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Thread: CMF orifice size

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    RBW Member trakrat is on a distinguished road trakrat is on a distinguished road trakrat's Avatar
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    rEvo

    CMF orifice size

    hi
    i'm wondering about why cmf orifice and pressure's on rebreathers are kept low 8-12 bar which restricts the max depth
    i suppose the smaller the jet and the higher the pressure needed to deliver the correct amount of o2 the more heat is produce in the jet?
    but at what pressure/orifice size will it become unsafe i'm sure there must of been some study done on this somewhere but i can't find any
    so any help would be appreciated
    rob

  2. #2
    Dark, cold and wet. DwayneJ is a glorious beacon of light DwayneJ is a glorious beacon of light DwayneJ is a glorious beacon of light DwayneJ is a glorious beacon of light DwayneJ is a glorious beacon of light DwayneJ is a glorious beacon of light DwayneJ is a glorious beacon of light DwayneJ is a glorious beacon of light DwayneJ is a glorious beacon of light DwayneJ is a glorious beacon of light DwayneJ is a glorious beacon of light DwayneJ's Avatar
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    rEvo III Mini rMS

    rEvo III Standard hCCR

    Re: CMF orifice size

    Quote Originally Posted by trakrat  View Original Post
    hi
    i'm wondering about why cmf orifice and pressure's on rebreathers are kept low 8-12 bar which restricts the max depth
    i suppose the smaller the jet and the higher the pressure needed to deliver the correct amount of o2 the more heat is produce in the jet?
    but at what pressure/orifice size will it become unsafe i'm sure there must of been some study done on this somewhere but i can't find any
    so any help would be appreciated
    rob
    Primary concern is the IP capabilities of the 1st stage. For example, the DS4 becomes unstable around 12+ bar. Again, as an example, Techme sells a modified DS4 spring to handle higher IP pressures.

    rEvo's come with a bolt to seal the CMF and with the removal of the pressure place, convert the unit from HCCR to ECCR.
    Last edited by DwayneJ; 18th February 2014 at 19:52.

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    RBW Member trakrat is on a distinguished road trakrat is on a distinguished road trakrat's Avatar
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    rEvo

    Re: CMF orifice size

    Quote Originally Posted by DwayneJ  View Original Post
    Techme sells a modified DS4 spring to handle higher IP pressures.

    rEvo's come with a bolt to seal the CMF and with the removal of the pressure place, convert the unit from HCCR to ECCR.
    yeah i'd heard all about the techme spring which is one of the reason i asked the question!

    on the hccr to eccr mod ,the main reason i bought the revo is i like the mccr better than eccr , i'm a control freak and like to run the unit myself not have a computer run it for me!

    so it's nothing to do with higher pressure/temp and o2 just the ease of buying a regulator?

    cheer dwayne

  4. #4
    RBW Member cameron is just really nice cameron is just really nice cameron is just really nice cameron is just really nice cameron is just really nice cameron is just really nice cameron is just really nice cameron is just really nice cameron is just really nice cameron is just really nice cameron's Avatar
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    KISS Classic

    Re: CMF orifice size

    Read about choked gas flow to understand the physics of it.

    You can run a very small orifice, like 0.002 and a higher pressure regulator from Swaglok. There are lots of sats to skin this cat. I have a 0.003 and it gets me down to 110 meters or so, which is fine by me.

    Cam

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