Motors for Driving Fire-Protection Pumps

pump hp input= (flow*pressure)/(1714*efficiency)

flow=gpm

pressure=psi

efficiency=pump efficiency % (pump calculated 75%)

(Electric motor efficiency calculated= 90%)

I would size for ~350hp

325hp min

thank you it is good formula I like it.

Further to this if we use a diesel engine ,would it be enough with 350 hp out put.

HP is HP, but when sizing for a diesel motor, you have to take into account the power-band and rpm ranges for the motor. It's easy to get "burned" by selecting an inappropriate motor for the job.

shankar from india

another simple formula:

HP = (gpm(imperial) x head in feet)/ 3300 for 100% efficiency

HP= (4000 x 220)/3300 = 266 hp for 100 percent efficiency

For 70% efficiency it is 266/.7 = 380 HP.

you will have to make another correction if the gpm given by you is american gallons.

1 psi = 2.2 head in feet

i stand to be corrected

bye - shankar

thank u for good reply what about diesel if we use that would its hp 380 enough or some correction is to be made.

I would suggest contacting your pump manufacturer (if you have the pump already), and have them recommend you an engine. Without knowing more of the details it would be hard to give an accurate answer here, as i would be assuming many key elements. Like i said before, its quite easy to select a inappropriate engine for the job.

Trust but verify!

Talk to the pump manufacturer and run the calculation. If there is a difference in the numbers ask questions and find out why. Learn something in the process.

4000 gal = 18.16m3. (Imperial gallon)

18.16m3/min = 0.302m3/sec

100psig = 689655N/m2.

689655N/m2 * 0.302m3/sec ≈ 209kW ≈ 279hp

Divide by, oh, say 80% pump efficiency, er, say 261kW or 350hp or so.

Add a bit for good measure, as one doesn't want the thing failing before the water reservoir dries up, er, say 300kW or 400hp would probably be adequate.

Would diesel-drive with a local fuel tank be a better selection, just in case the local power supply isn't available precisely when it is needed in anger?