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            Pumps are such a device, which transfer liquid from one place to another place by pressure difference.

Types of pump:
1.      Centrifugal pump
2.       Reciprocating pump

Centrifugal pump:
                        The pump which raises water or a liquid from a lower level to a higher level by the action of centrifugal force is known as centrifugal pump. A centrifugal pump is a rotodynamic pump that uses a rotating impeller to increase the pressure of a fluid. Centrifugal pumps are commonly used to move liquids through a piping system. The fluid enters the pump impeller along or near to the rotating axis and is accelerated by the impeller, flowing radially outward into a diffuser or volute chamber, from where it exits into the downstream piping system. Centrifugal pumps are used for large discharge through smaller heads.

                                                    Figure (1): Centrifugal pump  

                                    Figure (2):  Impeller

Working principle:

A centrifugal pump works by converting kinetic energy into potential energy measurable as static fluid pressure at the outlet of the pump. This action is described by Bernoulli's principle. With the mechanical action of an electric motor or similar, the rotation of the pump impeller imparts kinetic energy to the fluid through centrifugal force. The fluid is drawn from the inlet piping into the impeller intake eye and is accelerated outwards through the impeller vanes to the volute and outlet piping.


Circulating Water Pump is briefly known as CWP. In APSCL the CWP are used for water circulation through out the system. One CWP have a capacity of 40,000 tones/hour and weight of 126 tones. Its power consumption is about 6 MW.

Main parts of CWP:
Ø  Pump casing
Ø  Shaft
Ø  Journal and Thrust bearings
Ø  Diffuser
Ø  Impeller
Ø  Electric motor

Application of centrifugal pump in power station:

Ø  Circulating water pump
Ø  Feed water pump
Ø  Condensate pump
Ø  Fire fighting pump
Ø  Demi water pump
Ø  LP and HP heater pump
Ø  Dosing pump etc.

Reciprocating pump:
                        A reciprocating pump is also known as a positive displacement pump, as it discharges a definite quantity of liquid during the displacement of its piston or plunger.

Comparison of Centrifugal and reciprocating pump:

Serial No:
Centrifugal pump
 Reciprocating pump
Suitable for large discharge and smaller heads.
Suitable for less discharge and higher heads.
Required less floor space and simple foundation.
Required more floor space and heavy foundation.
Maintenance cost is less.
Maintenance cost is high.
Can handle dirty water.
Can not handle dirty water.
Can run at high speed.
Can not run at high speed.
Its delivery is continuous.
Its delivery is pulsating.
No air vessel is required.
Air vessel is required.
Need priming.
Does not need priming.
It has less efficiency.
It has more efficiency.


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                                          Figure: Boiler
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