Pump Calculation

Centrifugal, or positive displacement?

Do you have the pump curve?

What voltage?

its a centrifugal pump & 440 volt operation three phase in india

The current will decrease

Not necessarily; it depends on what kind of pump.

The system of puming is of interesting .From my practice pumping system can be designed easily to suit the requirement.Learn hydraulics and hydraulic machinery thoroughly and practice under a contractor for long

If you have a 50 mtr pump, it won't pump any higher than 50 mtr.

You would in essence be deadheading the pump.

Means water will not reach there & the current will reduce.

Correct.

....though it changes from being a pump to a convector heater.

Increasing the discharge pressure by a factor 70/50 (as here) will reduce the flow to about (50/70)² ≈ 51% of before; i.e., to about 25.5 m³/h; if the pump can even go that high at all. (You would moving quite far to the right on the pump curve, and maybe off of it altogether.)

I won't try to detail this right now, but if the pump volute can accommodate a larger impeller, you might be able to make this work. I think the pump is now using about 13-14 bhp, so the motor probably has some "headroom".) What is the actual FLC/FLA of the motor, which should be on its nameplate?

One item was misstated: for the scenario we are considering, the operating point would move to the left (not right) on the pump curve.

Impossible to say without more information. You need to draw pump/system curve and have a good think, then come back with a better description of the problem.

If design duty head is 50m, there's a good chance of no flow at 70m, as above the closed-valve head. But is the 70 (or 80)m the total head or static? What is the elevation of the reactor i/p relative to the pump?

Is the fluid water?

Cheers..........Codey

Current will incease; Flow will reduce; Yes, water will reach.

From the data given, we cannot be sure about any of those statements.

No. 2 is closest, but not 100%.

No.1 depends on the power/flow curve. Most pumps draw more power at increasing flow, but by no means all.

No. 3 - some pump curves have a hump in the middle. If so the design head 50m might be near the maximum, and closed-valve head lower than 50m. But that's an extreme case, even with a stable characteristic (continously rising) to closed valve, CVH could quite easily be less than 70m.

Correct, not sure:

Creech Pump Index = {GPM x Pump head x Specific Gravity x %Pump Efficiency} / {Watts}

The Creech Pump Index (CPI) is similar to the WATER HORSEPOWER:

Water Horsepower = {(GPM x Pump head)/ 3,956;

hence may work!

What are the rpm and diameter of the impeller? This will govern whether the pump can attain 70m of head at all. So far, the answer is neither yes nor no.

I'm sticking with no, until someone can show that the motor can produce enough power for the additional (significant) increase in head.

Deleted; see post below.

At 440/3, a 20hp motor should draw about 28 FLA. He is now drawing 20A; 20 x (70/50) = 28A; so at least this is ballpark.

And, with a healthy service factor, he may be ok if the impeller is up to it.

From what we know so far (not enough), we're not yet into the service factor of the motor. The impeller diameter and rpm (as mentioned earlier) also remain unknown.

It's probably all academic, anyway.

Quite possibly, but this situation would be a good exercise for covering the relevant concepts. I hope we can get more information about the specific pump involved, but maybe no one has access to the pump curve.

Do you have pump performance curves with you? Please see for yourself, how much maximum head with lower flow rate you can get from the curve? If you do not have the curves with you, contact pump manufacturer before posting your problem here.

"creating 3 kg/cm2 pressure near the i/p of reactor"

The i/p of reactor is at what hight? How much pressure is required there? Is the rated capacity of pump is 50m3/hr & 50 mtr head? Have you checked the curve for maximum head?

Please answer these questions to get correct reply for your questions.

<...can any body tell...>

Yes. The person with the pump characteristic curves can tell. Many of these have a power consumption curve attached, and the current can be calculated from that reading.

If in doubt, call the pump manufacturer, and ask there.