Vibration in pipeline disturbs volume meter, how to mitigate?

[MartinLe]

Here's the situation:
I have an installation with two CHPs, both with emergency coolers installed outside the building.
The cooling circuits are equiped with Heat meters each (volume sensor + temp. in flow and return), this is a regulatory requirement
The volume meters are beam type
The meters give implausible high values, including under conditions when there's no flow
A guy from the manufacuteres of the meters checked the installation and claimed that vibrations from the CHP disturb the signal, this checks out insofar as one error - high measured flow value when there's no flow through the pipe - only occurs when the respective CHP is running.

The first attempt at mitigation was to install more solid mounting for the pipes immedately before and after the flow meters. This did not work.

The pipes are insulated from the CHP with rubber compensators, vibrations is still noticable after the compensator.

The contractor suggested to install compensators before and after the flow meters.

Questions:
Under 'no flow' conditions, the emergency cooling circuit is not totally isolated from the motor cooling circuit. Is it possible that vibrations caused by the pump in the motor cooling circuit transmit are the problem? How to find out?

Are there compensators that are far better at not transmitting vibrations than the rubber compensators we use?

At this point think we need other flow meters that don't have a problem with viberations, I still want to understand if we have other options.

 

[LittleInch]

/Bit more data please..

CHP - Combined Heat and Power? or something else?
"The volume meters are beam type" ?? Please explain and if possible type and model no. Do you mean ultrasonic?

I would have thought that the vendor could have added a filter for the particular harmonic coming from the pumps, but if you can't screen this out electronically it sounds like the meter just isn't right for you.

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

 

[MartinLe]

CHP - yes, combined heat and power.

Beam type - terrible translation from Schwingstrahl by me, correct name would be static volume meters or fluidic oscillator
description:

https://www.sontex.ch/en/products/static-heat-meters/

This installation uses the superstatic 440

The frequency in the sensor depends on flow, so filtering one frequency would likely not work.

 

[LittleInch]

Fascinating - never seen one like that before, but in many ways is similar to a vortex meter I suppose.

Both can sensitive to external vibration due to their working principles so if you can't isolate the vibration or higher frequency noise then it doesn't look good.

It might also be that a fluctuating fluid pressure is causing micropulses which the meter is interpreting as the oscillations in a moving fluid.

Can't you isolate the system and then program the meters to be ignored if the valves are shut? Or even in use they gve you the wrong value?

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

 

[MartinLe]

In use, the system gives wrong values when the corresponding CHP is turned on (testing the circuit without a running CHP engine turned up plausible results).

The vendor also suggested cavitation as a possible problem and suggested raising the pressure in the circuit, this is something we need to check - is cavitation actually a likely culprit (Does the problem show up more often when the circuit is hot).

 

[rconner]

What flow rates are you dealing with? What kind of pipe, thickness and spacing of supports?

 

[MartinLe]

Pipe diameter: DN50, OD 60.3mm, thickness 2.9, steel
Flow rates: 0-7m³/h
Supports maybe every 4m, would need to be on site to be sure

 

[rconner]

Are you sure about that flow rate "per hour" (really oozing liquid would seem like miniscule vibration)? Could pumps be out of balance or some other problem? [In any case not sure what problem would be; however, noticed e.g. also at

http://www.guenthersupply.com/pdf/hanger-spacing-weight-chart.pdf

2" Sch 40 (a little thicker than yours) steel pipe has a 10 feet (~3m) maximum support spacing. Who knows, if velocity is really higher it might help a little to put in some more supports?

 

[hydtools]

Find and eliminate the source or cause of vibration.

Ted

 

[LittleInch]

Essentially using a system which relies on vibration as its measuring device in a system which has issues with vibration is just never going to end well.

Even if you cut out the pipe vibration you might not cut out the fluid vibrations.

Cut your losses now and swap it for a different sort of meter, say turbine or mag flow or pd.

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

 

[IRstuff]

I think that a meter ought to have specification detailing its uncertainty, which this one does not:

https://www.sontex.ch/en/download/datasheet-440/?wpdmdl=2771

That's a negative for me right there.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[MartinLe]

@rconnor - flow velocity is up to 0.7m/s, not sure I understand your remark?

By now I'm 90% convinced we'll swap the flow sensors.

 

[rconner]

Thanks, Martin (wasn't used to seeing flow like that, and I'm good with your conclusion -- I guess your first flow expression makes more sense)

 

[MartinLe]

Btw, talking to suppliers about flow meters is amusing:

Supp. 1:
MID for high glycol applications won't work. Sorry, all of our flowmeters are susceptible to vibration.

Supp. 2:
Yeah you could use an MID. What, who told you otherwise? We'll specify that it's a high vibration environment, no problem.

I'm seriously considering a mechanical device, have yet to find some good info on wether magnetite will be a problem.


p.s.
(ultrasonic has a problem at high glycol, c is slower)

Has anyone succesfully dampened vibration in a pipeline? I think a thick rubber sleeve for a short length, mounted on stiff supports, could do the trick (Or vice versa: stiff support embedded in material that absorbs energy. Or run the pipe through a water basin. or ...). Nothing I will gamble anyones money on in this project, but would like to know.