Welding a Tidy Tank.

[Swamp Donkey]

I have a tidy tank or slip tank that I use for my farm diesel. The tank has a little crack around the hole where I put the hand pump. I am assuming everyone knows what kind of tank I am talking about. If I weld it up with my lincon arc welder am I going to blow myself up? Keep in mind I am a half crazy farmer who is a tightwad.

 

[illflem]

Fill it with water and it won't blow up. Only problem is you have to take the diesel out to add the water that you will have to take out also.

 

[fest3er]

Originally posted by Swamp Donkey
I have a tidy tank or slip tank that I use for my farm diesel. The tank has a little crack around the hole where I put the hand pump. I am assuming everyone knows what kind of tank I am talking about. If I weld it up with my lincon arc welder am I going to blow myself up? Keep in mind I am a half crazy farmer who is a tightwad.

If you run a constant stream of high-volume air into and back out of the tank whilst welding (and after 'til it's cooled) you should be OK. To be on the safer side, you could use CO2 or Nitrogen.

Diesel evaporates slower than gasoline. So if you flush the air in the tank, and the welding only takes a moment or three, you should be OK. Otherwise, change the air in the tank with a plain CO2 fire extinguisher (gas only). If that ain't cheap enough, idle a gasoline motor and run the exhaust into the tank; that should be mostly CO2 and water vapor.

Let us know what you decide so we can tell a properly embellished story to the BD when he's old enough to enjoy such stories.

Fest3er

 

[daveshoe]

welding tank

I had a tank welded that was gasoline 30 years ago [ I'm sure no one would do it today] The guy who did it was hurt in a fire later ,so what does that tell you ?

The way he did it was to fill the tank with water . It was up yo me to remove the water -- almost impossible from a baffeled tank. The way I did it was to place a Knipco heater a sufficient distance to heat the tank hot to the touch . I placed a vacuum cleaner hose in the tank and blew exaust from the vacuum cleaner into the tank to dissapate the fumes . when the steam stopped coming , it was done

NOTE It was wintertime so the steam was probably only 90 degrees or so. You certainly don't want to heat it hot enough to produce steam in the summertime!!

READ THE SECOND SENTENCE OF THE POST AGAIN!!!

 

[Swamp Donkey]

Some more info... ... ... . The tank has been empty all winter. I do not think there are many light end hydrocarbons in there... ... ..... Hey just had another thought. I work in the oil and gas field and have access to an LEL detector. Lower Explosive Limit. This should tell me what I need to know. But any other ideas are stil welcome. Water is sounding good though. So is the gasoline exhaust trick... . Keep em coming.

 

[Steve Graham]

Another method is to fill the tank with dry ice. Let it sit for a while so it fills with CO2 and then weld. I just take the line off of my CO2 tank that goes to my beer keg and use that. That way I can't have any beer untill the weldings done.



Steve

 

[Whitmore]

Another method is to fill the tank with dry ice. Let it sit for a while so it fills with CO2 and then weld

I second this method it works well and by all means get the oxygen out and you will be safe

 

[David Oxland]

Swamp Donkey



Inert gas is certainly feasable. Tankers (ship) use boiler exhaust. Or buy some other kind of inert gas.



Also know of tanks being welded when full of diesel. As long as there isn't too much head pushing fuel out the crack. Seems an unconfortable idea but it's certainly better than being empty and not made gas free. . There was an operater near here who had an old, long unused, fuel tank; about 5000 gal. Paid a kid to cut it up for scrap. Killed the fellow. Hydrocarbons can keep perking out of sludge or old porosities for a long time.



David

 

[JTMcCracken]

Swamp Donkey, the proper way to do it is: purge the tank with argon, putting the argon in the bottom as it is heavier than air, and venting it out the top, preferably on the opposite end. Do it slow so you can gently displace the air with a slowly rising blanket of inert gas, to much pressure stirs the gasses together and takes longer. Purge with 6 to 10 times the volumn of the vessel, your top vent hole should be taped up with duct tape, just poke a hole in the tape with your pocket knife. Now buff the area clean with a wire wheel and weld away. The half crazy tightwad farmer way is to clean it up a bit and apply JB Weld. If you do fill it with fuel, try to be sure your working on sound metal, if it's thin and corroded you might just burn a larger hole and put your fuel on the ground. Have fun JTMcC.

 

[BigYellowIron]

Just run you a hose from your exaust pipe on your truck into the tank and let it run in there for a while, Then weld it up with the exaust still running in to it.



I have seen and done many fuel tanks like this and never seen one blow.





Adam

 

[Doc Tinker]

Another effective non-welding option is a fuel tank repair kit. Your NAPA store should have them. I get them at an independant parts store.



The kit includes a package of epoxy, sandpaper, soap (to seal the crack if fuel is dripping out) a brush and a strip of fiberglass fabric (for reinforcement). I've repaired fuel tanks on school buses that have held up for several years and passed the rigid state inspections.



I would say that your crack was cause by stress from the weight of the pump head trying to bounce around on the tank, so the above repair suggestion probably wouldn't be better than welding it. Just thought I'd mention it



BigYellowIron's suggestion works, but it's risky on gasoline tanks because you never know how long to let the exhaust flow thru the tank. We used to do that at the radiator shop until a tank blew after we thought it would be safe. The fuel tank flew across the shop and bounced off the wall. Fortunately no-one was hurt. The safest way we found to remove all vapors was by submerging the fuel tank in the radiator boil-out tank (a big tank of heated caustic acid) some fuel tanks were a pain to pull out of the boil-out tank, which stood five feet tall, while allowing the acid to drain back into the boil-out tank. All of this was 30 years ago, so I'm sure technology has come up with safer products that I'm not aware of. Maybe now they have pills that you drop in the tank to make them safe to weld on.



I did weld one diesel tank, not long ago, with fuel still in the tank. I did it with the cap on, but the vent open incase the vapors ignited and wanted to build up pressure. The heat did ignite the vapors in the tank but the burn was slow and it made a woosh sound for a few seconds. I dived out of the way, just in case, but once the oxygen was depleted the fuel didn't burn any more. I don't recommend that you do it this way though, because your results may not be the same and if any of the fuel that has been in the tank were tainted with gasoline, it would be more dangerous. I did this repair on a don't-give-a-dam day.





Doc

 

[fest3er]

Originally posted by Doc Tinker
... I did weld one diesel tank, not long ago, with fuel still in the tank. I did it with the cap on, but the vent open incase the vapors ignited and wanted to build up pressure. The heat did ignite the vapors in the tank but the burn was slow and it made a woosh sound for a few seconds. ...

Well, that's another option. Seal it up except for a vent, and deliberately ignite the fumes. Once burned, it won't burn again.

As to another reply suggesting using diesel exhaust: I thought of that, but decided diesel exhaust can contain too much fuel/oil.

Fest3er

 

[JHansen]

Drag it to the plant with you Donk when you've got a steamer coming out to wash engines or coolers or whatever. Have 'em steam on 'er for an hour or so and check it out with your LEL detector. Personally-even though it's diesel and not gas-I still wouldn't weld on it until you get an LEL reading of 0%.



The blanket gas idea is a pretty good one too. MIG shielding gas should work and be pretty easy to find.



Jason

 

[HGDMARTN]

I know this is somewhat off topic but I wanted to share it anyway. I have a current post about what to do with my 1974 motorhome. The biggest problem I have is with the crud filled gas tanks. Last Fall, I had one of them off to clean up and prepare for re-doing it. First thing I did was empty it and rinse it completely with water twice. Next thing to do was de-rust the outside and paint it. I had a sandblaster going around the outside of the tank. I had the pickups removed and got a little too close and the fumes ignited. Burned the crud out of my right hand and wrist. Tank and me both hit the deck. Scared me more than anything. Needless to say, someone upstairs was looking out for me. I learned a hard lesson that day; I don't fool with fuel tanks anymore. Too much risk. Next time my 8N Ford tank clogs I might just scrap it and buy another.



Be careful!

David

 

[RThompson]

illflem

Fill it with water and it won't blow up.









I've done this with gas and diesel tanks. Put a petcock in the bottom and slowly drain out the water till it gets below the crack by a couple of inches. As you are draining it down stick a torch in the fill pipe and burn down the fumes. Several applications of the torch and you are ready to weld. Keep the tank tipped to maximize water volume. This can be done with small gas tanks but you have to keep the fumes burnt out or they will build up and give you a pucker moment.

 

[Paychk]

When I was a younger man I worked as a fuel tank fabricator and we used CO2 from the MIG welder to displace all of the air in the tank, capped it loosely to keep sparks out and the shield gas in. Then weld away, we even welded tanks that were 1/2 full of gas using this procedure. The way we knew when it was ready for welding was smelling the CO2 coming out of the tank. As was previously stated, the entry point of the gas should be the high point of the tank.



BTW some of the tanks we welded you could hear the gas boiling inside, so don't tightly seal the tank as the build up of heated air or vapors from boiling contents could itself cause a rupture.



*** this is very dangerous and could result in death or injury if done improperly ***

 

[illflem]

John, now that you have several options on welding the tank you might want to consider why it cracked in the first place, probably from pushing the pump back and forth. You might want to weld on some sort of support while you're at it.

 

[Swamp Donkey]

Thanks for the tips guys. Illflem, thanks for the tip. I know it has cracked because of the hand pump, pushing it back and forth. I now have a elecric 12v pump for it so it should not get very much more stress on it. I will let you know how things turn out in a bit...

 

[cap-n-cray]

Argon

In the food processing industry when tig welding Stainless steel pipe, cap one end of the pipe with aluminum foil and pump argon in the other end. Make a small hole in the aluminum foil and make sure there is a positive pressure flow. This make a sanitary weld. The inside looks like the outside, smooth. It also prevents any fire. I have done gas line with this technique.



Cary