Centrifugal Pump Test Rig 5x3b46

TECHNICAL MANUAL --------------------------------------------------------------------------------------------------------------------------------

CENTRIFUGAL PUMP TEST RIG Centrifugal pump is a roto dynamic machine which develops 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 thrown 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 ‘DYNAMIC ‘ unit consist of a centrifugal pump driven by a A.C. motor. Input to motor is measured on energymeter. A measuring tank is provided to measure the discharge. Suction vacuum and discharge pressure is measured by gauges. A gate valve on discharge pipe varies the head. Thus, performance of pump can be estimated at various speed and heads. SPECIFICATIONS : 1) Centrifugal pump - 25 x 25 mm. size, base mounted, max. head 10 mtr., max. discharge 100 lpm. at 2700 rpm. 2) Motor :- A.C. 0.75 kw. 3ph. Induction motor. 3) Measuring tank 400 x 400 x 450mm. height, fitted with gauge tube and drain valve. 4) Sump tank - 600 x 900 x 600 mm. height. 5) Gate valve to control the head. 6) Pressure gauge to measure discharge pressure. 7) Vacuum gauge to measure suction vacuum. 8) Energymeter to measure input the motor.

EXPERIMENTAL PROCEDURE : 1) Fill up sufficient water in the sump tank. 2) Open the priming cock ( fitted on the delivery pipe ) and fill up water upto the funnel. Close the cock properly. 3) Shut off the discharge valve. 4) 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. 5) Slowly open the discharge valve, so that small discharge is observed. 6) Note down discharge head, suction vacuum, time required for 10 ltr. water collection in measuring tank and 10 revolutions of energymeter disc. 7) Note down the observations at different valve openings. OBSERVATIONS: Sr. No.

Pump speed rpm

Discharge Pr. (Kg/cm2)

Suction Vacuum mm of Hg

Time for10 lit. water collection, Sec.

Time for 10 rev. of Energymeter Sec

( Note : Pump speed is to be noted from laboratory tachometer which is not supplied along with the equipment ) CALCULATIONS: Kg/cm2

1) Discharge Pressure, Pd =

For water, 10 m height corresponds to 1 kg/cm2 ∴ Discharge head hd = Pd x 10 m of water. 2) Suction Head Suction vacuum, Ps = ∴suction head, hS =

mm of Hg. PS x 1000

______

Where, Sp. gravity of hg = 13.6 Sp. gravity of water = 1

13.6 _____

1

3) Total Head, h t = hd + hS + hf Where, hf = 2 mtr. is the assumed head loss due to friction. 4) Discharge Let time for 10 lits.water collection be tw sec. then,

0.01 Discharge, Q =

________________

m3 / sec.

tw 5) 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. 6) Electrical Input Let time required for 10 rev. of energymeter disc be te - Sec. 5 Electrical input power, I P =

____

te

3600 x

_________

kw.

500

Taking motor efficiency as 75% we have input shaft power ∴ S P = I P x 0.75 7) Over all efficiency of the pump ∴η

o

=

WP X 100 % SP _______

8) Graphs i) Operating characteristics - Plot the graph of discharge vs. total head, overall efficiency, input power and water power, at rated speed.

PRECAUTIONS: 1 ) Priming is must before starting the pump. Pump should never be run empty. 2) Use clean water in the sump tank. 3) Use all the controls and switches carefully. 4) Do not disturb the pressure gauge connections. 5) Drain all the water after the complition of experiments.