Hi All,
Had an old 9 kg gas cylinder in good condition laying around. What I needed was a portable air tank to run the stapler and brad gun while doing odd jobs in the Goldstream Camper. I didn’t want to run long air hoses from my compressor, especially for a job that would take ten minutes.
I did a bit of research beforehand, and these puppies have a
Test Pressure of 3 Mpa, or ~435 PSI to us folk. Mmmm, more than enough to make a compressed air tank out of I thought, considering I’ll be only using it at 100 – 130 PSI. Moreover, a 9 kg cylinder has the volume of about 22 litres – about half the capacity of the tank found on an “auto parts store” compressor.
I still wasn’t convinced, so I went to a website that listed pressures for LPG gas under pressure – just to be sure.
Well, I found out that LPG in a full 9 kg bottle at 30° C is ~145 PSI. And that’s easily achievable in a bottle left in the sun or similar. So there should be no dramas using compressed air.
So, all is good, and here’s my solution;
The trickiest bit was converting the gas POL fitting on the bottle, to BSP fittings that air compressors use. It turned out quite simple. I had an old POL hose, so I cut the end off it, and that gave me the connection that fitted into the gas cylinder valve.
I then tapped the inner portion of the POL fitting (the bit with the O ring on the end) with a ¼” BSP die (to about 10mm long), to accept a “T” piece as seen in the photo. I then screwed the “T” piece onto the POL fitting (with thread tape) and screwed it to the cylinder.
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Go to major hardware store and purchase some air fittings. How you set it up is your choice, but I did it like this;
On the top of the “T”, I added an open/shut valve and a male air fitting. This is where I charge the cylinder from the air compressor, via a hose.
Next, I added a threaded barb to the end of the “T” piece, and attached a short piece air hose (blue in colour in the photos), that in turn went to the Regulator/Water Trap (Note: you don’t really need a Regulator, as the cylinder is only ever pressurised to what the compressor is set at – but I like gauges!).
On the output end of the Regulator, I fitted a standard Nitto female coupling ready to accept an air hose and the tool of my choice.
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Apart from a coat of paint and a note saying “Compressed Air Only”, jobs done! I charge the cylinder to 130 Psi (this is Max limit recommended by the makers of the Regulator/Water Trap), using the air compressor and then disconnect. The Regulator is set to 90 PSI (as recommended by the makers of the tools), and away I go!
Cheers, Matt