centrifugal pump efficiency

[hhjlep]

I need to estimate an efficiency of a centrifugal pump, but do not have any specifications. This is what I know:

Single stage centrifugal pump

Static head: 100m

Motor power: 200 kW

Water quality: Poor. Water is pumped from the bottom of a gold mine. It is not slurry, but it does contain rock particles.

Given the limited information above, what efficiency can I expect? Rough figure such as 30%, or 50% will be sufficient.

Thanks

 

[trashcanman]

Given: P = 200 watts = 8850.7 ft.lb/min
H = 100 meters = 328 ft. head.
assume water is 62.4 lb/ft^3

ft.lb/min (power)= 8850.7 = ft^3/min (flow) x 62.4 x 328 ft/E (efficiency)

8850.7 = 62.4 x flow x 328/E

E = 62.4 x flow x 328/8850.7 = 2.312 x flow

Sorry. You have 1 equation, 2 unknows. No unique solution.

 

[Artisi]

The efficiency for the pumps, which should be hard metal slurry pumps would be round 50%. Using 200kW flow rate would be somewhere round 100l/s. fairly rought and ready but so is your enquiry.

 

[marcoh]

Is it possible to measure the flow rate and motor amps? These with the static head would allow the efficiency to be calculated.

 

[dabluffrat]

Easiest thing to do is go back to the pump vendor and ask for a sales curve for that pump model and running speed.

If you really want to do some calcs and "play around" (that's what I call it) with some numbers go look at the pump name plate.

You can measure motor amps to give you and idea where you're at on % load relative to motor FLA. In pump applications typically motors are sized so the max BHP (and FLA) coincides with ~120% of rated flow. If you're just under motor FLA then you can assume you're at or near rated flow (name plate flow). Use that flow and head to calculate a Specific Speed (not pump RPM... Google it if you don't understand) for that impeller. Use that specific speed number to search online for a pump OEM's sales curve for a similar pump design and application. Compare the head/flow they give for your impeller diameter (also on the name plate) to your "assumed" head/flow.

 

[rshayesteh]

efficiency=(H x Q x Specific Gravity) / (3960 x BHp)
units:ft, gpm, Hp
You should measure the flow rate, and the BHp at this flow (by measuring the amper)and specific gravity of pumped fluid and then simply use above equation.

Reza

 

[BigInch]

rshayesteh,

In this case I think he would get a divide by zero error.

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