high pressure gas charactoristics

[andy j]

I have been looking at purchasing a new twin set and have been looking into either 300 bar 10L or 232 bar 12L.
Having searched into old threads, i have read talk about how the gas charactoristics change at high pressure, one thread stated that even if 300bar of pressure was obtained it would not hold a volume of more than 270bar? Am i getting things mixed up and reading it wrong. I thought the volume of gas would be directly proportional to the volume and the pressure or am i missing something.
Can anyone explain

andy

 

[rongoodman]

Here's a thread discussing the same question. The linear relationship predicted between volume and pressure by the ideal gas law, PV=nRT, starts to break down at higher pressures.

 

[cool_hardware52]

At high pressures gases no longer follow the ideal gas laws. Real gas - Wikipedia, the free encyclopedia

More importantly would be the availability of 300 bar (~4500 psi) fills.

Tobin

 

[ajduplessis]

We have some operators that can supply 300bar, but as you already highlighted you are realistically only going to have 270, if that much. If I had to choose between 10l 300b or 12l 232b I would go for the latter. My reasoning as follow: The faber 12l 232 is a tall cylinder and not top heavy. You can either double them up with an isolator in a back mount configuration, or you could dive them in a side mount configuration. The have good buoyancy properties IMO. Double 12's should also be good for dives to at least 75m with deco stages.

I fill all my Faber cylinders to 240bar without any issue.

 

[andy j]

Thanks for the links but hey, thats way to complicated for me. I assume a line graph would look similar to that of a piece of steel once it reaches its yeild point.
Getting a good 300bar fill is no problem down here but if the bootom line means that a 300 bar fill gives equivilent air to 270bar then it does not appear to be worth the extra weight of the bottles when lugging your kit about.
The question is, why do they bother to make 300bar bottles?

 

[cool_hardware52]

Thanks for the links but hey, thats way to complicated for me. I assume a line graph would look similar to that of a piece of steel once it reaches its yeild point.
Getting a good 300bar fill is no problem down here but if the bootom line means that a 300 bar fill gives equivilent air to 270bar then it does not appear to be worth the extra weight of the bottles when lugging your kit about.
The question is, why do they bother to make 300bar bottles?

If you pump a bottle to 300 bar it will have more gas in it than it will at 270 bar. I have bank bottles that are rated to 6000 psi. I get a *lot* of gas out of them on the way from 6000 psi to 4500 psi.

Tobin