Welding propane tanks

[Haywire Haywood]

I've heard that propane will penetrate the metal of a propane tank and leech out over time. How bad is it to weld on a propane tank that has been open and purged of propane? I'm thinking about using a 100lb bottle for a hydraulic tank and explosions are not a desired effect.

Ian

 

[Richard_]

fill it with water , that should help

 

[slinger]

My dad always ran his truck exhaust gas through a flex pipe and into gasoline storage tanks he welded.

Don't know if it would work w/ propane.

 

[J.Gordon]

Both above post will work, remove the oxygen and nothing will burn.

 

[husky455rancher]

id fill it with water for a while myself. prolly let it sit a couple days then have at it.

the propane smell probly never goes away. i was using an old tank as one of 2extra expasion tanks on my dads big air compressor when i was da'ing my old camaro and my brothers old nova.

 

[injun joe]

well first off are you trained in welding explosive containers? people are certified in this stuff so i would take it to and expert first and have it done rite and live to tell the tale but there are some variables missing like technique, current, what process is being used and other stuff would help. or you can ask the guys at hobartwelding.com they know more about welding in general that its almost sickening.

 

[demographic]

A mate and I made a woodburning stove out of an old LPG bottle, it was to keep his shed warm in winter and I think we made a good job of it, as it was our first attempt its a bit rough and ready and if I were to worn on another I would meke it a lot neater, anyway as described in my write up we just emptied it by letting any gas we could out, filled it with water then emptied it so we were sure it didn't have any gas in it.
This writeup was off another site but its still our work all the same...

Alright its not exactly a tutorial because my phone camera was playing up so its missing some stages...

First of all, we got two empty gas bottles, took the valve off, filled them with water just to make sure they were actually empty.

Cut the tops off both of them making the cut out circle on one bigger than on the other so the bigger cut off top would make a fitted door for the other.

Then we cut a hole in the bottle for the smoke to escape from and put a grate in as well (multifuel) and thats about where the first pics start.
Theres a section of steel girder welded onto the bottom (what was the side) and thats where the ashes fall into a little metal ashtray.

Note, theres still a small hole to cover at what was the bottom of the bottle at this point but will now be tha back, otherwise the smoke will get out at the back of the stove.

You can't really see it in this picture but theres a big section of what was the side been taken out under the grate to allow ash to fall through into the ashtray...

The section of girder that will be the combined top and hotplate after I had attacked it with a gas axe showing the hole that the chimney coller will fit into...

And stove with ashtray and grate removed to show large cutout in gas bottle to allow ash to fall though...

Getting ready to fit it and in the second pic the door is tackwelded into position just to hold it..

Finished stove showing chimney collar, door in place and getting ready to fit it..

 

[demographic]

Ashtray...

Door wide open...

Stoking up...

Fancy a brew?

 

[JONSEREDFAN6069]

nice job, looks good. what kinda heat you getting outa it? looks kinda close to the wall, what are you using to shield the wall from the heat?

 

[demographic]

nice job, looks good. what kinda heat you getting outa it? looks kinda close to the wall, what are you using to shield the wall from the heat?

I don't have exact figures for what heat it chucked out and we don't have problems with EPA over here either, it really warmed the shed well all the same.
You can't really see it on the pictures but it was abouta foot to 16 inches between the stove and wall so it wasn't hard putting something in there.

We just leant a section of metal against the wall to protect it from radiant heat but since his cheapo compressor caught fire (the woodburner wasn't even burning that day, before anyone asks) and burnt his garage to the ground along with the three motorbikes in it, we have had to re-build the garage anyway.

As yet, we haven't put the stove back in to his far nicer and better insulated new shed yet.


When we do I suspect we will use Masterboard behind the stove though, the first time the stove was fitted was pretty much just a trial and I planned on making a stove with better air controls anyway.

The next one will have a damper in the stovepipe and a butterfly valve in an inlet pipe to controll the inlet, instead of just opening up the ash tray to allow more air in which I was never that keen on.

 

[uglydukwling]

I wouldn't do this to a tank that was going to be a pressure vessel again, but for a stove, planter, or any sort of decorative stuff, burning guarantees that there's no propane left. I just take out the fittings and let it sit a while. Then, the next time I burn a brush pile, I bury the tank in the pile, light it and walk away. Harder to do if you live in town, though.
I've made chimney cap/spark arrestors out of 20# tanks, pots to hang over the fire pit out of larger ones, etc. The scrap guy won't take them, so I might as well find something useful to do with them.

 

[Rookie1]

I work for a city and get them in the garbage al the time. I drain them take out the valve run water through them,let them sit a few days them cut in half with a torch. That smell never seems to go away but I guess the actual flamable propane does. Never had an issue yet. Knock on wood.

 

[powerstroke73L]

I work for a city and get them in the garbage al the time. I drain them take out the valve run water through them,let them sit a few days them cut in half with a torch. That smell never seems to go away but I guess the actual flamable propane does. Never had an issue yet. Knock on wood.

The stuff you smell is mercaptan. It's a chemical that is added to propane and natural gas so that leaks can be detected. Natural gas and propane are completely odorless otherwise. It's not flammable or otherwise harmful, but it will stick around long after all of the gas is gone. You have to remember that gases like propane boil off at temperatures WAY below room temperature, so once the container is depressurized every last trace of the gas leaves the container and escapes to the atmosphere. There's no issue with welding or drilling/cutting propane tanks. GASOLINE tanks and the like are a different story. The problem with gasoline is that it since it's a liquid it will hang around, get caught in seams and crevices and form varnishes and flammable gunk. Those tanks need to be steam cleaned/completely filled with water to be safely welded on.

 

[Rookie1]

The stuff you smell is mercaptan. It's a chemical that is added to propane and natural gas so that leaks can be detected. Natural gas and propane are completely odorless otherwise. It's not flammable or otherwise harmful, but it will stick around long after all of the gas is gone. You have to remember that gases like propane boil off at temperatures WAY below room temperature, so once the container is depressurized every last trace of the gas leaves the container and escapes to the atmosphere. There's no issue with welding or drilling/cutting propane tanks. GASOLINE tanks and the like are a different story. The problem with gasoline is that it since it's a liquid it will hang around, get caught in seams and crevices and form varnishes and flammable gunk. Those tanks need to be steam cleaned/completely filled with water to be safely welded on.

Very intelligent post. Thanks for the facts. Rep coming your way.

 

[Haywire Haywood]

How thick are those 100lb tanks? Structurally sound enough to weld a couple torsion axles to and use for the main cross beam on a splitter similar to the square tube they use on box store splitters?

Ian

 

[Crofter]

Water doesnt dissolve hydro carbons so doesnt accomplish much. I have used the exhaust of a gas engine as a continuous purge to weld on gas tanks and Fuel tanks. It is not recommended as being explosion proof because it still contains enough oxygen to provide an explosive mixture with certain fuels.

As one poster mentioned propane doesnt stay liquid once the tank is opened and if you run an air hose through for ten minutes or so there will not be any left for sure. That is the method I use. Again there is a catch that makes it not recommended and that is that liquid fuel can get trapped in mechanically lapped and welded seems and be released when you heat and cut on it; that was more possible in older style tanks. That would be a very long shot scenario and you can eyeball your way around that. Once you have it opened up a bit you are clear. The idea of putting it through a fire is a good one but best not have an audience! Make sure the valve is out first and light the fire with a long stemmed match!

Taking it to a place certified with sniffers and inert gas is pretty much out of
the question price wise.

I think Ian will come up with a way that will keep his name out of the obituary column!

 

[Haywire Haywood]

At work, they purge small crash worthy fuel tanks (Jet A or JP-5) before working on them by just taking the end off an air hose and putting it in the tank for a constant flow of air.. they let them go all day like that. This is liquid however and they don't weld on them seeing as they are a rubber bladder.

A little research tells me that propane tanks are generally only 4 or 5mm thick. Might not work for what I want from a structural standpoint.

Ian

 

[Rookie1]

What do you want to do with the tank Haywood. I believe it Is plenty strong for fabbing.

 

[Haywire Haywood]

It would make up the axle/tank of the splitter I'm putting together with torsion units welded onto the ends for wheels. The tongue would be welded to it as well as the engine mounts.

It being round would complicate matters anyway. I called a welding supply place looking for some 10 or 12" square tube so I could have a 15-20 gallon reservoir and they said that when you get into tube that large, it's hard to find something that doesn't have 3/8 or thicker walls. I was wanting something in the 3/16" range.

I might get some smaller square tube for the axle and use the propane tank in a non-structural way for a reservoir.

Ian

 

[Rookie1]

Ok I see what your saying. I like the idea of an integral part but you may be right about not being strong enough.