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PLBs Can Save Your Life

Discussion in 'Training, Practices and Equipment' started by letterboy, Mar 19, 2019.

  1. DandyDon

    DandyDon Old men ought to be explorers ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: One kilometer high on the Texas High Plains
    48,402
    4,202
    113
    If my camera or light leaks, it's ruined. If my PLB canister leaks, it gets wet but so what. Take the risk.

    Do you ever check the dip stick on your car or just drive until the oil light comes on? Another reason for opening daily is to ensure it opens easily.
     
  2. outofofficebrb

    outofofficebrb HARRO HUNNAYYY

    # of Dives: 200 - 499
    Location: San Francisco, California
    2,853
    2,149
    113
    True....

    Opening it each day can be to ensure it's dry (for those of us who don't have clear canisters) and opens fine. I am a worst case scenario planner and I can imagine needing to use it and opening it in a dire situation just to learn it doesn't work because it has been sitting in a self contained canister of water for who knows how long and it is longer than the IP rating for time or something. Worse, it could be dry but it won't open and that is the lifeline.
     
    DandyDon likes this.
  3. -JD-

    -JD- Eclecticist ScubaBoard Supporter

    # of Dives: 50 - 99
    Location: Greater Philadelphia, PA
    361
    194
    43
    Thanks, maybe ...

    I'm hoping @tridacna understands what I am getting at and knows off-hand without putting you through the effort. The pictures here and on the site are inconclusive to me.

    If the seal is circumferential, then simply having the 2 halves pushed together compresses the oring and makes the seal. The threading just keeps the 2 halves from pulling apart and can be just barely snugged to be reliable.

    With a "vertical" seal, the oring gets compressed by tightening the threads and the countering force seems to cause the threads to bind up and become very difficult to undo.
     
  4. outofofficebrb

    outofofficebrb HARRO HUNNAYYY

    # of Dives: 200 - 499
    Location: San Francisco, California
    2,853
    2,149
    113
    I am going to go with option 1 based on the design and how it gets put together and where the o-ring is in relation to everything else like the threads, etc.
     
    -JD- likes this.
  5. -JD-

    -JD- Eclecticist ScubaBoard Supporter

    # of Dives: 50 - 99
    Location: Greater Philadelphia, PA
    361
    194
    43
    Thanks!

    Interesting, I wonder then why tridacna was having trouble getting it open after compression ...

    Anyway have a great trip! I'll look forward to your experiences.
     
  6. outofofficebrb

    outofofficebrb HARRO HUNNAYYY

    # of Dives: 200 - 499
    Location: San Francisco, California
    2,853
    2,149
    113
    Thanks! I'll try to put together a video tonight...Maybe I am wrong - that would be likely. :wink:
     
    -JD- likes this.
  7. DandyDon

    DandyDon Old men ought to be explorers ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: One kilometer high on the Texas High Plains
    48,402
    4,202
    113
    Yep, I think that's how it works.
     
  8. outofofficebrb

    outofofficebrb HARRO HUNNAYYY

    # of Dives: 200 - 499
    Location: San Francisco, California
    2,853
    2,149
    113
  9. Lorenzoid

    Lorenzoid idling in neutral buoyancy

    # of Dives: 500 - 999
    Location: Atlanta, USA
    8,977
    5,467
    113
    Well, I don't have a camera housing, but it's my understanding that camera housing gaskets don't experience the friction that an o-ring does when the cylindrical cap of a canister slides against the o-ring. Rather, when you close a camera housing, the gasket is compressed. (This is where @-JD- 's terminology would come in handy if I were sure I understood which is which.) The canister seals the same way my twist-on dive lights seal: there's an o-ring that gets continuously rubbed between the concentric walls while the cap is being twisted on or off. Actually, I think mine has two o-rings, the other one being seated on a flange in the interior of the canister that would only get compressed when the cap is fully seated. So maybe mine has both a vertical and a circumferential o-ring. Still, I can't help but feel frequently opening and closing a threaded canister might invite more harm than good. The canister is designed to withstand the depths I take it to. If the seal is initially good, why would it fail, except perhaps when the o-ring gets truly old?
     
  10. outofofficebrb

    outofofficebrb HARRO HUNNAYYY

    # of Dives: 200 - 499
    Location: San Francisco, California
    2,853
    2,149
    113
    @DandyDon I remember the canister shipped with some instructions. Do you remember what it was specifically? I know one was about ensuring the o-ring was well lubed; this one comes way more lubed than anything else I have ever seen. I recall seeing something about twisting the two ends in opposite directions gently once the tightening ring is on there to ensure the tightening ring is seated nicely - do you remember? Or perhaps you still have the instructions?
     

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