Luxfer back in the scuba business

[WD8CDH]

The O2 limit is conservatively based on the 4350psi service pressure, not anything about the construction. In reality, 32% O2 in a 4350psi tank would be about the same PO2 in the tank as 40% O2 in a 3442psi tank.

I think this tank is more like a public beta test of composite SCUBA tanks. I think that they should have made a series of 4500psi SCUBA tanks from their 7000 series alloy rather than composite. Less change in tooling, unlimited life, mature technology, more rugged and cheaper.

Actually, a SCUBA tank made from 7000 series alloy with the wall thickness of a 6061 series 3000psi tank would have a far greater safety margin at 4500 psi than a current steel or aluminum SCUBA tank does at their rated pressures.

 

[SparticleBrane]

So why don't they use the 7000 series alloy?

 

[redacted]

And the big advantage over a modern steel HP 100 (3442) is ---- nada.

 

[fppf]

They limit the O2 content because the walls of the liner are extremely thin.

 

[mike_s]

The O2 limit is conservatively based on the 4350psi service pressure, not anything about the construction. In reality, 32% O2 in a 4350psi tank would be about the same PO2 in the tank as 40% O2 in a 3442psi tank.

huh?

what would tank pressure have to do with P02 on the gas supply a diver received?

the diver gets his gas supply (air, nitrox, etc) at the same "intermediate pressure" (usually 125-150psi) regardless of what tank it's connected to.

I've never seen PO2 calculated from tank pressure? do you have any references supporting this? Am I missing something here?

 

[fppf]

There have been debates and theories about the difference between PO2 and FO2.
Just like the same FO2 at higher pressure will tear up your lungs, they are starting to think the same happens with reactivity of materials.

But Luxfer is not limiting FO2 to 32%, they limited to 23%, which means they don't want them used for nitrox at all. So I don't understand you post either.

As for tank material, there are a lot more properties to look at when selecting a material than ultimate strength.

 

[Leadking]

They limit the O2 content because the walls of the liner are extremely thin.

The walls are not extremely thin. The tanks are a standard 80 that is fiberwrapped.

 

[Cave Diver]

The O2 limit is conservatively based on the 4350psi service pressure, not anything about the construction. In reality, 32% O2 in a 4350psi tank would be about the same PO2 in the tank as 40% O2 in a 3442psi tank.

I'm still trying to wrap my head around this statement. I'll be back after I've had time to unwind a bit and think about it...

 

[SparticleBrane]

The O2 limit is conservatively based on the 4350psi service pressure, not anything about the construction. In reality, 32% O2 in a 4350psi tank would be about the same PO2 in the tank as 40% O2 in a 3442psi tank.

I'm still trying to wrap my head around this statement. I'll be back after I've had time to unwind a bit and think about it...

Pressure total in a 3442psi cylinder = ([3442/14.7]+1) = 235ata. Using 40% O2: (0.40 * 235) = 94ata.
Pressure total in a 4350psi cylinder = ([4350/14.7]+1) = 297ata. Using 32% O2: (0.32 * 297) = 95ata.

Thus the pO2 in a 3442psi cylinder of 40% = 94ata, and the pO2 of a 4350psi cylinder of 32% = 95ata.

 

[fppf]

I don't think they just take an AL80 and fiber wrap it.
Most other fiber wrap cylinders just have a thin liner and then get wrapped for strength.