Neutral Aluminum 80

[ajanelle]

I picked up a neutral aluminum 80 (S80N) to use as a stage bottle thinking it was a normal Luxfer aluminum 80 (S080). I've been getting conflicting advice on whether or not I should use it as a stage bottle or not. My primary concern is that it will be too heavy and will be a pain to use. This comes from the preference people have for Luxfers over Catalinas as Catalinas are "too heavy". I have attached a chart that shows how much heaver a neutral 80 is than a normal 80. I haven't done any stage work so I'm not sure if this will actually be an issue but would like to hear some more opinions.

 

[Manatee Diver]

Technically you aren't supposed to put any mix over 21% oxygen in them (or the AL100s), but no one really pays attention to that.

 

[MattK911]

IIRC those buoyancy specs are without a valve.
Also remember to account for the buoyancy shift of diving freshwater (I assume you are). Then you add a 1.5lb valve, then a 1.5lb regulator then 6lb of gas “air”. And that’s just for one bottle.

I rigged one up for myself and the difference is noticeable to say the least. Now that being said it is manageable, just not ideal.

I have heard of people preferring them for mix, would be interested to hearing their side.

 

[ScubaSquatch]

Technically you aren't supposed to put any mix over 21% oxygen in them (or the AL100s), but no one really pays attention to that.

Why is that?

 

[Manatee Diver]

Why is that?

Going by memory here, but the DOT prohibits oxygen over 3,000psi in 3AL certified cylinders, and a few years ago they classified any mix over 21% oxygen to be considered oxygen.

 

[rjack321]

Going by memory here, but the DOT prohibits oxygen over 3,000psi in 3AL certified cylinders, and a few years ago they classified any mix over 21% oxygen to be considered oxygen.

That is not true about DOT but many shops won't boost over 3000psi so you end up with a short fill in a heavy tank.
Its fine as a deco bottle to drop somewhere hard on the entry. It's not useful as a stage you carry since when you go to clip it on the line even 1/2 full its a brick.

 

[MattK911]

It's not useful as a stage you carry since when you go to clip it on the line even 1/2 full its a brick.

It is worth noting that I used a “neutral” 80 twice as a bottom stage, so I was not dropping it. It was heavy enough even empty that I wouldn’t want to be dropping or picking it up.

 

[Manatee Diver]

That is not true about DOT but many shops won't boost over 3000psi so you end up with a short fill in a heavy tank.

Back on my computer and am able to quote and link

Federal law prohibits the dispensing of pure oxygen at pressures over 3000 psi in DOT-3AL type cylinders, and this would include most aluminum scuba cylinders since nearly all are 3AL class. Recently, the DOT has interpreted this regulation to include any gas mixture containing more than 23.5% oxygen, i.e. enriched air Nitrox. You should avoid high pressure aluminum scuba tanks such as the 3300 psi compact or neutral buoyancy aluminum tanks, or the 3300 psi AL100. Note that this concern does not apply to high pressure steel cylinders, depending on the service pressure of the scuba cylinder it may be filled with oxygen rich gases up to a maximum of 3442 psi.

How to Select a SCUBA Tank | Dive Gear Express®

 

[rjack321]

Back on my computer and am able to quote and link

How to Select a SCUBA Tank | Dive Gear Express®

That is a very obtuse reading of the CGA which many shops don't follow anyway - in fact any shop doing continuous blending or banking nitrox is in violation. N80s pretty much suck for a million reasons even without this roundabout unenforced "regulation" by citation.

 

[PfcAJ]

Neutral 80s are hot garbage for stage bottles.