Dr. A. Asha Professor/Mech Kamaraj College of Engineering & Technology

1. By
Dr. A. Asha, Prof/Mech
Kamaraj College of Engineering & Technology
CENTRIFUGAL PUMP AND RECIPROCATING PUMP
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2. PUMP
• The hydraulic machines which convert the mechanical energy into
hydraulic energy is called as pump.
• Hydraulic energy is in the form of Pressure energy.
• Mechanical energy is converted into pressure energy by means of
centrifugal force acting on the fluid is called centrifugal pump.
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3. PARTS OF A CENTRIFUGAL PUMP
• Impeller
• Casing
• Suction pipe
• Foot valve
• Strainer
• Delivery Pipe.
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4. CONSTRUCTION OF A CENTRIFUGAL
PUMP
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5. PARTS OF A CENTRIFUGAL PUMP
• IMPELLER :
a. Rotating part of a centrifugal pump.
b. Series of backward curved vanes.
c. Mounted on the shaft which is connected to the shaft of the motor.
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6. PARTS OF A CENTRIFUGAL PUMP
• CASING:
a. Volute casing
b. Surrounds the impeller.
c. Spiral type in which area of flow increases gradually.
d. Decrease in velocity increases the pressure of the water flowing.
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7. PARTS OF A CENTRIFUGAL
PUMP
• SUCTION PIPE :
a. A pipe whose one end is connected to the inlet of
the pump.
b. Other end of the pipe is connected to the sump.
• FOOT VALVE :
a. Non return valve fitted to the lower end of the
suction pipe.
b. Opens in the upward direction only.
• Strainer :
a. To filter any suspended particles.
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8. PRIMING
• It is the operation in which the suction pipe, casing, and a portion of
the delivery pipe is filled with water, from outside source before
starting the pump.
• The air from these parts of the pump is removed.
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9. WORKING OF THE CENTRIFUGAL
PUMP
• Priming
• The electric motor is started to rotate the impeller by keeping the
delivery valve closed.
• The rotation of the impeller causes strong suction or vacuum at the
eye of the casing.
• The delivery valve is opened after the impeller attains the normal
speed.
• The liquid is continuously sucked by the suction pipe and passes
through the eye of the casing.
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10. WORKING OF THE CENTRIFUGAL
PUMP
• The liquid is impelled out by the rotating vanes and it
comes of the outer tips of the vanes into the casing.
• The pressure head and velocity head is increased.
• The liquid enters into the casing.
• The kinetic energy is converted into pressure energy.
• The high pressure energy fluid passes through the
delivery pipe.
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13. WORKING OF CENTRIFUGAL PUMP
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14. CHARACTERESTIC CURVES OF A
CENTRIFUGAL PUMP
• It is defined as those curves which are plotted from the results of a
number of tests on the centrifugal pump.
• These curves are necessary to predict the behavior and performance
of the centrifugal pump when the pump is working at different flow
rate, head and speed.
• The following are the important characteristic curves of a pump
(a) Main characteristic curves
(b) Operating characteristic curves
(c) Constant efficiency (or) Muschel curves
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15. MAIN CHARACTERISTIC CURVES
• In this it consists of variation of manometric head, power , discharge
with respect to speed.
• For plotting Hm Vs N discharge Q is kept constant
• For plotting Q Vs N Hm is kept constant
• For plotting P Vs N Hm & Q is kept constant
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16. OPERATING CHARACTERISTIC CURVE
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• If the speed is kept constant the variation of manometric head, power
and discharge gives the operating characteristic curves of the pump
• The input power curve for pumps shall not pass through the origin
because when there is no discharge the pump required some power
to overcome the mechanical losses

17. CONSTANT EFFICIENCY (OR) MUSCHEL
CURVES
• For obtaining constant efficiency curves the Hm Vs Q and η Vs Q for
different speed are used.
• By combining these curves the constant η curves are drawn
• For plotting fist the horizontal lines representing constant η are drawn
on the η Vs Q curves. The points at which these lines cut the η curves
at various speeds are transferred to the corresponding Hm Vs Q
curves. The points having the same η are joined by smooth curves
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19. NPSH
• It is defined as the absolute pressure head at the inlet to the pump –
the vapour pressure head + the velocity head
• It is also defined as the total head required to make the liquid flow
through the suction pipe to the pump impeller
pa/ρg - pv/ρg + vs
2 /2g
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20. RECIPROCATING PUMP
• If the mechanical energy is converted into hydraulic
energy by sucking fluid into a cylinder in which a
piston is reciprocating, which exerts thrust on the
liquid and increases its hydraulic energy.
• TYPES OF RECIPROCATING PUMP:
a. Single acting reciprocating pump
b. Double acting reciprocating pump.
c. According to the number of cylinders
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21. CONSTRUCTION OF RECIPROCATING
PUMP
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22. WORKING OF THE RECIPROCATING
PUMP
• When the crank moves from A to C the piston moves towards the
right.
• The movement of the piston creates a partial vacuum inside the
cylinder.
• The atmospheric pressure > pressure inside the cylinder.
• The liquid is forced inside the suction pipe and opens the suction
valve and enters the cylinder
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23. WORKING OF THE RECIPROCATING
PUMP
• When the crank moves from C to A the piston moves from right to
left.
• The movement of the piston increases the pressure of the liquid >
atmospheric pressure.
• Suction valve closes and delivery valve opens
• The liquid is forced into the delivery pipe and is raised to the required
height.
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