Copper pipe joint Installation Question

[drew71]

Hi All
I'm new to this forum, but thought I would jump right in with a question.
I recently visited a work site to quote on some work & noticed an asian gentleman installing a pipe run to a remote condenser R22 display cabinet, he was silver brazing/silver soldering (depends where you are from) some nicely prepared joints with one of those small hand held MAPP torches that seem so common now, nice neat joints they were too, but I noticed he was bleeding the pipes with what according to the cylinder was food grade Co2 rather than Nitrogen.
Is this a common or known practice ? I've never heard of it before, I did say Hi and tried to ask but his english was about as good as my Vietnamese so there was much smiling and nodding and very little communication.

I'd be interested to hear any thoughts on this

Cheers

Drew

[FreezerGeezer]

Interesting. My immediate thought would be that the O2 component would possibly aid oxidation of the pipes?

[The Viking]

I thought that the black soot stuff we trying not to create inside the pipes was carbon based....

So if we instead of air add Carbon Di Oxide to the mixture.....Can't be good. I would even go so far as saying that it must be worse than not bleeding anything through the pipes.

[Samarjit Sen]

While brazing/soldering copper pipes, it is Nitrogen which should be passed through the pipes and not CO2. May be the person is not aware of the practice.

It would be better not to bleed than use a wrong gas.

[The MG Pony]

Carbon dioxid is fairly stable, it takes photosynthisis to really break it apart or other extreme energy input.

Argon or helium would have been a better choice had nitrogen been unavailible, but at MAPP gas temps it will have served its perpos of keeping free unbound oxygen out of the scene.

Do tests your self, for my self when doing home baked projects I've used propan! with great succes, remember it is free un-bound oxygen that does the bulk of damage, any thing to keep the free oxygen out of the pipe will do the job as long as the carier gas is stable at working temp!

Name of the game is to keep the O2 out of the pipe, For example hydrogen enriched N2 will actualy remove the soot by reducing it back to copper! as at the hi temps it will bind the oxygen up to its self forming super heated steam!

[Dan]

Hussmann corp 28 years ago was recommending using CO2 or dry nitrogen to keep the interior piping clean. It was only because of "politically correct" admonitions that the tech writing staff was advised to remove CO2 from the manuals. CO2 works just as well as dry nitrogen. Both are inert for brazing purposes. CO2 is often used as an oxidation eliminator in arc welding along with argon.

[taz24]

Hi All I'd be interested to hear any thoughts on this

Cheers

Drew

Hi Drew.

I've never used Co2 but it is the Oxygen that causes the Oxidization.
So logicaly removing the O2 with Co2 should work.

taz.

[Samarjit Sen]

This may be an interesting site :

www.copper.org

[drew71]

Thank you all for the info. I had assumed it would prevent oxide scale from forming, though I had thought it would be unsuitable because of moisture issues.

Thanks again everyone,

Cheers

Drew