Pumps

UNIT – IV

Chapter - 16

PUMPS

PUMPS

Man has been trying to find out some convenient ways of lifting water to higher levels for water supply and irrigation purposes from wells, ponds, etc. The idea of lifting water, by centrifugal force, was first given by the Italian engineer Vinci in the end of the 16th century.

Pump: Pump is a hydraulic machine, driven by a motor. The pump converts the mechanical energy developed by reciprocating or rotating motion of the pump into hydraulic energy. The hydraulic energy is in the form of pressure energy. This pressure energy is converted into potential energy, as the liquid is lifted from a lower level to higher level.

Uses of Pumps

 In a power plant, pump could be treated as the heart. If it fails, complete power plant cannot function, thereby resulting in huge loss in power generation. For this reason, pump industry attaches more emphasis on high reliability than on efficiency. Pumps are used for the following purposes:

•   Used to feed the water into the boiler (called Feed Water Pump) in power plants.

• Used to circulate water in the condenser (called Condensate Pump) for condensing steam in power plants.

• Used to remove the condensed steam from the condenser (called Condensate Extraction Pump).

• Used to transfer the oil fuel from the reservoir to its proper place in I.C. Engines.

• Used to force the lubricating oil into the moving or rotating parts of I.C. Engines.

• Used for irrigation purposes and in chemical industries, petroleum industries, etc.

1. TYPES OF PUMPS

 Pumps may be broadly classified into the following two types:

 1. Positive Displacement Pump: It is a pump in which the liquid is sucked and then pushed due to the thrust exerted on it, by a moving member. This results in lifting the liquid to the required height. Example: Reciprocating Pump

 2. Rotodynamic Pump: It has a rotating element, called Impeller. As the liquid passes through the impeller, its angular momentum changes. This results in an increase in the pressure energy of the liquid. Note that a rotodynamic pump does not push or displace the liquid as in the case of a positive displacement pump. Example: Centrifugal Pump