Domestic Water Pump Torque Curves

[JimmyJunior]

Hello:

I am an electrical engineer trying to convince the folks in my group that when replacing a 1940s vintage 50hp pump motor with a modern energy efficient replacement, a lot more has to be done than just supplying the nameplate data. I think that proper engineering practice would dictate obtaining the motor and pump curves (available)and based on the system configuration match a motor with the existing pump.

The folks in my group (non engineers) say that all that is necessary is the name plate data of the original motor and nothing more. They say I am "over-engineering" a simple installation.


What do you folks think?


Jimmy Junior, PE
Senior Electrical Engineer

 

[MikeHalloran]

To be thorough, you'd need to measure the pump's operating point if it's operable, or model the system and predict the OP ... just like some engineer did in the forties. Do you have reason to believe that he got it wrong, or that the system changed?

If the guy who signs your paycheck thinks you're over- engineering, then you are. No one else's opinion is relevant.




Mike Halloran
Pembroke Pines, FL, USA

 

[Artisi]

All you neeed to do is measure the current input on the existing motor at start and at the operating point and if the pump can run out on it's curve beyond the normal operating point you should also check it as well. As an electrical engineer you should be able calculate the power requirement and select an appropriate motor for the pump.

 

[BigInch]

Pump curves are always nice to have around, but always difficult to find when you need them.

I only need motor torque curves for start-up analysis for high static head lifts. Since most electric motors seem to deliver about 150% torque when starting, its seldom a critical concern.

A pump should always be matched with its system curve (and control valves) and IMO its always a good thing to check when renovating an old system, since its common for flowrates to change over the years. Listen to Mike's advice above, but check it anyway. Its a quick job and most of the time...nobody else needs to know.

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