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Thread: SCR vs CCR

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    SCR vs CCR

    Though I'd try to sort out which type gave what advantages, please feeel free to add to / correct. Then when we get a decent set of pros / cons / Limitations for each we can put an artical together for refernce for those thinking of which type to get :)

    PSCR Passive Semi-Closed Rebreather
    Extended gas durations
    Variable Mix based on available gas

    ASCR Active Semi-Closed Rebreather
    Extended gas Duration
    Set mix based on available gas

    MCCR Manual Closed Circuit Rebreather
    Extended gas durations
    Increased decompression benefit
    Set O2 addition

    ECCR Electronic Closed Circuit Rebreather
    Extended gas durations
    Increased decompression benefit
    Controlled Set Point

  2. #2
    Been thinking about this - I think that the terms passive and active should be reversed - its too late for that I know but here's my logic:

    There are two sorts of rebreather - semi-closed where some gas is dumped all the time and fully closed whereby gas is only lost when ascending.

    There are two sorts of gas addition - constant flow and some form of triggered addition.

    In an active SCR (like a Draeger or Azimuth) the gas is bled in continously at a rate such that the ppO2 is sufficient to sustain life and not too high to tox the diver. What is not used is wasted therefore when the diver is at rest more gas is lost then when working hard.

    In a triggered addtion SCR like the RB80 some of the gas is dumped on each breath and added when the CL bottoms out (OK so active SCR's also have ADV's but they are not normally triggered when swimming level). Because to this the amount of gas lost is keyed to the diver's breathing.

    All SCR's (for the time being) use one mix at a time as a drive gas and your diving profile is limited by that (unless you start to swop gases on the fly). For me this is the biggest drawback. You need to tailor your dive to the mix or vice versa. Monitoring of O2 level is not necessary but highly desirable

    MCCR's like the KISS also bleed gas in constantly lke active SCR's - however only O2 is bled in at a rate close to the diver's metabolism though it might need to be topped up occasionally. Diluent is added seperately.

    ECCR's use triggered addition except that the trigger is an electronically controlled valve which responds to the level of oxygen in the loop.

    All CCR's are more versatile in the dive profiles that you can carry out. Your maximum depth is still limited by the choice of diluent but they essentially blend nitrox or trimix on the fly. Monitoring of ppO2 is essential.

  3. #3
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    I guess this is a very simple point but will make it so we don't miss it.

    Simplicity - SCRs like the Dolphin and Ray are very simple to set up, clean, operate etc...

    Which means greatly reduced maintainence compared to a CCR.

    Stuart

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    PRISM Topaz & Sport KISS

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    Wait until you see a SportKiss. They are so simple it's gonna make you want to have one.

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    lol I have allreadybeen tempted to by decodivers evo....dont tempt me!

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    CCR2000, Megalodon, Homebuilt

    Norge, FGT, mk15, KISS, Inspo

    i have the classic kiss and believe you me, it is very simple to keep clean... :D

    /JOnny

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    Quote Originally Posted by JonnyB
    i have the classic kiss and believe you me, it is very simple to keep clean... :D

    /JOnny
    I could clean 5 SK's by the time you clean your CK, Jonny... ;)

    Seriously, the CK is also easy to clean in general, but if you want to get to every corner, the SK is much easier and quicker since everything is modular and could be taken apart with no tools.

    I have both units sat side-by-side dissembled to show new buyers and so far everyone bought the SK from me once they see how easy it is to maintain the SK.

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    Quote Originally Posted by decoweenie
    I could clean 5 SK's by the time you clean your CK, Jonny... ;)
    Not if you were wearing Johnny's outfit, though.
    Two, maybe three, but no more than that. :p

  9. #9
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    Types of RB

    Quote Originally Posted by Duncan Price
    Been thinking about this - I think that the terms passive and active should be reversed - its too late for that I know but here's my logic:

    There are two sorts of rebreather - semi-closed where some gas is dumped all the time and fully closed whereby gas is only lost when ascending.

    There are two sorts of gas addition - constant flow and some form of triggered addition.

    In an active SCR (like a Draeger or Azimuth) the gas is bled in continously at a rate such that the ppO2 is sufficient to sustain life and not too high to tox the diver. What is not used is wasted therefore when the diver is at rest more gas is lost then when working hard.

    In a triggered addtion SCR like the RB80 some of the gas is dumped on each breath and added when the CL bottoms out (OK so active SCR's also have ADV's but they are not normally triggered when swimming level). Because to this the amount of gas lost is keyed to the diver's breathing.

    All SCR's (for the time being) use one mix at a time as a drive gas and your diving profile is limited by that (unless you start to swop gases on the fly). For me this is the biggest drawback. You need to tailor your dive to the mix or vice versa. Monitoring of O2 level is not necessary but highly desirable

    MCCR's like the KISS also bleed gas in constantly lke active SCR's - however only O2 is bled in at a rate close to the diver's metabolism though it might need to be topped up occasionally. Diluent is added seperately.

    ECCR's use triggered addition except that the trigger is an electronically controlled valve which responds to the level of oxygen in the loop.

    All CCR's are more versatile in the dive profiles that you can carry out. Your maximum depth is still limited by the choice of diluent but they essentially blend nitrox or trimix on the fly. Monitoring of ppO2 is essential.
    Duncan,

    I like your analysis, and the way it breaks down. It may not be too late. If we agree on the nomenclature, and start using it that way, we might set a trend!

    Rob

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