Pumps

  • Classify different types of pumps.

  • Identify the components of a centrifugal pump.

The two main forms are positive displacement type and centrifugal pumps.
In positive displacement type, the volume of liquid delivered is directly related to the displacement of the piston and therefore increases directly with speed and is not appreciably influenced by the pressure.

e.g. reciprocating piston pump and the rotary gear pump
The centrifugal type depends on giving the liquid a high kinetic energy which is then converted as efficiently as possible into pressure energy.

Centrifugal pump converts the mechanical energy into pressure energy by means of centrifugal force acting on fluid, which rises water or liquid from a lower level to higher level. The main components of a centrifugal pump are:

  • Impeller

  • Casing

  • Suction pipe with a foot valve and a strainer

  • Delivery pipe

Solved Examples

Solved Example:

68-1-01

Which of the following pump is generally used to pump highly viscous fluid?

Solution:
A reciprocating pump is preferred for high head requirement, whereas centrifugal pump is preferred for high volume flow rate and continuous operation. But for delivering viscous fluid, a screw pump is preferred as the material flows along screw's spindle.

Correct Answer: C

Solved Example:

68-1-02

In a centrifugal pump, the liquid enters the pump:

Solution:
In any centrifugal pump, liquid enters into the pump from the center, and eventually whirled off by an impeller and collected throguh a volute casing tangentially.

Correct Answer: C

Solved Example:

68-1-03

A centrifugal pump is superior to a reciprocating pump because:

Solution:
A centrifugal pump, due to rotating nature has less vibrations as compared to reciprocating pump. Also, maintenance and installation of centrifugal components is comparatively easier. A reciprocating pump gives pulsating (intermittent) flow because it gives output only in the delivery stroke, which is also a disadvantage.

Correct Answer: D