Trouble finding Gas flowmeter
Trouble finding Gas flowmeter
(OP)
We have an application to measure inert gas flow in a 36" duct at just under 300 SCFH. There is flammable trace dust, which also melts at about 210F. So we're concerned about using a 'hotwire-type' sensor because the dust will melt onto the heated RTD causing measurement errors. We contacted Rosemount about their annubars, but got a response saying the flow was too low; they need roughly 450 SCFH. We cannot increase flow nor reduce the duct size. Also, the R.H. is somewhere about 90%. I've heard that heated sensors don't do well with saturated streams.
Any suggestions are appreciated!
Any suggestions are appreciated!





RE: Trouble finding Gas flowmeter
RE: Trouble finding Gas flowmeter
- Thermal Mass meter: Not sure if this is what you meant about 'hotwire-type'. It seems odd that a thermal mass meter would have a temperature that high. But it can be affected by coatings. http://w
- Can you reduce the duct diameter just in the space you need to measure? This will open the possible selection of meters.
- Target meter: Problem is accuracy and rangeability. Unfortunately, I can't find manufacturers now.
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RE: Trouble finding Gas flowmeter
RE: Trouble finding Gas flowmeter
RE: Trouble finding Gas flowmeter
Heres a nice list I found of solutions.
RE: Trouble finding Gas flowmeter
RE: Trouble finding Gas flowmeter
- thermal mass meters (which you already ruled out)
- annubar/pitot tube (which Rosemount already ruled out)
- turbines (which may be ruled out since you are 36" duct)
- clamp-on ultrasonic (need to determine maximum diamters)
Instead of reducing the duct, can you split the 36" duct into 4 10" ducts and then re-join? This way, you may be able to try using the turbines and ultrasonics.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
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RE: Trouble finding Gas flowmeter
I can't think of any reasonable solution. The flow is so low compared to the duct size that it is a challenge.
RE: Trouble finding Gas flowmeter
I'm curious to know how you establlished the current flow rate of 300 SFCH.
Dan
RE: Trouble finding Gas flowmeter
This opens up many possibilities, including mass flowmeters, if their heated wire/RTD is below 210 deg. F. I have contacted FCI, Rosemount, and Kurz; they are working on it.
Thanks again for your suggestions and (danw2) for questioning the data!
RE: Trouble finding Gas flowmeter
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376: Eng-Tips.com Forum Policies to make the best use of Eng-Tips Forums?
RE: Trouble finding Gas flowmeter
RE: Trouble finding Gas flowmeter