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  1. #1

    Default Loss of Gas at Max Penetration

    Over the years I have heard that if a failure is going to occur it will probably be towards the beginning of a dive. Today that was not the case. My buddy and I were about 3500' back in Ginnie (our planned turn is around 3700' with the gas we had) when a high pressure hose tore for seemingly no reason other than it was a few years old. Gas came pouring out. My buddy was in sidemount so he gave the signal, showed me what was happening and we headed out. He feathered the valve while exiting and was able to conserve a lot of gas that way. We moved quickly and did silt it up a bit but were able to get back to the stages without sharing gas.

    I just wanted to remind people to always dive conservative because sh*t does hit the fan every now and then.


  2. #2
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    Default

    Had the same thing happen last year and posted on it. It was right at max p. Luckily hp hoses look bad when you first see them, but then quickly realize its minor once you see what it is. I think that initial flow of bubbles caught out of the corner of your eye gets magnified in your brain.

    Good to point out that things do actually occur at the worst part of the dive. Its not just something people say.


    Sent from my iPhone using Tapatalk


  3. #3

    Default

    It's a good thing to remember as well that "thirds" was intended for use with a 3 man team. With a 2 man team it's right on the edge with no margin if one of the team suffers total gas loss at max p.

    On the other hand, with side mount where you have fully independent doubles, the likely hood of total gas loss is very, very low. And as noted above, you still have the ability to feather the valve and use much of the gas in the failed tank.

    Still, I don't dive to thirds even in side mount, but rather add in some fudge factors:

    - 1200 psi thirds, adding anything over 3600 to the reserve;
    - turning a couple hundred psi early to add to the reserve; and
    - turning even earlier based on restrictions, silt expected on exit, etc.

    NACD Cave DPV Cert # 666: Cave DPV Anti-christ

  4. #4

    Default

    I always assumed that people make contingency plans for failure at the worst time/location.

    I mean, where does a tire blow out on your car? Across the tire place during business hours or in the middle of the night in "fly over country" where all you hear after getting out is crickets - including on your cell phone. That's where a spare that was checked a day ago is worth it's weight in gold.

    As funny as Murphy's law sounds, stuff does happen at the worst time/location. Thanks for bringing this to our attention


  5. #5

    Default

    If one is already having a failure at max penetration one on the HP side of things is the absolute preferable as with feathering the gas loss is minimal.
    In a situation like that though I would likely choose not to opt into feathering from the getgo, but to close the tank and likely use 1/6th to 1/3rd of the "good" tank picking up speed to a "best" distance/Sac ratio heading out and get back to the "feather" tank closer back to the entrance knowing that most of the gas in the "broken" tank is still usable and not yet lost.
    Logic behind is: better speed getting out when not having to feather.
    Given that stages are involved it would not be unlikely that the stage would be reached even with such limited use of the "good" tank.


    But yes #### happens at the worst point in time, so be prepared..


    BTW this failure is one of the instances where actually a manifolded double is superior to the independent sidemount tanks as long as the "working" reg does not get another failure, you would simply shut off the failing reg and still have access to all remaining gas without any feathering..


  6. #6
    Member
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    Default

    Quote Originally Posted by Nitrogenius View Post
    If one is already having a failure at max penetration one on the HP side of things is the absolute preferable as with feathering the gas loss is minimal.
    In a situation like that though I would likely choose not to opt into feathering from the getgo, but to close the tank and likely use 1/6th to 1/3rd of the "good" tank picking up speed to a "best" distance/Sac ratio heading out and get back to the "feather" tank closer back to the entrance knowing that most of the gas in the "broken" tank is still usable and not yet lost.
    .



    I agree with most of that, but it also depends on which tank and the team. If all are in sm, it's not much of an issue. In my instance we were both in sm and it was my right tank. It was an easy decision to just shut down the long hose and drain down the left tank. Afterwards I contemplated different scenarios and wondered if I was in a 2 man team and the other person was in bm and it was my left tank what would be the best choice? Drain my donation tank or feather my non-longhose tank. Obviously that's planning for a total failure of the bm diver's gas supply, which is unlikely. And if you're having that many issues, somebody was out to get you. But I still don't know the right answer to that one. Personally I would feather the left tank and save my right tank if possible for another emergency, though that will slow exit some and increase sac rate.


  7. #7

    Default

    While we are at the topic of gas loss, let's not forget to keep a critical eye on the burst disks that could create a much nastier scenario.

    In both SM and BM we are going to lose at least one entire tank per blown disc. In BM even more depending on how quickly we isolate.


  8. #8

    Default

    Quote Originally Posted by Head Back! View Post
    I always assumed that people make contingency plans for failure at the worst time/location.

    I mean, where does a tire blow out on your car? Across the tire place during business hours or in the middle of the night in "fly over country" where all you hear after getting out is crickets - including on your cell phone. That's where a spare that was checked a day ago is worth it's weight in gold.

    As funny as Murphy's law sounds, stuff does happen at the worst time/location. Thanks for bringing this to our attention
    You are an optimist. Let me edit it for you:

    Option 1:

    I mean, where does a tire blow out on your car? Across the tire place during business hours or in the middle of the night in "fly over country" where all you hear after getting out is rattle snakes on the shoulder of the road - including on your cell phone. That's where a spare that was checked a day ago is worth it's weight in gold.

    Option 2:

    I mean, where does a tire blow out on your car? Across the tire place during business hours or in the middle of the night in "fly over country" where all you see and hear after getting out is snow blowing at 30 mph with -20 degree air temperature (-53 degree F wind chill) - including on your cell phone. That's where a spare that was checked a day ago is worth it's weight in gold.

    The daily planning and self sufficiency needed to live in South Dakota lends itself well to cave diving.

    NACD Cave DPV Cert # 666: Cave DPV Anti-christ

  9. #9

    Default

    Quote Originally Posted by Head Back! View Post
    let's not forget to keep a critical eye on the burst disks that could create a much nastier scenario.
    What's a burst disc...

    Safe diving,

    Rich

    Education, enjoyment and exploration.....
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  10. #10

    Default

    Quote Originally Posted by DA Aquamaster View Post
    You are an optimist. Let me edit it for you:

    Option 1:

    I mean, where does a tire blow out on your car? Across the tire place during business hours or in the middle of the night in "fly over country" where all you hear after getting out is rattle snakes on the shoulder of the road - including on your cell phone. That's where a spare that was checked a day ago is worth it's weight in gold.

    Option 2:

    I mean, where does a tire blow out on your car? Across the tire place during business hours or in the middle of the night in "fly over country" where all you see and hear after getting out is snow blowing at 30 mph with -20 degree air temperature (-53 degree F wind chill) - including on your cell phone. That's where a spare that was checked a day ago is worth it's weight in gold.

    The daily planning and self sufficiency needed to live in South Dakota lends itself well to cave diving.
    How did you know that my story happened in SD? Seriously. And did you recently move there from VA or was it the other way around?

    Either way, to even consider cave diving, flying airplanes, etc. you need to be an optimist. However, the next layer under a general "can do" attitude should always ask "How could Murphy kill me today and how am I going to prevent his success?"



 

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