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Propane Cylinder Conversion for Pneumatic Uses

Posted: Fri Jul 06, 2007 2:01 pm
by Big-mac
WARNING: THIS IS DANGEROUS DONT BE STUPID. PROPANE IS DANGEROUS IF HANDLED WRONG.

How much pressure does propane generate you say? It depends on the temperature:

At a temperature of 70° F, propane's vapor pressure is 124 PSI.
At a temperature of 162° F, propane's vapor pressure is 390 PSI.
Propane tanks are equipped with pressure relief valves that vent excess pressure. If the tank gets too hot, the tank will fart instead of explode :wink:

Normal propane cylinders, such as those used with portable grills have pressure relief valves set to 375 PSI. PRV settings for ASME tanks are 250 PSI. DOT engine fuel cylinders use PRV settings of 312.5. IT seems propane tanks are built to withstand at least 250 PSI. its logical to assume that any propane cylinder you are likely to encounter can withstand at least 200 PSI virtually indefinitely.





Image

You have to empty your tank so what i do is hook up a stove or torch fitting light it up and burn of the extra. There will still still be propane in the tank when you remove the Pressure relief valve but it won't be pressurized. To remove the Pressure Relief valve use the tool used to remove valve from bike tires. KEEP THE PRESSURE RELIEF VALVE YOU WILL REPLACE IT WHEN YOU ARE DONE. THe large valve in the middle is check you can just chuck itl.
Imagethe hole on the right is the valve you will be replacing. remove the large one in the middle in the same way

The next step is to wash the smelly gunk out of the tank. allow the inside to dry. now drill the hole in the middle to the size you require then tap for threads. next clean the cutting oil out and pour some paint in, make sure you dont get any on you new threads. swish the paint around coating the inside to prevent rust from the damp compressed air.

replace your pressure relief valve and your done now you have found use for that other wise useless tank.

Posted: Fri Jul 06, 2007 2:09 pm
by potatoflinger
That seems like it would work.......

Posted: Fri Jul 06, 2007 2:17 pm
by Big-mac
it works trust me :wink:

Posted: Fri Jul 06, 2007 3:34 pm
by turbohacker
Cool idea.
Maybe try and fill it with other things like acetylene or hydrogen :twisted:

Posted: Fri Jul 06, 2007 8:03 pm
by Jumpin Jehosaphat
Yeah, I read a tutorial on this a while ago. It wasn't a spudgun related site though. I'm planning on doing this once my first propane cylinder dies on me.

Posted: Fri Jul 06, 2007 11:50 pm
by Big-mac
its worth it instant chamber i plan on using a few on my revolver. also i didnt mention above that it works with the green coleman tanks. :D

Posted: Sat Jul 07, 2007 12:44 am
by clide
turbohacker wrote:Maybe try and fill it with other things like acetylene
Not if you value your life.


Good idea about painting the inside

Posted: Sat Jul 07, 2007 8:13 am
by Matheusilla
I used an oxygen cylinder that looks just like the propane tank above. However, I used it for a combustion by completely cutting the threaded piece off the top, threaded a 3/4" steel pipe in it's place, another on the side for a place to put ignition and then tig welded it securely. I love using it. It is one of the best combustions that I've ever had. With the threaded piece of pipe in the top I am able to have interchangeable barrels.

Posted: Wed Nov 04, 2009 2:00 pm
by metalmeltr
Don't use a paint that has strong fumes you will regret it.

Posted: Wed Nov 04, 2009 4:05 pm
by Technician1002
Big-mac wrote:its worth it instant chamber i plan on using a few on my revolver.
The opening into the cylinder under the valve in the neck is pretty tiny. They make a lousy chamber unless the hole is drilled out much larger. Most are too small to fit in the refill from a skinny ink pen. If you carefully remove the plastic sleeve and o ring, the bottom can be drilled out and the o ring and sleeve can be replaced to retain the original seal.

For my uses, I simply remove the undersized stock fitting and weld in something larger for more surge flow. :twisted:

Posted: Wed Nov 04, 2009 4:14 pm
by Mr.Sandman
Tech I SOO want that launcher. anyways I have used them as a chamber and all i can say is that i would rather use a c02 tank any day. The propane tanks require a good amount of modification to have an efficient flow.

Posted: Wed Nov 04, 2009 4:34 pm
by Technician1002
Mr.Sandman wrote:Tech I SOO want that launcher. anyways I have used them as a chamber and all i can say is that i would rather use a c02 tank any day. The propane tanks require a good amount of modification to have an efficient flow.
The larger sizes are fun too.
:D

You are right. They are a lot of work, but well worth it. The little tank has been tested to 110 PSI. I'm sure it would hold higher pressure with no problems. I just don't have a high pressure pump at the moment.

Posted: Sun Nov 08, 2009 9:38 am
by metalmeltr
i took mine to 180psi yesterday, no problems

Posted: Mon Nov 30, 2009 6:43 am
by Major Collins
that is the exact same tank i have that you have in the photo lol but mine is yellow haha and it isn't too difficult to make into an air tank.
and how much psi can this bottle take?

Posted: Mon Dec 21, 2009 7:54 am
by metalmeltr
Has anyone tried this wih the new small bernsomatic propleyne tanks yet? The tanks are the same diameter as the old mapp and propane tanks but they are only like 5 inces tall. I may convert one for a low volume high pressure tank.