If any circular chamber is introduced within the casing and the impeller as shown in Fig. (a), the casing is known being Vortex Casing. Completed introducing the circular chamber any loss of energy due to the production of eddies is reduced to a considerable extent. Thus the efficiency of the pump is stronger than the efficiency when only volute casing is provided.
3. Casing by Guide Blades: The casing is shown in Fig. (b) in which some impeller is surrounded with a series of guide blades mounted at a ring which is known as a diffuser. Guide vanes are designed in such a way that the water from the impeller enters some guide vanes without stock. Similarly, the area of the guide vanes increases, therefore reducing the velocity of flow through guide vanes consequently increasing the pressure of water. Special water from the guide vanes then passes within the surrounding casing which is in the utmost of cases concentric with the impeller.

• Suction Pipe with each Foot Valve also a Strainer: Each pipe whose one end is connected to the inlet of the pump also the other end dips into water into a sump is known as a suction pipe. Every foot valve which is a non-return valve or one-way type of valve is fitted at the lower end of the suction pipe. This foot valve opens only in the upward direction. Some strainer is also fitted at some lower end of the suction pipe.

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Fig. Different types of casing