The only thing I ever had explode on me in my years is after doing the electric in my home garage, the building inspector demanded the light switch wires be placed in conduit, and not just lining the wall. (the wall was going to be covered, but it wasnt at that point.)   Anyhow, I bought a different box and some gray conduit and installed it.  I do not remember how much time had passed, less than 30 minutes, I turned on the circuit, hit the light switch and POOF, you could hear it go out the top of the 4 footish tube.   Apparently, the electric sparked the glue fumes.   Didnt think much about it then, I guess it could have exploded the tube and took my face off, thinking about it now.  

Do the obvious drain the gas, then fill it with water and drain that out. Then you need a air hose with a small amount off air coming out stick it in the gas tank.  Make sure before you continue that there isn't any strong fumes in the tank. Then you can proceed with welding or brazing. Brazing would be even better as if the tank is rusty or not the brazing doesn't need to heat up as much. It only takes 900 degrees to liquify and then uses capillary action to get into the poors of the gas tank so will will create an all around better sealing solution to fixing a gas tank.  Plus the brazing won't rust. If you were to GMA MIG weld the tank that starts to oxidize and rust not long after depending apon the electrode wire being used.

It's a shame for someone to lose their life over something like this. With proper training and equipment, this could have been avoided.

You need a spark, fuel to burn, and oxygen to go kaboom. If your going to weld on something that contained a flammable product, get rid of the oxygen. A nitrogen purge into the drum in a well ventilated area is an accepted practice. Using car exhaust for the purging gas was mentioned on the forum at one point, which I think is not a bad idea either.

Some products leach into the walls of the container they are stored in, when the container is emptied, the walls will off gas the product and fill it with fumes.

I don't like the idea of air hoses from a compressor or filling with water, there are safer, better ways.

True74yamaha wrote:

Do the obvious drain the gas, then fill it with water and drain that out. Then you need a air hose with a small amount off air coming out stick it in the gas tank.  Make sure before you continue that there isn't any strong fumes in the tank. Then you can proceed with welding or brazing. Brazing would be even better as if the tank is rusty or not the brazing doesn't need to heat up as much. It only takes 900 degrees to liquify and then uses capillary action to get into the poors of the gas tank so will will create an all around better sealing solution to fixing a gas tank.  Plus the brazing won't rust. If you were to GMA MIG weld the tank that starts to oxidize and rust not long after depending apon the electrode wire being used.

 
I don't know who told you to purge a gas tank with a small flow of air, but it sounds like they were trying to get you to blow yourself up. When I was working as a Process Engineer in chemical plants, it was often necessary to weld on vessels that held hydrocarbons. I spent a lot of time working with Safety, Operations, and Maintenance getting those vessels into condition to weld on. If the vessel was clean, then a good wash to get the hydrocarbons out might be sufficient. If the vessel had any buildup, which was common in our business, the vessel would have to be thoroughly cleaned, which usually meant hydro blasting to get down to bare metal. A factory original gas tank on one of our vintage Mustangs usually has enough "varnish" to fall into this category.  If we were going to weld on the outside of a vessel, it was usually adequate to create an inert atmosphere in the vessel by filling with nitrogen and testing the gas in the vessel for oxygen content and Lower Explosive Limit. If there was a reason we could not inert the vessel and keep it closed, such as adding a nozzle, the vessel had to be cleaned and tested with the LEL meter to verify that it was hydrocarbon free. In addition to that, we usually set up high volume air movers to move massive quantities of air through the vessel to dilute any remaining pockets of hydrocarbons (it happens). Even with all this we would run continuous LEL readings, monitored by Safety personnel, who were authorized to shut down the welding at any time for any reason they thought could constitute a hazard. Operations contributed fire watch personnel equipped with fire extinguisher, fire hose, or whatever was appropriate for that job. The Fire Watch could also shut down the job.

Since I have seen this subject from both sides, hobbiest and professional, my recommendation is: if you have a gas tank that needs welding, find a shop that advertises "we weld gas tanks", give them your tank with instructions of what you need, then leave. Wait for them to call you to pick up your repaired / modified tank.

I have been welding for thirty years; I have MIG, TIG, stick, and OA. There is no chance that I would weld on a gas tank that has been in service for a while. If you have some gee whiz modifications you want to make to the stock tank, follow Mustang Steve's example of buying a new tank to modify. Leak check the modified tank with water before installing.

red351 wrote:

All this and todays my day to light the gas grill..........

Cue the drum roll......
 

57steve wrote:

During high school I worked for an old mech that pretty much did everything to a car that you can imagine.
We had a car come into the shop that had a hole in the tank and fuel was dripping at a pretty good clip. He went down into the pit and said (hand me the the stick welder with one of those little rods and turn it on). I did and promptly left the shop. He buzzed that leak and flames went into the pit. He stomped them out, charged the guy 50 bucks and off he went. The next week he showed me how to weld a gas tank that was out of the car, after we emptied it. He fired up his truck and connected the exhaust pipe to the filler neck of the tank, let the thing pump exhaust through the tank for 20 min and began to weld a crack. I left the building before the welding started.  He had no problems, but I am not going there. Just sayin!!

 
One born every minute. I'm there are others that did not survive such antics. At least you were smart enough to vacate the area.

Sal, hard hat divers stick weld underwater all the time. Maybe welding in gasoline isn't that different. I don't plan on finding out.

6sally6 wrote:

Well......"they say".....you can throw a lighted match in a bucket of gasoline and it will go out. It's the fumes from the gas that's the killer(pun intended) ...
 

I can tell you from personal experience that this is true.  Once when I was younger and dumber (i.e. when I was about 13 and thought I was bulletproof) my friends and I filled a large mason jar with gas and threw a match into it... the gas put the match out.

I'm so glad it did... looking back now I realize how bad it would have been if that glass jar had exploded into us... like I said, I was young and dumb.

gjz30075 wrote:

Pretty risky.  Doesn't the match have to pass through the fumes before reaching the liquid?  Just sayin....

I'm sorry to report that I did the same thing with a can of gas that I was using as parts wash....way, way, back in the day, only I did it with a cig.  Cool evening, no vapors, no woosh.  Cig got snuffed.

DUMMMMMMMMMMMMMMMMMMMMMMMMMMMB!!

BB
 

Last edited by Bullet Bob (6/01/2016 7:37 PM)

Michael H. wrote:

gjz30075 wrote:

Pretty risky.  Doesn't the match have to pass through the fumes before reaching the liquid?  Just sayin....

That's what I would've expected too. And I'm definitely not recommending that anyone try it.  I'm just saying that when I did it the gas put the match out... and Bullet Bob had the same experience except with a cigarette.

Huuuummmmmmmmmmmm....wonder what a bunch of Mississippi  good old boys wuz do'in with mason jars full of gasoline?!!!!
Ohhh never mind.....younger generation!
6sally6