Ali or steel stages

[Eoin]

I'm in the middle of the MOD2 (have to go to NDAC to finish due to equipment failure). I use 2 x ali 7 litres and will probably get an ally 80' later this year for the deeper stuff. I used to use steels with the twinset, but find alis much easier to wear in the water and out.

[Nigel W]

Thanks Eoin, I have subsequently tried steels and think I prefer ali. Since I was loaning kit I have gone for twin 7l ali, and agree with you I will get 80's later once I am doing more deep stuff or longer decos etc.

[Mark Chase]

Depends on the mix.


If i was diving two nitrox bailouts id dive two ali cylinders but be warned they float like hell when empty and you may need to send one up the line if you use it because two empty Ali 80s would be unmanageable if you were properly weighted at the beginning of the dive.


I dive Trimix so my deep bailout is 18/45 so I put 250bar of that in a steel 10 because its pretty neutral with trimix in. Then I put my Nitrox 50 (230bar) in an ali 80 Is a bit neg but no where near as neg as in a steel 10.


Dive two ALi 80s one with mix and one with Nitrox and your off balance. Same with two steel 10s. If you choose to dive all stages one side this makes no odds and the trimix tin under the nitrox tin can help with trim.

Some divers keep the fill pressure in the Ali80s down to make them float but thats no use to me whats so ever. I need every bar of pressure the tank will hold before going BANG.

ATB

Mark

[chrisMc]

I agree with Mark.

I have 14/60 in a steel 10
36/30 in an ali 7
80% in an ali 7

They are all pretty much neutral when full, and when empty will float so I would send them up.

Talking through with some cylinder testers, ali cylinders are known to fail a lot mroe frequently than steel ones and are a lot mroe expensive, they are also a lot bigger.

If I didnt already have my cylinders I would probably have my 36/30 in a steel 10 aswell.

[NotDeadYet]

I use ally 12.2's as bottom gas which aren't as floaty as 80's. In fact you can't fill them with nitrox or they become very negative at 232, nice on mix though. Other downside, they are heavy.

Originally Posted by chrisMc

Talking through with some cylinder testers, ali cylinders are known to fail a lot mroe frequently than steel ones and are a lot mroe expensive, they are also a lot bigger.

Ally bottles need a lot of care, they are very easy to damage and they don't like overfilling - if an ally says 204bar then they mean it. 80's have a much thinner wall than ally 12's (12kg(ish) for a yank made 11l as opposed to 16kg for a UK ally 12l). Look after them and there is no reason one won't last. I brought a stack back from the US when I lived there, I've sold them all since but I've got one left which still passes test (unoffically as they won't stamp it) which I bought in 1993. I've seen some that were as old as 1974 and still in test.

We must be the only country in the world where an ally 80 costs a fortune. Outside of Europe and it's f***ed up obsession with not recognising anyone else's standards unless they're written in four languages then ally 80's are piss cheap. You can buy an 80 in the US for the cost of a pony bottle here.

[Mark Chase]

Originally Posted by NotDeadYet

I use ally 12.2's as bottom gas which aren't as floaty as 80's. In fact you can't fill them with nitrox or they become very negative at 232, nice on mix though. Other downside, they are heavy.



Ally bottles need a lot of care, they are very easy to damage and they don't like overfilling - if an ally says 204bar then they mean it. 80's have a much thinner wall than ally 12's (12kg(ish) for a yank made 11l as opposed to 16kg for a UK ally 12l). Look after them and there is no reason one won't last. I brought a stack back from the US when I lived there, I've sold them all since but I've got one left which still passes test (unoffically as they won't stamp it) which I bought in 1993. I've seen some that were as old as 1974 and still in test.

We must be the only country in the world where an ally 80 costs a fortune. Outside of Europe and it's f***ed up obsession with not recognising anyone else's standards unless they're written in four languages then ally 80's are piss cheap. You can buy an 80 in the US for the cost of a pony bottle here.

Now you tell me, I just pumped my 80 to 250bar

ATB

Mark

[NotDeadYet]

Originally Posted by Mark Chase

Now you tell me, I just pumped my 80 to 250bar

ATB

Mark

Aluminium isn't the most resilient of metals, it fatigues faster than steel. At least when aluminium vessels blow they tend to tear apart rather than kaboom like steel

Don't forget these are 3000psi cylinders, regular 250bar fills are pretty much a 25% overpressure. Reinhard Buchaly told me he retires all his 80's after 4 years of overfilling because they won't all pass the hydros...

[buddyian]

Hi Nigel. I dive all trimix dives with 2 ali 11 ltrs. Did my course a few years ago with Bob. I cant recommend them and him enough . When you are in the water you do not know they are there. I am sure Bob will have done the calculations with you, 7 ltr cylinders are not enough .

[weazelz]

Originally Posted by NotDeadYet

Aluminium isn't the most resilient of metals, it fatigues faster than steel. At least when aluminium vessels blow they tend to tear apart rather than kaboom like steel

I would have thought that bailout cylinders should fare a bit better than stage/deco cylinders though. because they're not cycled each dive, rather just filled & left full, they should last a lot longer

[japandiver]

I have (and had) a hodge podge of stage cylinders from living and diving in the US, UK and Japan.

IMO, when you start out using deco cylinders then an Al 40, 3000psi cylinder is ideal - it is easy to handle and has great buoyancy characteristics. A great first stage and is just the right size for moderate dives where the deco times are less than 30mins.

When you want / need more gas then I find Alu 7l 232 bar cylinders good. Al 80's are also OK and personally I don't like steel stages - but others do. By the time most people need to buy additional stages then they know (or should know) enough other like-minded divers to borrow some different stages and try them before you buy.

Over-filling Al 300psi (207 bar) cylinders will knacker your cylinder. Guaranteed. From experience, if you routinely fill an Al 3000psi cylinder to 230 bar or higher then the neck threads will fail the go/no-go thread gage at a visual inspection. Overfilling so that when the cylinder cools it will be at WP is a common practice and will knacker your Al cylinder - Al does not elastically deform as much as steel at the overpressure.

Just my 2p

Hugh