>>> Matt-
   >>
   >>
   >> And to play the green card, how efficient is your compressor, your
   power
   >> lines and your coal fired generators etc. Also a real B if you run
   >> out of
   >> air and air drives tend to be very noisy.
   >>
   >> John
   >
   >
   > John
   > I wondered about that; as well as my compressor only goes to 800 - 1,000
   > psi. I wonder how they get the 4,500 psi, bloody BIG compressor I
   > suppose.
   > One thing which is a bonus here in Aussie, we don't have to pay for
   > air (at
   > the servo) unlike you chaps in the USA. It might cost as much to fill
   > with
   > air, using this system it may be you pay for gas in the US. Mind you
   > we pay
   > more for the fuel. We have been paying $1.50 ( Aust) a Litre, that's
   > about
   > $1.30 US a Litre  There's 3.8 Litres to a US Gallons to so that's
   $4.94 a
   > gallon.
   > Are you anywhere near that yet?
   > George (down under)



   I'm not sure about other ways, but at most scuba shops they have a tank
   farm of the standard 80 cu ft (?) 4 foot tall cylinders like the argon
   comes in for my TIG..  maybe 30 of them as one tank. Then, they have a
   compressor that is multi staged to get to the first level of about 2400
   psi that is in the tank farm, The final bump to 4500 comes at the tank
   filling pool. There, they expel the 2400 air to run a ram that pumps it
   up to 4500. Maybe they waste it 3:1 or 4:1 to get this 4500, but it is a
   simple mechanical device w/o power of its own. Similar to the device
   fire fighters use to get water from a source lower than they can suck -
   say 20 - 25 ft.

   Any way you look at it, not very efficient.
   -dave



This same device is used on house hold RO water units to fill the water
bladder to max cap.

Dan