Heating with propane/compressed air torch

Rather than use oxy /acetalyne or oxy/LPG (propane) I was looking at some German torches that use compressed air/LPG (propane).

Perkeo - Made in Germany: PERKEO Propane-compressed air heating, brazing and melting outfit KLEIN RISTA

This would be much cheaper to run in Australia as you wouldn't have the high annual bottle rental costs, and the oxy refill cost.

I want it for localised hard bronze brazing work (small repairs and fabrication).

Has anyone here had any experience with this gas/air combination ?

Rob

I run a air propane torch that i mainly use for heat treating. Whilst you can braze with it it is a struggle. It's right at the limit and you will spend a fair time getting thinks to temp, even then your surrounding them in kiln bricks and such to help concentrate the heat. It's nothing like oxy acetylene. It does excell at silver brazing though. That it beats oxy fuel at IMHO as it won't easily over heat the flux.

The compressed air - gas torches i have been around in no way can be recommended for brazing. The flame is just too big + cold.

Thanks for replying adama.

Yes, I was wondering if this would be the case. I was a bit suspicious of these guns as they seem to be aimed more at preheating and kiln use.

This one is also interesting:

http://www.flamefast.co.uk/PDFs/FLAMEFAST_T2 & T4 TORCH_DATASHEET_V1_LORES.pdf

I notice it's running at 4 psi for the compressed air. Do they all run this low ?

I currently use a Bullfinch 404 Auto brazing kit (UK made Propane gun) for small hard bronze brazing and it does a very good job up to about 1" solid.

Great for bronzing on carbide lathe tips etc.

Bullfinch Gas - Technical data: Autotorch brazing

I've used one of these for about 10 years, after I got rid of the oxy set. It's extremely cheap to run and is a bit more powerful than any MAPP gas units that I've used.

Cheers

Rob

I run a Siviert (sp i can never get that right) But yeah a bulfinch is much the same, just a bit lesser build quality. I have used a flamfast compressed air natural gas torch when i was in school. They maybe heat a bit quicker than your bullfinch, but at the end of the day the issue is much the same. For every 20% of oxygen thats reacting, you still have some 70+% other inert gases that are needlessly being heated. Thats what makes a oxy fuel flame hotter, its just components that are reacting, there's no inert gasses to also heat up!

You won't need much pressure, a flame only burns so fast with a given fuel in a given oxidizer. Blow more fuel + oxidizer in faster than the flame burns it and it will blow the flame out the nozzle & go out!

That said i also have a oxy propane cutting torch. It shares the regulator + hose + Bottle of the Sivert torch. Propane is cheep. Its also way safer than acetylene. The ctting torch flame can be a very usefull heat source, its still not oxy acetylene, but it can be used to braze with in a lot more similar way, just don't pull the magic lever once the jobs hot! propane bottles over here can be got with out rental, hence that only leaves rental on the oxygen! Which makes it a lot more affordable for only occasional use.

I once tried feeding a big old messer griesheim Oxyfuel torch with propane-air , and with a shop made head/tip, it actually worked. But performance was not much better than a good naturally aspirating torch...a GOOD one, there are some styles of silent turbo torches wich make wonderful flames but dont get quite as hot as the old noisy roaring ones get, utter crap.
From what i have been able to observe those run way too rich, i may try to fix that, should be doable.