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Thread: Dead in 7 Minutes - The Importance of a Continuous Flow Oxygen Orifice

  1. #21
    Dave Tomblin wedivebc has a reputation beyond repute wedivebc has a reputation beyond repute wedivebc has a reputation beyond repute wedivebc has a reputation beyond repute wedivebc has a reputation beyond repute wedivebc has a reputation beyond repute wedivebc has a reputation beyond repute wedivebc has a reputation beyond repute wedivebc has a reputation beyond repute wedivebc has a reputation beyond repute wedivebc has a reputation beyond repute wedivebc's Avatar
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    Re: Dead in 7 Minutes - The Importance of a Continuous Flow Oxygen Orifice

    Quote Originally Posted by Mark Chase  View Original Post
    I can only assume with UTD that they want a method of diving that can be used to any depth without altering the normal diving system. I am assuming that needle valves are out for reasons unknown and its obvious ECCR is not an option (id be disappointed if it were)
    I think one of the reasons for shunning any leaky valve has to do with the way they donate gas. Once off the loop in gas sharing situation the original config had a shut-off valve to prevent unmetabolized O2 from spiking the PO2. This lead to a failure prone oxygen system. By removing the leaky valve they simplify the setup and make gas donation a little less convoluted.
    Cheers,

    Dave....

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  2. #22
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    Re: Dead in 7 Minutes - The Importance of a Continuous Flow Oxygen Orifice

    I can see the thought process...but.... they talk about using sensors with PO2 displays.

    I've done a sanity bail on a KISS (same thing), when you go back onto the loop the first thing you do is exhale a lung full of low PO2 bailout gas into the loop to dilute it down. If its still hot you do a dil flush.

    Its interesting to see how other people think through and solve problems, but in this case the logic really doesnt seem to stack up. Still, each to their own, its not like I'd be diving that rig/procedure.

  3. #23
    RBW Member alpine44 is on a distinguished road alpine44 is on a distinguished road alpine44's Avatar
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    Re: Dead in 7 Minutes - The Importance of Verifying your ppO2 in shorter intervals

    I have (mis)used a CCR only twice but I think few of the experts will disagree that the ppO2 decay to deadly levels within a few minutes APPLIES TO EVERYONE metabolizing O2 from a closed loop IF NO OXYGEN IS ADDED.

    There are several ways Oxygen can be added to the loop of a CCR and several ways these methods can fail.

    Unless there is an O2 addition method that will NEVER fail, any diligent CCR user would be well advised to check the loop ppO2 IN SHORTER INTERVALS THAN THE LOOP DECAY TIME IN THE WORST CASE SCENARIO.

    In other words, if the loop can go hypoxic in X minutes WHEN (not if) O2 addition fails, then we HAVE TO verify the pp02 every X/2 or X/3 minutes.

    Verifying the ppO2 in shorter intervals than the loop decay to hypoxic will protect us not only from failure of the addition mechanism but also from our own stupidity like jumping in with the O2 closed or having something other than 100% O2 in the O2 bottle. (I again hope that experts concur).

    It appears, that some rebreather users seem to think that checking and interpreting ONE display several times a minute interferes with their diving fun and they hope that some mechanic or electronic contraption will relieve them of this life-critical duty.

    To put this notion in perspective let's just look at where the term "Tango Uniform" or "Tits Up" (supposedly) came from. Early artificial horizons displayed an airplane in normal attitude like this -v*v- (tits down). Tits up means inverted, which is bad news unless you intend to be that way and have the skills to return to normal before hitting the ground.

    An airplane does not just go Tango Uniform by itself and a CCR loop does not go hypoxic without reason. If this "suddenly happens", the pilot was simply asleep at the wheel for quite some time (several minutes in both cases).

    Any freshly FAA-minted pilot will have learned and ingrained to check 5 to 10 instruments several times per minute while listening to the radio, scanning the skies for traffic, looking at charts, changing radio frequencies, talking to passengers/instructors, etc. At the other end of the experience spectrum we have pilots like the famous Chuck Yeager who have refined this situational awareness to where they could correctly observe, interpret, and report hundreds of parameters.

    Why can airplane/helicopter/blimp pilots deal with the element of distraction that gets cited in the rebreather community as an inescapable and, to my surprise, excusable reason for screw ups?

    My explanation is that in the aviation community a reluctance or failure to frequently monitor attitude, altitude, and speed of your airplane is considered an expression of a fundamentally unsafe attitude. Subsequently, operators of airplanes who proclaim they can delegate the responsibility of ACUTE and CONTINUOUS situational awareness to any form of "autopilot" are not considered diligent and competent pilots but accidents waiting to happen.

    Also, the most hairy chested pilots who fly flame-trailing contraptions of raw machismo have absolutely no ego problem with using a PHYSICAL checklist to verify that they are in fact doing their job. I have yet to see a rebreather "pilot" with a physical checklist on a boat, on the water's edge, or even on the set-up bench. Real divers do not need this sissy stuff - WRONG.

    IMO there are systemic reasons, deeply routed in training and peer dynamics, that make aviation "safe by design". If CCR divers already refer to "flying" their units they might as well adopt these proven processes. (Unfortunately, the aversion towards DIR stands in the way of this progress as "They" were already smart enough to apply very similar philosophies and methods to OC diving and who wants to admit their success in that domain)

    A tiny hole in a ruby, while temporarily helpful, will not address the root cause of most rebreather fatalities - lack of diligence, awareness, and focus.
    Last edited by alpine44; 17th June 2011 at 21:10.

  4. #24
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    Re: Dead in 7 Minutes - The Importance of a Continuous Flow Oxygen Orifice

    Sort of a no-shitter article- seems like one of those things that every new rebreather diver should have found out sitting on their couch- you know, couch diving to find the limits of your machine. Of course, what isn't factored in, is the RADICAL change that is imparted by work- sure, 7 minutes sitting on the couch. Not nearly so much swimming hard, or under stress (when one might be more likely to skip the instrument check.) But I agree with Alpine44 above- that long with no check is inexcusable. And one sure as hell shouldn't ever be waiting 7 minutes between instrument checks, or even half that. In a nit-picky sort of way, the difference between aviation instruments and dive computers is that aviation instrumentation is designed to be interpreted quickly- so you can make your cockpit scan in a second and get back outside. With the exception of the X-Link, we haven't really figured that out- numbers are hard to interpret quickly- It is much easier to look at a colored bar graph and match size or color than it is to try to figure out what three numbers are telling you in a half second quick look. Since it seems appropriate, lets carry the aviation analogy one step further for a demonstration. I fly an older helicopter. The two main instruments you have to watch when maneuvering to prevent breaking the engine are shown as strips of colored LEDs with an LED number on the top. Green is good, yellow is mostly bad, height of the bars matter. If I am about to yank a turn, I can make a super quick glance at the colors and size of the bar, and tell roughly how much power I can apply. If I have lots of time to turn, I can read the number and apply the finite amount of power required. A newer helicopter I got to fly had both of these numbers mixed in one gauge- indicated by--- a colored bar. Green good, yellow almost bad, red bad, curved around in a clock shape. This added an additional quick look capability- the angle of the curve is easier to judge than a fixed bar. But in comparison, we haven't figured out this easier to use format for oxygen display. The X-link had a setup where you could see three bars that showed your oxygen in a fixed range, one color of course- but even this was much faster than trying to interpret three two decimal numbers and make the comparison in your head. This number thinking takes more time, and makes a diver less likely to check the gauge then when you can look over and just glance at the instrumentation, and intuitively know where your oxygen is. The situation is compounded when you are at the extreme edges- not enough helium, exhausted from a swim, etc, etc- when it takes an effort to think about the numbers. In these days of fancy fully-programmable, color displays, can we please take a lesson from aviation and think about a graphical display?

    rant off

    jason

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    Re: Dead in 7 Minutes - The Importance of a Continuous Flow Oxygen Orifice

    Quote Originally Posted by rchrds  View Original Post
    Sort of a no-shitter article- seems like one of those things that every new rebreather diver should have found out sitting on their couch- you know, couch diving to find the limits of your machine. Of course, what isn't factored in, is the RADICAL change that is imparted by work- sure, 7 minutes sitting on the couch. Not nearly so much swimming hard, or under stress (when one might be more likely to skip the instrument check.) But I agree with Alpine44 above- that long with no check is inexcusable. And one sure as hell shouldn't ever be waiting 7 minutes between instrument checks, or even half that. In a nit-picky sort of way, the difference between aviation instruments and dive computers is that aviation instrumentation is designed to be interpreted quickly- so you can make your cockpit scan in a second and get back outside. With the exception of the X-Link, we haven't really figured that out- numbers are hard to interpret quickly- It is much easier to look at a colored bar graph and match size or color than it is to try to figure out what three numbers are telling you in a half second quick look. Since it seems appropriate, lets carry the aviation analogy one step further for a demonstration. I fly an older helicopter. The two main instruments you have to watch when maneuvering to prevent breaking the engine are shown as strips of colored LEDs with an LED number on the top. Green is good, yellow is mostly bad, height of the bars matter. If I am about to yank a turn, I can make a super quick glance at the colors and size of the bar, and tell roughly how much power I can apply. If I have lots of time to turn, I can read the number and apply the finite amount of power required. A newer helicopter I got to fly had both of these numbers mixed in one gauge- indicated by--- a colored bar. Green good, yellow almost bad, red bad, curved around in a clock shape. This added an additional quick look capability- the angle of the curve is easier to judge than a fixed bar. But in comparison, we haven't figured out this easier to use format for oxygen display. The X-link had a setup where you could see three bars that showed your oxygen in a fixed range, one color of course- but even this was much faster than trying to interpret three two decimal numbers and make the comparison in your head. This number thinking takes more time, and makes a diver less likely to check the gauge then when you can look over and just glance at the instrumentation, and intuitively know where your oxygen is. The situation is compounded when you are at the extreme edges- not enough helium, exhausted from a swim, etc, etc- when it takes an effort to think about the numbers. In these days of fancy fully-programmable, color displays, can we please take a lesson from aviation and think about a graphical display?

    rant off

    jason

    Very good point, just make sure the color coding does not exclude us the color challenged (red and green the most challenged colors of the spectrum for many of us) so any of their combinations are an issues for us.
    Gabe

  6. #26
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    Re: Dead in 7 Minutes - The Importance of Verifying your ppO2 in shorter intervals

    Quote Originally Posted by alpine44  View Original Post
    A tiny hole in a ruby, while temporarily helpful, will not address the root cause of most rebreather fatalities - lack of diligence, awareness, and focus.


    Corect but thats not the point.

    I lernt on ECCRand dived it till 2007 when i switched to CMF CCR. Till than I thaught id been prety good at monitoring my PP02 (like most ECCR divers claim to be) and switchnig to a unit which didnt give a toss if I ignored it it just let me die, I soon discovered I was actualy prety crap at monitoring my PP02.

    Not because of the decay curve of matabolising it but because of the effects of going up and down and venting / adding gas.

    MCCR taught me how to become atuned to the critical parts of a dive and taught me how often and when to check my PP02.

    CMF just made it possable for me to scooter take picturs catch lobsters and send up spidge without putting task loading stress on me.

    Unlike ECCR its not good enough to let you get complacent but it is good enough to let you enjoy the dive.


    Pure MCCR is just a step too far.



    ATB

    Mark

  7. #27
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    Re: Dead in 7 Minutes - The Importance of a Continuous Flow Oxygen Orifice

    Quote Originally Posted by rchrds  View Original Post
    In these days of fancy fully-programmable, color displays, can we please take a lesson from aviation and think about a graphical display?

    rant off

    jason
    Paging Bruce: how about this for the Predator? I'd pay for it too.

  8. #28
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    Re: Dead in 7 Minutes - The Importance of Verifying your ppO2 in shorter intervals

    Quote Originally Posted by alpine44  View Original Post
    ~snip~ (Unfortunately, the aversion towards DIR stands in the way of this progress as "They" were already smart enough to apply very similar philosophies and methods to OC diving and who wants to admit their success in that domain)

    /~snip~

    Sort of reminded me of one of those kids toys where you crank and crank and finally . . . . . out pops the weasle.



    Franco

  9. #29
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    Re: Dead in 7 Minutes - The Importance of a Continuous Flow Oxygen Orifice

    If you get into situations where you need a constant flow because you got too involved getting a photo, pulling a port hole, catching that 10 pound Lobster, or any other demanding task that you don't take the time to read your handsets, pay attention to your HUD, or don't hear your Solenoid fire, then you shouldn't be diving a Breather....

    Richie

  10. #30
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    Re: Dead in 7 Minutes - The Importance of a Continuous Flow Oxygen Orifice

    Quote Originally Posted by apitkin  View Original Post
    Paging Bruce: how about this for the Predator? I'd pay for it too.
    This is a good suggestion. From avionics research it is clear that the brain interprets shapes quicker than numbers. We'll put it on the list.

    You still need to get at the numbers though for calibration and troubleshooting. That will have to be easily available.

    Bruce
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