There is a leak in the gas tank of my truck. I asked my neighbor where I could by a new one.
He told me to take the gas tank off, turn it upside down and run a hose from a car exhaust into the tank for fifteen minutes or so. That would chase out all of the ogygen, and it would be safe to weld the gas tank even if there was still gas in it.
I told him he was insane.
He said he’s done it himself and it’s perfectly safe.
I told him that if you tried Russian Roulette once without blowing your head off that didn’t mean that it was safe, it just meant you were an idiot.
He got upset and said that mechanics do it this way all the time. I said no way, they clean and empty the tank thoroughly.
I don’t know how safe your neighbor’s suggestion is (doesn’t sound too safe to me), but, if I was to weld a gas tank, I would empty the gas, then fill it with water (to drive out the vapors), empty it again, and begin the welding.
Definitely do not just empty the gas without filling it with water afterwards, that will just leave all the vapors waiting for a spark. Your neighbor’s suggestion is probably safer than doing that!
I repaired mine one time. I soldered it.
First I removed it and then emptied it.
Next I filled it with water.
Next I turned it over and let a small amount of water out, just enough to make a small air pocket where I was to solder.
Then I soldered it.
Worked great.
I do not recommend this to anyone but it is just my experience.
I have often heard of welding a gas tank while it is full…It is supposedly far safer to weld on it while it completely full rather than when it is only partially full.
You won’t catch me doing it either way.
it is probally better totally full - but there is still air at the top. the filler pipe comes down a little preventing you from filling it all the way. during the gas crisis, people could get their tanks expanded to hold more - what the shops did was to saw off that section of pipe.
also if the tank is soild (except for the leak) I would suggest trying 2 part epoxy made to repair gas tanks (any good auto store should have it). I have used it and it lasted more then 5 yrs (it outlasted the car too).
Go to a auto parts shop, ask for the most experienced mechanic present, pateiently explain your question, then allow him to pick out a new tank for you.
Here is the procedure I have seen professional welders use and I have done this myself and lived write about it:
Empty gasoline from tank. (Keep in mind, the most eplosive gas/air mixture occurs sometime between when the inside of the tank is damp with gasoline [when the tank is filled with pure gas vapor] and when all the gas has evaporated and the vapors have left the tank so I wouldn’t hold a tank that I had just emptied the gasoline from up to a hot exhaust pipe.)
Fill with water.
Empty water from tank.
Hold over exhaust pipe to displace air with oxygen-poor exhaust fumes.
It is true that welding a gas tank when it’s full of gasoline is actually safe. Fumes in a closed tank containing liquid gasoline are too rich to ignite. If the crack is on the bottom, you may have to tear the hole larger so that you can put the gas cap on, turn the tank upside down and fill it with gasoline through the hole. -And that’s no big deal because you have to use a large patch anyway, you can’t just lay a bead down even if it’s just a little crack. More trouble than it’s worth, usually, but it won’t explode. - MC
The reason the full tank is safer than the partially filled one is that liquid gasoline–though flammable–does not ignite as easily as one might think. The vapours, however, are incredibly easy to light and are (much) more abundant in the partially filled tank (more air to be filled).
My uncle, a commercial plumber, familiar with all facets of welding (including underwater - MUF diver) tried this. He took all the precautions listed above and exploded the tank and nearly himself. I also refer you to mealypotatoes post.
My father was a professional welder. I’ve watched him do it before, so I know it works fine. The tank MUST be full, 100% with gasoline and welded as cold as possible.
Although one thinks that Gasoline is flammable, it isn’t(well, it’s mildly flammable). The fumes are nearly explosive, and that’s why the fuller the tank, the safer the weld.
It freaked me out when I watched the old man weld it, but we all made it through just fine
I’ve heard the old stories about how you can extinguish a match in pool of gas, if you could only move the match fast enough to immerse it in the fuel before the fumes mixed with fire. It makes sense because you two things to start a fire… fuel and oxygen.
Now on to the point I intended to make… I know someone who was going to cut a 55 gallon with a torch. (High School Vo-Ag {FFA} class) He filled the drum with water, emptied it, and began cutting it… KABLOOIE! He was in a wheel chair for over a year.
My opinion… it’s just not that difficult to go to a salvage yard and pull a gas tank out of a trashed auto.
My uncle was changing his oil while smoking once, and I was like, uh… that’s pretty dumb, Tim (I’m named after him) and he took his smoke out and dipped it in the oil and said “A cigarette’s not hot enough to catch up oil.”
A guy I work with, Mark, says that when he was younger, he used to work at a gas station. One day the tanker rolled in and the driver started filling the underground storage tanks. Mark noticed the driver is smoking. Thinking this might be just a temporary brain fart, Mark walked out and told the driver, “Hey! Do you realize you’re smoking?”
The driver, reports Mark, “got a wild look in his eye,” slowly took the cig out of his mouth, and flicked it into the underground gasoline tank.
Now I know that there’s only a narrow range of concentration of gasoline vapor that will ignite, so the air near the driver’s mouth doesn’t contain enough gasoline to explode, and the air near the surface of the liquid gas contains too much gasoline to ignite. But it seems like somewhere in between, the concentration is just right, and the cigarette must’ve passed through that space on its way into the tank. Seems like a cigarette’s hot enough to “catch up” gas.
There’s a shop around here that will repair gas tanks. They drain the tank and fill it with inert gas. The process is pricey, and often more expensive than buying a junkyard tank. A local fire truck factory was extensively burned when an employee brought his own car into the shop to weld on a trailer hitch. The gas tank blew up.
The method I used was safe, at least it did not catch fire or explode.
When I was younger I took the gas tank off my 60 pontiac catalina convertible and soldered it using the method I explained.
Many years later I watched a professional welder weld a cap on a fuel tank while there was fuel in it. This tank was 15 feet in diamater and 30 feet high. Boy that was exciting when it caught fire. It took three fire extinguishers to put it out.
nuf said.
