Compressed Air / Propane Torch

J

joedhiggins

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May 31, 2016
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Seeing as I have hundreds of gallons of propane sitting around and I despise spending money where I don't need to, I have been thinking about building a torch running off of compressed air and propane, so as not to waste oxygen just to either preheat a large part or to get localized heat on parts that are too awkward to get into a forge.

Has anyone made one? I am guessing that all I really need to do is basically design a small forced air burner with my air supply coming from the compressor instead of a blower. Is there anything fancier to it than that? The couple I have found online use a venture style flare instead of the flares we often use on blown burners.

My basic plan was to use either 1/2 or 1/4 pipe for the torch stem, and T into the torch stem for the gas. My worry is that I need about 4% propane to make it all work. So in order to run the propane without concern of backflow, I think I would need to use a small diameter nozzle for the propane at high pressure. Or alternatively, run the compressed air at a low PSI through a large hose. I suppose I could model it all out and run the calculations, but that is a lot of work i would be replicating if someone has already built one of these things.

Anyone have experience with this?
 
Go to a flea market or pawn shop and get an old welding/cutting torch set. It will run on propane/air. Use the regulators as normal. Flash back valves would be a good idea.

A home brew torch and control is best called a BOMB.
 
I have extra torches/ regulators. I just sort of figured there would be danger there too. Wasn't sure the torch would sustain combustion with standard oxygen concentrations and didn't know if it could handle the 5x pressure you would need to run over an oxy/propane setup.

Will get some oxy propane heads give it a try.
 
Just hook the oxygen hose to a compressor set at 100PSI. Turn the oxygen (air) regulator all the way down and turn on the gas. Open the gas regulator until you can light the torch and adjust both regulators as needed. It won't work for welding/cutting, but for a lower flame for heating or brazing, it should be fine.

I have seen several makers build a blown burner that used compressed air and propane. If you just want to heat stuff, you could build one with a longer burner tube and make it hand held.
 
Last edited:
Stacy E. Apelt - Bladesmith said:
I have seen several makers build a blown burner that used compressed air and propane. If you just want to heat stuff, you could build one with a longer burner tube and make it hand held.
Click to expand...

This is what I was referring to. I just figured the higher pressure air as compared to a blower would require comparatively higher pressure propane. Which would presumably require a small nozzle (like a mig tip) which wouldn't be required in a traditional blown burner.
 
A 1/4" needle valve on the air line will regulate it just fine. It isn't pressure you need for the air, it is volume. The gas is also regulated by a 1/4" needle valve.
 
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