Steel or ali stages

nigelh

I'm perplexed why that's a reason to use Ali?

I took my two steel 7L/232bar bailouts on holiday last year filled with bottom mix and pure O2 and transfer filled the YBOD from them and went home, 12 dives down to 40 meters later, with over 90bar in each. Isn't that the scenario you are describing?

I never actually took them in the water but the only gas I needed from the boat was fills on the suit inflate bottle. Am I missing the reason for using Ali here?

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nigelh

Mike Costanzo

Aluminum, one of many reasons for going to ccr from oc was to lighten the load.

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Mike Costanzo
CK #318

zzzzzzzz

Hi Nigel,

It seems we are in agreement that there is no hard and fast rule for steel vs aluminum for bailout when it comes to transfilling. It certainly should not be a primary driver for tank selection. The objective of the post was simply to raise it as a factor when considering the effect on the overall gear package in various scenarios.

The statement was based on the absence of HP steel tanks. The initial post did reference that this could be an advantage and depended on the setup. It is a factor and by no means the only one.

In my case, HP steel tanks have been avoided for the most part due to inadequate fills, too hot on fill, never enough time to get proper fills, dissappointment on cooling...

The benefit of LP on the Rebreather and aluminum elsewhere is just in that scenario. You raise an important point that 232 bar tanks have even higher pressure making them attractive when combined with LP on the RB.

Interestingly, HP steels were designed to improve weight versus capacity issue of large LP steels.

Personally, both types are used depending on the scenario, though steels have been preferred for certain applications as well.

Is there a single outstanding choice? Never! It's large bulky crap no matter how you slice it.

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z

nigelh

Right. I think we're living on different sides of the planet with different normalities.
In the UK 232bar is normal with only steels available at 300bar. Those are our HP and LP. 300bar is still considered a bit freaky in some circles.

I had a 300bar twinset and the view that it was strokey and I'd never get nitrox or trimix fills got boring as I was doing it routinely.
I went for 7L stages in steel having had to trash a set of Alis that I was given as they needed expensive 'extra' tests due to being an out of date material. Also they were 207 bar. Steel is just steel. I liked their slightly negative at all points characteristics so they stayed down rather than finding the rear ends bobbing up under my arms and getting between me and things I might want in a hurry (valves). Also they were noticeably physically smaller for the same internal volume.

I'd go for personal choice but somebody offering a reason that I didn't understand perked my interest.

thanks.

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nigelh