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Thread: Getting low on dil...

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    Getting low on dil...

    I was on a long dive, a lot of saw tooth profile, and my dil was getting much lower than I'd preferred.

    So I switch to .5 setpoint, and manual added O2 the rest of the dive to keep my setpoint and keep dill usage down.

    Now I'm new to CCR, so don't blast me if this is bad or stupid, but I cant think of any reason it should be. I'm just flying manual like in class.

    thx!

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    HammerMeg

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    Re: Getting low on dil...

    You might want to consider running your wing off a BO tank or your Drysuit off a dedicated small tank. Assuming your not doing that already. Also, consider adding the ability to plug you offboard tank into the loop as an additional DIL supply.

    Running O2 manually should not have much of an impact on conserving DIL unless you were also running a saw tooth profile on your PO2 control. Which depending upon the dive might be a bigger issue. Of course I could be wrong or missing something in what you are saying.

    I would also say there is no reason to lower the set point to 0.5 if all you want to do is stop the solenoid from firing before you can add O2 to manually adjust.

    John
    Last edited by jkaterenchuk; 18th March 2013 at 20:56.

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    Re: Getting low on dil...

    I run my suit off of a BO bottle, but wing from dil. I don't use my suit for buoyancy though, just enough to take the squeeze off. Once I get a meg stand, I'll have a 13cf bottle to drive wing and suit. Once I get the stand/bottle, the bcd connection on my bail out could be plumbed into my manual add for dil reserve.

    I guess now in thinking about it, changing setpoint is just adding O2 manually, instead of through the solenoid, and no savings in dil anyways. Its seemed like a good idea at the time during the dive. Its kind of like when I rocked climbed, we had what was called "Psychological" protection, some little tiny chock stuck in a crack, if you fell on it, it'd probably never hold anyways, but you felt better with it there. :) thx!

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    Re: Getting low on dil...

    Diluent use has nothing to do with set point.

    The sawtooth profile is what kills your diluent volume. Dumping your loop before you correct set point will minimize gas usage on ascents. Then again thats more for conserving O2.

    Minimum loop volume and weighting is the biggest culprit for Diluent usage.
    I have my BC on the diluent as well but I rarely touch my BC and just need to break the squeeze on my drysuit. Im weighted for no air in my BC, comfortable drysuit, full BO cylinders and minimum loop volume.

    Cam

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    Sorta New Member w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley's Avatar
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    JM Hammerhead

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    Re: Getting low on dil...

    Don't know if you use your ADV, but some of us turn it off once we get to depth. That allows us to manually add dil during the dive & eliminate the ADV diluting our O2 on deco. This tends to saves dil on the dive and O2 on the deco.
    Bill Ripley

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    Re: Getting low on dil...

    A "saw tooth" profile will always crank through your dil. Like Bill says, your ADV injecting won't help you out there either. If you want to dive this profile, you have to learn how to deal with it. I dive some quarries where I'm up & down over roads throughout the whole dive and it really destroys the dil (+ no shut-off ADV on a rEvo). I've put a whip on my B/O, mostly for shooting bags, but if I'm diving saw tooth and get low on dil, I'll swap out the wing hose & put on the B/O whip. Don't want to rely on this for big dives, but for quarries....for me...no problem. YMMV

    Franco

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    Re: Getting low on dil...

    Quote Originally Posted by w ripley  View Original Post
    Don't know if you use your ADV, but some of us turn it off once we get to depth. That allows us to manually add dil during the dive & eliminate the ADV diluting our O2 on deco. This tends to saves dil on the dive and O2 on the deco.
    Hmm, hadn't thought about that on deco, at 15ft, just shut off adv, although with a setpoint of 1.4, you are on pure O2 anyways.

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    Sorta New Member w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley is a name known to all w ripley's Avatar
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    JM Hammerhead

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    Re: Getting low on dil...

    Quote Originally Posted by Jeff Pack  View Original Post
    Hmm, hadn't thought about that on deco, at 15ft, just shut off adv, although with a setpoint of 1.4, you are on pure O2 anyways.
    If you turn it off at 20 feet you will really see a difference (less setpoint drops, fewer O2 adds, etc), or at least I do. Until you cut it off you really don't notice just how much that sucker is triggering dil adds.

    You might take a look at what PO2s you can actually attain at 15 feet and shallower. Once you get to 15 feet it gets pretty difficult to fly the higher ones, and you can use a lot of O2 trying.

    BTW, I always dive with my OTS CL OPV closed, as well. With the OPV closed and the ADV closed, I find I'm in a much better position to maintain my min loop.

    What started me closing my OPV in the 1st place was this: I had a sidemounted stage bottle's 1st stage depress my O2 manual add button on a long scooter run, and found that my O2 bottle was fully depleted when I stopped, or when I reached 4000 feet back in the cave. With the scooter's motor turning and the water flying by my head, I couldn't hear the O2 being added or escaping out of the OPV. Had the OPV been closed, the O2 would have never run out of it and my CLs would have been so inflated that I would have discovered the problem before it really became one.

    Anyway, just keeping it closed removes one potential source for unintentionally dumping dil or O2.

    One other suggestion if you want to further conserve O2 is to put more of it in your dil. Cave dives, where I'm not going much deeper than 100 feet, my dil is 32%. Really makes a difference on a 5+ hour dive.

    Good luck.
    Bill Ripley

    Rebreathers are something that we have to go to in order to dive the way we want to dive. They are not something we go to for any other reason.

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    Re: Getting low on dil...

    Quote Originally Posted by w ripley  View Original Post
    If you turn it off at 20 feet you will really see a difference (less setpoint drops, fewer O2 adds, etc), or at least I do. Until you cut it off you really don't notice just how much that sucker is triggering dil adds.

    You might take a look at what PO2s you can actually attain at 15 feet and shallower. Once you get to 15 feet it gets pretty difficult to fly the higher ones, and you can use a lot of O2 trying.

    BTW, I always dive with my OTS CL OPV closed, as well. With the OPV closed and the ADV closed, I find I'm in a much better position to maintain my min loop.

    What started me closing my OPV in the 1st place was this: I had a sidemounted stage bottle's 1st stage depress my O2 manual add button on a long scooter run, and found that my O2 bottle was fully depleted when I stopped, or when I reached 4000 feet back in the cave. With the scooter's motor turning and the water flying by my head, I couldn't hear the O2 being added or escaping out of the OPV. Had the OPV been closed, the O2 would have never run out of it and my CLs would have been so inflated that I would have discovered the problem before it really became one.

    Anyway, just keeping it closed removes one potential source for unintentionally dumping dil or O2.

    One other suggestion if you want to further conserve O2 is to put more of it in your dil. Cave dives, where I'm not going much deeper than 100 feet, my dil is 32%. Really makes a difference on a 5+ hour dive.

    Good luck.
    In class, I was taught the OPV is always closed except for an O2 flush, so its always closed on my Meg. I'll try next deco with the adv shut down. I don't use higher dil, because I do a lot of deep dives (relatively speaking for many of you :) I'd rather go lighter on dil O2, and if I don't dive so deep, let the computer add O2 to bring up setpoint.

    But as soon as I go hotter on dil-O2, I have a hard floor. I'd rather "some" flexibility. So far, its dil that's my big use, I don't use much O2.

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    Re: Getting low on dil...

    Quote Originally Posted by Jeff Pack  View Original Post
    In class, I was taught the OPV is always closed except for an O2 flush, so its always closed on my Meg. I'll try next deco with the adv shut down. I don't use higher dil, because I do a lot of deep dives (relatively speaking for many of you :) I'd rather go lighter on dil O2, and if I don't dive so deep, let the computer add O2 to bring up setpoint.

    But as soon as I go hotter on dil-O2, I have a hard floor. I'd rather "some" flexibility. So far, its dil that's my big use, I don't use much O2.
    take more dill then ,,

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