# How to open a propane tank?



## SE18 (Feb 10, 2018)

Someone threw away a somewhat rusty propane tank that I'd like to open and make a propane forge with. It has a screw sort of top, but I'm wondering if unscrew it there will be pressure. I'm thinking to take it out in the field and from 50meters blow a hole in it with my 9mm. Not sure if it will explode. Follow-on question is, is the next step to fill tank with water to ensure all LPG is out then safe to start cutting? I have some fire wool (forget the name of it) to line inside of the tank. Much thanks. I always do safety check on this forum before doing something questionable.


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## magicniner (Feb 10, 2018)

I use a couple as leaf and garden waste burners, I knocked the valves clean off with a big hammer then left them inverted for a few days before cutting the tops off with my plasma cutter, no drama.


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## dlane (Feb 10, 2018)

Open valve to let out pressure ,


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## Grumpy Gator (Feb 10, 2018)

_ Newer style tanks have a spring-loaded safety valve inside the opening that only releases after you attach the regulator.
**G** _


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## Bob Korves (Feb 10, 2018)

dlane said:


> Open valve to let out pressure ,



Turn valve counter clockwise.   

Propane tanks are very dangerous, even after emptying them and letting them sit a while.  Fill it with water before using heat or making sparks on it.


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## vocatexas (Feb 10, 2018)

If you shoot it with a 9 mm it might end up in the same neighborhood as Elon's car...Please record and post to You Tube if this is your method of choice. 

Bleed the pressure off, then remove the valve. Fill with water, empty, fill again. Cut with water IN the tank. That's the way we do it around here.


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## Ray C (Feb 10, 2018)

If you have argon or CO2, flood the tank with either of those two and put a bleeder hose in there while you're cutting.   No oxygen, no boom.   Some people throw a chunk of dry ice in the tank.  When the white gas starts coming out the top, it's filled with CO2 and safe to cut.


Ray


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## magicniner (Feb 10, 2018)

SE18 said:


> I'm thinking to take it out in the field and from 50meters blow a hole in it with my 9mm..



You need at least one friend there so you can say "Hold my beer and watch this!"


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## rwm (Feb 10, 2018)

I have used several of these for furnaces. Here was my method. First attach it to a grill and turn on the valve for a while to make sure there is no pressure in the tank. Then use a large pipe wrench with a cheater bar to unscrew the valve from the tank. These are on really tight. You will need to use a ratchet cargo strap around the tank to hold it to something so it doesn't rotate. I have also heard of people tack welding a flat cheater bar to the metal ring on the bottom of the tank. Just don't get the tank itself too hot! Once you get the valve off, fill it with water using a funnel. It will smell like gas due to the smelly oil they put in the tanks. Then drain the tank for cutting. I used an angle grinder to cut as needed. This technique avoids the 9mm hole which may not be correctly placed depending on your marksmanship!
Robert


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## magicniner (Feb 10, 2018)

If you knock the valve off and leave the cylinder inverted for a week then both gas density and diffusion will do something, if ignorant of these then stick with the recommendation of Elfin's Afety. 
Inert gas flooding is the best and safest way to render the cylinder safe, think exhaust fumes ;-)


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## Billh50 (Feb 10, 2018)

The last time I took the valve off a propane tank, it was still pressurized even after I opened the valve and it stopped releasing gas. When the valve unscrewed the tank shot about 20 ft and then spun around 3 or 4 times till the rest of the gas came out. So be careful.


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## Terrywerm (Feb 10, 2018)

I've used a few over the years for various projects. I always connected them to a BBQ grille to use up the last of the gas, then simply removed the valve. After that, filled it with soapy water, then drained it and cut away.

Rinsing with plain water will still leave some of the oily Mercaptan residue behind (the odor agent in LPG) making you think that there may still be gas in the tank, but filling completely with soapy water and then draining it will get rid of all of the actual propane gas and will fill it with plain old air that still smells like Mercaptan. The soapy water should get rid of most of the oily substance left behind. Cut away after that.


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## SE18 (Feb 10, 2018)

Billh50 said:


> The last time I took the valve off a propane tank, it was still pressurized even after I opened the valve and it stopped releasing gas. When the valve unscrewed the tank shot about 20 ft and then spun around 3 or 4 times till the rest of the gas came out. So be careful.


thanks; that was what I feared


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## RJSakowski (Feb 10, 2018)

If an LP tank has been used for a while, the some of the smelly oil will separate out.  Propane will be dissolved in the oil and outgas slowly.  After bleeding any residual LP by opening the valve, Unscrew the valve slightly.  This will break any seal and allow any residue LP to bleed off.  When it is bled, (soapy water test for leaking gas) it will be safe to completely unscrew the valve.  Once the valve is removed fill with water.  Drain and cut away.


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## Ulma Doctor (Feb 10, 2018)

just as a point of information...and i don't recommend anyone else trying it-

small camp stove propane cylinders did not explode when shot with a .357 mag or .22 caliber. both having lead bullets and low fuel levels in the cylinders- they sure do spin around like a top on steroids though
MYTH BUSTED


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## Terrywerm (Feb 10, 2018)

Ulma Doctor said:


> just as a point of information...and i don't recommend anyone else trying it-
> 
> small camp stove propane cylinders did not explode when shot with a .357 mag or .22 caliber. both having lead bullets and low fuel levels in the cylinders- they sure do spin around like a top on steroids though
> MYTH BUSTED



Yup - both lead and copper are non-sparking materials. Not enough heat created as the bullet punctures and deforms the steel container to cause ignition of the gas, and definitely no spark.  Result: WASTED AMMUNITION!


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## BtoVin83 (Feb 10, 2018)

On the bright side if you mess up the propane can is self opening.


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## FanMan (Feb 10, 2018)

I'm told .22 hollowpoints with a cigarette lighter flint stuck in the hollow point will produce sufficient sparks... 

When you flush a tank with water, consider that wherever you dump the water will smell like gas (or rather, mercaptan) for some time.  When I flushed a 120# tank and drained it in my yard, people were reporting a gas leak for several days afterwards...


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## cg285 (Feb 10, 2018)

propane tanks do not explode all the time like on the movies.. i forget the ratio exactly but it is like 2.? to 9.? parts per million to ignite. i routinely service lp tanks and on asme tanks when i have to replace a part, and the tank is mostly full, i open the valve (in a ventilated area) wide open until the lp freezes. then i do what i need to.
dot tanks i would connect a hose and burn off or expel the gas, remove the valve and follow some of the suggestions above. 

years back i have welded on partially full gas tanks, with a torch, after inducing halon. however our govt says halon is bad. like coffee or beer


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## kd4gij (Feb 10, 2018)

Do not try this at home.


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## dlane (Feb 10, 2018)

Wondering if his truck has any holes in it 
Cans of Starting fluid works better and cheaper


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## dulltool17 (Feb 10, 2018)

Well.....that looked like fun.....reckless, perhaps, but fun.


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## Wreck™Wreck (Feb 10, 2018)

By far the best way to cut open a gas cylinder is to have someone else do it and watch them from a considerable distance.


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## kvt (Feb 10, 2018)

TerryWerm said:


> Result: WASTED AMMUNITION!


It was not wasted if it was fun.   
Or am I always wasting ammo. 

I have an old connector for a regulator,   so when connected it just vents the tank.  Remove Valve, Often a pain,  then follow the fill with soapy water,   They do make nice little forges


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## silence dogood (Feb 10, 2018)

Forget the propane. Use the helium tanks that are for balloons.  The tanks look the same except painted red.  There are even instructions on the side of the tank on empting them and removing the valves for recycling.


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## dlane (Feb 10, 2018)

I made my forge from a portable air tank ( cheaper than propane tank ) a little larger too ,made the burner also.


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## Alittlerusty (Feb 11, 2018)

After your sure the tank is empty, lay tank on its side sit on it then place a wrench on the valve and strike wrench with 3+ lb hammer. That will break the sealant/loctite they use on the threads. The valves aren’t threaded on overly tight then fill with water to just below where You will be cutting and have at it. Also many of the propane tanks I have repurposed have had a heavy coating of zinc paint on them nasty stuff


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## Ray C (Feb 11, 2018)

... Slightly Off Topic here but, here goes.  

If you're searching for metal tanks for various projects, keep your eyes open for discarded hot water heaters.  Each one houses a treasure (10 ga or heavier metal tank) and you won't need to worry about blowing yourself up to Kingdom Come.

Ray


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## larry4406 (Feb 11, 2018)

SE18 - can't help you but I am following along and hope to see your finished forge in action.  I'm just down RT29 from you halfway to Warrenton.


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## SE18 (Feb 11, 2018)

I'll be sure to post pictures of progress, which I expect to be quite slow. & Larry, you or anyone invited over anytime.


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## RJSakowski (Feb 11, 2018)

In past times, I've made a few coal fired forges using a stainless quarter barrel.


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## Silverbullet (Feb 11, 2018)

Phosphorus tip tracers will ignite anything they strike or pass through. We had a member in our club had some shotgun tracer rounds , ended up starting a grass fire out on the edge of the trap field. I'd also think the tungsten rounds would ignite a gas tank.


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## dlane (Feb 11, 2018)

I have a pellet rifle that would lite it up, but I make my own pellets


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## SE18 (Feb 12, 2018)

well, it seems that shooting the tank from a distance might be safer than twisting off the cap and having it blow up in the air (or somewhere else) like one person reported in this post.


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## ericc (Feb 12, 2018)

For forge shells, I prefer to use helium party balloon tanks that people leave on the curb for the garbage truck.  These are pretty safe when empty, and it is easy to make sure that they are empty.  For the small propane tanks, they can be emptied with a torch head.  When the flame is useless, there is almost no propane left.  I just cut the top off with a hacksaw.  Go real slow at the end, not so much to avoid an explosion, but to avoid that disgusting smelling puff of gas that comes out.  I still have to find a good use for these things, but if you cut off the tops you can throw them in the recycling bin (otherwise not allowed).


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## Eddyde (Feb 12, 2018)

7.62 Nato tracers at 250 yards min.


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## SE18 (Feb 15, 2018)

I used my 9 mm today at about 35m. First shot nearly deadcenter. Lots of spray but nothing dramatic. When I went to carry it back, more smelly gasses came out from bottom; still smelly hours later; IMO much much safer to shoot from distance with non tracer rounds than try to unscrew the cap yourself. Or better yet, get a helium party tank as suggested.


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## SE18 (Feb 15, 2018)

SE18 said:


> I used my 9 mm today at about 35m. First shot nearly deadcenter. Lots of spray but nothing dramatic. When I went to carry it back, more smelly gasses came out from bottom; still smelly hours later; IMO much much safer to shoot from distance with non tracer rounds than try to unscrew the cap yourself. Or better yet, get a helium party tank as suggested.


(guess it was 20 yrs USMC training, though I wasn't a crack shot)


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## wawoodman (Feb 15, 2018)

larry4406 said:


> SE18 - can't help you but I am following along and hope to see your finished forge in action.  I'm just down RT29 from you halfway to Warrenton.



You might see him flying overhead...


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## Eddyde (Feb 15, 2018)

dlane said:


> I have a pellet rifle that would lite it up, but I make my own pellets


When I was a teenager I used to make incendiary pellets from strike anywhere matches! Oh the fun to be had....


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## SE18 (Feb 19, 2018)

Here's an update: I'm still alive, first of all, not on rocket to moon.

First, I filled the tank with water thru the bullet hole, after struggling and failing to twist off the main valve (photo). Then, I plugged said hole with piece of bike rubber tubing. Then, in about a minute, I hacksawed off main valve (much easier than struggling with it!). Then, with tank full of water I used a metal cutoff wheel 4.5" on my cheapy HF angle grinder to grind off the top. It will be a while before I do anything else. I believe the way I proceeded was the safest. I could sure smell propane for days, even after filled with water. It's probably not a job for feint of heart. BTW, if you look carefully in the last photo of the tank open you can see the spent bullet. It only went thru the bottom. Also, I unscrewed that thingamagig, which was on pretty tight.


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## cg285 (Feb 19, 2018)

Billh50 said:


> The last time I took the valve off a propane tank, it was still pressurized even after I opened the valve and it stopped releasing gas. When the valve unscrewed the tank shot about 20 ft and then spun around 3 or 4 times till the rest of the gas came out. So be careful.



all the dot tanks have a liquid level valve built into the pol valve. flat blade scew driver to loosen and expel


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