The Stovebolt Site Forums The Shop Area General Truck Talk Gas tank removal - safety question

Hi All,

Searched this but didn't find anything specific to my question, so here goes. I'm getting ready to pull the gas tank out of my '51 GMC 100 to get it hot tanked. I've gotten everything out of the way, ready to drain the bit of gas that's in it. Seems to me that the empty gas tank will be pretty dangerous since it's still full of fumes. What's the safest way to handle this thing? One spark in the wrong place and BOOM! Advice? Also wasn't sure where to post this, but it'll get moved to the right place, I'm sure.

Thanks,

David B

The empty gas tank will be OK - just keep sparks and open flame away from it. After draining out all the fuel, remove it from the truck. Let it air out for a few days to get rid of any excess fumes.

David,

There is a pretty specific ratio of fuel (fumes) and oxygen required to result in an explosion, so I don't think things are quite as dangerous as they seem.

If you are going to have the gas tank cooked anyway, why not fill it with water after you drain it to purge most of the remaining fumes.

I went to a seminar put on by Standard Oil years ago where we tried to ignite a fuel/air mixture in a special chamber using static electricity as the ignition source...it was pretty difficult to do unless that ration was right on the money.

Stuart

A tank is actually safer with a few ounces of gas in it than one that's been sitting empty for awhile. The gas fumes will purge the air out of the tank, and the resulting too-rich mixture can't possibly burn due to lack of oxygen. If you want to be absolutely sure there's no possibility of a burn, stick a piece of garden hose into the tailpipe of another vehicle, put the other end into the empty tank, and fill it with exhaust gas. I've done repairs on leaky fuel tanks with a torch and a brass rod after filling the tank with exhaust fumes. All the oxygen gets displaced by the exhaust gas, which is mostly CO2 and water vapor.
Jerry

I work as an environmental manager & I generally remove about 50 tanks a year. These are the large 10 to 20,000 gallon variety. We pull gas, diesel, motor oil & waste oil.

You can reduce the vapors in two ways. Allow the tank to sit, fully vented in the sun for a few weeks or wash it with strong detergent & water (see below)

The goal of either method is to get to less than 25% of the lower explosive limit of gasoline. Your local fire department may be able to measure this for you using an explosimeter.

You can clean you tank with a 4 : 1 mixture of water & Simple Green or similar product. This will break down the gasoline, reduce the fumes & allow you to flush out the tank. The rinse water is technically considered hazardous waste because it will contain traces of benzene. You should dispose of the waste in accordance with local, state & federal law.

Thanks all for the good advice. I feel much better about diving in on this now. This site is a terrific resource.

David B

that is an old trick but very dangerous. if you are doing repairs on the tank, if there are any unburnt gasses in the exhaust you are creating a deadly situation. in this case it would be ok but they are no more dangerous than a gas can for your mower. if you need to do repairs on a tank the safest way is to keep a supply of Co2 or argon in the tank

i think the main thing stay calm while you are removing it. i usually like to have a cigarrette while i'm doing it so i don't get nervous. hr

Got everything apart except getting the tank itself out of the truck. I'll do that 1st thing in the morning.

I think I've learned a valuable lesson here. Now that I can really see how full of varnish and debris the tank is I realize that I wasn't smart to run the truck with the uncleaned tank on it. Fortunately I only ran it a little bit after I had rinsed and drained the tank with fresh gas and had a fresh fuel filter on before the fuel pump. That filter picked up a lot of junk just in the short amount of run time the truck got. Of course it couldn't trap varnish. The brass shut off valve on the bottom of the tank was nearly stopped up with all the crap in it. It came apart and cleaned up fine, but if it's this nasty the tank's got to be as bad or worse.

Anyhow, tank comes off and goes to get hottanked and tested tomorrow. Carb is off to Larry Isgro for a rebuild - beautiful work I've seen from that guy. Hoping to get it all back together in the next week to 10 days. Thanks again for all the suggestions.

Now if I could just find that pack of smokes... Oh yeah, I left them by the gas tank...

David Bush

here is what i did to prevent large debris from entering into my tank
http://s67.photobucket.com/albums/h298/1951otter/?action=view&current=582585-R1-048-22A-1.jpg
i now have an under bed tank.

Don't you guys remember Fire Marshal Bill coming to your grade school with a mason jar, with gas in it. He empties it, washes it with soap and water, dries it and holds a match over it, swoooooosh!!! pop! "Still some fumes in there" he says. Just keep it away from sparks and fire and don't ever trust it. Clean it your self or have it vatted. I know you didn't say you were going to do any repairs, so don't do any repairs. The junk yards are full of old tanks (at least the ones out in the country) and they don't blow up. Don't put anything in it, just get it tanked. When I get out of the burn unit here, I'll write some more.

David,

Just a thought...if a new tank is available for your particular rig, how does that price compare to a boil out and possible repair to your old tank.

Stuart

Pretty neat. What type of thread sealer are you using on a fuel line where you're putting the pipe joints?

David Bush

Getting it hot tanked will cost about $75 if it doesn't need repair. New tank is about $200. Got the old tank out this AM and it looks surprisingly good (compared to the rest of the truck), but it's FULL of nasty looking crap.

David B

If you are looking at a new tank, you might want to do a search for posts on the subject. It seems that they come with a fitting that is difficult to match and also sometimes cross threaded.

Remove the tank and fittings. Blow compressed air through the small port on the bottom for a few minutes or until you notice the smell dieing off.

If you're nervous about that, plug the bottom fitting and fill the tank with water, then drain. NOTHING will ignite after that.

Technically speaking, blowing compressed air through any fuel tank will, at some point, bring the fuel/air ratio into the 'scary' zone and is the wrong approach...as near as I recall.

As was mentioned earlier, a fuel rich environment is relatively safe as is a oxygen rich one, but if you start to mix it up with compressed air, or air movement, you will at some point hit the magic ratio and it could be barbecue time.

Stuart

i've seen PG&E GAS Co. welders, stick weld directly on a 175 PSI gas main and NADA
stu's right... if you're scared about anything and you're going to get it hot tanked and or welded

FILL IT w/ WATER
as far as new tanks go....
It seems that they come with a fitting that is difficult to match and also sometimes cross threaded. I remember this too.......
weld i new steel 1/8'' sheet or donut on the bottom and retap your own NPT thread hole

Done deal. Tank's at the radiator shop that's going to hottank it. Local outfit that's family owned and run. I think it's going to be usable so no new tank, I hope. Should know by Monday.

David B