Hello everyone this is N Murali Mohan, working as a assistant professor in JNTUA college of engineering pulivendula, in this chapter covers the all topics, if any topics missing please inform I will correct and then upload.. thank you all

1. CHAPTER-V
PUMPS
N MURALI MOHAN
JNTUA COLLEGE OF ENGINEERING PULIVENDULA
DEPT OF CIVIL ENGINEERING
PULIVENDULA

2. Introduction
 The hydraulic machines which converts the
Mechanical Energy into Hydraulic Energy are
called Pumps.
 The Hydraulic Energy is in the form of Pressure
Energy.
 If the Mechanical Energy is converted into
Pressure Energy by means of Centrifugal force
acting on the fluid, the hydraulic machine is
called Centrifugal Pumps.

3. Introduction
 The Centrifugal pump acts as a reverse of an
inward radial flow reaction turbine.
 This means that the flow in centrifugal pumps is
in the radial outward directions.
 The Centrifugal pump works on the principal of
forced vertex flow, which means that when a
certain mass of liquid is rotated by an external
torque, the rise in pressure head of the rotating
liquid takes place.

4. WHAT IS CENTRIFUGAL PUMP ?
 Centrifugal pump is a hydraulic machine which
converts the mechanical energy into pressure
energy and a centrifugal force acting on the
fluid in the pump. In general, the hydraulic
machines which convert mechanical energy
into hydraulic energy are called pumps.
 Generally, a centrifugal pump works when a
certain mass of liquid is rotated by an external
torque, the rise in pressure head of the rotating
liquid takes place.

5. WHAT IS CENTRIFUGAL PUMP ?
 The centrifugal
pump acts as a
reverse of an
inward radial flow
reaction turbine. It
is a basic working
principle of the
centrifugal pump.

6. DIFFERENT TYPES OF CENTRIFUGAL
PUMP
 According to the construction, application,
design, and service, there are three types of
centrifugal pump are available.
1. According to the shape of impeller and casing.
2. According to the type of impeller.
3. According to the working head.

7. DIFFERENT TYPES OF CENTRIFUGAL
PUMP
 These three types of centrifugal pumps are also
divided into sub-three categories.
 According to the shape of impeller and casing
a)Volute or spiral casing type pump
b)Vortex ( whirpool ) casing type pump
c)Diffuser type pump

8. DIFFERENT TYPES OF CENTRIFUGAL
PUMP
 According to the type of impeller
a)Closed or shrouded impeller
b)Semi-open impeller
c)Open impeller

9. DIFFERENT TYPES OF CENTRIFUGAL
PUMP
 According to working head
a)Low head centrifugal pump
b)Medium head centrifugal pump
c)High head centrifugal pump

10. Main parts of a Centrifugal Pump
 The following are the main parts of a Centrifugal
Pump:
1. IMPELLER
2. CASING
3. SUCTION PIPE
4. FOOT VALVE
5. STRAINER
6. DELIVERY PIPE

11. IMPELLER
 Types of Impellers:
1. Open Impeller
2. Semi – Open Impeller
3. Closed Impeller
4. Vertex Impeller
5. Cutter Impeller

12. IMPELLER
 The rotating part of a Centrifugal Pump is called
IMPELLER.
 It consists of a series of Backward Curved Vanes.
 The Impeller is mounted on a shaft which is connected to
the shaft of an electric motor.

14. Casing
 As we know casing surrounds the impeller
and guides the water and also raises the
static head. These are designed in such a
way that the kinetic energy of water at
the outlet of impeller is converted into
pressure energy. Mainly three types of
casing are used for centrifugal pumps.

15. Types of Casings
 The following the three types of the casings are
commonly adopted:
1. Volute Casing
2. Vertex Casing
3. Diffuser Casing

16. Volute Casing
 The volute Casing, which surrounds the Impeller.
 It is of spiral type in which area of flow increases
gradually.
 The increase in area of flow decreases the
velocity of flow.
 The decrease in velocity increases the pressure
of the water flowing through the casing

17. Volute Casing

18. Vortex Casing
 Vortex casing is a circular chamber placed in
between the casing of the pump and the
Impeller. Formation of eddies is reduced for
the circular chamber and the loss of energy is
reduced to a considerable amount. Efficiency
of a pump in vortex casing is much higher
than the efficiency of a volute casing.

19. Vortex Casing

20. Casing with Guide Blades
 This type of casing, the impeller is surrounded by
a series of guide blades mounted on a ring
which is known as diffuser. The guide vanes are
designed in such a way that the water from the
Impeller enters the guide vanes without stock.
Increase the area of guide vanes reducing the
velocity of flow through guide vanes and also
increasing the pressure of water. Now the water
from the guide vanes passes through the
surrounding casing which is connected with the
Impeller.

21. Casing with Guide Blades

22. Diffuser
 A diffuser is a set of
stationary vanes that
surround the impeller. The
purpose of the diffuser is
to increase the efficiency
centrifugal pump by
allowing a more gradual
expansion and less
turbulent area for the
liquid to reduce in
velocity.

23. Suction pipe with a foot valve and
a strainer:-
 Suction pipe of centrifugal pump's one end is
connected to the inlet of the pump and other
end dips into water in a sump. Foot valve is a
one-way type valve that is fitted at the lower
end of the suction pipe. It is open only the
upward direction. Strainer is also fitted at the
lower end of the suction pipe.

25. Delivery Pipe
 It is a pipe whose one end is connected to the
outlet of the pump and another end delivers the
water at a required height is known as a delivery
pipe.

26. Priming
 It is the process of filling Suction pipe, Casing
and Delivery Pipe upto delivery valve with water.
 Used to remove the air from these parts.
 It is of two types:
1. Positive priming: The one which speeds up
processing.
2. Negative Priming: The one which the slows
down the processing.

27. Priming

28. How do they work?
 Liquid forced into
Impeller.
 Vanes pass kinetic energy
to liquid: liquid rotates
and leave the impeller.
 Volute Casing converts
Kinetic energy into
Pressure Energy.

29.  It consists of an Impeller
rotating with in a Casing.
 Liquid directed into the
centre of the rotating
impeller is picked up by
the impeller’s vanes and
accelerated to a higher
velocity by the rotation
of the impeller and
discharged by
centrifugal force into the
Casing.

37. Work Done by the Centrifugal
Pump

44. Multi stage Centrifugal Pump
 If a centrifugal pump consists of a two or more impellers,
the pump is called a multistage centrifugal pump.
 The impellers may be mounted on the same shaft or on
different shafts.
 A multistage pump is having the following two important
functions.
1. To produce a high head
2. To discharge a large quantity of liquid.

45. Multistage centrifugal pumps for
high Heads
 In order to secure high head, a number of impellerswill be
assembled in series or impellers willbe fixed on same shaft as
displayed here in followingfigure.

46.  The waterfrom suction pipe will enterin to the first impellerat its inlet
and will be discharged at the outletof this impellerwithincreased
pressure.

47.  Water with increased pressure, discharged from
first impeller outlet, will be taken to the inlet of
second impeller i.e. water with increased
pressure coming out from outlet of first impeller
will enter in to the second impeller inlet with the
help of a connecting pipe as displayed here in
following figure.

48.  Pressure of water coming out from outlet of second
impeller will be more as compared to the pressure of
water coming out from the outlet of first impeller.
 Therefore, we can conclude that pressure at the outlet
could be increased further if more impellers mounted on
same shaft.
 There is one equation, as mentioned below, which will
provide us the total head developed by a multistage
centrifugal pump.
 Total head developed by a multistage centrifugal pump
= n x Hm
 n = Number of identical impellers mounted on same
shaft
 Hm = Head developed by each impeller

49. Multistage centrifugal pumps for
high discharge
 In order to secure the high discharge, pumps will
be connected with each other in parallel as
displayed here in following figure.
 Each pump of such multistage centrifugal pump
will take water from a common sump and will
deliver the water to a common pipe. Delivery
pipe of each pump will be connected with this
common pipe as displayed here in figure.

51.  Each pump will work here against same head.
 So, we have seen here the basic concept of multistage
centrifugal pump and their function in pumping system.
We have also seen here the arrangement of impellers in
multistage centrifugal pump depending on demand of
high head or high discharge.

66. Cavitation
 Cavitation in pumps is the rapid creation and
subsequent collapse of air bubbles in a fluid.
 When the Net Positive Suction Head Available
(NPSHa) is lower than the Net Positive Suction
Head Required (NPSHr), cavitation will begin to
occur.
 In many cases, the force of cavitation is strong
enough to pit metal components of the pump,
like the impeller, and damage pump seals.

67. Cavitation damage of Impeller

68. POOR PUMP INLET CONDITION
 Disruptions to flow may have several causes, from system
design to component degradation. Common causes of
flow disruption that result in cavitation:
 Excessively long inlet piping
 Higher than expected fluid viscosity
 Clogged inlet
 Clogged filters and strainers
 Restricted or collapsed inlet hoses
 Poorly specified pump

69. DISCHARGE CAVITATION
 At extremely high discharge pressure, some fluid
circulates inside the pump instead of discharging. Fluid
trapped between impeller and housing at very high
velocity cause a drop in pressure, creating the same
conditions as for suction cavitation.

70. HOW TO RECOGNIZE PUMP CAVITATION
 Cavitation sounds like marbles or gravel circulating
through the pump, pipes, or hoses. The effects of
prolonged cavitation are visible on the pump impeller
and other components.
 Typical indications of cavitation:
 Noise
 Vibration
 Seal/bearing failure
 Impeller erosion
 Higher than usual power consumption

71. HOW TO PREVENT PUMP
CAVITATION
 Start by identifying the cause of the pressure
drop. In many cases moving the pump closer to
the fluid source and removing as many bends
and valves as possible corrects the problem
because each component causes additional
pressure drop. When suction lift is too high to
maintain pressure, move the pump closer to the
fluid source or move the fluid source closer to
the pump.

72.  Enlarging suction lines can also be
effective. In some obvious cases, a
blockage occurs in piping or hoses near
the pump. Clear those blockages to
resolve the issue. Clean suction lines by
clearing debris. Avoid blowing the debris
back toward the fluid source because it’s
likely to create a blockage again.

73. 1. PUMP SELECTION
 The best way to prevent cavitation is to select the right
pump for the application. Cavitation increases as pump
head falls or as capacity increases, so selecting the
correct pump to maintain a positive margin of NPSHa
above NPSHr is the best first move.
 NPHS at the inlet depends on atmospheric pressure,
friction losses in the suction piping, and flow velocity. A
good rule of thumb is for pressure at the pump inlet to be
10% greater than the pump’s specified NPSHr. For
example, if NPSHr is 10 feet, NPSHa should be at least 11
feet.

74.  When purchasing new pumps, consider the pump
design and always question whether it meets the Net
Positive Suction Head (NPSH) requirements.

75. HOW TO INCREASE SUCTION HEAD
AVAILABLE
 Raise and maintain tank liquid level
 Elevate supply tank
 Reduce piping losses from too many fittings or too small
diameter
 Replace collapsed or compromised components
 Clear solids from inside of pipes
 Clear suction strainer
 Replace corroded pipe
 Check for a gasket protruding into piping

76. 2. ADDRESSING DISCHARGE
CAVITATION
 Discharge cavitation occurs when
pressure at the discharge end of the
pump is too high. High discharge pressure
limits the volume of fluid flowing out of the
pump, causing high-velocity fluid to
recirculate between pump impeller and
housing, causing cavitation.

77. COMMON CAUSES OF DISCHARGE
CAVITATION
Clogged filters
Pipe blockages
Poor piping design

78. PREVENTING DISCHARGE
CAVITATION
Keep reducers as close to the pump
as possible.
Install control valve, if needed, on the
discharge side—never on the suction
side.
Avoid pockets where air or vapors
can accumulate.

88. Thank you