Water Torch

Q: I’ve got a second-hand type A+ “water” torch. Unfortunately, it doesn’t work—what am I doing wrong?

A: I don’t know the specifics of the Microweld unit, but I can give you some background information on this type of torch. They are basically electrolysis units, passing an electrical current through a water-based electrolyte. That generates bubbles of oxygen at one electrode and at the other electrode, bubbles of hydrogen; which burns (oxidizes) when the two gases are recombined. Because the gas generation system is closed, the evolving gases generate enough pressure to operate in a torch tip, if they are evolved rapidly enough. In essence, these things are fancy-shaped water tanks with a massive DC power supply hooked up, and a few valves and switches.

I’ve never taken one of these torches apart, but I assume the two electrodes are in separate gas generation chambers, so the oxygen and hydrogen are only mixed at the torch, not in the machine itself. This would thus prevent explosive accidents. Also, to slow the combustion rate, most such units bubble the fuel gas through a vapor-fluxing unit, which adds components to the fuel that cool the flame and slow the combustion rate, as well as making the flame somewhat friendlier to metals in terms of oxidation. Here in the U.S., there are several brands of these “water torches” available, in a variety of sizes and capacities.

To troubleshoot the thing, once you’ve got it apart, start by making sure the power supply is actually sending power to the electrodes in the water. A broken or corroded electrode or wire will stop the unit from working. Using a voltmeter, you can determine if this is the problem. After that, check the various switches and valves. There is probably a pressure-sensing switch somewhere in at least one of the gas collection chambers (or however it’s rigged up) to regulate how fast gases are generated. Your gas valves, at the torch or elsewhere, need to be operating correctly (for example—can you blow through the tubes when they’re open?)

You have to remember that current will not flow through distilled water. The water tank is refilled with distilled water as it’s used, but the initial filling must include some sort of salt or other electrolyte, to carry the current. The exact material to use is generally specified by the manufacturer. If there’s a vapor-fluxing unit or similar attachment, the torch will probably not burn correctly if that’s not also filled with the right reagents.

Remember to check the obvious things. Is there a fuse that’s blown? Is it plugged in? I know, it sounds stupid, but ask any electronics repairman and you’ll get stories of “broken” equipment that simply hadn’t been correctly plugged in, or was plugged in to an outlet with a blown fuse, or itself had a blown fuse on the equipment. It’s happened to me, a few times, spending lots of time trying to figure out why something doesn’t work, and in the end, it’s simply due to some really silly thing like a bad plug.

by Peter W. Rowe M.F.A., G.G.