Using CO2 as a purging gas instead of Nitrogen

**KickedGinger** · 04-26-2013, 05:57 AM

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

**jpsmith1cm** · 04-26-2013, 06:04 AM

Originally Posted by KickedGinger

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.

**Capz** · 04-26-2013, 05:52 PM

CO2 is a corrosive gas and should not be used.

**Capz** · 04-26-2013, 06:05 PM

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.

**KickedGinger** · 04-26-2013, 06:32 PM

Originally Posted by Capz

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.

**Capz** · 04-26-2013, 06:45 PM

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.

**syndicated** · 04-26-2013, 06:47 PM

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

**duckman373** · 04-26-2013, 10:08 PM

Don't CO2 racks use stainless pipes?

**BALloyd** · 04-26-2013, 10:30 PM

Originally Posted by duckman373

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.

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**mspanky** · 04-26-2013, 11:05 PM

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.

**MicahWes** · 04-27-2013, 12:30 PM

CO2 is NOT corrosive in its pure form.

**Pascone10** · 04-27-2013, 02:13 PM

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..