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Failure of back-plate single tank adapter (Bolts)

Discussion in 'Buoyancy Compensators (BC's) & Weight Systems' started by apivonka, Oct 8, 2019.

  1. apivonka

    apivonka Registered

    # of Dives: 0 - 24
    Location: Tampa, Fl
    johndiver999, my hog SS BP has slots and what you suggested is one I'm thinking on trying

    The Hog Wing has tank two bars on it that act like a sta, yet not enough as my tank moves around with out the STA.
  2. rhwestfall

    rhwestfall Woof! ScubaBoard Sponsor

    # of Dives: 200 - 499
    Location: "La Grande Ile"
    Which likely means you are not tightening it properly/enough or you have really poor cam bands..
    Johnoly, eelnoraa and divad like this.
  3. KDAD

    KDAD Contributor

    # of Dives: 50 - 99
    Location: Northern New Jersey
    I like the STA and gave gotten into the habit of check it before every dive. After a while it seems to have stopped coming loose or as often but I still check it frequently.

    I don't think that the bolts would come loose in a single dive but over time and should be able to be caught before separating.
  4. Marie13

    Marie13 Great Lakes Mermaid ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Great Lakes
    Are you regularly checking that the wing nuts, etc., are tight?
  5. icechip

    icechip ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Maine
    +1 on Marie13's suggestion: check and tighten each time. I also run the bands through the backplate and so do not need a STA.
  6. divad

    divad ScubaBoard Sponsor ScubaBoard Sponsor

    Glad you're OK and got all your stuff back..............but....... stop doing whatever you were doing, or not doing.

    Re using the built-in "stay" : soak the cam-bands before tightening. They get looser when wet especially when new. Also, the bands should take effort to close, so that once they get past the fulcrum, they snap themselves closed.
  7. Colliam7

    Colliam7 Tech Instructor Staff Member ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Kents Store, VA
    Unless I have misread your post, it is not clear that you have documented 'failure' of the bolts. If I have misread your post, my apologies. You say that the 'bolts were gone'. Are you saying that the threaded bolts were completely missing from the STA? That would be extraordinary - for the bolts to be completely missing, both bolts would have to shear right beneath the bolt head, so that the STA would cleanly separate, the bolt heads would drop out from under the cam band threaded through the slots in the STA, AND the bolts, with wing nuts attached, would then have to drop out of the backplate. Not impossible. But, improbable. And, the fact that, per your description, the wing was still attached to the STA, suggests that the bolts were still in place on the STA.

    In my experience, it would be equally probable that the wings nuts simply came unscrewed.
    I am going to presume something here - that you had kept your rig assembled the whole time, rather than breaking it down after each dive trip.

    IF that was the case, there is no surprise. The wing nuts get loose over time. Yes, there is - or there certainly SHOULD BE - a lock washer (hopefully present, in your case) between the wing nut and the flat washer. Nonetheless, as a ROUTINE part of your gear set-up, you should check the wing nuts for tightness.

    IF you routinely disassembled your rig between dive trips, then the culprit is most likely a failure to appropriately tighten the wing nuts when you assembled your rig.
    Actually, as I understand your post, the failure was that the STA separated from the BP, and the cylinder was attached (by cam band) to the STA.
    Yes, that is true. But, the issue is most likely NOT the weight on the bolts. It is whether the wing nuts were sufficiently tight.
    Certainly, if you wish to thread your cam bands through the plate, and avoid use of a STA, that is fine. If you wish to use a STA, then you need to regularly check the tightness of the wing nuts.

    I routinely use a STA. I have had wings nuts come loose several times - when I failed to check their tightness before a dive. In each case, that was user error on my part, not equipment failure. In each case, I sensed there was a problem simply because the cylinder seemed to 'swing' from side to side during the dive. On one occasion, I even executed that OW skill that some divers suggest is completely unnecessary - I removed the scuba unit underwater (at 110 feet), tightened the wing nuts, re-donned the scuba unit, and continued the (otherwise uneventful) dive.
  8. happy-diver

    happy-diver Skindiver Just feelin it

    # of Dives: 1,000 - 2,499
    Location: knowone here!
    M.M.O. stabilisers keep the tank close and permit NO movement and NEVER loosen
    with a spring washer and wingnut
    tightened with a tool


    and would never loosen more with a nyloc nut


    Tank stabilisers are made from a longitudinal slice of rubber hose and a length of bungee
    flim flam at the best, and stabilisers not utilising the plate slots, are defeating the purpose

    So tighten your wingnuts with a tool

    Doubles is different
  9. wetb4igetinthewater

    wetb4igetinthewater Instructor ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: Seattle
    Where did you get that? Something I'd like to try.
  10. marcin.a

    marcin.a Solo Diver

    # of Dives: 500 - 999
    Location: Canberra, Australia
    In my opinion the direct cause of this incident was both wingnuts unscrewing and dropping of the bolts. Most likely they were not screwed tightly on the mandatory spring washer. Vibration of a motorboat can do real magic to loose bolts. Good all ended OK and the only harm was the embarrassment. As others said, check your nuts before diving.
    It was mentioned in this thread to ditch STA or put cambands through the wing and the plate (if possible). For me this is not a solution. Exactly the same problem might affect doubles where the STA/cambands trick is not an option. Not to say that dropping doubles are more harm than a single tank. IMHO the only acceptable solution is checking the wingnuts before each dive. Same as checking each second stage reg, gauge, beer can, etc.

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