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Thread: Possible silly question,

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    New Member wreckferret is an unknown quantity at this point wreckferret's Avatar
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    Possible silly question,

    Hi,

    Would it be possible to use a SCR at depth with trimix as the main gas ?

    If not why ?

    Sorry if this sounds very stupid but I don`t know a lot about the tech side of rebreathers.

  2. #2
    RBW Member decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie's Avatar
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    Quote Originally Posted by wreckferret
    Would it be possible to use a SCR at depth with trimix as the main gas ?
    Short answer is yes.

    Long answer is still yes but with certain procedures. The exact procedures will depend on which SCR you are thinking about, but most will require a "travel" gas to get to depth where the bottom mix is safe to breath.

    Think of SCR as similar to OC. Even if the trimix is in the normoxic range, going thru the SCR at shallow depth will reduce its fiO2 due to the amount of gas discharged per breath, etc. so might not breathable from surface.

    Regardless, you will need to switch to a deco mix on the ascend for deco purpose anyway, thus using the same deco mix as travel mix on the way down.

  3. #3
    New Member Pawel is on a distinguished road Pawel is on a distinguished road Pawel's Avatar
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    Lightbulb

    I believe OMG Azimuth AF is the only recreational SCR designed specifically for trimix. It has two separate flow valves for two on-board mixes. It also has on-board bailout (2x10L) needed for up to 100m dives.

    Cheers,

    Pawel
    www.AliensOfTheSea.com/HDTV

  4. #4
    Stefan Besier caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7's Avatar
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    PRISM Topaz & Sport KISS

    (still owned) MK15

    Welcome Dave.

    In addition to Phi's answer, few SCRs are set up for trimix use when you buy them.
    Using mix in passive addition SCRs like the RB80, EDO04 or Tourill is usually not a problem as gas addition is keyed to you RMV, so they add it as needed. The manufacturers of these units all offer gas switchblocks that allow you to switch supply gases as Phi described. Gases can be plugged in UW, so if you need more than two gases that is possible.

    The only active addition SCR set up for trimix afaik is the Azimuth AF. It has two gas blocks that each allow you to match the flow rate to the O2 content you use. The Azi AF replaces the two 4 ltr tanks with two 10 ltr tanks. If you need more than two mixes you'll have to modify the unit.

    AFAIK training, including the use of trimix, is only offered for the RB80 and Azimuth AF.
    On other SCRs you're on your own.

  5. #5
    RBW Member decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie's Avatar
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    Quote Originally Posted by Pawel
    ...recreational SCR designed specifically for trimix...
    Is that not an oxymoron ? :)

    Anyway, that's still so not true. What do you think the PVR-BASC and RB-80 were designed for ?

  6. #6
    RBW Member decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie has a reputation beyond repute decoweenie's Avatar
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    Quote Originally Posted by caveseeker7
    The only active addition SCR set up for trimix afaik is the Azimuth AF...
    ... from the manufacturer.

    However, there are plenty of people diving the Dolphin with trimix. The first one who did that dived the Doria on the modified A1 years ago, AKAIR.

  7. #7
    Stefan Besier caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7 has a reputation beyond repute caveseeker7's Avatar
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    PRISM Topaz & Sport KISS

    (still owned) MK15

    Correct, Phi.

    Dräger had plans of building an "80 Meter" Dolphin at one point, they made prototypes and ANDI even wrote a few tickets, but Dräger decided to can the project.

    They have, however, given some very limited factory support to a few divers that have modified their units for mix use, having their engineers look over the modifications and help out with suggestions and even bits.

  8. #8
    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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    Hollis Prism 2, Megalodon

    CCR Instructor Trainer

    Quote Originally Posted by caveseeker7
    Correct, Phi.

    Dräger had plans of building an "80 Meter" Dolphin at one point, they made prototypes and ANDI even wrote a few tickets, but Dräger decided to can the project.

    They have, however, given some very limited factory support to a few divers that have modified their units for mix use, having their engineers look over the modifications and help out with suggestions and even bits.
    Do you know of anyone who has pictures or info on this RB? I think they called it the Dolphin 80. I am wondering how they worked.
    Cheers,

    Dave....

    www.wedivebc.com

  9. #9
    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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    Hollis Prism 2, Megalodon

    CCR Instructor Trainer

    Quote Originally Posted by decoweenie
    Is that not an oxymoron ? :)

    Anyway, that's still so not true. What do you think the PVR-BASC and RB-80 were designed for ?
    I think Pawel means recreational as opposed to military/commercial. We tend to forget that what we call technical diving is still recreatonal.
    Cheers,

    Dave....

    www.wedivebc.com

  10. #10
    New Member wreckferret is an unknown quantity at this point wreckferret's Avatar
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    Thanks.

    The main reason for asking this was, when I use twin 12L`s for trimix dives deeper than 70m my bottom gas doesnt last long.

    Rather than spend a fortune on a YBOD could I get away with SCR .

    I would still carry 10L x 2 of deco gas.

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