Q: I’m trying to get my air-acetylene Little Torch to burn hotter, and I thought I’d try oxygen rather than compressed air. Would it make sense to generate my own oxygen by electrolysis of water?
A: It can be done, but it’s not all that simple. However, if you do it with a home-built setup, remember that you’re also generating hydrogen, and the Little Torch works quite well using hydrogen and oxygen as fuel and oxidizer. Most industry standard “water torch” designs do not separate the oxygen and hydrogen streams, but leave the gases mixed, as the mixture is perfect for complete combustion. However, an oxy-hydrogen flame is enormously hot. Too much so for many uses, as well as too hot for many torch designs, in part because the combination burns so rapidly that unmodified, the flame tends to travel back up into the torch, instead of staying at the tip. Water torches solve this by passing the gas mix through a vapor-fluxing unit, where the absorbed solvent vapors lower the speed and temperature of combustion to something manageable, as well as giving the flame a reducing nature, which is useful for soldering.
A limit to making your own oxygen generator is that you’ll have little control over the oxygen pressure you generate. Normal water torches are not adjustable in this regard. They operate at quite low pressures, with a switch that simply turns current on and off to keep the pressure where the system wants it. It’s not so simple to build a system that gives you variable gas pressures such as the Little Torch is designed to use.
The other alternative you might consider is an oxygen concentrator. Oxygen concentrators extract oxygen from the air, instead of by breaking up water into oxygen and hydrogen by electrolysis. Their output is not as pure as bottled oxygen, but it’s fine for a torch setup. I seem to recall the delivered mix is something like 85 to 90 percent oxygen, which should be fine. I’ve seen the things for sale on eBay, and you might find used ones for sale from local medical supply firms, perhaps units that ar not longer able to be certified for medical use, or are out of warranty, etc. Prices vary. You won’t need anything more than the smallest such unit for a Little Torch.
But from what i’ve seen, frankly, you’ll still be spending more money than if you just used an oxygen tank. I’m not sure of prices where you are, but here, a small oxy tank and cheap regulator would cost me a bit over a hundred dollars, with refills for the tank perhaps twice a year if I used the torch frequently, and those refills cost around 20 US dollars. Not that excessive, really, considering the alternatives.
by Peter W. Rowe M.F.A., G.G.