View Full Version : Welding SS tank
02-17-2005, 10:27 PM
I have a SS tank that I use to haul Desiel fuel in. It appears that when the tank was made the fabricator ground his weld too much and it has cracked and leaks. I would like to reweld it using TIG with Argon gas. If I fill the tank with water up to near the weld area and fill the space above the water with CO2, will the CO2 gas leaking through the crack affect the weld quality or maybe just tap into the Argon gas? Would it work just to put the gas in the tank and not have any pressure on the tank. I am only talking about 1/2 Lb. of pressure. I have a small bottle of CO2 that I have used for this type of repair on steel tanks but this is the first stainless tank that I have need to repair.
Thanks for any thoughts on this.
Charlie I have a few years experience in the natural gas and crude oil pipeline business. The only way to weld on any metal that contains a flammable is to have all the oxygen completely gone or have only oxygen (AIR not pure oxygen!!!!) in the tank. I am not trying to scare you but I hope I do scare the hell out of you. I had a good classmate of mine blow himself into pieces so that they couldn't find any parts of him. He was an excellent experienced welder welding on a diesel tank on a tractor. It was full of diesel fuel. Unfortunately this was a common practice. it saves time and money. The only way to really safely weld on a tank that has contained flammables is to drain and completely steam the inside out. Then blow it out with dry air. Then take an explosive meter and check the inside of the tank. If you don't have access to an explosive meter then steam it out for a long time until you're absolutely sure there are no vapors left. Even residual vapors that have been absorbed into the metal can cause an explosion. This is what the hot steam is used for.
02-17-2005, 11:05 PM
Got a buddy who welds gas tanks by hooking a exhaust from a running engine up to them, letting them Purge with Non-explosive Non-flammable gas then he welds the heck outa them. If there is no "oxygen" it won't explode. SO he says.
Last Jeep I had (46 dodge panel body on a wagoneer frame), I got that rascal caught on a stump caved in the gas tank, I tried to braze it, blowed all the dents out of it twice. I had it full of water and was trying his method I thought.
Easy way to get hurt if you aren't lucky or careful. Be both.
02-17-2005, 11:18 PM
My buddy runs a welding shop & his best customer is a huge tractor-trailer repair shop across the street. He's welded dozens of diesel tanks by purging with a hose connected to the exhaust of his pickup truck. He leaves the truck runnig for 10-15 minutes before welding, and all during the welding. He has yet to kill himself, however he is still young.
02-17-2005, 11:21 PM
Jim...we've both had the same experience then! A well respected, very experienced weldor around here did the same thing some years ago. That was his "claim to fame". He would weld any tank, anywhere! He got away with it for years until the big bang went off. Killed him instantly. I welded a few myself...with the tank full...that was a standard practice back when. Not anymore! I won't touch a tank anymore without it being steam cleaned and tested.
I've heard that many times: That hasn't happened to me..........yet?
The problem with that type of practice is you can get away with it a hundred times. But it only takes one tiny mistake and it's all over. At the end of my workday I always wanted to go home.
02-18-2005, 12:38 AM
Filling it most of the way with water will reduce the volume of any potential explosive mixture. A cupful of fuel vapors is far less dangerous than a whole tankful.
Not safe, but at least much less dangerous.
If the remaining volume is purged of oxygen, or even purged of enough oxygen to make the mixture too "rich", then the seam can be welded easily and relatively safely.
Any nonflammable gas can be used- CO2, argon, nitrogen, even helium, but that's pretty expensive. Engine exhaust works fine- it's pretty well, er, exhausted of unburnt oxygen.
On stainless, you'd want argon, just like you're back-shielding.
If it were me, I'd fill it about halfway with water, then use a hose off the argon regulator to purge the tank for a while. Then fill the tank the rest of the way, while still letting the argon hose bubble into the water. Pull the hose and cap the tank, keeping a small "bubble" of presumably mostly-argon inside. You'll have to guess how much void to leave so the weld isn't completely underwater.
Then block up the tank so the seam to be welded is uppermost, so the argon bubble floats to the underside of it. Weld as usual.
I agree with the rest- never, never, never weld or cut on anh "empty" tank, 'cause they're never truly empty. But, they can be welded safely, if you take steps to minimize both fuel and oxygen.
02-18-2005, 01:29 AM
Charlie, where is Prospect.,OR? I live in Waldport, OR. I looked on the map and could not find Prospect. Please be careful! (a war story) Back in the days when a buddy and I was attempting to race stockcars. We found an old Hupmobile chassis that had been out in the weather for 50 + years. To make a long story short, when we applied a torch to the gas tank to remove the filler neck from the tank,,, we blew the door off of the shop and ruened our new found gas tank! The moral of the story is: "let someone else weld the tank" Who has the right equipment.
i`m one of those moorons who weld fuel tanks freq. dont really want to, but good customers are hard to find and the work needs to be done so.....first off, unless you have access to a RECENTLY calibrated o2 meter, FORGET about "inerting" the tank. w/out the o2 meter its nothing but an uneducated guess, one that could cost you [or someone close] a life!
[i remember a good friend begging me to turn his buddies 55 gal drum into a BBQ grill for a superbowl party a few yrs ago. he SWORE that the drum was gas free and had been sitting for yrs empty. i refused to put a torch or grinder anywhere near it, but agreed if he would recip saw the drum open,i`d weld on legs,hinges etc. so we head over to said buddies house in my welding rig, turn the corner at his street and see the fire trucks/cops/ambulance.....i got physically sick and stopped the truck and barfed out the window while he ran up to the house to find out what happen`d. apparently the guy found another person with a small oxy/acet unit for AC work, and proceeded to show his 10 yr old son how to work it. the boy was DOA and the father lived for about a week, then died when this supposedly "empty" drum exploded!]
i have access to an o2 meter from the small shipyard i sub repair work from but i dont trust it as it does`nt get calibrated near enough for my taste! if the customer is too cheap to "GAS FREE" the tank, then they can find someone else to weld it! i regularly do the 2000 gal deisel tanks in the fishing vessels here and this is how we gasfree them
open fuel filler/gauge bung whatever
drain/pump tank down to empty
add appropriate amount of dishwashing detergent [i like DAWN tm]
fill with RUSHING water[for lots of soapsuds]
drain tank [again]
now heres the important part~
connect a compressed air hose to a fuel bung/tap or whatever and BLOWDOWN the tank! do this untill you cant smell any fuel in the exhausted air.
remember~ FUMES THAT CONNOT COLLECT/COMPRESS CANNOT EXPLODE!
yes virginia, you can still start a fire inside the tank using this process, especially diesel tanks as theres so much trash/silt in diesel and it collects in corners and can still be set fire, but diesel reqiures a certain amount of heat to support fire, and these are usually handled by a fire hose[spray near and cool the area] the fishing vessels i do come w/out hatches on thier fuel tanks, i have converted nearly every one here [and qiute a few from other ports on the gulf coast] by fabricating/installing hatchways. if theres no hatchway, i will reluctantly sawzall [recip] the initial cut. if there is a hatchway, it gets removed and then i`ll cut the "door" from where i`ll enter the tank [in the bay where the leak is] with a torch [oo tip]as the hatchway allows for fire suppression.....heres a pic of one tank i`v done:
now in the case of a "sealed" tank [only a filler and tap] i would wash the tank out then either weld it with air running through it or blow it down good then purge with argon [maybe tape the filler up with a 3/8" hole and a pc of rubber taped on as a "flapper valve" and weld with argon running through it.
fumes that cannot collect/compress cannot explode...direct qoute from the 1st class shipfitters handbook [circa 1945] newport news shipyard...old tech for sure, but the properties of fire havent changed all that much! supertankers are gasfree`d in much the same way, a number of "butterworth" holes in the deck in which a rotating geared elevation dropping[1 degree for every revoloution] watergun is installed. these are hooked up to a boiler [hot water is preferred] and the tank is then washed down. waterguns are then removed and blowers are installed in the same holes [half blowing/half exhausting] untill the tank is safe....now i`v posted this on more than one forum, from repairing motorcycle tanks to welding forums and it never fails to draw a flame, but this IS how the professionals do it,[the shipyard i sub from does NOTHING but commercial gasfree`ing, my company, and my buddies, do all their fab and repair work.
far better to wash the tank and blow it down, than to trust your car[where a faulty temp sensor can enrich mixture enough to be dagerous] and blow the damn thing up!
02-18-2005, 08:50 PM
Thanks for the replys. As this is the first time that the tank has had fuel in it, my thoughts was to fill the tank part way with water and purge with the CO2 or purge with the argon. Guess I will wait a month untill the weather gets warmer and fire up the boiler and steam out the tank.
Normaly I will not weld on any tank that has had gas or desiel in it. As a child of about eight or nine years old, I had a real eye opener about matches and gasoline. I was not cute with out any hair or eye lashes. I do want to get the tank repaired but believe me what you have said will be kept in mind, as I have not dipped into my retirment enough and I don't want the wife and her boyfriend spending it.
A friend had me weld up a gas tank for his Essex. He needed to check the fit of the tank to the car. I told him that if he put any gas in the tank I would not make any changes on the tank.
Lugnut; Prospect is about half way between Medford and Crater Lake Park on highway 62. Just a wide spot in the road. I worked for PP&L here in the hydro-elect plants untill they made me an offer, 7 years ago, that I could not turn down. The door never hit me in the butt as I went out. http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif http://bbs.homeshopmachinist.net//biggrin.gif
02-19-2005, 12:51 AM
Charlie,is it a large tank?If it is then "drumming" could be the cause of the crack.I have seen it many times,especially in mobile tanks.When the fuel expands and contracts it stresses the welds and they eventually crack.A lack of baffles on a boat tank will do the same quickly when the fuel sloshes back and forth.
When I used to build fuel tanks I never plain welded a corner,I always butted the two sheets into a piece of round bar or pipe.Even better is a trunked corner,45* instead of a 90* All of the tanks used on or near water now are doulde wall with pipe seams,can't spill a drop,even after a collision.
02-19-2005, 07:47 AM
Pay attention to what KLLA says and remember, it's the fume that cause the wxplosion, not the liquid.
02-19-2005, 08:30 AM
The other day a local guy was grinding on a U.P.R.R.new, never had fuel in it, fuel tank to be put on a train car and Boom, killed him and injured others. They say it had a liner in it that was never cured and the grinding caused heat and formed a pocket of gas which blew.This sounds kind of hokie to me .
02-19-2005, 08:05 PM
Weird the tank is only 20X36 inches. I was going to use the tank to haul extra diesel for the truck.
IOWOLF that does sound strange but having started to cut up a warming over for the SS that it was made of I changed my mind after the insulation went poof a couple of time. I was using a plazma cutter and that would get pretty hot.
Any how thanks for the replys fellows. http://bbs.homeshopmachinist.net//smile.gif
02-20-2005, 01:06 PM
Thee ae safer ways to fix this problem - corvette shops sell a material to coat the insides of fuel tanks - this stuff really works well too. It can save a rusted out tank and put it back into service reliably.
I do not know the trade name of the product though...
02-20-2005, 01:09 PM
<font face="Verdana, Arial" size="2">Originally posted by Thrud:
I do not know the trade name of the product though...</font>
POR 15 I think, or it is one of the POR products.
02-20-2005, 10:05 PM
Thanks I had forgot about that stuff. Eastman sells something like that also.