Centifugal Pump Flowrate 2

[CARF]

Dear all,

We measured the power take up of an old cenrifugal pump.
It has 50 kW motor which is taking 35 kW electrical power.

Is there any generic method I could apply to get a very rough idea (+/- 30%) what flowrate this pump is producing?

The feed piping is 400 mm, 2 meters long , 1 meter elevation.

The upstream piping is 300 mm, 84 meters long, 6 meter elevation.

Many thanks for helping,
CARF

 

[katmar]

The deep vacuum makes a huge difference. My calcs show that you are still close to your 500 m[sup]3[/sup]/h. Putting a pressure gauge on the pump discharge would give some useful information and a cross-check. My estimate is that the pressure at the pump discharge would be about 85 kPa, making my overall pressure difference very close to Quark's.

Katmar Software
Engineering & Risk Analysis Software

http://katmarsoftware.com

 

[waross]

Further to freefallingbody's post.
I worked with a very knowledgeable enginner who would use the "Shut-in" method and measure the watts at no flow. He would measure the watts at full flow and take the difference as an indication of work done.
You need a wattmeter.
Re; Power factor. the power factor on the nameplate of a motor is the power factor at 100% load and rated voltage only. At any other loading or applied voltage the power factor will be different.
respectfully

 

[CARF]

Thanks, good idea,

We MEASURED current at full load (water pumping):

Current was 62 Ampere.

So the power take up was SRT(3) * 380 * 62 * 0.85 = 34.7 kW
So say 35 kW.

Indeed we could do the same at zero load (no water, pump and motor running)only meachanical load. Will the pump survive a small run without water? Mechanical seals.

Thanks all, I will let you know the results of the tank trial real soon.

CARF

 

[waross]

THE SHUT IN TEST IS DONE WITH THE PUMP FULL OF FLUID.
With the pump pumping and the meter in place, close the discharge valve for just long enough to read the meter and then open the valve again.
You should try to aquire a wattmeter for the test. The power factor will be enough different at part load to seriously affect your results.
If you have access to power factor capacitors, try connecting different values until you get minimum current. At that point the power factor wil;l be close to 100% and When the power factor is corrected to 100% it will stay at 100% through out the load range from light loads to heavy loads. The ammeter will then give quite an accurate reflection of the watts. (After you have added capacitors for minimum current use 100% for the power factor in your equation.)
respectfully

 

[CARF]

THE SHUT IN TEST IS DONE WITH THE PUMP FULL OF FLUID.

We will do a Waros said and let you know the results.
We will install a pressure gauge at the discharge of the pump. So we will measure pump power take up and pressure at several valve settings.

Best regards and thanks for helping,
CARF