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Thread: Differences between eCCR’s and mCCR’s design that may effect mortality rates

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    Shearwater Copis Diver Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy's Avatar
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    Differences between eCCR’s and mCCR’s design that may effect mortality rates

    I’m hoping that this thread can be for a productive discussion between those who want to debate which design differences between eCCR's and mCCR's may contribute to reducing accident rates. This thread is not intended to be a debate about weather training and skill are the only factor in mortality rates…that’s been beaten to death and I think we all understand the point, training and vigilance are at the very least the number one contributing factors to keeping you alive under water and yes, all rebreathers can kill you. I do believe, even though I’m starting this thread, that it's best to continue emphasizing that the biggest factor effecting safety in any kind of rebreather is diver skill, so please, lets leave that argument to other threads.

    I wish to expand on some of the points that have come up in other similar threads lately. I believe there is value in attempting to identify the possible contributing factors to the reduced mortality rate specifically due to design differences between mCCR’s and eCCR’s. I believe this could lead to improvements in eCCR design or style of operation that could some effect on mortality rates.


    I've only used a Kiss in a pool and am by no means an authority on it's function, but it is the mCCR that i am most familiar with so that is my main mCCR to compare with the eCCR’s I’m familiar.

    From limited talking around, it seems that an orifice that is well matched to metabolic rate/o2 consumption results in a very stable PO2 through much of the dive, requiring manual injection mostly on ascent. So, since addition is so rare maybe it's not the regular checking of PO2 and adjusting that leads to fewer fatalities. Certainly the mindset could be the major factor and I think it is also possible that it's the constant flow orifice or maybe the BOV. Also, it may not be any one thing but rather the cumulative effect of a wide range of factors.

    The main factors that i can see that set the KISS apart from an eCCR are:

    - use of a BOV (though some eCCR's have them too)
    - a constant flow orifice that requires some "topping off" by the diver but provides a minimum of life supporting o2...basically a positive feedback loop for oxygen addition as apposed to the negative feedback loop of the eCCR
    - No electronic controller driven solenoid…less dependent on electronics to govern gas balance. (it would seem that orifice cloggin is a lot less likely than electronic malfunction, so it appears the balance of risk between the two favors the constant orifice)
    - the diver must be engaged, especially on ascent where po2 drops the fastest.
    -not the best build quality, but apparently more than adequate in the ways that count.

    A BOV may turn out to be one of the deciding factors. Perhaps the use of a constant flow orifice and the diver for additional injection works better because it's a kind of positive feedback loop (based on cumulative causation) for O2 addition preventing hypoxia as apposed to the negative feedback loop of an electronic controller driven solenoid. Interestingly, hyperoxia does not seem to be at all common on the KISS, responsibility for avoiding that is left entirely up to the diver.

    Perhaps there could be a hybrid of the eCCR and mCCR that would be the best of both worlds. Certianly adding a BOV to eCCR’s is becoming more common.

    While the sample group will remain very small for quite some time to come, making any kind of comparison of limited value, the sample group of living divers and the fatality group are growing and watching accident reports for things like weather or not there was a BOV on the rig or weather the diver was known for “flying manually” will be of interest to me. (A standardized accident report would be a very good thing for us to create and promote to track contributing factors. At this point we are very in the dark with respect to fact driven accident analysis.)

    There is one difference with the KISS which I’m most apt to point to with respect to it’s potential effect on mortality rates, it’s the constant flow orifice. Incorporating some version of it into the eCCR may turn out to have the biggest effect, diver skill not withstanding, in accident rates. Since I’m drawn mostly to eCCR’s for their apparent advantages, I’m tempted to think of ways to hybridize the o2 injection system with mCCR’s, of course this may just be going further in the direction of complicating things, if so, it won't likely proove worth it.

    Perhaps the positive feedback system of the constant flow orifice with a solenoid assist would be helpful, closely matching the metabolic rate of consumption of the diver but can be “topped up” by the electronic controller if the diver fails to respond to a precipitous drop in PO2 (a version of flying an eCCR manually) while at the same time showing warnings through the HUD, Handset and Buzzer (provding the advantage of additional warning of the typical eCCR).

    Or maybe simply using all the bells and whistles of an eCCR like a HUD, temp stick (vision), PO2 warnings, buzzers with the one acception of leaving out an electronic controlled solenoid, instead incorporating a KISS style constant flow orifice. Maybe this would be the best of both worlds, requiring the diver to add oxygen beyond the minimum required to sustain life while reducing the risks associated with a electronics injection malfunction.

    Your thoughts?

    Gill Envy

  2. #2
    RBW Member Retardboy is an unknown quantity at this point Retardboy's Avatar
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    Re: Differences between eCCR’s and mCCR’s design that may effect mortality rates

    What about reprograming a standard eCCR so that you can`t set the electronics to high setpoint? One setpoint only, 0,2 ppO2, enough to sustain life, but so low that you would massively violate decompression obligation if you don`t pay attention. However, I think your idea of replacing the solenoid with a CMF orifice is a better idea.But how should the issue with depth limitation be solved? An adjustable needlevalve like the Pelagian uses is one solution.

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    RBW Member PaulTG2 is a name known to all PaulTG2 is a name known to all PaulTG2 is a name known to all PaulTG2 is a name known to all PaulTG2 is a name known to all PaulTG2 is a name known to all PaulTG2 is a name known to all PaulTG2 is a name known to all PaulTG2 is a name known to all PaulTG2 is a name known to all PaulTG2 is a name known to all PaulTG2's Avatar
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    Re: Differences between eCCR’s and mCCR’s design that may effect mortality rates

    Hello,

    Having followed quite a bit of the mCCR/eCCR/SCR discussions have been interesting. It is almost impossible to not read these ongoing debates if you watch the boards for more than a week. It seems easier to just discuss politics and religion.

    I've thought along the same lines of having an orifice on an eCCR. Fitting it would certainly be easy as nothing else would need to change. With a shut-off you could choose to use or not to use. It would save wear and tear on the solenoid and batteries and provide for a longer safety interval should the electronics or solenoid fail closed.

    On the other hand it is one more thing to deal with, another thing to fail, another part to maintain, another issue when trying to determine safe depth limits for the kit....

    I'll dive the Meg for a while until I figure out all the other niggling details.


    Not certain it would have prevented many of the accidents. In the end changes and considerations need to be driven by the true causes of incidents and accidents. Having some organization that is able to get the real facts on accidents (ala the NTSB) would probably go farther in increasing safety than various debates that keep recurring.

    --p

  4. #4
    Shearwater Copis Diver Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy's Avatar
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    Re: Differences between eCCR’s and mCCR’s design that may effect mortality rates

    Quote Originally Posted by Retardboy  View Original Post
    What about reprograming a standard eCCR so that you can`t set the electronics to high setpoint? One setpoint only, 0,2 ppO2, enough to sustain life, but so low that you would massively violate decompression obligation if you don`t pay attention. However, I think your idea of replacing the solenoid with a CMF orifice is a better idea.But how should the issue with depth limitation be solved? An adjustable needlevalve like the Pelagian uses is one solution.
    That is a possibility as well, using decompression as one of the motivations to be persistant in monitoring AND manually adjusting po2. My concern is that you still are not getting the electronics out of the actual injection process, which seems to either add the necessary impetous to stay actively on top of one's po2 and or gets electronic malfunction of the injection system out of the picture.

    Gill Envy

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    Re: Differences between eCCR’s and mCCR’s design that may effect mortality rates

    Quote Originally Posted by Gill Envy  View Original Post
    I’m hoping that this thread can be for a productive discussion between those who want to debate which design differences between eCCR's and mCCR's may contribute to reducing accident rates. This thread is not intended to be a debate about weather training and skill are the only factor in mortality rates…that’s been beaten to death and I think we all understand the point, training and vigilance are at the very least the number one contributing factors to keeping you alive under water and yes, all rebreathers can kill you. I do believe, even though I’m starting this thread, that it's best to continue emphasizing that the biggest factor effecting safety in any kind of rebreather is diver skill, so please, lets leave that argument to other threads.

    I wish to expand on some of the points that have come up in other similar threads lately. I believe there is value in attempting to identify the possible contributing factors to the reduced mortality rate specifically due to design differences between mCCR’s and eCCR’s. I believe this could lead to improvements in eCCR design or style of operation that could some effect on mortality rates.


    I've only used a Kiss in a pool and am by no means an authority on it's function, but it is the mCCR that i am most familiar with so that is my main mCCR to compare with the eCCR’s I’m familiar.

    From limited talking around, it seems that an orifice that is well matched to metabolic rate/o2 consumption results in a very stable PO2 through much of the dive, requiring manual injection mostly on ascent. So, since addition is so rare maybe it's not the regular checking of PO2 and adjusting that leads to fewer fatalities. Certainly the mindset could be the major factor and I think it is also possible that it's the constant flow orifice or maybe the BOV. Also, it may not be any one thing but rather the cumulative effect of a wide range of factors.

    The main factors that i can see that set the KISS apart from an eCCR are:

    - use of a BOV (though some eCCR's have them too)
    - a constant flow orifice that requires some "topping off" by the diver but provides a minimum of life supporting o2...basically a positive feedback loop for oxygen addition as apposed to the negative feedback loop of the eCCR
    - No electronic controller driven solenoid…less dependent on electronics to govern gas balance. (it would seem that orifice cloggin is a lot less likely than electronic malfunction, so it appears the balance of risk between the two favors the constant orifice)
    - the diver must be engaged, especially on ascent where po2 drops the fastest.
    -not the best build quality, but apparently more than adequate in the ways that count.

    A BOV may turn out to be one of the deciding factors. Perhaps the use of a constant flow orifice and the diver for additional injection works better because it's a kind of positive feedback loop (based on cumulative causation) for O2 addition preventing hypoxia as apposed to the negative feedback loop of an electronic controller driven solenoid. Interestingly, hyperoxia does not seem to be at all common on the KISS, responsibility for avoiding that is left entirely up to the diver.

    Perhaps there could be a hybrid of the eCCR and mCCR that would be the best of both worlds. Certianly adding a BOV to eCCR’s is becoming more common.

    While the sample group will remain very small for quite some time to come, making any kind of comparison of limited value, the sample group of living divers and the fatality group are growing and watching accident reports for things like weather or not there was a BOV on the rig or weather the diver was known for “flying manually” will be of interest to me. (A standardized accident report would be a very good thing for us to create and promote to track contributing factors. At this point we are very in the dark with respect to fact driven accident analysis.)

    There is one difference with the KISS which I’m most apt to point to with respect to it’s potential effect on mortality rates, it’s the constant flow orifice. Incorporating some version of it into the eCCR may turn out to have the biggest effect, diver skill not withstanding, in accident rates. Since I’m drawn mostly to eCCR’s for their apparent advantages, I’m tempted to think of ways to hybridize the o2 injection system with mCCR’s, of course this may just be going further in the direction of complicating things, if so, it won't likely proove worth it.

    Perhaps the positive feedback system of the constant flow orifice with a solenoid assist would be helpful, closely matching the metabolic rate of consumption of the diver but can be “topped up” by the electronic controller if the diver fails to respond to a precipitous drop in PO2 (a version of flying an eCCR manually) while at the same time showing warnings through the HUD, Handset and Buzzer (provding the advantage of additional warning of the typical eCCR).

    Or maybe simply using all the bells and whistles of an eCCR like a HUD, temp stick (vision), PO2 warnings, buzzers with the one acception of leaving out an electronic controlled solenoid, instead incorporating a KISS style constant flow orifice. Maybe this would be the best of both worlds, requiring the diver to add oxygen beyond the minimum required to sustain life while reducing the risks associated with a electronics injection malfunction.

    Your thoughts?
    WOW Gill, you have come a long way in a year, great ideas and thoughts--have some GREEN !!!!!!!!!!!!!!!!!!!!!!

  6. #6
    Shearwater Copis Diver Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy's Avatar
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    Re: Differences between eCCR’s and mCCR’s design that may effect mortality rates

    Quote Originally Posted by PaulTG2  View Original Post
    Hello,
    ....
    I've thought along the same lines of having an orifice on an eCCR. Fitting it would certainly be easy as nothing else would need to change. With a shut-off you could choose to use or not to use. It would save wear and tear on the solenoid and batteries and provide for a longer safety interval should the electronics or solenoid fail closed.

    On the other hand it is one more thing to deal with, another thing to fail, another part to maintain
    yeah, it would only be worth it if the threshold of diminishing returns was overcome. i'm leaning in the direction of not even having solendoid injection be an option.

    Quote Originally Posted by PaulTG2  View Original Post
    Not certain it would have prevented many of the accidents. In the end changes and considerations need to be driven by the true causes of incidents and accidents. Having some organization that is able to get the real facts on accidents (ala the NTSB) would probably go farther in increasing safety than various debates that keep recurring.

    --p
    Amen, brother!

    Gill Envy

  7. #7
    Shearwater Copis Diver Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy has a reputation beyond repute Gill Envy's Avatar
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    Re: Differences between eCCR’s and mCCR’s design that may effect mortality rates

    Quote Originally Posted by silentscuba  View Original Post
    WOW Gill, you have come a long way in a year, great ideas and thoughts--have some GREEN !!!!!!!!!!!!!!!!!!!!!!
    hey Curt, thanks!

    Gill Envy

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    Re: Differences between eCCR’s and mCCR’s design that may effect mortality rates

    A few comments:

    Quote Originally Posted by Gill Envy
    The main factors that i can see that set the KISS apart from an eCCR are:

    - use of a BOV (though some eCCR's have them too)
    - a constant flow orifice that requires some "topping off" by the diver but provides a minimum of life supporting o2...basically a positive feedback loop for oxygen addition as apposed to the negative feedback loop of the eCCR
    - No electronic controller driven solenoid…less dependent on electronics to govern gas balance. (it would seem that orifice cloggin is a lot less likely than electronic malfunction, so it appears the balance of risk between the two favors the constant orifice)
    - the diver must be engaged, especially on ascent where po2 drops the fastest.
    -not the best build quality, but apparently more than adequate in the ways that count.
    -Er... there is nothing wrong with the build quality -- it's excellent.
    -You might as well throw 3 indepedent displays in to the mix.

    Quote Originally Posted by Gill Envy

    There is one difference with the KISS which I’m most apt to point to with respect to it’s potential effect on mortality rates, it’s the constant flow orifice. Incorporating some version of it into the eCCR may turn out to have the biggest effect, diver skill not withstanding, in accident rates. Since I’m drawn mostly to eCCR’s for their apparent advantages, I’m tempted to think of ways to hybridize the o2 injection system with mCCR’s, of course this may just be going further in the direction of complicating things, if so, it won't likely proove worth it.
    This presently exists in the form of a "Hammer-KISS" or eKISS. I have one. Not sure what the numbers are, perhaps 30


    Quote Originally Posted by Gill Envy
    Perhaps the positive feedback system of the constant flow orifice with a solenoid assist would be helpful, closely matching the metabolic rate of consumption of the diver but can be “topped up” by the electronic controller if the diver fails to respond to a precipitous drop in PO2 (a version of flying an eCCR manually) while at the same time showing warnings through the HUD, Handset and Buzzer (provding the advantage of additional warning of the typical eCCR).
    Some subset of eKISS divers opt to plug their orifice. Maybe units without orifices plugged should be termed m/eKISS units (or, more generally, m/eCCR).


    I do think a constant flow orifice is inherently less likely to fail than a solenoid (no moving parts excepting the manual add).

  9. #9
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    Re: Differences between eCCR’s and mCCR’s design that may effect mortality rates

    Seems to me these options are already available.

    There are parachute systems out there for the KISS and there are people out there diving Megs HHs and YBOSs manually with the solenoid as back up.

    It seems to me that you can offer a new training system (like Cedric's Breather idea) to formalize the use of such systems or you can piss in the wind trying to convince others that its a good idea.

    At the end of the day it was summed up beautifully for me on another thread. A astute diver said, (please excuse paraphrasing here) some divers buy kit of the shelf and just expect it to work. When it doesn't they send it back to base to get fixed bitch about it ands expect it to work when it gets back. Some divers buy kit and just accept that hours of fettling fiddling and messing around with soldering irons is part of the game.

    If i was doing DIR CCR I think id be insisting everyone dived a Copis MEG with HUD.

    What do you think leon? send me a free Copis Meg and ill get it all started straight away :D

    ATB

    Mark Chase

  10. #10
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    Re: Differences between eCCR’s and mCCR’s design that may effect mortality rates

    Quote Originally Posted by Mark Chase  View Original Post
    If i was doing DIR CCR I think id be insisting everyone dived a Copis MEG with HUD.

    Thats why i just added a Shearwater HUD to my KISS Classic


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