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Twinset build

Discussion in 'Dive Equipment' started by Mako-JD, Sep 26, 2017.

  1. Tewdric

    Tewdric Member

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    Im in as reserve cameraman :)
     
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  2. Mako-JD

    Mako-JD Active Member

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    Ok twinset isolater question.

    Fully or partial open, couple of turns. I understand why; Quicker to shutdown.

    BUT...does this restrict the tanks from equalizing at all ?? Or does it just not work like that
     
  3. hawk

    hawk Doing It Rong
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    IMO - all the way open. That way you can guarantee that the way you are turning it is correct.
     
  4. Tribal Chestnut

    Tribal Chestnut Active Member
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    All the way and back a smidge for me.
     
  5. AndyW

    AndyW Member

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    The isolator only needs to be slightly open for the two cylinders to equalise. So the two common options are, as you say, fully open or a couple of turns open.

    Fully open: Flow checks are easy. It's always in the same position. If it needs to be closed then there's no mix up. You will be turning it the way you intend.

    Partly open: If it turns both ways then you can be confident that it's open. If it needs to be closed then it's a quicker process ASSUMING you don't balls it up in a moment of madness and go the wrong way.

    Closed: Dive it closed and only open to equalise. Needs to be done regularly. Bit too much faffing for my liking.

    Very slightly open: It will still equalise but a 1/4 turn will isolate if you need to. However much easier to nudge closed without realising.

    I have dived both fully open and partly open. I have little preference. The isolator is at the back of your head so if you can reach that then turning the knob is easy. Closing it is a pretty quick process anyway. The key thing, for me, is who I'm diving with. Therefore, I'm more likely to have it fully open. In the event that a buddy needs to operate your valves, it's much more likely they will struggle with the "lefty loosy, righty tighty" than you will.
     
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  6. hawk

    hawk Doing It Rong
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    When the poo really hits the fan, never underestimate a human's ability to mess up. Righty tighty seems sensible and easy to remember now but when you have bubbles blasting behind your head and are task loaded, it's very easy to get it wrong.
     
  7. Mako-JD

    Mako-JD Active Member

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    So for the extra seconds it takes nearly full open. And am I correct with, regardless of amount open gas will equalise between both tanks.
    I am crossing over to BSAC. So will probably do there twin course anyway at some point.
     
  8. AndyW

    AndyW Member

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    Fully open, not nearly. Just don't wedge it open.

    Try and get someone who knows what they're talking about rather than an instructor who has some experience of diving a twinset the way that their instructor with some experience of a diving a twinset taught them.....

    That's not a BSAC dig at all. It's just to make sure you get the best of what, sometimes, can be variable instruction.
     
  9. hawk

    hawk Doing It Rong
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    I would always say fully open - with a tiny (no more than a tenth) back if you must. This is life support equipment and I want to be able to check immediately (5m) that my valves are open. the only way of easily doing this IMO is to try and open it to have it hit the back stop.

    Gas will equalise between tanks but at different rates depending on pressure.

    I personally wouldn't. BSAC is not really a tec agency and so I would do something like a TDI intro course.

    @Tel - what's the latest with BSAC and hog looping?
     
  10. timmyg

    timmyg Super Moderator
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    There are a small number of BSAC instructors who are authorised to teach Primary Donate on twinset courses upwards. I am one of them. It’s not been rolled out fully yet as the materials and demo videos still need to be finalised.


    TG

    Sent from my iPhone using timmytalk
     
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  11. Mako-JD

    Mako-JD Active Member

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    I asked about PD as I hog now on a single, answer was bungee it up or swap out hoses. This is only required for training only
    For club diving it fine to hog if buddy's were on the same page
     
  12. Vanny

    Vanny Active Member

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    FWIW I go with the couple of turns open. It will equalise fine. It's only moving the amount of gas you breathe in at anyone time. Practice shutting down until it's muscle memory , not a thought process.

    That said the wife dives her twin 7's with a slob knob due to neck issues and fully open as lefts and rights get a bit confusing :whistling: .

    I think ideally just open for quick shut down and preservation of gas is ideal so long as your ok doing that.
     
  13. Doomanic

    Doomanic Dinosaur Wrangler
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    This.
     
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  14. Vanny

    Vanny Active Member

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    Honestly not being pedantic , but on ccr do you fully open the O2? I was taught and continue to only open it 2-3 turns.
     
  15. Dave Whitlow

    Dave Whitlow Well-Known Member

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    3 turns is also what I was taught as, unlike OC, there is never any need for a high flow rate and it needs shutting down quickly if there is a stuck open solenoid flooding the loop with O2.
     
  16. Doomanic

    Doomanic Dinosaur Wrangler
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    I was taught the same.
     
  17. Zubar

    Zubar Active Member
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    I go with all the way open, on all valves, no slight turn back. It avoids any doubt or confusion.
    IF I did any truly solo diving I would consider having a partially open isolator to aid in a self help situation and save time when the only gas in the world is that on my back.

    I'd not heard about the ccr o2 thing but makes sense as it is a very low flow rate (compared to OC), you have 3 sensors to tell you if it's dropping/rising, and have the tins inverted so that helps things I guess.
     
  18. Wibble

    Wibble Fish don't talk
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    Fully open and a gnat's cock back. Easier for a flowcheck and totally unambiguous if under the influence of narcosis or panic.
     
  19. Mako-JD

    Mako-JD Active Member

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    Ok apecks twin 12s now mine. Had to postpone due to boiler packing up

    they did not come assembled, so question is when putting in isolator is it supposed to screw fully into K valve. If I do this when putting bands on it binds up the valve so it won't move. Or. Do you set the isolator so it moves free even though all the threads are not fully in Then is it finger tight on the nuts or do you wrench then down As I thought if you whack isolator on some overhead that it should move rather than break. Sorry if this question a bit of a inchohernt mess Yes I can pay someone to do it but I like to know my own kit
     
  20. Wibble

    Wibble Fish don't talk
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    Main thing is not bending the manifold when assembling/disassembling and especially when it's assembled and the bands are tight.
     
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