Pump is a mechanical device used to increase the pressure energy of a fluid. The pumps are used as water – handling device in construction projects. The water is required to handle for human consumption, drainage and dewatering. The liquid handled by the pumps may be water, oil, milk, sludge etc. In construction works the water may be pure or dirty.

1. Prepared by
Prof. Ashish Makwana
Civil Engineering Dept. - MEFGI
1Prof. Ashish Makwana

2. PRESENTATION
OUTLINE…
• Introduction
• Types of pumps
• Functions of various components
• Working of a pump
• Reciprocating pump with air vessels
• Centrifugal pump
• Priming of the pump
• Comparison between reciprocating pump and
centrifugal pump
• Factors affecting selection of pump
2Prof. Ashish Makwana

3. INTRODUCTION
• Pump is a mechanical device used to increase
the pressure energy of a fluid.
• The pumps are used as water – handling device
in construction projects.
• The water is required to handle for human
consumption, drainage and dewatering.
• The liquid handled by the pumps may be water,
oil, milk, sludge etc.
• In construction works the water may be pure or
dirty.
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4. INTRODUCTION (continued..)
• Pumps are extensively used in construction
projects and are required to perform various
operations such as:
– Removing of water from pits, tunnels etc.
– Unwatering cofferdams.
– Lowering the watertable for excavation.
– Supply of water for many types of utility
services.
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5. INTRODUCTION (continued..)
• These pumps are required to perform their
functions under severe conditions and handling
of water which may be muddy, sandy or
corrosive.
• The pump selected should, therefore be able to
handle all these types of works and dependable.
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6. TYPES OF PUMPS
• Positive displacement pumps:
– Reciprocating pumps
– Rotary pumps
• Rotodynamic pumps
– Volute pumps
– Circular pumps
– Diffuser pumps
– Vertical turbine pumps
– Centrifugal pumps
– Mixed flow and propeller type of pumps
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7. Fig. Reciprocating pumpProf. Ashish Makwana 7

8. Functions of various components:
• Piston and cylinder: Piston works inside the
cylinder. The movement of the piston is obtained
by a connecting rod, through the rotation of a
crank.
• Suction pipe: It connects the source of water
(sump) and the cylinder, water enters the
cylinder through suction pipe.
• Delivery pipe: It connects the cylinder and the
overhead tank. Water is discharged from the
cylinder into the delivery pipe.
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9. • Suction valve: Which admits the flow from
suction pipe into the cylinder. It is a one way
valve.
• Delivery valve: Which admits the flow from the
cylinder into the delivery pipe. It is also a one
way valve.
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10. Working of a pump:
• During the suction stroke, piston moves towards
right in the cylinder, thus creating vacuum in the
cylinder.
• This vacuum causes the suction valve to open
and the water enters the cylinder.
• During the delivery stroke, the piston moves
towards left in the cylinder, thus increasing
pressure in the cylinder.
• This causes the suction valve to close and
delivery valve to open, and the water is force
into the delivery pipe.
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11. • It is suitable for less discharge and higher
heads.
• It cannot handle dirty water.
• The supply of water is not continuous i.e. supply
is Pulsating.
• Sometimes it requires air vessels.
• It does not require priming.
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12. Reciprocating pump with air vessels:
• An air vessel is a cast iron closed chamber,
having an opening at its base, through which the
water flows into the vessel or from the vessel.
• The vessel is filled up with compressed air.
• The air vessels are fitted to the suction pipe and
delivery pipe, close to the cylinder of the pump.
• During the first half of the delivery stroke, the
piston moves with acceleration thus forcing
water into the delivery pipe with a velocity more
than the mean velocity.
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13. • The excess flow of water, flows in to the air
vessel thus compressing the air inside the
vessel.
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14. Fig. Reciprocating pump with air vesselProf. Ashish Makwana 14

15. • During the second half of the delivery stroke, the
piston moves with retardation thus forcing the
water into the delivery pipe, with a velocity less
than the mean velocity.
• The water, stored into the air vessel, then starts
flowing into the delivery pipe, thus making up the
deficiency of the flow. Hence, uniform flow of
water is obtained.
• Similarly, on the suction side the water first flows
from the suction pipe into the air vessel during
first half of the suction stroke, and then from air
vessel to the cylinder, during the second half of
the suction stroke.
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16. Centrifugal pump:
• The pump which raises water or liquid from a
lower level to a higher level by the action of
centrifugal force, is known as centrifugal pump.
• The component parts of centrifugal pump are:
– Impeller
– Casing
– Suction pipe
– Delivery pipe
– Foot valve
– Strainer
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17. Fig. Centrifugal pumpProf. Ashish Makwana 17

18. 1. Impeller:
• It is a wheel or a rotter, with number of blades or
vanes fitted on it.
• It is fixed on a shaft.
• The shaft is connected to electric motor.
• The function of the impeller is to provide
centrifugal head and to produce high pressure.
• There are three types of impeller:
– Close impeller
– Semi open impeller
– Open impeller
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19. 1. Impeller: (continued…)
• It is interesting to know that the action of a
centrifugal pump is reversed of the reaction
turbine.
• In a reaction turbine, the water at high pressure
is allowed to enter the casing which gives
mechanical energy at its shaft.
• Whereas in a pump, the mechanical energy is
fed into the shaft and water enters the impeller
(attached to the rotating shaft) which increases
the pressure energy of the out-going water.
• The water enters the impeller radially and leaves
the vanes axially.
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20. 2. Casing:
• The impeller is enclosed in a water tight casing,
having a delivery pipe in one of its sides.
• The casing for a centrifugal pump is so designed
that the kinetic energy of water is converted into
pressure energy before the water leaves the
casing.
• The casing is also called chamber.
• There are three types of casings:
– Volute casing (Spiral casing)
– Vortex casing
– Volute casing with guide blades
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21. Fig. Types of Casings
(a) Volute casing
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22. Fig. Types of Casings
(b) Vortex casing
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23. Fig. Types of Casings
(c) Casing with guide vanes
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24. (a) Volute casing:
• In a volute casing, the impeller is surrounded by
a spiral casing.
• Such a casing provides a gradual increase in the
area of flow which decreases the velocity of
water with a corresponding increase in pressure.
(b) Vortex casing:
• It is an improved type of a volute casing, in
which the spiral casing is combined with a
circular chamber.
• In a vortex casing, the eddies are reduced to a
considerable extent and efficiency is increased.
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25. (c) Volute casing with guide blades:
• In this type of casing, there are guide blades
surrounding the impeller.
• Theses guide blades are arranged at such an
angle, that the water enters without shock and
forms a passage of increasing area, through
which the water passes and reaches the delivery
pipe.
• The ring of the guide blades is called diffuser.
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26. 3. Suction Pipe:
• This is a pipe connecting the pump and the inlet
of the pump.
• A non return valve is provided at the lower end
of this pipe.
• This valve does not allow the water to drain out
of the pipe, when the pump is not running.
• The suction pipe of a centrifugal pump, plays an
important role in the successful and smooth
working o the pump.
• A poorly designed suction pipe causes
insufficient net positive suction head, vibration,
water hammer, noise and excessive wear etc.
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27. 4. Delivery Pipe:
• This is a pipe connecting the pump outlet to the
delivery tank. A delivery valve is provided near
the outlet of the pump, in order to regulate the
flow in to the delivery pipe.
5. Delivery Pipe:
• Delivery valve is provided with strainer near the
outlet of the pump to regulate the flow into the
delivery pipe.
6. Foot valve and strainer:
• A foot valve with strainer is connected at the
bottom of the suction pipe to avoid the entry of
foreign matter.
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28. Priming of the pump
• If impeller is running in air, it will produce a
negligible pressure which may not suck water,
from its source through the suction pipe. Hence,
in order to operate the pump, it is necessary that
the pump should be filled with water.
• This process of filling the suction pipe and
impeller with water before starting the pump is
called Priming.
• Generally, priming is done by pouring water into
the impeller through a funnel provided on the top
of the casing.
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29. • As the water fills the impeller, the air present in it
will escape through the air vent valve.
• After all the air in the impeller and the casing is
removed, the air vent valve is closed and the
pump can be run.
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30. Comparison between reciprocating
pump and centrifugal pump
Reciprocating Pump
• It is suitable for less
discharge and higher
heads.
• It cannot handle dirty
water.
• The supply of water is
not continuous. i.e.
supply is pulsating.
Centrifugal Pump
• It is suitable for large
discharge and small
heads.
• It can handle dirty
water.
• Supply of water is
continuous.
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31. Reciprocating Pump
• Sometimes, it
requires air vessels.
• It does not need
priming.
• Complicated in
construction, because
of more number of
parts.
• More space required.
• Total weight of the
pump is more.
Centrifugal Pump
• No air vessels are
required.
• Needs priming.
• Simple in construction
because of less
number of parts.
• Less space required.
• Weight is less.
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32. Factors affecting selection of pump
• Required discharge
• Required head or lift
• Type of liquid to be lifted
• Specific speed of pump
• Length of suction pipe and its diameter
• Length of delivery pipe and its diameter
• Cost of pump, maintenance cost
• Efficiency of pump
• Life of the pump
• Use of pump, whether continuous or intermittent
• Requirement of foundation
• Requirement of power to run the pump
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