Fluctuating flow 2

[Leo165]

Fluctuating flow (e.g discharge of PD pumps) effects the performance of differential pressure flow meters ? Other type of flowmeter better for measuring pulsating flow ?

John165

 

[bimr]

Probably not a good application for a differential pressure flow meter. All differential pressure meters exhibit a square law relationship between head and flow rate which severely limits the usable flow range (typically 4:1).

A Coriolis meter or a positive displacement meter are most likely better selections. The choice of meter will depend on the accuracy required and the fluid properties.

http://info.smithmeter.com/literature/docs/tp0a014.pdf

 

[LittleInch]

In a simple response, Yes and Yes.


Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BigInch]

I'd try an ultrasonic meter for pulsating flows. They also have a greater flow range for when widely variable flow rates are desired.

 

[lilliput1]

Is the high pressure tap of the differential pressure meter located downstream of the check valve at pump discharge?

 

[Leo165]

yes.

John165

 

[zdas04]

With ultrasonic meters in pulsating flow you have to be careful that the time of flight in still fluids is not an integer multiple of pulsation frequency. I didn't check that once and got an error of nearly 15%. I sped the pump up a little bit and the error dropped off--only helpful with a VFD on the pump driver, the time of flight is a function of the meter and the measured fluid and really can't be changed.

I've had good results from turbine meters downstream of duplex and triplex plunger pumps. It seems that the inertia of the rotor tends to average pulse magnitude to some extent. Nothing will make a dP or Coriolis meter give you repeatable or verifiable results downstream of a duplex or triplex plunger pump (although Coriolis meters seem to work well downstream of a quintiplex pump).

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[bimr]

What is the desired accuracy and the fluid properties?

 

[lilliput1]

The Coriolis flow meter is applicable to pulsating flow.

 

[europipe]

And put a pulsation damper in the discharge.

 

[georgeverghese]

If you arent too fussed about accuracy, pump speed would give you a reasonable indication of flow with a recip pump, if pumping viscosity is constant, and you know what the volumetric eff is at that viscosity.

 

[zdas04]

Pulsation dampers work to mitigate the macro effects you get from a plunger pump (e.g., the pipe shaking itself apart), but can't make much difference on the micro effects that mess up gas measurement.

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist

 

[europipe]

Leo,Is this about gas?
pd pumps are mostly small liquid pumps

 

[Leo165]

Europipe ! Yes , it is Liquid pump.
Bimr ! Am not sure , But I think it should be 1 % Full scale.

John165

 

[bimr]

You can use a positive displacement meter. Because these pd meters measure a volume precisely it does not matter if the flow is pulsing. They will follow the increase and decrease of flow found in reciprocating pumps of all types.

 

[zdas04]

bimr,
That works as long as the "chamber" is full every time. I've gotten errors from both neutating disks and turbine meters from flow that was pulsing enough to spin them faster than they could fill. Generally a problem with a discharge to atmosphere through a variable nozzle that was opened too much.

[bold]David Simpson, PE[/bold]
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. Galileo Galilei, Italian Physicist