I have an empty 20 pound propane tank that's too old to be refilled. Is there any reason I shouldn't convert it to be used as a compressed air tank?

 

Shouldn't be any problem. Propane is typically around 150 PSI. I'd go with 120 PSI as a top safety limit.

 

Thats a great idea, I've got an old propane tank that needs a new use.

 

Air Tank Conversion Kit

this was made for r12 freon tanks, but it should be adaptable to a propane tank

 

Just make sure to at least air the tank out for a while first, I have flushed them with water as well. You'll want to flip it over and drain it at least once a week as well to help prevent moisture buildup.
Most propane tanks are rated at 250psi.

 

I wouldn't flush with water. Might cause rust. Turn it upside down in the sun to drain out any oil from the propane.

 

Don't do it, they aren't coated on the inside to resist rust. The higher than atmosphere pressure will accelerate the rusting. You need a tank valve(unlawful to put anything thru the left handed Propane valve other than Propane or leak testing nitrogen), pressure gauge, relief valve and hose for the tank. By the time you bought all those, and the fittings you could have bought a portable air tank. Get caught transporting it and you could be in for a nasty fine. Bump a pressurized tank and you could be wearing part of the tank. The same holds double for freon tanks, as they are thinner.

 

Please, he could get all the parts he needed to convert it for 10-15 dollars if he looked around. I'd assume he has a water separator on his compressor anyways. Even if you were that paranoid about rust, you could just dump a bit metal paint into the tank and swish it around to evenly coat the insides and let it sit for a day or two to dry. I know many people who run air tanks, they fill them with humid air, leave them outside, never drain the water out, etc., and I have not seen one fail yet.

 

FYI All
DOT Propane cylinders (portable tanks) are built with a 375 psi working pressure. Asme containers (home tanks) are 250 psi working pressure and 4 to 1 safety margin
I have never seen a air receiver that was lined only water tanks

regards

 

I have an older steel 100lb tank that we use at the farm. I cut the valve off at the neck and then drilled and tapped it for a pipe tee. Added a gauge, pop-off, and quick-coupler to it.

Check E-bay for the propane / air tank conversion valve. It is left-handed thread and has a port for gauge and pop-off along with the 3/8npt for a standard coupler.

 

The old style propane valve is exactly the same as the valve on an acetylene cylinder so fittings can be bought at any welding supply.

 

I bought an 8 gallon air tank for $40 bucks from Lowe's. Take that old cylinder to the recycler your city runs.

 

I use a 20lb tank for that very reason. Put a guage and fittings on it. It works good for a tire or two.

 

I got a 26 gallon compressor. Really works great on ALL my tires. I only had the tank to air up the snoblower which only worked on one tire. After all the hassle of getting it aired I now can run from my air tools to my airbrush.

 

I just keep the full size spare aired to 45 lbs and carry a 25 ft air hose with chucks on both ends. Takes up a lot less space.