CO2 Injection

[Erick D]

Hello,

I am an EE and really have no knowledge in fluid dynamics. I need to inject CO2 gas into an air line. This is a regular air line as someone would have in a shop. It has an air pressure regulator and a hose of 25 ft. At the end of the hose there is a air nozzle gun. When I actuate the gun I would like air and CO2 gas to come out of the gun. I was thinking that if I put the CO2 gas at a higher pressure it would inject it to the hose (like adding the CO2 at the start of the hose with a Tee). But I am not sure what that would do to the air regulator. Am I going on the right direction here, or is there an easier way to do what I want to do. FTI the air pressure upstream the regulator is 100 psi and down stream is 50 psi.

Thank you very much in advance!

 

[1503-44]

Yes, you will have to inject the CO2 at a slightly higher pressure than the pressure of the air (when flowing) at the injection point. The lowest pressure point, near the gun, will be easier.

When the gun closes, pressure in the whole system will tend to rise to the higher of the air regulator's delivery pressure set point, or the CO2's source's pressure, which will cause that one's, probably the air, to backflow into the CO2 delivery line, if its pressure is less than the air pressure at the tie-in point. To prevent any backflow into the CO2 supply line, you might want to put a check valve in the CO2 line there. A needle valve between ckeck valve and tie-in point may allow you some control of the CO2 delivery rate while maintaining the CO2 pressure high enough at all times to do so. The air pressure regulator will tend to close if and as delivery pressure rises, closing entirely when the regulator's delivery set pressure is reached. That will tend to stop any CO2/air mixture from backflowing into the air's supply source.

Make sure all components have a pressure rating that exceeds the higher of either air, or CO2 maximun source pressure.

Only use this gun in a well ventilated area. Too much CO2 will, at the least, give you one heck of a headache.