2 replies to this topic

AS i read that that pumps suction lift is to 34.7 ft of water @ atm pressure, (and in actual cases it's not more than 22 ft for positive displacement pump and 15 ft for Centrifugal pump) but how the water in the house hold which is some time more than 200 ft deep.
how we can get water from that depth?
What type of pumps we used thereeither submersible pump or some ejector is used?
How ejectors works?
what is meant by donkey pump?
Vaccumm concept is too much tricky, i pardon that i asked too much questions in one thread sorry for that,
waiting for your kind response

with kind regards

[djack77494]

sadaf,
The amount of suction lift that is theoretically possible can be calculated by:

[(P1-P2) - V.P.] * 2.31 / s.g.

In this equation, all units are Imperial (feet, pounds, etc.). Variables are as follows:

P1 = Source Pressure, psia
P2 = Destination Pressure = pressure at centerline of pump's suction nozzle, psia
V.P. = Vapor Pressure of Fluid, psia
s.g. = Specific Gravity of the fluid at pumping temperature, unitless (referenced to water at 60F)

One obtains a value of about 34 feet starting with a "standard atmosphere" of 14.7 psia and a specific gravity of 1.0. Vapor pressure is neglected - for water at 60F, the actual vapor pressure would be 0.26 psia, so the actual maximum suction head is more like 33.4 feet.

Practically speaking, such a lift could not be achieved. All pumps have an NPSH requirement that must be subtracted from the above. Also subtract frictional and acceleration losses and the lower numbers in your posting seem much more reasonable.

When you hear of water being raised from 200 feet, one of two things is happening. Most likely, there is a well (submersible) pump being used, whose "workings" are located far below ground. Alternately, as in the case of most oil extraction, the reservoir will be under pressure, and the value of P1 will be much more than 14.7. Ejectors have the same requirements; they are often (incorrectly) referred to as vacuum pumps. Look for other threads or vendor site to understand how ejectors work. Sorry I can't help with a definition of "donkey pump".
HTH,
Doug

Respected djack,
Thankyou for your kind reply,
As you mentioned the formula, there is some mis conception in my mind how one can know what is the suction pressure at the center line of the pump, is it measured by some gauge , how one should know this pressure may by my question is little foolish as i am still student, so i have not had enought engineering scence what should be the actual condition is?
if the pressure in reservoir which is placed in the suction lift is greater than atmosphere more than 3, 4 what would happen in this case? Please give me a clear picture, i think my question is little bit foolish, but please if you give me a hint, i will make it possible to cover all the stuff. Thankyou with kind regards.