pump flow rate 1

[waqasmalik]

i want to use a submersible pump for irrigation purpose.My head is 135 ft.TDH can be around 150 or 155 ft.I want a flow rate which could flood the 8 acres of land in 8 hours.From this i will select the horse power of motor.Can any one help me plz

 

[miningman]

No problem at all after you supply the assumed infiltration rate as well as the assumed evaporation rate. Unless the area to be flooded is perfectly flat , some indication of the surface gradients would be usefull as well.

 

[fel3]

Also, how deep do you want to flood the field? Add the flood depth to the depths lost to infiltration and evaporation (per miningman) to get the total depth of water required, then multiply by the area to get the total volume you need to pump. Divide by time for the flow rate.

Here in Central California, we lose around 0.3 to 0.5 inch per day in the summer to evaporation. In the winter when it's foggy, we lose almost nothing. Infiltration losses will depend on your soils. Sandy soils are almost impossible to flood, while tight clays are easy.

For example, let's assume you want to put 2 inches of water on a level field. Let's further assume that the evaporation loss will be 0.3 inch and the infiltration loss will be 1.3 inches. Skipping the intermediate steps, I get 3.63 cfs or 1,629 gpm.

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"Is it the only lesson of history that mankind is unteachable?"
--Winston S. Churchill

 

[LittleInch]

I agree very much with fel3 above. "Flood" is a very loose term and dependant on your soil condition may never happen.

Making some wild assumptons such as "flood" means 10cm of water and infiltration and evapaoration in 8 hours is double the flat volume, you get

8 acres - 32,500m2 = 3,250 m3 * 2 = 6,500 m3
Flow rate of say 800 m3/hr. With a lift of say 50m, shaft power is approx 155 kW with pump eff of 0.7. Elec in will therefore be about 170-180 kW.

This probably needs a field test with a tanker and a much smaller bunded area to see how much soil infiltration you get, but should be a reasonable ball park figure to use.

The "prioductivity of your well may be your first proble as this is quite a large volume in a short ime and you will draw down the aquifer locally.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Artisi]

As usual, insufficient basic information meaning everyone is second guessing what is an easy problem if only given the necessary data.

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.)

 

[clay87]

Assuming you're not a rice farmer and that "flood" means an avg depth of 6" to make sure water gets everywhere...requires 4 acre feet in eight hours, or 2700 GPM. That's 100 HP imparted to the water, requiring about 150HP at shaft, 130 kVA in the line. Evaporation should be negligible compared to putting down 6 inches in 8 hours. If you're soil is moist, then seepage should also be small.

As Artisi suggests, you're gonna get some variety in your response, but maybe you just need a ballpark:
My estimate was for 6", requires 2700 GPM and 150 HP motor
LittleInch wants 10", requires 3500 GPM and 200 HP motor
fel3 wants 2" after seepage, giving 1630 GPM (would need 100 HP motor)

My suggestion would be to change 8 hours to 24 hours (if possible) and reduce pipe, pump, and well costs dramatically.

Important question: Is 150 ft the required head of the pump or the water level in the well?