Originally Posted by 61 chevy
I would venture to say the 260 + 260 cubic feet. ...So 260/12 ( my uneducated guess on cfm of hvlp gun )=21.666. So I would guess that you would have no more than 21 minutes of supply available at this rate. Although the actual time would be less if you figure in the effect of flow verses presure. It is a holiday weekend and I refuse to embark on such mathmatical formulations.
You know,I found a couple of tables for calculating the volume of gas in a compressed cylinder and found the volume of the Oxygen cylinder used in my Oxy-Acetylene torch setup (and probably the same size cylinder for Nitrogen,about 5' tall,called a K cylinder) 1.76 cubic feet-I would have figured more,but filled to about 3000psi, the one tank should last around 20 minutes at 12CFM @50psi. I had to do little estimation of a few factors but it should be close,it backs up the estimation by 61 Chevy above (nice job!).
That's 20 minutes(or slightly less) of trigger fully depressed,as if you just sat there with the trigger all the way down.Maybe someone with more painting experience than I could give an idea on about what percentage of the time during a paint job the trigger is down and the paint is flowing (not time spent moving around the car,getting position,starting and stopping etc.) Maybe someone could give you an example on how long it takes to lay down a complete coat on a particular car and for what percentage of that time the trigger is down and you can then figure on how far you can get on a tank.
The pressure to which the tank is filled by your supplier will also effect the entire equation of course.