Hello Members,
Thank you for allowing me to post my question.
This is a question of gas flows used in welding, but since the flow ultimately exits through an open tube to atmosphere, I think experts on this Venting forum may be able to assist.
I am using a mixed gas comprised of 75% Argon + 25% Helium which is purchased (premixed) in a standard shop cylinder. The gas is specified to have dewpoint of -105 degrees F, which is quite dry. My standard flow rate from the cylinder is set at 40 cubic feet per hour (CFH) which is measured and adjusted by means of an accurate rotameter type flow meter. Now I must add to this flow, an auxiliary gas supplied from a separate cylinder which is 100% Argon at a flow rate of 25 CFH and also has a -105 degree F dewpoint. The mixed gas and the straight auxiliary gas exit through separate tubes into a common mixing chamber which is open to atmosphere so neither affects the flow of the other.
Sounds simple so far, but my question is how to calculate the total flow (in terms of CFH) of Argon and total flow (in terms of CFH) of Helium ?
For the 75/25 mix at 40 CFH, is it simply { (75% x 40 CFH) + 25 CFH } for the Argon and {25% x 40 CFH} for the Helium? Something tells me my calculation must account for the weight or mass of the individual Ar and He.
One last detail that might be important, the gas pressures are dropped down from cylinder pressure through a 2-stage regulator to 125psig before it exits the regulator and enters the flowmeter.
Please advise if you can help or if perhaps I'm in the wrong forum.
Thanks,
Tom