oxyacetylene torch
August 30, 2010 12:26 PM   Subscribe

Bought a garage sale oxyacetylene torch. Is it safe? Is it repairable?

So I paid $50 for tanks, hose, regulators, welding and cutting tips (if that's the right terms). The set seems pretty old. The welding handle says 'Harris'. The tanks have gas in them and I was able to light it (but not well, I'm pretty inexperienced). The tanks have some rust on the bottom (not too much, I think) and the on/off handle for the acetylene tank is missing -- I used a small wrench to open it. How concerned should I be about the whole thing? The regulator gauges don't reset to zero when they're off (fully counterclockwise). Can I just replace those gauges?
posted by luge to Home & Garden (10 answers total) 1 user marked this as a favorite
Bring the whole setup to a welding supply store - they should be able to assess it.

Do you know how to safely open and close the tanks, and in what order? It may be that you're leaving some residual gas in the lines if the gauges are not going to zero.
posted by backseatpilot at 12:32 PM on August 30, 2010

Oxyacetelyne torches should be checked every five years to make sure they're safe.

You should be able to contact Harris here or at the toll free number listed on that page. They should be able to direct you to the nearest "official repair" shop to get it assessed.
posted by zarq at 12:36 PM on August 30, 2010

Just wanted to make sure you know to be careful when testing pressure and everything. To quote the Wikipedia article on acetylene:

"For use in welding and cutting, the working pressures must be controlled by a regulator, since above 15 psi acetylene will decompose explosively."
posted by komara at 12:45 PM on August 30, 2010

Confessed gas tanks should have their latest inspection date stamped on them; no shop should refill a tank whose inspection is out of date. The CGA promulgates standards and should have more info
posted by TedW at 12:48 PM on August 30, 2010

Best answer: Yeah, there's a main tank valve that isn't supposed to have a handle so it can't be opened accidentally, then there are valves to the hoses that are roughly equivalent to a garden faucet handle but open clockwise and close counterclockwise, and then there are valves on the handpiece. Close the main valves with a wrench (there's actually a tool for that, though), with the valves to the hoses open you open the handpiece valves to bleed the lines of gas. You'll hear it and see the gauges go down. Then close the hose valves and then the handpiece valves.

This is important because on an old setup the hoses are the dangerous part. You should replace them even if they look pristine because you don't know how old they are. If a hose were to burst or even just leak and ignite (or fill a room with gas) that would be a bad thing. Compounding that is the fact that leaving gas in the hoses degrades them faster.

If there's any doubt that the rust is only surface rust, the tank is dead. Explosive decompression of these gases, however unlikely, is another bad thing.

You don't mention a striker. It's a self contained flint and steel that you can strike with one hand. If you lit it with a lighter, don't do that again. Even some professionals do it, but it's really stupid. The real problem is that if you're lighting it with a lighter then that means there's a lighter around the torch. There shouldn't be a lighter anywhere in the vicinity. If you get near a lighter with that oxyacetylene flame it will blow up. Yet another bad thing that can happen.

Seriously, don't take any chances with this thing. Be a little scared of it. You have a tank of bomb sitting right next to a tank of oxygen. I've used a setup like this professionally for six years and I've never had or seen a major accident, and I mean to keep it that way.

So, basically, nthing, "get it inspected."
posted by cmoj at 12:53 PM on August 30, 2010 [2 favorites]

Response by poster: Yikes. I will definitely be taking it to the local welding shop for assessment. Thanks!

cmoj, yes I used a striker and I will bleed the lines as soon as possible.
posted by luge at 1:13 PM on August 30, 2010

Another important thing about a striker is that it puts your hand considerably further away from the business end when you are lighting it and that kind of peace of mind is well worth the $5 it'll set you back.
posted by quin at 1:25 PM on August 30, 2010

I was driven by the recent MeTa thread to reread my answer, and realized I might have mentioned these things:

There is such a thing as an anti-blowback valve that would prevent a fire from travelling back up the lines to the tanks. They're sort of expensive and, again, I've seen lots of professionals (and a university) who don't have them. I know one of my setups does and one doesn't. The one that doesn't really should. If you're being careful about everything else you might feel it unnecessary, but absently pointing your flame at a line, or dragging a line across hot work can and does happen.

I also meant to say more about bleeding the lines and why. I sort of implied that it was just because there might be leaks in the lines, which is true, but not the whole story. Not only do both oxygen and acetylene degrade rubber, but constant pressure in the hoses degrades it. There's a braided sleeve around them to help prevent this, but it doesn't totally.

There is a Mythbusters episode about trying to get pressurized tanks to blow up/become rockets. That episode is a pretty good illustration of how it is with these things. It takes either unfortunate circumstances or actual effort to get these tanks to go wrong, but it's a very grisly scene if they do. The object is to keep the possibility of failure of your equipment as remote as possible so you can worry about being eaten by pigs and struck by lightening instead of your rusty oxygen tank.
posted by cmoj at 12:23 PM on December 19, 2010

cmoj: "If you get near a lighter with that oxyacetylene flame it will blow up"

Could you explain how this works? Do you mean, if the lighter is close enough that the flame heats it, the butane will boil off and rupture the lighter?
posted by d. z. wang at 3:37 PM on December 19, 2010

Yeah, I just mean that the flame is very hot and it would burn through the plastic of a lighter, like, instantly if it actually touched it, or quickly rupture it if the flame was just sort of pointed at it for a little while, depending on the distance.

I just phrased it that way to emphasize the bad idea-ness of it.
posted by cmoj at 5:13 PM on December 19, 2010

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