Flowmeter scales

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Date

02-12-2008

Posted by steamer on February 28, 2008, 11:39 am

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>Ed:
>The proper name for the ball type flowmeters is variable area flow
>meters or Rotameters. Some vendors are:
>Brooks Instruments
>Cole Parmer
>King
>Vogtlin (should be an umlaut on the o but my keyboard and I don't know how)

--Very useful; thanks a bunch! :-)

--
"Steamboat Ed" Haas : Don't forget to spay and
Hacking the Trailing Edge! : neuter your politicians...
www.nmpproducts.com
---Decks a-wash in a sea of words---

Posted by tdoodyNS@austin.rr.com on February 28, 2008, 2:09 pm

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> Actually 20 cfh (of C25) is what I nearly always use. Question is what's that
> fudge factor ..
>
> Grant

I think it is the ratio of the gas densities.

I found a listing in a Victor regulator data sheet that lists the
correction factors, using air as 1.00, as follows:

argon 0.85
CO2 0.81
helium 2.69
nitrogen 1.02

So, if you have a flowmeter in one scale you just need to multiply by
the ratio of the ratios (got that?). Example: a flowmeter for CO2 but
is now using argon. If the CO2 scale shows 50 cfh, then the actual
argon flow would be 50x0.85/0.81 = 50x1.05 = 52 cfh

I checked this against my multiple scale flow meter, which gives the
following rough ratios:
Ar to CO2: 1.03
Ar to helium: 0.325
Ar to nitrogen: 0.857

Within my eyeball measurement tolerances, this appears to be pretty
good correlation to the Victor correction factors.

I think this is also reasonably close to the square root of the ratio
of the gas densities (don't aks me why it should be the square root).
The listed gas densities are, as follows:

argon 0.1114 lb/cubic foot
CO2 0.1235
helium 0.0111
nirogen 0.0782

Similar Threads	Posted
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