CENTRIFUGAL PUMP TEST RIG - MANUAL

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CENTRIFUGAL PUMP TEST RIG

INTRODUCTION TO CENTRIFUGAL PUMPS
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 machines is called Centrifugal Pumps.
The centrifugal fan with consists of a blower driven by FHP Motor with a series of curved redial vanes. Air is drowning in near the hub, called the blower eye, and is whirled round at high speed by the vanes on the blower as the blower rotates at high rotational speed. The static pressure of the air increases from the eye of the blower to the tip of the blower in order to provide the centrifugal force on the air. As the air leaves the blower tip it is passed through diffuser passage which converted most of the kinetic energy of the air into an increase in enthalpy and hence the pressure of the air is further increased. The blower may be double sided, having an eye either side of the unit, so that air is drowning in both side. The advantages of this type is that the blower is subjected to approximately equal forces in an axial direction. In practice nearly half the total practice is achieved in blower and the remaining half the diffuser. A pressure ratio of around 4: 1 can be achieved with the centrifugal fan.

The Centrifugal pump acts as a reversed 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 principle of forced vortex 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. The rise in pressure head at any point of the rotating liquid is proportional to the square of tangential velocity of the liquid at that point. Thus at the outlet of the impeller, whose radius is more, the rise in pressure head will be more and the liquid will be discharged at the outlet with a high pressure head. Due to this high pressure head, the liquid can be lifted to a high level.

Main Parts of Centrifugal Pump: -
  • Impeller
  • Casing

Impeller: - The Rotating Part of 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 an electric motor.
Casing: - The Casing of a Centrifugal Pump is similar to the casing of a reaction turbine. It is an airtight Passage surrounding the impeller and is designed in such a way that the kinetic energy of the water discharged at the outlet of the Impeller is converted into pressure Energy before the Water Leaves the casing and enters the delivery pipe. Centrifugal pump is a rotodynamic machine, which develop dynamic pressure of liquid by virtue of rotation for pumping of liquid to a higher height. In centrifugal pump, liquid in the impeller of a pump is made to rotate by external force, so that it is through away from the center of rotation. As constant supply of liquid is made available at the center liquid can be pumped to higher level.
The ‘UNICOOL’ unit consists of a centrifugal pump driven by a Dimmer Control motor. Input to motor is measured on energy meter. A measuring tank is provided to measure the discharge. Suction vacuum and discharge pressure is measure by gauges. A Ball valve on discharge pipe varies the head. Thus, performance of pump can be estimated at various speed and heads.

SPECIFICATIONS: -
Centrifugal pump 25 x 25 mm. size, base mounted,
Motor: - 1 H.P. Dimmer Control motor directly coupled to pump.
Measuring tank ---- x ---- x -----mm. height, fitted with drain valve.
Sump tank 600 x 900 x 600 mm heights.
Ball valve to control the head.
Pressure gauge to measure discharge pressure.
Vacuum gauge to measure suction vacuum.
Energy meter to measure input the motor.

EXPERIMENTAL PROCEDURE: -
  • Fill up sufficient water in the sump tank.
  • Open the priming nipple plug (At the top of pump) and fill up water up to the nipple and then tight the plug.
  • Shut off the discharge valve.
  • Start the pump. As discharge valve is closed, no discharge will be observed, but discharge pressure will be indicated. This is called ‘Shut off head’ of the pump.
  • Slowly open the discharge valve, so that small discharge is observed.
  • Note down discharge head, suction vacuum and time required for 10 ltrs. Of water level rise in measuring tank and 10 revolutions of energy meter disc.
  • Note down the observations at different valve openings.
  • Repeat the procedure for any different speed.

OBSERVATIONS: -
S.
NO.
PUMP SPEED
(RPM) N
DISCHARGE
PRESSURE
(Kg/cm2) Pd
SUCTION VACUUM
(mm of Hg) Ps
TIMES FOR 10 Lt.
Water level rise
(Sec) tw
TIMES FOR 10 rev. of
Energy meter
(Sec)











CALCULATIONS: -
Discharge pressure Pd = __________Kg/cm2
For water, 10 m height corresponds to 1 Kg/ cm2
Discharge head, hd = Px 10 m of water.

Suction Head-
Suction vacuum, Ps = ________mm of Hg
ps = 13.6
Suction head, hs = -------- x ---------
1000x1
Where,
sp gravity of hg = 13.6 and Sp gravity of water = 1

Total Head, ht = hd + hs + hr
Where, h= 3 mtr. Is the head loss due to Friction?

Discharge: -
Let time for 10 Cm. Level rise be tw sec.
.380 x .380 x .010
Then, discharge, Q = ------------------------- m3 / sec
tw

Output power (or water power)
W.Q. ht
WP = --------------- kw
1000
Where,
W = Specific weight of water = 9810 N / m3
Q = Discharge m3 / sec.
ht = Total head, mtrs.

Electrical Input: -
Let time required for 10 rev. of energy meter disc be te sec.
10 3600
Electrical input power, Ip = ------- x -----------
te 1300

Where, Energy Meter constant = 1300 Imp / kw / hr.

Taking motor efficiency as 60% we have input shaft power
SP = Elect. I.P x 0.60

Overall efficiency of the pump: -
WP
ŋo = -------- x 100%
SP

PRECAUTIONS
Priming is must before starting the pump. Pump should never be run empty.
Use clean water in the sump tank.
Operate all the Controls Gently.

                                                                           CALCULATION        
OBSERVATION TABLE: -
Sr
No.
Pump speed
(RPM) N
Discharge
Pressure
(Kg/cm2) Pd
Suction
Vacuum
(mm of Hg) Ps
Times for 10 lit water level rise (Sec) tw
Time for 10 rev of Energy meter (Sec) te
1
2400
0.35
200
5.65
20.9
2
2400
0.47
160
6.37
22.12
3
2400
0.57
130
8.22
23.06
4
2400
0.65
95
12.68
26.72


CALCULATIONS: -
1) Discharge Pressure Pd = 0.47 Kg / cm2
For water, 10 m height corresponds to 1 kg / cm2
Discharge head, hd = 0.47 x 10 = 4.7 m of water

2) Suction Head –
Suction vacuum, Ps = 160 mm of Hg = 160x13.6
Suction head, hs = --------- x --------
1000x1
= 2.18 m of water
Where, sp gravity of hg = 13.6
Sp. Gravity of water = 1

Total Head, ht = hd + hs + hr
Where, hr = 2 mtr. is the head loss due to friction
ht = 4.7 + 2.18 + 3
= 9.88 m of water

Discharge –
Let time 10 lts. Level rise be tw sec.
0.01
Then, Discharge, Q = --------
6.37
= .90 x 10 m3 / sec

Output power (or water power)
W.Q.h­
WP = --------------- kW
1000

Where, W = Specific weight of water = 9810 N / m3
Q = Discharge m3 / sec
Ht = Total head, mtrs
9810 x .90 x 10-3 x 9.88
WP = ------------------------------------
1000
= 0.097 kW

Electrial Input –
Let time required for 10rev. of energy meter disc be te Sec. = 10x 3600
Electrical Input Power, IP = ------------- x ----------- = 22 1300
= 0.362 kW
Where. Energy meter constant = 1300 rev / kw / hr
Taking motor efficiency as 60% we have input shaft power
SP = 0.362 x 0.75
= 0.29 kW
Overall efficiency of the pump
.097
ŋo = -------- x 100% 
     = 0.29   = 22%

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