Flowing inert gas while brazing copper tubing

[dstaley]

Hey guys,
I'm preparing to braze some copper tubing in my pole barn for compressed air. I have some Blockade for filler, and I have learned that it's helpful to flow an inert gas through the tubing while brazing to reduce/eliminate corrosion inside the tubing during the brazing operation, usually using nitrogen. I don't have any nitrogen, but I do have a spare cylinder of 75% Argon/25% CO2 which I assume is not suitable, but I thought I'd ask before spending the money on a bottle of nitrogen.

Have any of you tried 75/25 welding gas for brazing when in a pinch?

 

[Caduceus]

I see that this is an older post with no replies, but I'll give it some attention anyways.
I've never brazed copper for compressed air. I've only soldered it. Brazing is typical for higher pressures that require stronger joints.
Also, if it's for compressed air and not for medgas, brazing with a flux coated silver bearing brazing rod should suffice, without the use of inert gases.

 

[dstaley]

Thank you so much Caduceus, I appreciate your response.

I stumbled on a really nice air compressor years ago, it was new, 2-stage, and cuts out at 185 PSI- a bit higher than I was used to before, but that's what the spec sheet says it should do, so I guess it's designed to work this way. Given this higher pressure, even though I set the regulator to supply 90PSI to my piping system I wanted to ensure that in case of regulator failure I have some margin of safety above normal tank pressure. On other forums (yeah, internet info- grain of salt and all that) I saw opinions from those that seemed knowledgeable that brazing was the best way to go in an ideal world. I value peace of mind, so I did some research and bought some Blockade on eBay.

I don't have a tank of nitrogen so I might just braze them in free air. Should I use a small rosebud tip for this (oxy/acetylene) or something different? I have never brazed copper before, but I have soldered it plenty and brazed other metals occasionally.

 

[johnjh2o]

If your brazing just for safety reasons you could accomplish the same thing with a 100 lb relief valve after your regulator.

John

 

[Caduceus]

I would say with the potential of reaching 185 psi. the Blockade as well as the rosebud tip should do fine. John has a good point with the relief valve. If you are concerned about regulator failure, the relief valve would also give added protection to equipment attached to the air line. Most pneumatic tools operate at 90 psi, but heavier and better quality can use up to 150 psi. Manufacturer recommendations will come with most tools and equipment.

 

[dstaley]

Thank you, guys. The relief valve is a good idea, I need to check on that. A 200PSI one at minimum should be added. I'll need to weigh my options regarding a 100 PSI relief valve vs. remembering to be diligent in turning off the compressor's power when I won't be in the barn for a few days at a time. I'd hate to have that compressor running 24/7 for a few days just because of a regulator failure when unattended.

I really appreciate your input!