This document provides an overview of pumps, specifically centrifugal pumps. It defines a pump as a hydraulic machine that converts mechanical energy to hydraulic energy in the form of pressure. Centrifugal pumps are described as using centrifugal force to lift liquids from a lower to higher level by developing pressure. Their main components are identified as the impeller, casing, suction pipe, and discharge pipe. Impeller types and casing design are discussed. Priming, cavitation, net positive suction head (NPSH), efficiencies, and losses are also summarized. Reciprocating pumps are introduced and classified as either single or double acting. Positive displacement pumps are contrasted with centrifugal pumps in terms of pressure and volume capabilities.

1. ME 1102
Study of Pumps
MD. ZAHIRUL ISLAM
B.Sc. In Mechanical Engineering ,BUET.
Lecturer ,AUST

2. Pump
The hydraulic machines, which convert the
mechanical energy into hydraulic energy, is
called pump. Hydraulic energy is in the
form of pressure energy.

3. Classification of Pumps

4. Rotadynamic pump (Centrifugal pump )
Centrifugal pumps are the machine which employ
centrifugal force to lift liquids from a lower level to
higher level by developing pressure.
Main Components
1. Impeller .
2. Casing .
3. Suction pipe .
4. Discharge pipe .

6. Different Parts of a Centrifugal Pump
Impeller
The wheel fitted with a series of backward
curved vanes is known as impeller.

7. Different Parts of a Centrifugal Pump
 Types of Impeller:
1. Shrouded or closed impeller ( fig A)
2. Semi open impeller (fig. B)
3. Open impeller (fig. C )

8. Casing
The casing of a centrifugal pump is an air tight chamber covering
the impeller.
Volute type Casing.
The cross-sectional area of the
casing is gradually increased .
Kinetic energy of fluid is
converted into pressure energy .

10. Priming
 Obviously an impeller running
in air would produce only a
small head.
 The first step in the operation
of a centrifugal pump is to fill
the pump with the liquid to be
pumped.
 This process is called the
priming of the pump.
 Priming is done by pouring
liquid into the funnel provided
for this purpose.

11.  Cavitation is defined as the formation of bubbles and vapor
filled cavities in a flowing fluid as a result of reduction in
fluid pressure.
 Vapor cavities are formed when the pressure at any point in
a flow field falls to the vapor pressure of the liquid at that
temperature.
 The negative pressure at any point in a pump should not
exceed the limiting pressure given by
 Hn = Ha – Hv
 Hn  limiting negative pressure head
 Ha  atmospheric pressure
 Hv  vapor pressure head
Cavitation

12. Effects of Cavitation
1. The normal flow pattern is changed as the cavitation occurs.
This disturbs the smooth flow.
2. The hydraulic machines indicate a sudden loss in efficiency
as soon as cavitation occurs.
3. As cavitation occurs, it may cause vibration. It may further
lead to fatigue stresses and excessive wear.
4. Cavitation is usually accompanied by noise.
5. The cavitating parts in the flow phenomenon cause an
increase in the drag force.
6. Some of the boundary material may be eaten away at the
points where cavitation occurs. It is known as pitting.

13. Net Positive Suction Head
 NPSH is defined as the net head in meters of liquid that is
required to make the liquid flow through the suction pipe
from the sump to the impeller.

14. NPSH required
It is a function of the pump design. This is positive head
in meters absolute required at the pump suction to
overcome pump internal head losses. Pump
manufacturer generally provide this information.
NPSHa must always be greater than NPSHr or
damage to the pump will occur due to cavitation.
NPSH available
It is available head at inlet of the pump.

15. • Static Head:
• Static head is the difference of
elevation between the liquid
surface in the sump and that in
the reservoir to which the
liquid is delivered.
• Hs = hs + hd
• hs  suction head
• hd  delivery head

16.  Manometric Head:
 The manometric head is the
head developed in the
pump. It is equal to the
energy given to the liquid
by the impeller minus the
losses in the pump.
 Hm = Energy Given – Losses
in the pump
 Hm = Hs + Losses in the pipe
+ Vd
2/g

17. Efficiencies
Mechanical Efficiency
It is defined as Power developed by the impeller to the
power supplied by the motor.

18. Manometric Efficiency
It is defined as ratio of power developed by the pump to
the power supplied by the impeller.

19. Overall efficiency

20. Various Losses in Pump
20
ShaftPower
ImpellerPower
WaterPower
Static
Power
Mechanical Losses
Hydraulic Losses
Losses in Pipes

21. Reciprocating Pump
Single Acting

22. Types of Reciprocating Pump
Two types
1. Single Acting Reciprocating pump .
2. Double Acting Reciprocating Pump .
Double Acting

24. Positive Displacement Pumps
24
Positive displacement pumps always produce a fixed
amount of liquid to flow per revolution unlike the non
positive displacement or dynamic pump
Works with high pressure comparing the dynamic pump
Small and compact size
Good performance
 But Why we use centrifugal pumps ?
For low pressure and high volume flow generally used for
supplying purpose
 For which reason the Positive Displacement Pumps ?
For high pressure and fixed volume purpose , generally
used for fluid power