Problems calculating pump flow

[RJ08]

Hi all,

got a bit of a problem with a pump.

Data:
liquid handled: hydraulic oil
discharge pressure: 70-80 kp/cm2g
suction pressure: 0-0.1 kp/cm2g
efficency: 75%
speed: 3550rpm
rotation: clockwise
seal type: mechanical
weight: 13kg
frequency: 60Hz
voltage: 440V
Viscosity @ 40degC is 32.5
viscosity @ 100degC is 6.4

is there anyways of calculating pump flowrate from this

thank you

 

[RJ08]

sorry forgot this info:

viscoty units are cst and the inlet and outlet pipe diameter are 80mm

thanks

 

[Krasek]

it would be possible but rather very inaccurate to calculate flow based on power (you did not provide this information) and efficiency as electrical energy is transferred into fluid kinetic energy ---> therefore, the density is needed too

 

[RJ08]

thanks for the help but this was the only info given to me.

if the density was known how would the flow be known?

would this be accurate?

 

[rbcoulter]

Why not look at the pump curve?

 

[dcasto]

if you knew the amps on the motor, you could calculate the work. From the work and the efficency, you know the work that went into the pump. You know the head difference in pressure or density *head in feet, so you can calculate flowrate from that.

 

[Artisi]

Flow meter - no guess work involved

 

[RJ08]

how could nobody think of that?

If there was a flow meter available it would be used

 

[Artisi]

Well that may well be the case - but possibly you didn't actually think of asking to borrow or rent one. Flow meters of some kind are usually used to measure flow if you need accuracy - not wild guessing and wishful thinking as you seem to have in mind.

 

[RJ08]

it was just put to me from an engineer, I did not know if it was possible from that data. That was all I asked, so your theory of "wild guessing" seems strange. Just dont come in with daft comments.

 

[rbcoulter]

If you are constrained by the information available then there is no way to determine the flow rate.
This is easy to see in that the data provided could apply to a significant range in size & style of pumps. The weight of the pump and inlet /outlet diameter do not help much at all.
You could assume that it is a 3" centrifugal style pump. You could probably look up a typical pump curve for that on the internet.

 

[maddocks]

Can you confirm the pressure units? is it kg/cm2?

 

[HEC]

As Krasec states if power, from motor amps, was a given then a flow rate could be estimated. Alternately if it is a positive displacement pump and the displacement per revolution were given a flow could also be estimated. From what has been supplied, flow cannot be determined.

Mark Hutton

 

[MJCronin]

RJ08...

Are you aware that temporary, clamp-on ultrasonic flow meters exist that can measure flow accurately ?

They do not work on all liquids, but I would assume that hydraulic oil is a clear liquid that should be acceptable to this kind of meter.

I would at least attempt a flow measurement befor I would be forced to "guesstimate" an answer.

One example of many, many vendors

http://www.rshydro.co.uk/ultrasonic-flowmeter.shtml

Let us know about your final decision

-MJC

 

[dtlb26]

agree with dbcoulter

Get pump data information from nameplate, contact supplier or search online for pump curve.

Check pump pressures in field (dead head condition), see where you are on the curve.

If you believe this is incorrect, troubleshoot (rent a flowmeter, timed 5 gallon bucket test, receiver level drop over time, etc).

 

[smckennz]

Hi RJ08
The answer is "no"
But I can tell you already know that.
Perhaps you might want to elucidate.
Clearly the information you have been given is insufficient for the task.
Cheers
Steve