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Thread: One Way Valves

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    One Way Valves

    Hi All,

    Lately I've been musing on the less exciting RB parts that are nevertheless very important, I wanted to ask if anyone has come across any other types of one way valve?

    Obviously Mushroom valves are well known and most common in breathing hoses, I'm also aware of the sprung plate design used by the Russians in their IDA series rebreathers and the "barn door" style used by Fenzy.

    Clearly there are pro's and con's to all these designs, they all contribute to WOB to a lesser or greater extent thats for sure!

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    Hi Ben
    I think it is definetely the right Part to Focus on as ist causes high flow resistance. I am not familiar with the Fenzy design, could anyone please provide a picture? was it used in all their units?
    Thanks alex

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    Re: One Way Valves

    Very cool! Thanks for the link. Some of todays hotshots could learn a thing or two.

    Peter

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    Re: One Way Valves

    Speaking of valves, I recently read Mr Eveland's contributions about the UT-240 rebreather and the efforts to reduce WOB on that machine. He states that the turbulence created by a mushroom valve is a major loss in the loop.

    The russian popper valve is cool, but still has the drawback of being small and making the gas turn a sharp corner. The fenzy one is closest to this idea...

    What about having the valves as flat plates on some sort of cage, just like the reeds on a 2 stroke engine?

    Possible to package this to DSV proportions? Worth a thought :)


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    Re: One Way Valves

    Quote Originally Posted by yorkie_chris  View Original Post
    Speaking of valves, I recently read Mr Eveland's contributions about the UT-240 rebreather and the efforts to reduce WOB on that machine. He states that the turbulence created by a mushroom valve is a major loss in the loop.

    The russian popper valve is cool, but still has the drawback of being small and making the gas turn a sharp corner. The fenzy one is closest to this idea...

    What about having the valves as flat plates on some sort of cage, just like the reeds on a 2 stroke engine?

    Possible to package this to DSV proportions? Worth a thought :)

    I couldnt see why an adaptation of that would work....it would also possible reduce hose gurgle...

  7. #7
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    Re: One Way Valves

    Exactly! In-line mushroom valves are always in the way of gasflow to some extent. Where & how the rim will fold is unpredictable and varies from part-to-part; and no matter how it does fold, it is an impediment to the gas trying to flow around it. The UT240 valves were enormous, but still contributed significantly and erratically to flow resistance.

    So, first: imagine the mushrooom valve's stem moved off-center, or eliminated by clamping at the valve's rim. You now have a predictable fold pattern; and a larger "sail" area to power a shorter length of rubber fold.

    Then, reshape the mushroom itself to augment the flow through the asymmetric opening action we've created. The valve should be somewhere between a teardrop and a rectangle.

    Finally, orient the now-asymmetric valve to favour airflow. No longer straight in-line with the airflow, it should be somewhere between 30 and 90 degrees, so that airflow describes a gentle Z as it slips under the open "hatch."

    I'd begun working in this direction, with highly encouraging initial results, when the whole UT thing died. It would be nice to see the concept carried forward.

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    Re: One Way Valves

    Quote Originally Posted by yorkie_chris  View Original Post
    Speaking of valves, I recently read Mr Eveland's contributions about the UT-240 rebreather and the efforts to reduce WOB on that machine. He states that the turbulence created by a mushroom valve is a major loss in the loop.

    The russian popper valve is cool, but still has the drawback of being small and making the gas turn a sharp corner. The fenzy one is closest to this idea...

    What about having the valves as flat plates on some sort of cage, just like the reeds on a 2 stroke engine?

    Possible to package this to DSV proportions? Worth a thought :)


    Also known as duckbill valves One way Valves - Duckbill Valves, Flapper Valves, Umbrella Valves

  9. #9
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    Re: One Way Valves

    Quote Originally Posted by UT 240 designer  View Original Post
    Exactly! In-line mushroom valves are always in the way of gasflow to some extent. Where & how the rim will fold is unpredictable and varies from part-to-part; and no matter how it does fold, it is an impediment to the gas trying to flow around it. The UT240 valves were enormous, but still contributed significantly and erratically to flow resistance.

    So, first: imagine the mushrooom valve's stem moved off-center, or eliminated by clamping at the valve's rim. You now have a predictable fold pattern; and a larger "sail" area to power a shorter length of rubber fold.

    Then, reshape the mushroom itself to augment the flow through the asymmetric opening action we've created. The valve should be somewhere between a teardrop and a rectangle.

    Finally, orient the now-asymmetric valve to favour airflow. No longer straight in-line with the airflow, it should be somewhere between 30 and 90 degrees, so that airflow describes a gentle Z as it slips under the open "hatch."

    I'd begun working in this direction, with highly encouraging initial results, when the whole UT thing died. It would be nice to see the concept carried forward.
    we had prototypes made of non-symmetrical valves, and in gasflow analysis, it showed a bit lower resistance, as you could orient the major gasflow at the optimum place referenced to the barrel in the DSV

    but the problem was that the valve did not close as nice as the symmetrical valve that is currently used mostly, unless you gave it a shape that it forced itself to close always, but then again the resistence went up... so we stayed with the symmetrical Drager valve

    paul
    Last edited by paulraymaekers; 6th January 2012 at 16:17.
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  10. #10
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    Re: One Way Valves

    While one-piece "duckbill" valves have the advantage of an in-line airflow, their operation involves significantly greater material distortion and thus greater energy to force flow through than mushroom valves. The "rooftop" flapper valves, as Yorkie shows, such as used in 2-cycle engines is more appropriate: greater open cross-section with smaller energy required to open and more sail area to do so.

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