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Theory
How will you obtain an expression for the minimum speed for starting of a centrifugal pump?
Explain following terms: Net positive suction head, Priming, Cavitation in pump
With neat sketch explain construction and working of submersible pump.
Discuss the various characteristic curves of a centrifugal pump.
Enlist the various types of impeller used in centrifugal pump and explain any one from it with a neat
sketch.
Give classification of Reciprocating pump. Draw neat sketch of single acting reciprocating pump.
Compare Reciprocating pump with Centrifugal pump. Draw theoretical indicator diagram of
reciprocating pump and explain function of air vessel.
Write short notes on: Hydraulic intensifier and Air lift pump
Testing of pump as per B.I.S.
With neat sketch explain construction and working of Mud pump and deep well pump
Write brief note on: Multi-stage Centrifugal pump.
Prove from the first principles that the work saved in a single–acting reciprocating pump by fitting an air
vessel is 84.8%.
Derive expression for the pressure rise in the impeller of the centrifugal pump by neglecting the frictional
and other losses in the impeller.
What is an air vessel? Explain with a neat sketch the working of air vessels in a reciprocating pump.
Examples
A double acting reciprocating pump is fitted with an air vessel on suction side close to pump. The suction
lift of pump is 4.5m. The length and diameter of suction pipe are 7.5m and 80mm resp. The stroke of
piston and its diameter both are 200 mm each. Coefficient of friction is 0.01. The atmospheric pressure
head is 10.3m and separation pressure head 2.5m of water absolute. Determine:
i. The speed at which separation commences
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology, Rajkot
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Questions
Jun – 11
Sr.
No.
4. Hydraulic Pumps
Dec – 10
Fluid Power Engineering (151903)
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Fluid Power Engineering (151903)
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ii. Maximum permissible speed without air vessel.
The impeller of centrifugal pump is 1m in diameter and rotates at 1500 rpm. The blades are curved
backward and make an angle of 30° to the tangent at the periphery. Calculate the power required if the
velocity of flow at outlet is 20m/s. Determine the head to which water can be lifted when a diffuser
casing reduces the outlet velocity to 60%.
A centrifugal pump running at 900 rpm is working against head of 18m. The outlet diameter of impeller
is 380 mm and outlet width is 40mm. If outlet blade angle is 28° and manometric efficiency is 78 %, find
discharge of the pump.
Find the power required to drive a centrifugal pump which delivers 0.04m3/sec of water to a height of
20m through a 15 cm diameter pipe and 100 m long. The overall efficiency of the pump is 70% and co
efficient
of friction f=0.015 used in Darcy’s equation.
A centrifugal pump has impeller of 25 cm diameter at inlet and 50 cm diameter at outlet and runs at 1600
rpm. The vanes are set back at an angle of 300 to the outer rim if velocity of flow through impeller is
constant at 3m/s and entry to the impeller is radial. Calculate the vane angle at inlet and work done on the
wheel per kg of water.
A centrifugal pump raises the head of water through 4m and delivers 1.5m3/sec. The speed of the
impeller is 180rpm. The impeller diameter at the outlet is 1.3m and area at the periphery is 0.3m 2. The
ratio of the outlet at the inlet diameter is 2m and vane angle at the outlet is 30°. Determine the hydraulic
efficiency, power required and minimum starting speed.
Find the power required to drive a centrifugal pump which delivers 0.04m3/s of water to a height of 20 m
through a 15 cm diameter pipe and 100 m long. The overall efficiency of the pump is 70 % and coefficient of friction f = 0.015 in the formulae hf = 4flv2 / 2gd.
During a test on a centrifugal pump the following readings were obtained
Pressure gauge reading = 1.32bar
Vacuum gauge reading = 300 mm of Hg
Effective height between gauges = 0.45m
Power of electric motor = 22 k W
Discharge of pump = 85 lit/sec
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology, Rajkot
4. Hydraulic Pumps
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Prepared By: Bhavin J. Vegada
Page 4.33
Fluid Power Engineering (151903)
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4. Hydraulic Pumps
Diameter of delivery pipe = 150 mm
Diameter of suction pipe = 200 mm
Determine overall efficiency of pump.
Find the rise in pressure in the impeller of a centrifugal pump through water is flowing at the rate of 15
liters per second.. The internal and the external diameters of the impeller are 0.20m and 0.40m
respectively. The width of the impeller at inlet and outlet are 1.6cm and 0.6cm.The pump is running at
1200rpm. The water enters the impellers radially at inlet and impeller vane angle at outlet is 30°. Neglect
losses through the impeller.
Department of Mechanical Engineering
Darshan Institute of Engineering & Technology, Rajkot
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Prepared By: Bhavin J. Vegada
Page 4.34