Motor Horsepower/Kw for a Pump

[Patankar09]

The pump name plate is showing pump input 18.5 kw. What kw motor to be connected??? What if I connect it with 18.5 Kw motor.
The pump is for water service with details as - Q=100 m3/Hr and H=50 Mtr RPM 2940

 

[MFJewell]

If the working fluid is water at 20 C, I get 13.625 kW.

P(kW)=9.81*H(M)*V(m3/sec)*SG(1.0)

 

[LittleInch]

But only at 100 efficiency!

The 18.5 kW represents an efficiency of>70%.

It also doesn't seem to include end of curve operation so an 18.5 kW motor is either right on the limit or could trip if you operate beyond 100 m3/hr

I would go for 25 kW motor myself.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[JJPellin]

As a general rule, I prefer to size the motor to able to run the pump to the end of the published curve with the highest specific gravity that is expected during normal operation. In some cases, this is impractical and we opt to size the motor to cover the highest anticipated normal flow rate at the highest anticipated specific gravity. I size the motor to meet these target conditions without running into the service factor.

Johnny Pellin

 

[Artisi]

Without having seen the curve and other data, you need to assume the 18.5 kW shown is sufficient for the unit.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[LittleInch]

still sounds uncertain to me, but agree - you need the pump curve to be sure and also whether there is any chance for the pump to flow more than what sounds like its stated duty point.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[MFJewell]

But only at 100 efficiency!

Correct, and that was my point. If the calculated theoretical value for pumping power is 13.625 kW, then after accounting for efficiency losses, 18.5 is probably OK.