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co2 flow control

I have just completed my first co2 injection setup and thought I might
share my experience and ask a few questions.

Finding a tank and regulator was easy. I just went to a Praxair retailer
and bought it.  Connecting the regulator to the needle valve was a more
difficult task.  I found no solid hardware connection but was able to find
a 1/4 inch hose to 1/8 NPT fitting and a 1/8 NPT to 1/8 inch hose fitting
at Parker Hose and Fitting.  Having found these fittings I was able to
return to Praxair and connected the regulator to the needle valve via a 5
foot, 1/4 inch air line.  For the needle valve I first tried the ARO FO1
from Grainger and found this flow control valve would not provide less than
3 bubbles per second with a Dupla bubble counter.  I then replaced this
with an ARO NO1 and then achieved a slow enough flow.  However it is
difficult to adjust this valve because it is at the very bottom of its

Is the often recommended Nupro valve also at the very bottom of its
adjustable range? The Nupro representative I talked to thought an S series
valve might be more appropriate for this application.  Another valve and
regulator sales person sent me in the direction of a metering valve instead
of a needle valve and suggested the following manufacturers Hoke, Parker
and Nupro.  When I called representatives for these manufactures I needed
to specify my aperture size and flow volume to find an appropriate valve.
I have inquired with ARO regarding the aperture and flow specifications for
their valves but they were only able to provide maximum flow ratings of .25

Can anyone estimate the usual flow volumes needed for co2 injected tanks?
my  guess is between 100 ml and 3000 ml an hour.

I recall a post detailing calculations for duration of 10 lb co2 tanks but
couldn't find the post in the archive. Is that poster reading?

Jeff Kropp
Oakland CA