Welding on storage tanks

[JayDogg]

A buddy of mine who does alot of welding told me he was a little skeptical on doing any welding on any refurbished propane tanks. He said that the fumes can be contained in the steel inside the tank and performing any welding he said could cause an explosion. Has anyone ever run into this issue? I know alot of you guys have dont welding on the propane tanks to accomplish making your own storage. Should he be worried about this? If the tank is flushed with bleach and water for a few cycles, wont the gas vapors and smell be gone? Any help would be great.

 

[DaveBP]

If you are at all uncertain about how much propane is in the tanks fill them with water.

Have them fairly level with one of the big fittings at the very top. This would be a good time to put out that cigarette and try not to strike a spark with a hammer by banging on any reluctant fittings.

Open that fitting (often the gauge is biggest, might as well get that out of there) and fill it completely with water. Put a jug of bleach in there if you want to reduce the smell. Let it sit a day and then drain it. It will probably still smell a bit but hopefully not nauseating.

Pretty common to hear the concern that propane can still come from the "pores" of the steel and explode. And a lot of folks don't realize that the smell is due to a chemical that is added to the propane to warn of a leak because propane has no smell itself. That smell can persist long after ALL the propane is gone. And once the propane is gone it won't come oozing out of the tank walls. It can be hard to convince the superstitious.

 

[timberr]

That's what I did with my 500 gal. tank and no earth shattering kaboom happened.

Good luck

 

[chuck172]

The propane tank can explode. Don't listen to anyone that says it's safe, do it. Go to a good welding forum. Ask there. You will hear stories that will scare the piss out of you. Be careful.

 

[JustWood]

Flame thrower maybe . Explosion doubtful. Not sayin it absoluteLEE won't. Some friends and I have experimented with quarter stiks of TNT. Duct tape a quarter to the brass valve , cracked the valve, walk 2 hundred yds away and shoot quarter stick with 30-06. Blown the valve off and had a flame thrower but never an explosion other than TNT.
I think the only way a tank wood explode is if it were in a fire and built extreme pressure, valve closed and the entire tank were red hot . They make em with brass valves so the valve melts in a fire and the tank just flames off. I realLEE doubt there wood be a problem welding one if empty and valve removed. Filled with water I see no possible way for a fire or explosion unless maybe the tank were double wall.
Local guy here welds fuel tanks and pumps air into a dried tank for a few minutes before and during welding.

 

[chuck172]

O.K JayDogg, all the experts say "go ahead and weld it, it probably won't explode". Well, if you flush it out and weld it while full of water it probably "probably" won't explode and you probably wont get killed.
I've been a steamfitter/pipe welder for the past 35 years and I've welded on tanks before. The proper way is to have someone who knows what they are doing do a "sniff test" on the tank for combustable gas. Prior to that the tank should be flushed and purged with an inert gas, like nitrogen.
It's the empty tanks that explode.
Best thing to do is farm the job out.

 

[JustWood]

Filled with water I don't know how an explosion could happen. Buuuuuutttt! Read some of these reports before welding. I've weld patched alot of large 1000 gal+ steel diesel tanks with no booms and I'll continue.
http://ncsp.tamu.edu/reports/CCOHS/ccohsListb.htm

 

[Elderthewelder]

you need to treat any container that has contained a flammable with extreme care and caution prior to doing any hot work on them, as a bear minimum open up all the vents/bungs/caps and let air out, if you happen to have a air compressor, hook up a air nozzle, tape the handle down so it will always blow air and stuff it inside the tank for a day or so or longer if you neighbors dont complain about the noise, also if you have a pressure washer do the same thing with it as with the air, or take it to a car wash. you can never be carefull enough with welding around these things

 

[DaveBP]

Here it is after midnight and I just now got home from a crappy evening of trying to hack my way through bad job documentation on (of all things) parts for robotic welding equipment so I'm just a wee bit grumpy. I try not to post when I'm in a pissy mood but I just can't let this go as the thread has progressed.

There are a lot of weird flammables out there that might have been in a tank. Especially those that are liquid at normal temps and pressures are very hazardous. Nitrogen purging and all that is probably a good idea for some of those things. Particularly when you're not sure what was in there and what has been done since.

However, except for some parts of Antarctica in the winter maybe, unpressurized propane is always a gas. It's very flammable but not explosive unless it's mixed with air. When you have a propane tank that you don't know for absolute certain has all the propane removed you have to remove it yourself or risk the horror stories you heat about. Opening the ports and letting the gas drain out or blowing it out with compressed air will create a mix of propane and air inside the tank for a while until the percentage of propane to air is too dilute to explode. How long is that time? I don't know. Strike a spark and see if the required time has passed. Putting air into a tank filled with propane gas DOES create a bomb for an unknown amount of time. You feeling lucky today?

Filling the tank with water gets ALL the gas out as fast as your garden hose can move water. When the tank is full of water there is no more propane to worry about. The propane dealer I got my tanks from fills tanks he's sending to scrap with water and pumps the water out and cuts a big hole in it with a torch before all the water is out of it. When I got mine home (he didn't cut them) I plumbed a fan into them with 1" PVC pipe and ran air through them for about a month sitting in the hot sun during August. No more smell.

Thanks for letting me vent. Stay safe.

 

[MarkJ]

Jeeze I'd like to just find a decent used 500 gal tank. For some reason I just can't seem to get my hands on one.

 

[RobC]

There a bunch of "how to weld" threads from before..... Here's a good one....
https://www.hearth.com/econtent/index.php/forums/viewthread/23046/

 

[snowman49820]

My dad has been welding automotive gas tanks for years, some with small amounts of gas. He just pipes in the exhaust from his JD110 lawn mower. Years ago I had a bunch of guys over from school, you would of thought they just seen a giant grizzly bear.

 

[chuck172]

There is heck of a lot of unburned fuel in engine exhaust and all it takes is the right mix of air in that exhaust to create an explosion even if the tank was otherwise free of fumes.
Don't do it!!