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  1. #1
    Se a vida Gary's Avatar
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    Droptanks: 80% or 100%

    We've always had 80% in our 12L droptank, generally for a couple of reasons

    a) a diver needing a droptank may be task loaded and may not stick rigidly to a 6m stop
    b) we can get higher pressure 80% (generally 240-250bar) than O2 (200bar)
    c) I as a diver used 80% rather than 100% so its a carry-over from that

    Having used our droptank a couple of weeks ago via a RescueEAN for an ancillary oxygen supply, I gave it further thought, and I'm wondering if we should change ours to 100%

    Thoughts?
    It is far better to be trusted and respected that it is to be liked."

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    Putting the FU in SNAFU The Duck's Avatar
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    I like O2 but if it comes to needing the skippers gas I'll take whatever's going and alternate between being very thankful and cursing myself for having f*uked up so bad that I'd blown both my primary & backup plans!
    Do not despise the snake for having no horns,for who is to say it will not become a dragon? So one just man may become an army! - The Water Margin

  3. #3
    Established TDF Member DiverMike's Avatar
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    80% for the following reasons
    - a 230 bar fill (over 180b in most places for O2) means more gas
    - CCR divers bailing from a CO2 hit will be more likely to tox
    - there was a 3rd one but I forgot.

    if you go 100% putting it on 6.5m of line will limit the damage.

    Id also make sure it was clearly marked with mix and mod as no one pays attention to boat briefs (which seats are the fares under?) but when the bottle arrives at 6m it's good to know what it is.

    Are their any liability issues with a boat providing a drop tank?

  4. #4
    AKA Devon Diver Roy's Avatar
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    Quote Originally Posted by Gary View Post
    We've always had 80% in our 12L droptank, generally for a couple of reasons

    a) a diver needing a droptank may be task loaded and may not stick rigidly to a 6m stop
    b) we can get higher pressure 80% (generally 240-250bar) than O2 (200bar)
    c) I as a diver used 80% rather than 100% so its a carry-over from that

    Having used our droptank a couple of weeks ago via a RescueEAN for an ancillary oxygen supply, I gave it further thought, and I'm wondering if we should change ours to 100%

    Thoughts?
    I'd think 80, primarily for reason a.

    But as the Duck said, I'd just be grateful for whatever arrived (if clearly marked, of course).
    Diving is life, the rest is just surface interval!
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  5. #5
    Moderator GLOC's Avatar
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    What depth Gary?
    Quote Originally Posted by DiverMike View Post
    80% for the following reasons
    - a 230 bar fill (over 180b in most places for O2) means more gas
    - CCR divers bailing from a CO2 hit will be more likely to tox
    - there was a 3rd one but I forgot.

    if you go 100% putting it on 6.5m of line will limit the damage.
    80% at 6m or 80% at 9m? The latter will cause the same issues for toxing with high pO2.

    Regards
    Last edited by GLOC; 21-05-2013 at 09:22 PM.
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  6. #6
    Se a vida Gary's Avatar
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    Quote Originally Posted by GLOC View Post
    What depth Gary?
    6m
    It is far better to be trusted and respected that it is to be liked."

    "You're a bit like Doc Martin, only less funny" anonymous

  7. #7
    Nicotine, valium, vicodin... notdeadyet's Avatar
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    I've always been a fan of oxygen for deco particularly when it's deco in the shit but I can understand the practical aspects of EAN80.

    Marginally higher fill pressure but also marginally longer deco compared to O2, I suspect they might cancel each other out.

  8. #8
    Established TDF Member Barrygoss's Avatar
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    Quote Originally Posted by Gary View Post
    We've always had 80% in our 12L droptank, generally for a couple of reasons

    a) a diver needing a droptank may be task loaded and may not stick rigidly to a 6m stop
    b) we can get higher pressure 80% (generally 240-250bar) than O2 (200bar)
    c) I as a diver used 80% rather than 100% so its a carry-over from that

    Having used our droptank a couple of weeks ago via a RescueEAN for an ancillary oxygen supply, I gave it further thought, and I'm wondering if we should change ours to 100%

    Thoughts?
    A drop tank of 80%, because we're really talking a minute or two deco saved.
    A 18L of O2 on the boat. Cos that's where I really need it, on the journey back to port.

    B

    In the man cave piccie from FB, that's a steel 18L in silver in the corner
    Last edited by Barrygoss; 21-05-2013 at 09:39 PM.
    Rebreathers are like women; they pretend to love you, whilst taking all your money and trying to kill you.

  9. #9
    Last of the Mohicans gobfish1's Avatar
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    02 for on the boat , drop tanks should be sorted by the dive team , feek me they will want you to have a diver ready to jump in next .. ,

    if you want to toss a cylinder over the side o2 , 6m if the diver is going to tox best move to 3m asap , closer to topside the better

    dont go there m8.

    divers gets a o2 hit on one of your drop tanks , whats going to happen ,, adw time .
    Last edited by gobfish1; 22-05-2013 at 12:35 AM.

  10. #10
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    I would probably go for 100%.

    • If task loaded then I hope the diver will be hanging on a line, the line the tank is on if nothing else, and will not go deeper than the line allows.
    • If administered to a bent diver on the surface O2 is apparently far more valuable to them than 80%, or at least I am sure I read that somewhere.
    • If they are running a rebreather with low or lost O2 supply they can use it to inject O2 into the loop via the manual adds, if you make sure there is a LP inflator hose on there.


    Only downside I see is the added risk of Tox. If they are that close to a tox that 100% triggers it and 80% doesn't then they should probably sit on air for a while or get out the water and breath the O2 up there while waiting for a helicopter.


    Having read some of the other posts my answer is assuming there is only room for one extra cylinder on the boat, which is sometimes the case, otherwise I choose onboard manned deco chamber with O2, martinnis and sexy nurses.
    Last edited by Iain3; 22-05-2013 at 05:17 AM.


 
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