Question for all you gas welders

peter nap

peter nap

Joined
Nov 27, 1999
Messages
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I have a full size welding setup and an arc welder and am buying a TIG.

I also have a little Mapp gas torch and that seems to be the one I always reach for. The problem, as all you that have them know, is the O2 is expensive in those little throw away tanks.

I had an idea this morning....two actually. The first is to make a coupling that connects the regulator from the O2 to the hose, and to take it to a friendly welder in the area and refill from his O2 tanks.

Then another thought occurred to me....Just how O2 is in plain compressor air. I have no idea but if I can weld in my gas forge using blown air, why can't I fill one of these firefighter tanks I have from my compressor and use it as O2. It certainly won't give me as hot a burn but I rarely need true welding heat with that torch. 1500 to 1600 F is about the hottest I ever need. I haven't tried it yet but I may tonight when I get time.

Any ideas on the subject?
 
By saying that you have a full size welding set up do you mean a o/a torch? If this ie what you are saying here is what I do. I have a Victor torch and have a 000 tip (had to special order it) this is what I do nearly all my soldering with, even SS. I have never used a Mapp gas torch so can't help there. Gib
 
MAPP temps: oxy...3600F air....2300F

That's from Rio Grande. I'm assuming they mean aspirated ambient air like in a Bernz; ie, no tank. Pressurized air should produce a bit more heat.

Air contains about 20% oxygen, if that's what you were asking, Don.

My concern about filling air into tanks would be to make absolutely certain there's no oil from the compressor in the mix. At the very least, once oily-compressor air has gone in a tank, NEVER refill with pure oxy. Also, never re-use a hose or regulator for oxygen once compressed air has been passed through it. Oxygen+oil creates an explosive mixture. You'd also need to really scrub the air of any moisture to avoid rusting inside the tank and valve.

Personally, Don, I wouldn't even want to consider trying it unless I had an oilfree compressor and a helluva scrubber. But then, maybe I'm just a wuss about this. I think I like the approach of scabbing some oxy off the "friendly welder's" tanks much better. His tanks would have to be pretty full, though, to get much in the small bottle. Pressures will simply equalize.

There's gotta be a reason, though, that whenever you see an air/gas "X" torch, there is no air tank, just ambient aspirated air. Somehow the idea's giving me the heebie-jeebies that I'm missing something important.
 
I'm sitting here looking at tanks in the Rio Grande catalog. The disposables contain 1.1 cubic feet of oxy. The smallest pony tank, about three times the size, contains 20 cubic feet.

This suggests that the pressure in a full "teenie" is much less than what a "real" tank will hold.

So, scrub that idea I mentioned about filling from a "full" tank. That 2200 PSI may well blow one of the "teenies".
 
Mike has it right.

I also recall that most bottles are filled with liquid, not gas. You'd be better off going to a welding supply house that has the right equipment to safely refill your bottles.
 
The little bottles are non refillable Tom. It's like the small tanks of propane I use in my camping stove. I refill them from my forge tank.

I took a break a little while ago and tried it. Propane behaves better than the Mapp gas with the compressor air. Still not what I'm looking for though. I may try to make a mini forge torch to get a better mix and see if I can burn my beard with that. :footinmou

Of course, I could stop being so cheap and go buy some proper tanks.
 
Most supply houses will rent tanks. I have bought them in the past, but am not sure that it pays in the long run.
 
Steve, the ones here do much like propane exchanges on the smaller tanks. You have to purchase the initial tank and they do an exchange for refill. The larger tanks are rented but the monthly rental is prohibitive.
 
fitzo said:
Pressurized air should produce a bit more heat.
Click to expand...

Speaking purely from physics point, wouldn't compressed air caue temperature to be lower than that of "normal" air (at normal pressure) ? It willexpand once it's out of the nozzle and gas expansion means colling down; the ratio of oxygen versus other gasses (mostly nitrogen anyway) is the same in HPA as it is in "normal" air so with all the extra oxygen that gets to fire there's extra inert gas too. Does this make any sense :confused: :D
 
I remember when they came out with little ox bottles that are the same size as the propane bottle. I thought I had me a great tool but by the time I got the flame adjusted the ox was out. Believe they were 10 bucks a pop at the time. No I didn't feel like I got ripped off......
 
I palyed a little more and decided it was more trouble than it was worth. I sent one of my employees that seemed to not have enough to do, to get some tanks :D
 
Don
it's done all the time
Propane and compressed air.
the Dentist down the road is set up this way to do his gold work.

the oil problems runs with the O2 not the compressed air I believe.
on acetylene bottles they put oil in the valve to keep water from freezing in them in the winter.
 
Dan, that's why I said a bottle filled with compressed air can never be returned to oxygen. Boom!

However, I didn't know what oil going through a torch nozzle would do, either. So, it's good to hear what you said. Thanks for the correction.

My major concern was Don not burning another sock and the rest of the body around it! :eek: :D
 
fitzo said:
Dan, that's why I said a bottle filled with compressed air can never be returned to oxygen. Boom!

However, I didn't know what oil going through a torch nozzle would do, either. So, it's good to hear what you said. Thanks for the correction.

My major concern was Don not burning another sock and the rest of the body around it! :eek: :D
Click to expand...

I missed the bottle thing you wrote I guess Ray

in turn I don't know what oil they use either
but I think it's on the high pressure side of the O2 that is the problem,
you know that thing,,
escaping High pressure causes heat,
heat causes fire in oil,
O2 causing real fast fire in the oil on fire
caused by the pressure thing again , this could get repetitive,, :eek: :D

Roger just needs to use the dip bucket more. I'm not sure I'd like wet feet though :confused:
 
Seems like around here you have to pay an initial deposit (which is still alot cheaperthan a tank, think its about $75 for a big tank) and then just pay to have it filled/exchanged (another $15 or so) In the long run its a heck of a lot cheaper than those little bernz torch kits.
I'd love to have a full set up, but like a lot of other tools, I wouldn't use it quite enough to justify the initial cost. (torch kit and deposit on 2 tanks) :grumpy: Someday though :)
 
Around here there's only one gas place left...Airgas. It is always best to buy a "lifetime lease" on their tanks as opposed to purchasing your own. This allows you to haul them in and exchange them on the spot.

They encourage this by letting your "owned" tank sit there until there's absolutely nothing else left to do with their leased tanks or cleaning the windows, emptying trash, etc., then they'll fill yours. Sometimes three weeks of waiting. Periodically, you have to get your "owned" tank recertified, too, for more cost. Convenient.

In fairness, though, when I paid $125 lease fee for a 100 lb propane tank for the forge, it did come with a "free" $64 fill of propane. It's almost empty now; I'm afraid to find out how much it'll be with the prices skyrocketing.
 
I saw a demostration one time where a fly was put in a plexiglass container(approx. 4"x4"x6") with the bottom being open. It was sitting on a piece of 1/2" glass on a table. The container had a fitting on one end where a hose could be connected. Oxygen was introduced to the inside of the container under low pressure. When the concentration reached a certain level--BOOM. The oil on the flies body reacted with the O2. It was correctly stated above about never using anything for O2 that has had compressed air in it.
 
As a group, this must be the smartest bunch of people I've ever met. Who else would know half the crap this bunch does?:D
 
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