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Needle valves in CO2 systems
I have heard many on this list claim great value for the use of a needle
valve in a pressurized CO2 system. Attempting to check it out, I was quite
disappointed.
First some numbers:
Flow L/day 1 = 2.315E-05CFM
Input pressure, psi 30
Output pressure 15 15 delP
Specific Gravity 1.5 Re air=1.0, CO2=1.5
Temperature, F 70
Cv=CFM/(22.7*sqrt((p1*delP)/((460+T)*sg)))
Cv= 1.355E-06 = 0.0000013554
Now assuming we set the regulator for 30psi and want 15psi out of the
valve, with a flow of one liter per day, we need a valve operating at a Cv
of .000001
I have not yet found such a valve. One writer suggested the ARO line,
their smallest current valve is a 119-307-103 and the company's tech
support waffles on the question of whether it will run all the way to shut
off. I bought one and tried it, it does nothing to stem the flow. The Cv
is way too large, it is intended for much larger flows.
Now maybe there is a valve that can be set to a Cv of .000001. You should
expect that its maximum Cv would be about .0001. But I haven't found
it. Hoke does make a "micro-metering" valve, but it is very expensive.
Does anyone else have a proposed valve for use in this application?
--
Dave Gomberg, San Francisco mailto:gomberg at wcf_com
NEW Planted Aquaria Magazine: http://www.wcf.com/pam
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