Feeding compressor nitrogen

[bchannell]

I saw a mention of feeding a compressor, (ie GX compressor) nitrogen to avoid moisture and it got me wondering. I work on HVAC equipment almost every day and go through bottles of nitrogen like crazy. I have a regulator and even a orifice bleed to bleed nitrogen through copper pipe while brazing to avoid oxidation. Why couldn't you feed N2 to the compressor at very low flow to totally eliminate moisture in the system?

 

[dgeesaman]

I saw a mention of feeding a compressor, (ie GX compressor) nitrogen to avoid moisture and it got me wondering. I work on HVAC equipment almost every day and go through bottles of nitrogen like crazy. I have a regulator and even an orifice bleed to bleed nitrogen through copper pipe while brazing to avoid oxidation. Why couldn't you feed N2 to the compressor at very low flow to totally eliminate moisture in the system?

It should work.

Do hvac guys ever mess around with the 6000psi bulk N2 tanks? Because then you could buy a regulator and skip the compressor.

 

[TN_Yankee]

The beauty of feeding a compressor at 10psi or so (or booster (e.g. Altaros)) is that you can pretty much drain the nitrogen tank, as opposed to having to refill it when it drops below the minimum you can fill a rifle to (e.g. 2500 or 3000 psi).

 

[elwoodblues]

Its the only way I fill any of my guns. I spent the last 50 years in the welding and compressed gas biz so I had lots of filling methods and gases available to try
Yes Helium is faster than N2 but leaks much easier (small molecules) and is way to expensive. Tried argon too as thats what window a door makers use between glass panes and hard to get leaks but larger molecule doesn't move as fast so gun shoots slower. I could get and use 6K nitrogen but the bottles weigh over 400 lbs the regulator for 6K a good one costs more than I paid for a GX CS4. So the std industrial tanks work fine for me and use the pump as pressure builder and never have to turn in a partial tank . Nitrogen is the most abundant gas that comes from Air separation process and is the cheapest to make. It is available probably everywhere, welding supply stores, beer and wine distributors, farm and tractor stores etc Aii you need is a bottle, regulator and a hose with the fittings to go to you pump. so far the only inlet sizes I've come accross are 1/2"npt inlet on GX cs2 , the tuxing twin is 1/4 " npt and the CS4 is 1/4" npt inside at the filter connection. Hope this helps someone, sorry for the long post.

 

[Mcleod]

Its the only way I fill any of my guns. I spent the last 50 years in the welding and compressed gas biz so I had lots of filling methods and gases available to try
Yes Helium is faster than N2 but leaks much easier (small molecules) and is way to expensive. Tried argon too as thats what window a door makers use between glass panes and hard to get leaks but larger molecule doesn't move as fast so gun shoots slower. I could get and use 6K nitrogen but the bottles weigh over 400 lbs the regulator for 6K a good one costs more than I paid for a GX CS4. So the std industrial tanks work fine for me and use the pump as pressure builder and never have to turn in a partial tank . Nitrogen is the most abundant gas that comes from Air separation process and is the cheapest to make. It is available probably everywhere, welding supply stores, beer and wine distributors, farm and tractor stores etc Aii you need is a bottle, regulator and a hose with the fittings to go to you pump. so far the only inlet sizes I've come accross are 1/2"npt inlet on GX cs2 , the tuxing twin is 1/4 " npt and the CS4 is 1/4" npt inside at the filter connection. Hope this helps someone, sorry for the long post.

Outstanding write up. Thank you.

 

[rcs9250]

It would not be difficult to inject nitrogen (N2) into your compressor. The thing you want to prevent is wasting N2 by feeding too much or feeding too little N2.
If I were going to do it I would fabricate an intake manifold that attaches to compressor that would have a connection for the N2 and also have a reed valve that would allow air to be drawn in if the N2 stops or aren’t feeding enough N2.
I would also have a flow meter on the N2 tank so you could have a reference for future sessions flow setting.
It would be fairly easy to learn your required flow setting by watching the reed valve to see if it is fluttering/opening.
The reed valve opening should be about the same size as the compressors intake port in case the N2 gets cut off so that the compressor doesn’t start pulling a vacuum. Fabricating a reed valve with a piece of mylar would be pretty simple.
A differential pressure gauge could also be used to monitor intake pressure but would not eliminate the danger if the N2 stopped. You most likely would be able to hear a sound change of your compressor if no reed valve was used. My Alkin is loud enough and I wear hearing guards so I possible would not hear a noticeable difference. I think the safety of the reed valve is important and wortwhile.
The main idea of this set up is economical use of the N2 supply.
A lot of work to go through, but this PCP thing is non stop tinkering (for me anyway). But that’s what keeps me engaged.

PS- I looked in McMaster Carr for a pre-made/engineered check valve but nothing jumped out at me.
It is also possible to attach a scuba second stage regulator to your compressor intake. You would need to supply N2 to the scuba regulator at about 100psi.

 

[elwoodblues]

The only time you waste the Nitrogen is leaving the tank on. you know how I know that. all you need is enough feed that you gauge does not zero out during filling, Ive switched to a flowgauge style regulator. I set my flow rate a little higher than the CS4's pumping rate so about 20cfh the way these work is thru a metered orifice the gauge is really a pressure gauge with CFH markings based on that orifice no manifold needed

 

[bchannell]

It should work.

Do hvac guys ever mess around with the 6000psi bulk N2 tanks? Because then you could buy a regulator and skip the compressor.

No, we would never use anything that high pressure. My guess is that it is for some specialized industrial use. When I called the local gas supplier, whom I've dealt with a lot, he acted like I had a loose brain screw. He had to make a bunch of calls just to tell me he wouldn't be able to get it in my area.