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Thread: Loop volume

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    Loop volume

    This may be covered in class. I don't know. What is the effect of increasing or decreasing loop volume in a rebreather. For instance, if one were to switch to 6 foot long hoses, 9" diameter hoses or a 5 liter counterlungs?


    I don't have a rebreather yet - looks like a prism.
    Last edited by Kristi C; 30th June 2014 at 17:36. Reason: Edited per posters request

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    Re: Loop volume

    The effect of having 6ft long 9" hoses would be like swimming with a half inflated boat on your back, you'd need a tonne of lead and look like a moron

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    Loop volume

    Other implications as well, include changes in how fast oxygen additions will affect total mixture, rate at which you can purge the loop/fill the loop, etc. I think the buoyancy issue is maybe not the most important.

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    Re: Loop volume

    I'm sure you will find out, but..

    The longer the hoses (in comparison to their diameter) - the greater the breathing resistance.

    The bigger the loop volume the more your buoyancy changes with any change of depth (same %age change in pressure but bigger absolute change in volume)

    In general the 'fixed airspace' (the scrubber and hoses) is a small as it needs to be and designed for minimum work of breahting, the lungs again are big enough for you to take a full breath (plus some margin), but you try to keep them with as little air in as possible (i.e. they are just about empty when you have breathed in), this 'minimum loop volume' keeps life simpler

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