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Thread: Override depth limitation with CMF.

  1. #31
    RBW Member Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P is just really nice Igor P's Avatar
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    Re: Re: Override depth limitation with CMF.

    Quote Originally Posted by Rod Abbotson  View Original Post
    Its really no different from a fixed orifice, it just that it is an adjustable fixed orifice...you basically use the same amount of oxygen at depth as you do on the surface...the PPO2 is kept stable by addition of diluent during descent to keep the loop volume constant. Main advantage of a needle valve is its not depth limited like a CMF with a fixed IP first stage (basically limited to approx 80m which is 9 bar thus no flow occurs). So basically the difference is how the first stage is used in conjunction with the feed system.
    Hi Rod,

    As I wrote I know all this about CMF and orifice use as I dive mCCR with leaky valve (otifice). There was a strange statement I think was missleading. Not your's but someon else. Anyway, thank you for trying to help. You explained very clear and understandable.

    But its ok ....lets return to OP post and original topics....

    Sent from my PAP4500DUO using Tapatalk 2
    Last edited by Igor P; 21st September 2013 at 18:14.

  2. #32
    Tinkerer madvic is an unknown quantity at this point madvic's Avatar
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    Re: Override depth limitation with CMF.

    Mike;

    Of course every one knows that a Rebreather is a NOT zero tasking rig... I meant ZERO, (or almost ZERO) about the behavior of the needle valve as a CMF with variable set point in my configuration (with the Isolator valve, in the first stage (explained in the very first post of the thread).

    Other people;

    I only wanted to share with the RB-community a new Idea, and to have as much feedback as I can about THIS IDEA, nor the alternative methods, nor other things. I wanted to know how feasible is, and to ask about the possibles problems that could arise with this particular configuration.

    I already new the others strategies (well the miniregulator in line strategy no..). I repeat I share this idea with you ALL in order to have advice and feedback for the senior people that knows a lot more than me. In the 30 posts Only John Liddiard has said something about the idea. (Thanks John!!).

  3. #33
    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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    Re: Override depth limitation with CMF.

    I always felt a depth compensated reg feeds MAV and a non compensated feeding an orifice was the simplest way. Let's face it what percentage of the dive are you actually below the IP range of the non compensated reg?
    Cheers,

    Dave....

    www.wedivebc.com

  4. #34
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    Re: Override depth limitation with CMF.

    Quote Originally Posted by wedivebc  View Original Post
    I always felt a depth compensated reg feeds MAV and a non compensated feeding an orifice was the simplest way. Let's face it what percentage of the dive are you actually below the IP range of the non compensated reg?
    Great minds think alike....
    Very Respectfully

    Roland Somodi

    sent from my Commodore 64 using Wizard of War....

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    Re: Override depth limitation with CMF.

    Quote Originally Posted by wedivebc  View Original Post
    I always felt a depth compensated reg feeds MAV and a non compensated feeding an orifice was the simplest way. Let's face it what percentage of the dive are you actually below the IP range of the non compensated reg?
    Quote Originally Posted by rolanddiver  View Original Post
    Great minds think alike....
    Along those lines, I direct you to this post from Slow Diver, complete with photo:
    http://www.rebreatherworld.com/showthread.php?t=45679
    Ken

    Quote Originally Posted by Dsix36  View Original Post
    Just remember that listening to an idiot such as myself may very well get your arse dead.

  6. #36
    RBW Member michael hearn is a jewel in the rough michael hearn is a jewel in the rough michael hearn is a jewel in the rough michael hearn is a jewel in the rough michael hearn is a jewel in the rough michael hearn is a jewel in the rough michael hearn is a jewel in the rough michael hearn's Avatar
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    Re: Override depth limitation with CMF.

    Quote Originally Posted by madvic  View Original Post
    Mike;

    Of course every one knows that a Rebreather is a NOT zero tasking rig... I meant ZERO, (or almost ZERO) about the behavior of the needle valve as a CMF with variable set point in my configuration (with the Isolator valve, in the first stage (explained in the very first post of the thread).

    Other people;

    I only wanted to share with the Rebreather-community a new Idea, and to have as much feedback as I can about THIS IDEA, nor the alternative methods, nor other things. I wanted to know how feasible is, and to ask about the possibles problems that could arise with this particular configuration.

    I already new the others strategies (well the miniregulator in line strategy no..). I repeat I share this idea with you ALL in order to have advice and feedback for the senior people that knows a lot more than me. In the 30 posts Only John Liddiard has said something about the idea. (Thanks John!!).
    hi
    sorry, the answer wasent really directed at you , just wanted to clarify that for me personally if im going to have a CMF ,just want it to do its job when its neeeded and not have to think about it , of course its great to come on with new ideas this helps things progress, keep on with it and see how far you can take it , i am always trying to think of new stuff, 9 times out of 10 it come to nothing but maybe 1 time ill come up with an idea that may be useful to someone other than my self .so dont stop thinking up stuff
    cheers
    mike

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    Re: Override depth limitation with CMF.

    I think it is not bad idea but at the same time I think it adds to complexity.....as I dont understand how would you manipulate with the valve if on your onboard O2 tank or it is meant for offboard O2 supply?

    Sent from my PAP4500DUO using Tapatalk 2

  8. #38
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    Re: Override depth limitation with CMF.

    Quote Originally Posted by michael hearn  View Original Post
    no way id want to put 12-20bar o2 in my medium pressure circuit just to increase CMF depth limit, short term solution , long term strain on components
    mike
    Has there ever been any problems attributed to higher IP ?

    I understood that putting an 0.003" (in place of standard 0.0035") orifice in a KISS was a fairly standard mod that had been successfully used for years. I'm considering doing mine.

  9. #39
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    Re: Override depth limitation with CMF.

    Quote Originally Posted by mike_123  View Original Post
    Has there ever been any problems attributed to higher IP ?

    I understood that putting an 0.003" (in place of standard 0.0035") orifice in a KISS was a fairly standard mod that had been successfully used for years. I'm considering doing mine.
    Even with very high IP a regulator that feed a CMF is not specially prone to seat failure because it is a continus flow, in fact its a constant slighly open status, there is no cyclic opening and closure like on an OC use witch is the main cause of wear and failure.

    Dont forget to close the bottle and to emptying the regulator when not in use, so there is no more counterpressure from the spring and so no problem.

    I use IP 16.5 for more than 8 years with not a problem

    regards

    Marc

  10. #40
    Tinkerer madvic is an unknown quantity at this point madvic's Avatar
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    Re: Override depth limitation with CMF.

    Quote Originally Posted by Igor P  View Original Post
    I think it is not bad idea but at the same time I think it adds to complexity.....as I don't understand how would you manipulate with the valve if on your onboard O2 tank or it is meant for off-board O2 supply?
    The mod its intended for the Onboard O2 supply. Its the same as a capped reg but you have attached to the cap an "insulator or equalizing pressure valve". You dive as if the rig has a CMF but you have a needle valve pre-set with the 1bar IP in the reg chamber (so you have about 8bar in the pipes).

    If the unlikely event (yes you are right Roland and Dave) of going nuts and perform a deep dive, you just unlock this valve and the reg became compensated again, so you need to adjust at this time the needle valve (better do this first), and after that open the the reg valve. At this point two options:

    1-// You complete the dive as if you where flying with comp reg and needle valve or:

    2-// You close again the reg valve and you dive with another needle pre-set (In this case CAUTION, when you ascend the reg will have internaly a full load of Bars that will rise like hell the differencial IP from the outside and your plumbings, like Marc T woow 16.5bars!!!) In this case the solution is to open again the valve at 40mts (or whatever) and have another preset for your needle valve at this depth.

    BUT if you dive 99.9999% without trespasing the deep limits, its okay with this mod; You will never touch the reg valve and so you will dive the same as if you dive with a CMF.

    Its like to have a CMF reg that could override the depth limitations when you want. And If you don´t want it will be exactly the same as CMF (and of course an inherent benefit is that you could play with the needle valve with the capped reg; increase of metabolic rate, currents, or whatever...).

    this way you have a "variable like CMF", with the possibility to trespass the depth limit.
    And by the way its a very cheap mod...!!!!
    :)
    Last edited by madvic; 23rd September 2013 at 15:51.

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