Luxfer 4350Psi AL Tank?

[KOMPRESSOR]

I looked at bringing 300 bar cylinders to the U.S. market about 4-5 years ago and after reviewing the buoyancy characteristics abandoned it. They are so negatively buoyant that when diving anything that the U.S. market was accustomed to meant having to use a lift bag WHILE you dive.
Talk to any diver that used a Heiser cylinder!

Lee

They are not compatible with wetsuits, if that's what you mean. Neither are they good with shell suits with thin undergarment. But for some who use the more affordable 7 mm neoprene dry suits, a 300 bar tank is quite ok. No need for much lead either. For the past 6-8 years 300 bar tanks have been more sold than 200 bar tanks here. Now 232 bar will most likely take over the market, since they are quite the best compromise between air efficiency and boyancy.

 

[alpaj]

Hello there, Hmm this is a very interesting problem that I hadn't really thought about. The problem of high pressure tanks (>300bar). So I thought that having spent a rudy large amount money on university chem was fairly use less. If it's good enough for scuba it's good enough for me. The formula you are looking for is actually the ideal gas law. I shall explain: The amount of pressure in you tank really doesn't mean that much to you. Divers think that the pressure they see on their guages is actually "how much" is in the tank. That's false. What matters to you as the diver is how many molecules of O2 are actually in the tank (well Nitrogen N2 is also fairly important). In any case it's the number of molecules that sustains your body not the pressure. Lucky that we have some super smart chemists that have worked out how to relate the pressure(p) to actual number of molecules (n). Pressure is directly related to molecules as long as the temperature and the volume stays the same. The Temperature (T) change due to cold water etc is negligable and the expansion and contraction of your tank is also negligable (ie. no volume change) so that we get:

p times V = n times R times T (pV=nRT) (where R is ideal gas constant)

So V,R, and T are constants so the only thing changing is pressure and n number of molecules. This means that the two are directly related and as long as people remember that the two are not equal there should be no problem. For example if one tries to dive on a 3 liter bottle @ 3000 psi they won't get very far. Yet most aluminum 80's at @ 3000 psi serve us quite well. The pressure is the same yet number of molecules are very different. So where is the problem? I just said that more pressure equals more molecules provided the volume of the bottle is the same???? Well the above law holds true for lower pressures. Yet gases stop behaving idealy once you increase the pressure on them. Each molecule has a force between it and the other molecules (basic Chemistry). At low pressures these intermolecular forces are not very significant BUT as you increase the pressure in the tank each of those molecules starts bumping into his neighbour so now as you increase the pressure the forces beween the molecules becomes greater and greater. And thus at high pressures adding x number of molecules increases the preassure much more then adding x number of molecules at a low preassure because at high pressure they are allready squished. Hmm I had fun writing this I hope it's not too long.
Fun diving

 

[Leadking]

They are not compatible with wetsuits, if that's what you mean. Neither are they good with shell suits with thin undergarment. But for some who use the more affordable 7 mm neoprene dry suits, a 300 bar tank is quite ok. No need for much lead either. For the past 6-8 years 300 bar tanks have been more sold than 200 bar tanks here. Now 232 bar will most likely take over the market, since they are quite the best compromise between air efficiency and boyancy.

That's the choice I made. We started with Worthington to make 3442 psi (230 bar)
cylinders.

Lee

 

[Hoosier]

Thanks guys.... I learned somthing today. Even my engineering degree (environment) didn't catch that issue.... LOL...

Leaking reminds me of Heiser 190, 4400 psi that I mentioned a big HP tank in the previous post.

 

[Bowzer]

Surprise! It is warmer there in Norway than here in Upstate NY. And I use a wet suit...

 

[WarmWaterDiver]

I can say as much as that this is correct. It's "common knowledge" among divers in Norway since we have a lot of divers using 300 bar tanks. It's even explained at any PADI OW course. Although not many of us can explain WHY. Neither can I. But so it is.

The real explanation is no real gas behaves as an ideal gas under all conditions.

The compressibility factor is often mistaken as a constant, but that is a fallacy as it can (and does) vary with temperature and pressure for a given pure substance, much less a mixture of gases like air, or other mixtures we use for scuba breathing media.

Often, the Law of Corresponding States can be used to address this which says the behavior will be similar at a similar distance from the critical point - so ratio of temperature to critical temperature, and pressure to critical pressure, are used for such yardsticks.

 

[KOMPRESSOR]

Surprise! It is warmer there in Norway than here in Upstate NY. And I use a wet suit...

Sunday's dive:

Water at surface down to 30 ft: 35F
Water from 30 to 45 ft: 37-38F
Water below 45 ft: 39F

Air temp was nice, 35F and some wind. I suppose I should thank you guys for the globel heating, 'cause the "normal" thing now i january is 2 ft of ice on the lake!...