HP Steel 13/19cuft bottles?

[lundysd]

This may seem like an unintelligent question, but why haven't I seen any 13 or 19 cuft HP steel bottles? Do they even exist? It certainly makes sense to me, being able to have that extra amount of air in a redundant source....

Scott

 

[Doc Intrepid]

This may seem like an unintelligent question, but why haven't I seen any 13 or 19 cuft HP steel bottles? Do they even exist? It certainly makes sense to me, being able to have that extra amount of air in a redundant source....

Scott,

They do exist, OMS continues to sell a nice little 13 cu ft steel bottle for drysuit inflation (argon). You can see it here:
http://www.omsdive.com/gas_sys.html

OMS is currently going through some transformations, but for quite awhile they've had a small 20 cu ft steel tank also. I'm not finding it on their webpages currently, but on their website home page its the slender blue cylinder in the image over the "cylinder care and warranty" link.

In terms of argon bottles, there is no real valid argument against the steel 13 except relative cost. For the longest time OMS only offered it with this funky vertical valve, which was a PITA, but I see they've now put a standard format valve on it. The real issue is that you can purchase about 2.7 or so aluminum 6 cu ft tanks for the price of one - it's an expensive little bugger.

In terms of stage/deco bottles, no one carries the really small tanks. Generally if you need deco gas you'll carry a 40 cu ft bottle. A 30 will often work for many divers, but most often guys simply standardize around 40s and 80s.

Speaking in general terms, you'll see some debates here, but Luxfer aluminum stages and deco bottles gain bouyancy as they empty. Their butt ends rise up and tend to float above and behind the diver, flowing with the slipstream and getting up and out of the way. The concept is that they thus enhance streamlining. Steel stages and deco tanks remain negative, whether full or empty. So they tend to continue hanging beneath the diver, acting like a keel. (Not so streamlined.) While there are many divers who prefer steel deco tanks and stages, in general I think its safe to say that more divers use aluminum stage and deco bottles than use steels - in those parts of the world where aluminum bottles are available and affordable.

So, a steel 20 cu ft bottle is a fairly expensive, specialty item; and is not going to be, generally speaking, in real high demand. Thats why you don't see many of them around. Hope this helps.

Doc

 

[lundysd]

Thanks for the info; I have seen the OMS bottle before, but I wasn't sure if the argon bottle was okay to use as an airsource-- is there any problem with using this as a pony rather than the argon?

Scott

 

[lamont]

would rebreather divers have any use for those?

 

[Doc Intrepid]

Thanks for the info; I have seen the OMS bottle before, but I wasn't sure if the argon bottle was okay to use as an airsource-- is there any problem with using this as a pony rather than the argon?

Depends on how you define the word "problem". Sure, the OMS steel 13 could be used as a pony bottle. The question is why would you want to?

1. The steel 13 is wicked expensive. Somewhere between $240 and $340 if I recall correctly, and depending on what its bundled with. You can purchase two new Luxfer 40s for that much ching.

2. The steel 13 is steel. Refer back to why steel sling tanks are often considered less desirable. Plus its worthless as a deco bottle, whereas an aluminum 30 or 40 can be used as a deco bottle when the time comes.

3. The steel 13 is dinky. Lets review the math. (Lets first set aside all dead horses flogged regarding why ponies suck.) There you are at 132' for too long, when what do you know, Lloyd Bridges swims up and cuts your hose. Lets assume you're surprised and dismayed by whats occurred, so your RMV jumps up to around 1.3 cu ft per minute. Lets further assume it takes you around 1 minute to figure out you're hosed (no pun intended), clutch & grope, react, etc. Then lets assume that while you're still annoyed at the inconvenience, you have the presence of mind to ascend at a rate of 30 feet per minute to your 10 foot safety stop - from 132' to 10' at 30 fpm is 4 minutes. Then, since you were audacious and carpeing the diem at 132', a safety stop of 3-5 minutes is not out of line. Then perhaps another minute to rise, seed bubbles and all, to the surface. So at an estimated total response time of ~11 minutes or so on your redundant gas source at a consumption rate of 1.3 cu ft per minute, you'll need 14.3 cu ft of gas. You'll consume a tad more at depth, and a tad less at your 10' hang, and its all a huge guesstimate anyway. But the point is, thats straight up. No entanglements, no monofilament, no currents, no nasties. Add another 3-4 minutes at depth to work on your 'issues', and you'll need ~19.5 cu ft in it.

So while there are many other options such as gas planning, buddy planning, dive planning, etc. to ponder, if we're only talking about pony bottles at least lets look at what you may want one for. Fewer minutes on it? Sure. How lucky do you feel?

If you're going to go through the bother of having one at all, though, I submit you might want one with more gas in it than 13 cu ft.

FWIW. YMMV.

 

[Doc Intrepid]

would rebreather divers have any use for those?

quite possibly. I'm not familiar with the many different types of rebreathers.

 

[lundysd]

Doc, I was afraid this would spiral into the dreaded pony debate, but your comments made me laugh so hard I'm delighted that it did (in a way).

You are completely correct -- a 13cuft bottle isn't enough for a real solid OOA situation. I was asking the steel bottle question in hopes that 13cu ft of HP tank would equate to enough, because the standard 13cuft tank obviously isn't. If I can't find something else I'll just settle for a 19cuft AL pony though.

Thanks for the input

Scott

 

[Doc Intrepid]

No worries Best of luck with that.

Doc

 

[lamont]

I was asking the steel bottle question in hopes that 13cu ft of HP tank would equate to enough, because the standard 13cuft tank obviously isn't.

I guess an HP tank does deliver slightly more because when the tank is finally sucked down to the point where the regs stop working, the HP tank will have a smaller water volume and for the same final psi will contain less, and more will therefore have been used. But that's very small and negligible compared to the difference between a 13 cu ft and a 19 cu ft tank...

 

[Leadking]

the Megalodon uses 13's the Inspiration 19's