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Thread: Activating the sorb on a CCR Bail out Rebreather

  1. #11
    RBW Member DeepB is an unknown quantity at this point DeepB's Avatar
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    Re: Activating the sorb on a CCR Bail out Rebreather

    Quote Originally Posted by rohan  View Original Post
    As for newbies, why only newbies? You too "experienced" for that? My eyes roll at what some people practice and maybe not their fault, the way they are taught.
    At the end of the day, your life, up to you.
    you misunderstood me. i said I AM to unexperienced (aka newbie) to not follow procedures i was taught in my course until i am very sure it is not needed.
    as for the more experienced divers i guess they have their reasons to do it either way.

    Quote Originally Posted by sea2summit
    If you learned it what exactly did you learn other than "pre breath for 5 minutes"?
    i learned that the scrubber needs that amount of prebreathing to funkcion properly (temperature, humidity).

    regards
    DeepB

  2. #12
    Doing What Works jcook is an unknown quantity at this point jcook's Avatar
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    Re: Activating the sorb on a CCR Bail out Rebreather

    Wow, way off the original topic as I assumed.

    Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about. We are taught to pre-breathe to start up the chemical process of the sorb heating up and removing the CO2. If you ever look at a scrubber with some sort of temp reading, you will see the temp go up after a few min (depending on ambient temp) dramatically, like 10F or so degrees. Yes even modern sorb needs to have the chemical reaction started, it may take less time but it still needs to be done, if not you are putting your life at risk.

    Anyways back to the original topic please! How are you guys using you BOB's for the first few min? Thanks.
    Last edited by jcook; 27th June 2010 at 19:56.

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    Re: Activating the sorb on a CCR Bail out Rebreather

    Quote Originally Posted by jcook  View Original Post
    Wow, way off the original topic as I assumed.

    Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about. We are taught to pre-breathe to start up the chemical process of the sorb heating up and removing the CO2. If you ever look at a scrubber with some sort of temp reading, you will see the temp go up after a few min (depending on ambient temp) dramatically, like 10F or so degrees. Yes even modern sorb needs to have the chemical reaction started, it may take less time but it still needs to be done, if not you are putting your life at risk.

    Anyways back to the original topic please! How are you guys using you BOB's for the first few min? Thanks.
    aah, CO2 is the activator and Heat is the byproduct...

  4. #14
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    Re: Activating the sorb on a CCR Bail out Rebreather

    Quote Originally Posted by jcook  View Original Post
    Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about. We are taught to pre-breathe to start up the chemical process of the sorb heating up and removing the CO2. If you ever look at a scrubber with some sort of temp reading, you will see the temp go up after a few min (depending on ambient temp) dramatically, like 10F or so degrees. Yes even modern sorb needs to have the chemical reaction started, it may take less time but it still needs to be done, if not you are putting your life at risk.
    Easy to settle this question experimentally (where's Simon Mitchell when you need him?) by measuring the CO2 in the inhale limb of the rebreather when you start breathing from it. I know what the answer's going to be, because I see it every day in patients under anaesthesia breathing from a rebreathing system that uses a CO2 absorbent that works in exactly the same way (and some rebreather divers use underwater).

    You don't need to prebreathe to start the scrubber working. The chemical reaction starts immediately. Just because it takes a few minutes for the rise in temperature of the sodalime to diffuse to the thermistor in the temp stick doesn't mean the reaction isn't already going.

    A useful way to make sure your BOB is working is to breathe it during the descent, then switch to your main unit.

    Andy

  5. #15
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    Re: Activating the sorb on a CCR Bail out Rebreather

    Actually, I think the task loading is worth it. Yes, the sorb should be almost immediately active, BUT, there's a tremendous psychological comfort in KNOWING your BOB will work immediately. LOTS of issues with early bobs flooding on descent, and also, you often have to breathe the loop of the bob to move gas round the loop/ensure a good mix of the gas in the bob...

  6. #16
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    Re: Activating the sorb on a CCR Bail out Rebreather

    Quote Originally Posted by DeepB  View Original Post
    you dont really think that you will detect a CO2 bypass by prebreathing 5min not stressed at the surface?
    Take your scrubber out, breath off it for 5 minutes while you are walking down to the waters edge with your bailout tanks and let me know how things go.
    Cheers,

    Dave....

    www.wedivebc.com

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    Re: Activating the sorb on a CCR Bail out Rebreather

    Quote Originally Posted by jcook  View Original Post
    Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about. ...
    my God....

    have you ever done any testing on sorb? in a lab, in practice?
    so don't spread such nonsense!


    put a breather with good sorb in the ansti machine, at 40m depth, water at 4° celcius, let the system cool down completely, breath the unit cold (no CO2 injection) for 10 minutes
    then inject 1.6 l/m STPD CO2 in the unit, and see what comes out at the end of the scrubber:

    NOTHING, ZERO, NADA

    no CO2 at all: the scrubber works from the very first breath!

    and now tell me about your testing, and how you found the opposite result!

    paul
    www.rEvo-rebreathers.com
    ...."Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about!"...
    .... to get more accurate CO2 injection in the breathing machine we put 2 mass flow controllers in series ...
    .... The noise is a few tens of nano-volts, so DL were able to reduce the output voltage ...
    .... radial scrubbers give longer dwell time than axials...
    .... the earth is flat and ...

  8. #18
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    Re: Activating the sorb on a CCR Bail out Rebreather


  9. #19
    RBW Member DeepB is an unknown quantity at this point DeepB's Avatar
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    Re: Activating the sorb on a CCR Bail out Rebreather

    Quote Originally Posted by wedivebc  View Original Post
    Take your scrubber out, breath off it for 5 minutes while you are walking down to the waters edge with your bailout tanks and let me know how things go.
    yes, of course, but if you have a 100% bypass you must have done something terribly wrong. and on the unit i dive (Kiss Classic) i dont know what could cause this other than forgetting the whole scrubber.
    but again, i am just a beginner, and there might be many things i am not thinking of.

    regards
    DeepB

  10. #20
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    Re: Activating the sorb on a CCR Bail out Rebreather

    Quote Originally Posted by jcook  View Original Post
    Wow, way off the original topic as I assumed.

    Yes you have to pre-breathe to activate the scrubber sorb, anyone who says different doesn't know what they are talking about. We are taught to pre-breathe to start up the chemical process of the sorb heating up and removing the CO2. If you ever look at a scrubber with some sort of temp reading, you will see the temp go up after a few min (depending on ambient temp) dramatically, like 10F or so degrees. Yes even modern sorb needs to have the chemical reaction started, it may take less time but it still needs to be done, if not you are putting your life at risk.
    Uhm, I guess life is but a dream. I must be dead and am just too stupid to realize it. I only pre-breathe the unit when the scrubber bed is cold. i.e. <10C No one in our group has ever had a problem.


    Dale

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