Anybody heard of it, or is it another one of those tails? I needed to repair a gas tank last week, any my boss claims that if you put dry ice in the tank, it will purge the tank of any flammability. I chose to steam clean the tank which did work without any problems. But, the genius that was doing the welding, put the electric fuel pump back in, as well as seal up any other openings so that he could pressure check it. We did have a small pin hole, hit it with the tig, and foof! No surprize, as the fuel pump still had fumes, and now the tank was totally sealed with no where for the fumes to go. Really didn't do anything other than open the weld back open about two inches. This sent my boss over the edge claming that if we had put the dry ice in it, there wouldn't have been any problem, but in my eyes, with the fumes trapped, I don't think the ice wouldn't have done anything. I would really like to know if anybody knows for sure if this is fact or fiction. Would make a good episode of Myth Busters!
The dry ice would sublimate to CO2 gas, that would not support combustion. Even with the fumes in the pump I don't think there would be enough oxygen to support combustion. it would make for a nice experiment though. jerry
Jerry, you must have some kind of special tool in your collection that would take care of this problem without any gas involved! My point on this issue, was that nobody could say for sure that it would work, and I didn't want to risk the safety of one of my guys for a maybe. I knew the steaming would work, which it did, until stupidity took over when I wasn't looking!
The hazard of tank welding is the fuel. Get the tank COMPLETELY dry inside and it won't have any vapor to light. Flush the inside with a good degreasing solution like Castrol Super Clean and then poke an air hose down in it, preferably outside in the sun. Let it run all afternoon and every trace of fuel should be evaporated and blown away. Use your nose to tell you when you are done. If the steel inside is as dry and clean as the outside, you should be safe. Don't rush. If it still smells of gas, repeat this process. Any "tricks" are really just a gamble.
We weld tanks. Tanks are cleaned with inert cleaners and sometimes steam cleaned. or hot tanked. We then flood the tanks with argon, C25 or CO2. Argon is completely inert, CO2 and C25 are mildly reactive in the welding process. All will not support combustion. Dry ice is CO2 and will go from a solid state to gasous as it warms (pulls heat from surrounding area). My only concern with dry ice is the cooling effect on the metal which may not be desirable. For you welders- 30 years ago I built a fuel tank for a buddys diesel out of a 55 gal drum. Oxy fuel welded with a carburizing flame... guess what happened... not real loud, but squirted pretty far! Scared the **** out of everyone in the shop. Good turning point for a 17 year old though, that is when I decided I needed to get educated.
The method I have used and still use, pipe the exhaust from a running car into the gas tank, let it run for a few minutes and start welding. Carbon monoxide does not support combustion either. I have welded on alcohol and gas tanks fresh out of the cars this way and never had a problem.
I would just take it to a radiator shop and have them clean and throw in a liner. Its not that expensive. The tank must have other areas that are weak. That will prevent future leaks.
REJ is right on the money, we do it all the time. Exhaust run in it for 5 minutes and its safe to weld on..
Filling the tank with CO2 from dry ice would prevent combustion inside the tank, but what about the gas fumes it pushes out? A mechanic in my home town was burned to death when an open pan filled with gasoline pretty much blew up in his hands. He had walked through the garage with it, leaving a trail of vapor behind. When another mechanic lit a torch it followed that vapor over 30' to light the pan of gas! A freak accident for sure, but my Dad was in shock because it killed a friend of his. I'd say steam clean the tank outdoors, then use the dry ice trick, and do the welding in a well-ventilated area where fumes will be carried off quickly. Overkill? Maybe, but who wants to be the proof that something 'nearly always' works?
for what its worth, i've welded on several gas tanks with no problem. i was doing the exhaust thing one day and my wife asked me why i was doing it and i explained that i was trying to get the fume's out so i wouldn't blow my self up. She said why don't you just use dawn dish washing liquid detergent? it cuts grease oil etc. tried it and their was no odor, then very cautiously ran a torch by the filler neck and nothing happened. anyway that was several years and many tanks ago and i'm still here to tell about it.
I have to disagree with you about the carbon monoxide not supporting combustion. It IS very flammable! It's likely the carbon dioxide in the car exhaust that is keeping things from going BOOM. It ,along with other products of combustion ignite and cause a backdraft explosion. Basically smoke is unburned fuel and when it reaches ignition temperature with the correct oxygen ratio it will combust.... http://en.wikipedia.org/wiki/Carbon_monoxide
How can it reach the ignition temperature when there is no oxygen to support combustion?? I am not trying to start anything, I just made a statement as to what has worked for me. I have done this probably 40-50 times on fuel tanks that had anything from diesel to hi-octane(116) racing fuel and never had as much as a "****" out of the tanks. If you have smoke coming out of your exhaust, most likely you are running way too rich or have a ring problem, depending on the color of the smoke.
I've welded on several fuel tanks using the exhaust method. But after reading Jethro's post and checking out Wikipedia "NO MORE" I've been Lucky.
what about filling up the tank with water,...all the way almost to the top,....basically up the point to which you'll be welding?? I have an old model T tank I want to fix the filler threaded bung on and was thinking about it,....??? Jason
I hook 'em up to the exhaust on a running vehicle, same theory and it works, I don't know why dry ice wouldn't work, but I probably wouldn't try it on one all sealed up for reasons as obvoius as gas fumes.
Rej..I didn't mean to say yours or other methods don't or won't work. It's just the misconception about carbon monoxide. It's often confused with carbon dioxide. I've even heard of guys burning the gas fumes out of a tank before welding. They soak a rope with diesel and put it in the tank and stand back and light it. It's supposed to shoot a long flame then go out ,then they proceed to weld. I'm too chicken to try that ,I've filled tanks with water or used a co2 extinguisher to fill the tank with non flammable gas...the reason the exhaust from a car works is probably from the carbon dioxide in car exhaust along with water vapor. I've only ever seen a car gas tank explode once in a car fire...impressive! I sure wouldn't want one go off while I'm straddling it
i DON'T KNOW MUCH BUT I AGREE WITH tERRY IN THAT A GOOD SOAPY HI PRESSURE CAR WASH [AND FLUSH] WILL RENDER ANY TANK SAFE ENOUGH TO WELD IT UP....ALSO IT WILL MOST LIKELY REMOVE A LITTLE OR ALL OF ANY LOOS STUFF AC***ULATED IN A TANK THAT CO2 OR DRY ICE OR EXHAUST WILL LEAVE BEHIND-right? AFTER I DO A TANK THIS WAY I CLEAN THE REMAINING WATER OUT WITH WHAT ELSE-...........GASOLENE........
Jethro, I tried burning one out once and it split it at the seams, no biggy I had to weld it anyway. I was at an old wrecking yard once and this nimrod was going to cut some very old tanks up. I'm not sure why, the boss/owner ran out just as he hit the first tank in the pile with the torch. launched him like a cannon guy at the circus. Very impressive. He didn't get fired because the boss said someone had to watch out for him. OH something I ment to throw out there, we used to solder motorcycle tanks etc when they didn't have much of a leak. Used an old heat in on the fire type of soldering iron and soft solder. Worked like a champ and you didn't have to do anything special with the tank, never got hot enough to make any difference.
Gas can hang around a long time. When I was building my headers, I used bits and pieces from several sets of used headers. As I was welding (using a henrob), the pipes were almost constantly barking at me.
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