Flow of Fluid in Piping

Motor Power = voltage x current.

Pump Power = flowrate x pressure, where

flowrate = volume / time

Pump Power = efficiency x Motor Power

flowrate = Pump Power/pressure = efficiency x Motor Power / pressure

These might help.

Pipe Friction Loss Calculations

Pipe flow and friction pressure drop, head energy loss | Darcy formula

Provide more information and you can get more helpful feedback.

The difference in pressure across the pump indicates its operating point on the pump characteristic curve. The flow is indicated on the characteristic curve for that pressure difference.

Dear Sir,

You mean, if I have pump discharge pressure and return line pressure - by seeing the characteristic curve, difference in the flow is the quantity of fluid flowing through the pipe. Right

Is there any other method by looking power drawn by motor and see the corrosponding flow in power - flow curve. How accurate is the result. If, the curve is for water I think no problem. How to get, if the fluid is different than water. If by some example, I will understand fast

Regards for the support.

All centrifugal pump curves are derived using water. The QH curve (Quantity - Differential Head curve) gives the Head, not the pressure. In other words, the QH curve for a centrifugal pump is valid for any fluid density. (Beware highly viscous and non-Newtonian fluids).

Pressure is given by P = pgH. The power curve on the QH curve will state for what specific gravity fluid it is for. If not specifically stated then it is 1 for water.

Remember, it is the system resistance curve that governs where the pump runs on its curve - at the intersection of the two.

Thanks

Measuring pump differential and using the QH curve is the easiest way, but don't forget you will be measuring pressure, not head, so if the fluid SG is different from 1 (water) need to allow for that.

Measuring current gives a useful cross-check, using the Q vs power curve. You also need voltage, motor efficiency and power factor. Eff and PF probably estimates as the motor is unlikely to be running at rated power.

If you don't have a power curve you can calculate flow from differential pressure and power, using power = Q*ΔP (in the correct units).

Generally you need to account for the motor power factor when converting current to kw or hp displayed on the pump curve. Between 50% and 90% of the motor current goes to power to run the pump, depending on the % load of the motor rating. The manufacturers data for that motor or similar design will have motor amperes at 0%, 25%, 50% and 75% load. From experience, there is significant in calculated flow

Many pump performance curves have a current drawn curve adjacent to the flow/pressure performance curve, making such a palaver unnecessary.

A pressure gauge each side of the pump takes out the need to consider motor current, rendering the pump performance rightly outside the Electrical Engineer's concerns. Generally, a pressure gauge accompanies a pump for exactly that reason.

Not current, ever, power in hp or kw, far different. Too many options dependent on motor design or operating voltage to show motor current (amperes) on a pump curve.

Acknowledged.