changing motor power 1

[cams1975]

Hi

If i change my pump motor from 18.5 kw to 11kw is there a way to calculte the new flow and pressure the pump will deliver( assuming the impellers etc remain the same)

 

[nickelkid]

The bhp of the pump has not changed. If the bhp is higher than 11kw you will over load the driver.

 

[JRLAKE]

I am lifting a 100 lb block by applying 200 lbs of force. The lift takes 10 seconds. No pulleys are involved.

How long will the lift take if I reduce the force applied to 50 lbs?

 

[whoowho]

If one has a performance curve for the pump, and you know where on that curve the pump normally operates, then one can calculate the BHP to determine if the hydraulic horsepower is less than or equal to the motor horsepower.
In English units: BHP = [head(FT) x flow(GPM) x SG] / [3960 x eff.] Convert the resulting BHP to kw units and if it is less than 11 kw, then there should be no change in the pumps operating point.

 

[cams1975]

many thanks

 

[JRLAKE]

To answer the question, changing the HP of the electric motor driving the pump has no effect whatsoever on the pump's operating point, unless the RPM's also change.

 

[Artisi]

Why do you want to fit an 11Kw motor - do you want the pump to produce less flow or head and thought this is the way to achieve it?

Knowing what you want to achieve will assist with a sensible answer.

 

[BigInch]

Its possible that the smaller motor will run more efficiently, if it is loaded within the optimal range. For example, an 11 kw motor delivering 10 kw (90.9% load) should actually run at a higher efficiency than an 18.5 kw rated motor delivering 10 kw (54% load).

 

[cams1975]

Why do you want to fit an 11Kw motor - do you want the pump to produce less flow or head and thought this is the way to achieve it?

Knowing what you want to achieve will assist with a sensible answer


The original motor has gone down and cant get replacement for a few weeks but i have 11kw motor in store that i could use for the time being

 

[Artisi]

It will depend on the kW needed to drive the pump at the duty - do you know how many amps the 18.5 kW used when operating? Knowing this, there is a chance that we can make an estimate if you can use the 11kW - also can the flow be reduced - if you can afford to reduce flow by throttling the discharge via a valve this will further reduce the amount of power input which might allow the use of the 11kW motor.

 

[BigInch]

Motor fritzed. Now that's a pretty damn good reason for temporary replacement ... if I ever heard one.

 

[JRLAKE]

Hopefully the bigger 18.5 kW motor didn't fritz because it was undersized...