Re: Looking for a new tank

Ray paintball is different in so many ways...any place when you first fill i
get 4500 psi but after 5 minuts it is down to 3900 psi and that is that...no
explanation needed.
fill the navy with your system, not paintball ;-)
"RayC" <ray@xxxxxxxxxxxxx> wrote in message
news:g5GdnfK81N3LW2fbnZ2dnUVZ_qSonZ2d@xxxxxxxxxxxxxxxx
Jeff Goslin wrote:
Geez, for once I agree with Tony. Ray, you should know what you're
talking about before you give advice on a subject that involves high
pressure gas, because people can get killed if they use it wrong.

Some of the things you say would be considered as "picking nits" if I
were to bring them up, but one of them is definitely NOT a nit. Two
tanks of the same size, in your example, 68ci, one of which is rated at
3000psi, the other at 4500psi, but each one happens to be currently at
2250 psi at the moment in time. BOTH of those tanks will fire the exact
same number of shots, assuming all other things being equal. The reason:
it doesn't matter how much they CAN hold, it matters how much they ARE
holding.

The difference in number of shots comes in on the top end of things. A
4500psi 68ci tank gets about 1000 shots, or about 300 more than a 68ci
3000psi tank, because of the extra 1500psi at the top end of the fill.
Thus it is the PRESSURE of the air, not the QUANTITY of air that matters
on a HPA tank and it's ability to deliver shots for a period of time.
Increase the size of the tank, and the amount of shots increase, yes, but
that would be true regardless of the pressure of the tank, so it's
irrelevant.

Remember the ideal gas law: PV=nRT.



You didn't read everything I wrote. My main point was that whoever was
filling the guys tank was doing a crappy job and having a higher rated
tank wasn't going to help him one bit.

And as far as quantity of air, you are saying exactly what I was saying. I
said ... "If the two cylinders are the same size (let's just say both are
68's for this example), at the same pressure; 2250; they both have exactly
the same amount of air. However at the rated pressures; 3000 and 4500
respectively; the 4500 has 50% more air volume and will last you 50%
longer than your 3000. "

And it _IS_ volume that makes a difference.

Every shot takes a certain amount (volume) of air from the tank. To make
it easy, let's say it uses five cubic inches at atmospheric pressure for
easy math. A 3000 PSI (200 bar) 68 holds 13,600 cubic inches of air at
full pressure. One shot will drop the pressure to about 2998 and the
volume of compressed air to 13,595 cubic inches. A 68 cubic inch cylinder
rated to 4500 psi (300 bar) holds 20,400 cubic inches of compressed air.
One shot drops the pressure to about 4498 and the volume of compressed air
to 20,395. If you fire each down to say 1000 psi, you will get about 1800
shots from the 3000 and 2700 from the 4500 based on my example numbers...
about 50% more.

All of this doesn't mean a thing if the guy can't get get good fills.

While my math may be off a little here and there and I don't know the
specifics for paintball guns as far as operating pressures, I know
compressed air. It has been my business since the early 80s and my job in
the Navy before that.



--
Ray Contreras
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http://www.coltri-usa.com
http://www.rayzplace.com


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