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Thread: Are mCCR's safer than eCCR's?

  1. #11
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    Re: Are mCCR's safer than eCCR's?

    Yes...

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    Re: Are mCCR's safer than eCCR's?

    Quote Originally Posted by Abbo  View Original Post
    If something goes wrong with an eCCR, there is nothing adding O2 till you hit the manual add. In that case, you quickly metabolize the O2 in your loop and need to add to avoid passing out.
    Let's be sure we're being accurate, because we are living in 2008 and the design on my eccr will not only warn me via the HUD and the vibrating mouthpiece if the PO2 drops drastically, but it will also automatically add O2 into the loop when the PO2 gets to .19.

  3. #13
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    Re: Are mCCR's safer than eCCR's?

    Quote Originally Posted by sfldiver  View Original Post
    Let's be sure we're being accurate, because we are living in 2008 and the design on my eccr will not only warn me via the HUD and the vibrating mouthpiece if the PO2 drops drastically, but it will also automatically add O2 into the loop when the PO2 gets to .19.
    Until the crystal oscillator driving the processor stops working, or there is just the right power noise or battery bounce, or a short on a scrubber stick connector, or a big ESD shock, or the O2 sensors take out the ADC because the internal load fails on one sensor causing it to generate a very high voltage, or any one of lots of other failure. Unless your eCCR meets EN61508, I can virtually guarantee it has lots of these single points of failure. I can demonstrate them on most units quite easily.

    Alex

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    Re: Are mCCR's safer than eCCR's?

    Quote Originally Posted by AD_ward9  View Original Post
    Until the crystal oscillator driving the processor stops working, or there is just the right power noise or battery bounce, or a short on a scrubber stick connector, or a big ESD shock, or the O2 sensors take out the ADC because the internal load fails on one sensor causing it to generate a very high voltage, or any one of lots of other failure. Unless your eCCR meets EN61508, I can virtually guarantee it has lots of these single points of failure. I can demonstrate them on most units quite easily.

    Alex
    I assume something is going to fail, which is why I adhere to frequent PO2/system monitoring self-discipline to addresses most of that.

    My Rebreather displays the PO2 on both handsets. I monitor my handsets/hud frequently and always carry a backup deco computer linked to an independent 4th cell. Plus, I always try to really pad the amount of gas I carry as bailout/deco, which adds another layer of comfort in my backup.

    The only thing I would like to have is a BOV, but I'm holding out for a smaller and more streamlined design, other than the larger Golem one most Optima divers use. However, I do keep my bailout 2nd stage on a very short cord around my neck at all times.

    I feel very comfortable with the extent of redundancy currently contained within my setup.

    Adrian

  5. #15
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    Re: Are mCCR's safer than eCCR's?

    Quote Originally Posted by sfldiver  View Original Post
    Let's be sure we're being accurate, because we are living in 2008 and the design on my eccr will not only warn me via the HUD and the vibrating mouthpiece if the PO2 drops drastically, but it will also automatically add O2 into the loop when the PO2 gets to .19.
    Yes and No. As Alex explained things can still go wrong. I'll hapily accept that the rebreather becomes safer over time. However every time we seem to make the same wrong assertion. It is not the rebreather that kills it is the rebreather/diver combination that is responsible for the outcome. My biggest fear is that a more reliable rebreather lowers the awareness of the diver diving it. So the frequence may go down but if the likelyhood of a diver not picking up on issues increases then the overall rate can still go either way.

  6. #16
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    Re: Are mCCR's safer than eCCR's?

    Hello,

    I think this has been discussed quite well. Alex, in the OR rebreather threads, provides very compelling information on this subject.

    Regardless of why it is, the best publicly available data set (Alex's) very clearly supports a statement that KISS style manufactured rebreathers are safer than eCCR manufactured rebreathers. It is recognized that the data set available doesn't fully explain why, although the likely causes provide some guidance.

    Many valid debates are ongoing on terms of why it is so, but I don't think you can reasonable suggest the conclusion isn't valid.

    In the end you can ignore the available data set and come to whatever conclusions you want -- but you should be honest that without some data it isn't a supportable position.


    Sincerely,

    Paul
    Last edited by PaulTG2; 15th August 2008 at 22:08.
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    Re: Are mCCR's safer than eCCR's?

    Quote Originally Posted by sfldiver  View Original Post
    Let's be sure we're being accurate, because we are living in 2008 and the design on my eccr will not only warn me via the HUD and the vibrating mouthpiece if the PO2 drops drastically, but it will also automatically add O2 into the loop when the PO2 gets to .19.
    As I said, "if something goes wrong with your 'breather". Alex has pointed out a host of things that can go wrong and take out your electronics. The simplest, which he didn't mention, is your batteries failing on you: I'm ashamed to say I had that happen on me once. Some batteries have a fast decay curve at the end of their lives - so fast that you never see a low battery warning. No drama: I shot a bag and manually added till I reached the surface; nothing bruised but my pride. It taught me a few valuable lessons.

    Even if you have working electronics, your solenoid can fail - open or closed. If it fails closed, it won't be firing when your PO2 hits .19.

    So, even with an Optima, things go wrong. The unit gets old and parts fail (like us really). If it's not adding O2, you must. Without a CFO, that's a full-time job while you're rising in the water column. That was my point: trust is a vice.

  8. #18
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    Re: Are mCCR's safer than eCCR's?

    Let the dead rebreather divers chime in on this one. Take a poll on who was using an eCCR vs mCCR.

    I wonder if they would switch if they could do that last dive over again???

    (no disrespect intended to the deceased or their families)


    russell helsley
    seattle, usa

  9. #19
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    Re: Are mCCR's safer than eCCR's?

    Quote Originally Posted by rhelsley  View Original Post
    Let the dead rebreather divers chime in on this one. Take a poll on who was using an eCCR vs mCCR.

    I wonder if they would switch if they could do that last dive over again???

    (no disrespect intended to the deceased or their families)


    russell helsley
    seattle, usa
    Or more usefully compare accident rates vs just the number of accidents. Unless you know how many hrs diving get logged on each type theres no real way to evaluate hazardousness.

    Anybody know if there is any reliable info on how many RB dives are done each year? Heck for all we know they may be safer than OC on a per dive basis.

  10. #20
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    Re: Are mCCR's safer than eCCR's?

    mCCR has failure possibilities as a eCCR has. We can have O2 feeding problems. On a mCCR a orifice can clog from dirt or rust. On the eCCR we can have problems with solenoids (open -closed).On the electronic is similar - O2 cells problems will be the main problem, but this is the same for both. A flooded displays, empty batteries? The same problem for both. A frozen controller that indicate a nice 1.2 PPO2 also when no Oxygen is be injected is a construction fault and can happen on eCCR only, but should not, if the system design is OK. A eCCR with one main and one secondary (two different electronics,different batteries ...) is quite save. I prefer one handset and one HUD with smithercode. If there is a possibility to isolate the solenoid you can fly the unit manually if You have solenoid problems and still use the same O2 tank.The biggest difference witch makes mCCR saver than eCCRs is the practice and training on both units. A mCCR diver looks his handset or HUD much often because he know he will not live long without doing that. A eCCR will control the PPO2 less and if the unit works great for years maybe get to much confidence on the electronic.So the key factors come down to the diver

    PS: I use a eCCR in hybrid mode with a gas flow of 0,7l/min
    Last edited by gerstl_ossi; 16th August 2008 at 19:22.

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