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Thread: Getting the most out of your O2 tank

  1. #31
    Phil Siswick, Tango PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick's Avatar
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    Re: Getting the most out of your O2 tank

    Quote Originally Posted by nigelh  View Original Post
    I'm going on holiday in a fortnight and I'll take a J of O2, a J of Helium and the Haskell so you probably can guess I don't really care about consumption that much.
    That's more like it!

    Cheers,

  2. #32
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    Re: Getting the most out of your O2 tank

    Quote Originally Posted by PhilSiswick  View Original Post
    Is that right? I'd have thought that, if you have a low setpoint, the gas you'll be dumping will be made up more of dil than O2, because you'll be putting less O2 in to the mix that you are dumping. In my (admittedly limited) experience with the Vision, I'd say that there is a noticeable difference in the gas that you dump if you ascend on 1.3 rather than 0.7 - all of that difference has to be O2, as you're not adding any dil.
    Hmm, you are quoting me out of context :p

    What I was saying, is that for any given setpoint, the amount of "wasted" O2, ie. O2 not metabolized but release to the water, during ascent, is independant of ascentspeed. Reason, assuming a constant total loop-volume during the ascent, the volume released will only dendent on start-depth. Since PP02 is also constant, then it follows, that wasted O2 only denpends on PPO2-setpoint, and Total loopvolume.

    When ascending with a low setpoint, say 0.7, you waste less O2, than when ascending with 1.2. I still say that the amount is independant of ascent-speed!

    Quote Originally Posted by PhilSiswick  View Original Post
    I think you've got that the wrong way around - empirically, it feels as if the unit is putting a hell of a lot of O2 in shallow to keep the PO2 at 0.7. That's a pretty high FO2 to maintain. I agree with you about the loop volume to a point, but I think you should be focussing more closely on loop volume shallower, as it's amazing how much bouyancy change you'll get from one injection from the solenoid (which it'll be doing more often at this depth).
    Yes, what I meant to write, was that you should/could focus on both at shallows. The advantage of keeping the high setpoint at lower depth, was to avoid hypoxic loop-content at surface pressure.
    The amount of O2 (moles/free O2) released to the water from say 40-39m or 5-4m, with the same setpoint are actually not same (think about it).
    So therefor the method is actually not independant of depth, and is more effective when shallow.

    Quote Originally Posted by PhilSiswick  View Original Post
    Of course, I stand to be corrected on all of this. I'm a newbie too, but this is based on what I've experienced, mapped back to what I think I know. I'm also sitting at my desk in London, not diving, so who knows?
    We'll see when I get my own RB

    I lost the spreadsheet calculation I did originally . So the attached sheet is a new one.
    Attached Files

  3. #33
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    Re: Getting the most out of your O2 tank

    Quote Originally Posted by nigelh  View Original Post
    ... Hence an intelligently driven MCCR might outperform our computer controlled systems if O2 consumption is that important to you...
    Lowering setpoint to .7 does't mean you have to dive that setpoint. There's still the option of keeping it on 1.3 manually while using the .7 setpoint as a safety-net that kicks in when you screw up the manual management.
    Doing that would give you the MCCR advantage while still enjoying the ECCR ones.

  4. #34
    Phil Siswick, Tango PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick has a reputation beyond repute PhilSiswick's Avatar
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    Re: Getting the most out of your O2 tank

    Quote Originally Posted by Hanssing  View Original Post
    Hmm, you are quoting me out of context :p

    What I was saying, is that for any given setpoint, the amount of "wasted" O2, ie. O2 not metabolized but release to the water, during ascent, is independant of ascentspeed. Reason, assuming a constant total loop-volume during the ascent, the volume released will only dendent on start-depth. Since PP02 is also constant, then it follows, that wasted O2 only denpends on PPO2-setpoint, and Total loopvolume.

    When ascending with a low setpoint, say 0.7, you waste less O2, than when ascending with 1.2. I still say that the amount is independant of ascent-speed!
    Got it - couldn't agree more. Sorry I misunderstood the first post.

    Yes, what I meant to write, was that you should/could focus on both at shallows. The advantage of keeping the high setpoint at lower depth, was to avoid hypoxic loop-content at surface pressure.
    The amount of O2 (moles/free O2) released to the water from say 40-39m or 5-4m, with the same setpoint are actually not same (think about it).
    So therefor the method is actually not independant of depth, and is more effective when shallow.
    Also agree - it's an interesting point.


    We'll see when I get my own RB
    Enjoy it when you do - it's tremendous fun (especially having these conversations!

    Cheers,

  5. #35
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    Re: Getting the most out of your O2 tank

    My advice to lower your o2 consumption is to also chill baby chill but more importantly -- never exercise again and become as out of shape and as fat as you possibly can.

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