Magnetic flow meter?

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Colliewood

Colliewood

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Hi guys need your help. I have a electro magnetic flow meter for brine controlled by a masoneilon 31000 series globe valve.

the meter gives a stable reading when the control valve is opened anywhere from 0-10% but opening the control valve any further causes the flow measurement to fluctuate wildly, sometimes full scale fluctuations.

I have simulated 4-20mA and I get a stable reading with no fluctuation at all.

the flow at the end of the run is a constant steady flow

I’ve done a bench test using water and the flow meter worked perfectly

I’ve installed grounding rings as the pipe is pfa lined through the whole circuit and it didn’t fix it( the pipe section of the flow meter is pp lined with hastelloy electrodes). The flow meter doesn’t fluctuate when there is no flow , it stays on 0kg/hr which is good

I’ve noticed when looking at the measured values while in the parameters that the measured conductivity fluctuates a lot , 5000-20,000 us/cm every couple seconds. I would think the conductivity should stay the same as the liquid is being pumped in a loop and isn’t changing or mixing at all

I’ve had a vortex analog flow meter in series with The electro magnetic flow meter and the vortex meter gives a stable reading whereas the magnetic one fluctuates a lot. What should I do now? Should I purchase new one or the issue can be fixed?

Thoughts???
 
Colliewood said:
Hi guys need your help. I have a electro magnetic flow meter for brine controlled by a masoneilon 31000 series globe valve.

the meter gives a stable reading when the control valve is opened anywhere from 0-10% but opening the control valve any further causes the flow measurement to fluctuate wildly, sometimes full scale fluctuations.

I have simulated 4-20mA and I get a stable reading with no fluctuation at all.

the flow at the end of the run is a constant steady flow

I’ve done a bench test using water and the flow meter worked perfectly

I’ve installed grounding rings as the pipe is pfa lined through the whole circuit and it didn’t fix it( the pipe section of the flow meter is pp lined with hastelloy electrodes). The flow meter doesn’t fluctuate when there is no flow , it stays on 0kg/hr which is good

I’ve noticed when looking at the magnetic flow meter measured values while in the parameters that the measured conductivity fluctuates a lot , 5000-20,000 us/cm every couple seconds. I would think the conductivity should stay the same as the liquid is being pumped in a loop and isn’t changing or mixing at all

I’ve had a vortex analog flow meter in series with The electro magnetic flow meter and the vortex meter gives a stable reading whereas the magnetic one fluctuates a lot. What should I do now? Should I purchase new one or the issue can be fixed?

Thoughts???
Click to expand...
Any assistance will be highly appreciated!
 
Could there be cavitation at the flow meter at full flow?

P.S. Be patient. We don't get paid for being here. It can take 24 hours or more for everyone with an opinion to see and respond to questions.
 
LarryFine said:
Could there be cavitation at the flow meter at full flow?

P.S. Be patient. We don't get paid for being here. It can take 24 hours or more for everyone with an opinion to see and respond to questions.
Click to expand...
Yes,

I understand dude, don't worry.
 
22120-0259 EST

Colliewood:

Your subject title is magnetic flow meter, then you say something about electrodes. What is the theory of operation of this device?

.
 
Colliewood said:
Hi guys need your help. I have a electro magnetic flow meter for brine controlled by a masoneilon 31000 series globe valve.

the meter gives a stable reading when the control valve is opened anywhere from 0-10% but opening the control valve any further causes the flow measurement to fluctuate wildly, sometimes full scale fluctuations.

I have simulated 4-20mA and I get a stable reading with no fluctuation at all.

the flow at the end of the run is a constant steady flow

I’ve done a bench test using water and the flow meter worked perfectly

I’ve installed grounding rings as the pipe is pfa lined through the whole circuit and it didn’t fix it( the pipe section of the flow meter is pp lined with hastelloy electrodes). The flow meter doesn’t fluctuate when there is no flow , it stays on 0kg/hr which is good

I’ve noticed when looking at the measured values while in the parameters that the measured conductivity fluctuates a lot , 5000-20,000 us/cm every couple seconds. I would think the conductivity should stay the same as the liquid is being pumped in a loop and isn’t changing or mixing at all

I’ve had a vortex analog flow meter in series with The electro magnetic flow meter and the vortex meter gives a stable reading whereas the magnetic one fluctuates a lot. What should I do now? Should I purchase new one or the issue can be fixed?

Thoughts???
Click to expand...
Flanges bonded to meter? Are you using gaskets on the lined pipe at the meter? One may be in a bad position and creating cavitation. How about 90°'s? Are the pipes configured correctly as far as lengths on both sides? Is flow direction correct? And does the meter know you're flowing liquid? If set to gas, I've seen readings like you state... check those things and get back to us.
 
If it worked perfectly on bench but not when installed in field, review the installation for compliance with the manufacturer specs.
As mentioned in other post, distance from 90's is important.
Basically everything that 4-20ma said is spot on.
Keep us up on your progress
 
We use Turbine flowmeters and this is what the manufacturer recommends as far as spacing upstream and downstream.
 

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I suspect your piping layout for the mag. I have installed and worked on mags from 1” to 24” and the mfgs have requirements for straight piping upstream and downstream.
Also mags work best with a high velocity flow. What is the FPS flow and what are the mfgs specs?
Do you have a full pipe?
 
Is your flow control valve upstream or downstream of the mag? If upstream what kind of valve is it and how many pipe diameters from the mag?
 
Magmeters tend to be pretty bulletproof as long as you follow the directions.

I would lean towards turbulence or air in the line. Unfortunately there's so many different things it could be without knowing more about your installation it's really really tough to give you good advice.
 
I would guess something with the piping. Bends and cavitation were mentioned. Also consider a joint might be sucking air at higher flow.
 
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