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  1. #1
    Join Date
    Dec 2009
    Posts
    147

    Using CO2 as a purging gas instead of Nitrogen

    Does anyone use c02 to purge with while welding instead of nitrogen?
    Is nitrogen drier? or is c02?
    We have a tank of c02 for blowing out condensers and have always used c02. I have never really questioned what we should use but I want to be a better tech and part of that is using the right equipment.
    They use c02 as a refrigerant so it must be ok to use as a purging tool right??
    Let me know guys!
    thanks

  2. #2
    Join Date
    Sep 2008
    Location
    Western PA
    Posts
    25,548
    Quote Originally Posted by KickedGinger View Post
    Does anyone use c02 to purge with while welding instead of nitrogen?
    Is nitrogen drier? or is c02?
    We have a tank of c02 for blowing out condensers and have always used c02. I have never really questioned what we should use but I want to be a better tech and part of that is using the right equipment.
    They use c02 as a refrigerant so it must be ok to use as a purging tool right??
    Let me know guys!
    thanks
    I have used both and I cannot tell a difference between the results.

    Some try the argument that CO2, in the presence of water, forms carbolic acid. This is true. Since we're evacuating the system to remove moisture, I don't see this as a major issue.

    Depending on the CO2 grade that you buy, it may or may not have a significant quantity of moisture in it.

    I like CO2 because there is a LOT more of it per can. I DON'T like it because that thing is HEAVY dragging it up to and across the roof.

  3. #3
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    427
    CO2 is a corrosive gas and should not be used.

  4. #4
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    427
    But it is ok to drink it but you wouldn't if you knew what is in it or should say what use to be in it prior to the soda bottlers pushing for higher purity beverage grade co2. I was in the ind gas business for 27 years. I can't count the amount of times I had to dump large co2 tanks full of product due to high levels of a poison gas. (The name escapes me, I been away from this stuff for six yrs). This gas would rise to the top of the tank and would not liquify but never the less, if a sample from the tank after a 20 ton delivery came back positive, we would be called out to dump it. Funny thing is, Coke never shut down. They kept filling soda. But keep in mind, product withdrawal was from the liquid side or bottom of the tank and the -5F liquid is vaporized with steam or electric heaters.

  5. #5
    Join Date
    Dec 2009
    Posts
    147
    Quote Originally Posted by Capz View Post
    CO2 is a corrosive gas and should not be used.
    Can you back this up with evidence?
    It cant be that bad if there is a big push for c02 as a refrigerant.

  6. #6
    Join Date
    Jul 2011
    Location
    Lehigh Valley, PA
    Posts
    427
    I'm not a scientist or a metallurgist, I cannot back it up. I do know co2 cylinders are required to be retested every 5 years rather than 10 yrs as for nitrogen, argon because it is considered corrosive. I was taught not to use co2 in refrigeration systems. I'm old school, try and do things correctly & safely. If co2 is okay to use why hasn't it been accepted for the last 30 years as a purge gas? I never read one time anywhere where is can be substituted for nitrogen. Have you? But I do know co2 is much heavier than nitrogen. I'd never for anything but blow out dusty condensers. Would really suck as a leak tester in a pressurized system, too dense.

  7. #7
    Join Date
    Feb 2010
    Location
    Calgary, Alberta
    Posts
    1,102
    CO2 is considered an inert gas under normal conditions.
    It is used for MIG welding but it can make steel more brittle due to the CO2 reacting to the high temps.
    I'd be reticent to use it as a shielding/purging gas for brazing copper without proof it won't react with the joint in the long term

  8. #8
    Join Date
    Dec 2001
    Location
    Phoenix, Az
    Posts
    1,243
    Don't CO2 racks use stainless pipes?

  9. #9
    Join Date
    Jan 2010
    Location
    Vancouver Island
    Posts
    334
    Quote Originally Posted by duckman373 View Post
    Don't CO2 racks use stainless pipes?
    High side is stainless. Low side is copper. From what I have seen. Makes sense given the price of stainless.

    Sent from my SGH-I747M using Tapatalk 2

  10. #10
    Join Date
    Mar 2003
    Location
    Cochrane, AB
    Posts
    604
    Beverage grade co2 cannot be used as a refrigerant due to it's many contaminants. The grade used in racks is sometimes called Coleman grade.

  11. #11
    Join Date
    Oct 2009
    Location
    Raleigh, NC
    Posts
    794
    CO2 is NOT corrosive in its pure form.

  12. #12
    Join Date
    Jan 2008
    Location
    In the work truck
    Posts
    2,997
    ALL tanks are to be hydro tested every 5 years.. Some ( Firefighting tanks etc.) that are not made of steel or aluminum must be disposed of after 15 years.. other then that as long as they pass hydro are good to go.

    But in response to capz I never heard of a hydro on a tank longer then 5 years.. I mean air is not corrosive and that needs to be done every 5 years..
    Gotta have the right tool for the job!

    Where is all the stuff MADE IN THE USA?

    "Thats what we do Troy. Incredible, Invisible, Imbelivable things. We are an Unseen, Unknown, Unvincible fraternity of craftsman.."

  13. #13
    Join Date
    Feb 2010
    Location
    Calgary, Alberta
    Posts
    1,102
    Quote Originally Posted by MicahWes View Post
    CO2 is NOT corrosive in its pure form.
    It is when heated during welding!

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