What's the Right Motor for This Pump?

Is it a centrifugal pump?

Please detail your calculations. How do you conclude this?

Do you have the pump performance curve?

How about a measure flowrate through the system? Or a discharge pressure on the pump?

it is a centrifugal slurry handling pump. I have done my calculations and the show that a much lesser motor can actually do that job done by a 132kW motor. The static head is about 14m and the pump is discharging to the hydro-cyclone. The feed pressure to the cyclone should be at 56kPa and the flow rate is at 104.47 litres/second(DESIGN HYDRO-CYCLONE VALUES).

a) If the pump needs less than 45KW Motor over its total range of operation there is absolutely no reason why the 132KW motor is put. However confirm this.

b) The 87KW is not thrown away by you but the cost of buying the higher KW motor has beem.

c) The performance of the motor (efficiency) is much better when the 45KW motor is driving a 45KW load rather than a 132KW motor driving a 45KW load and in the condition (35% FLC) i am surprised.

d) In case you are going to need the motor of 132KW - try to run it in permanent Y thatway atleast you can improve on the efficiency (though nowhere nearer to the 45KW motor) - there is a thread already available in CR4 in case you want to ask what it is. You can google it too.

e) The motor pump combination looks to be a bad idea.

f) Check what manufacturer has recommended and why.

One should always be suspicious of odd combinations of pumps and motors, The unit were most probably designed for another purpose or site.

If the delivery on the pump is in any way throttled it will consume more kW than required. The power is proportional to the delivery and the pressure in the pump. The pump also may not work at optimal efficiency either.

It may be better to replace the pump and the motor.

sb's got it right as usual, but there is a terrible mismatch between what is installed and the data that you give. If we assume that the installed motor was correctly sized for the pump then you are running the pump at a very peculiar point on the curve. I assume that in your calculations you have taken account of the system losses, density etc that you do not mention.

A quick check to see if your calculations make sense is to measure the current with a tong tester and calculate the electrical power being consumed and see if this matches the hydraulic power that you have apparently calculated. A pressure gauge on suction and discharge would help to confirm the differential head used in your calcualtion etc...

A pump curve would be most useful.

Check if the torque, speed, power of the pump to match with that of motor. Generally the torque of the motor is ignored especially during start up for pump.. May be the torque is the only reason to put 132 KW otherwise 40 kw shoudl as per your calculations

In this case P.F. of your motor is very low.This means your motor is terribly underloaded.Check the no load current of 132 Kw motor and no load current of 45KW motor.Difference between these two is the power you are throwing out.The actual power drawn by the pump is same for 132 KW and 45KW.

Hi all,

Perhaps if you send to us the necessary data someone ( I am a volunteer), could check teh calculations.

I was involved in a mining project, I have a spreadsheet for pumps calculations/estimation.

Best regards

Ernesto