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over fill a low pressure steel tank?

Discussion in 'Advanced Scuba' started by bug catcher, Feb 9, 2012.

  1. bug catcher

    bug catcher Solo Diver

    # of Dives: 200 - 499
    Location: Wisconsin
    46
    10
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    I have a friend whom wants to buy a steel 120 L.P. used, but in hydro & visual. The selling owner runs a scuba shop and said he had een over filling the tank. He says steel tanks don't stretch much and if one fillis the L.P. to 3000 lb you get almost 170cuft of air. I thought the neck of the tank could be damaged by this over fill, he says not to worry. He wants $200.00 for the tank, should my friend buy it? Thanks for your opinions!!
     
  2. g1138

    g1138 Marine Scientist

    # of Dives: 500 - 999
    Location: Charleston, SC
    3,068
    806
    113
    Tanks get filled to 5/3 their working pressure during hydro, so a Faber LP 120 with working pressure of 2640psi will be filled to 4400psi during hydro.

    What the owner did is often called a cave fill, some cave divers will do that for the extra gas. The tank should be alright, I personally don't like to fill LP's that high just based on principle of the posted working pressure, but it's not something that's going to make that tank explode on it's own.

    You could suggest to take the tank in for another visual at your expense. If it passes you pay the $200 minus cost of visual. Just a suggestion if your friend really wants the tank at that price.
    I don't know enough about tank buying to tell you if you're getting a deal or not.
     
  3. LiteHedded

    LiteHedded Great White

    4,074
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    the tank is not damaged from overfilling. trust me.
    I'd fill that thing to 4000 psi without blinking an eye
     
  4. PfcAJ

    PfcAJ Orca

    # of Dives: 5,000 - ∞
    Location: St Petersburg, Fl
    7,884
    7,171
    113
    Overfilling LP tanks is perfectly fine (from a pragmatic point of view). I've got a set of 104's thats older than I am (not that I'm very old, I'll leave that to Litehedded) thats been overfilled from day one. You've got nothing to worry about there. If it looks good on the inside, the threads are in good shape, and it passed hydro, go for it.

    Now, I would worry about being able to swim up that heavy azz tank from the bottom if your BC failed. That might be an interesting experience for you. Check out the concept of a 'balanced rig'.
     
  5. James R

    James R PADI Pro

    # of Dives: I'm a Fish!
    Location: Austin, TX USA
    2,721
    1,134
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    This practice seems to be the default for FL divers. I have yet to hear of a tank exploding like a giant grenade :shocked2:
     
    DogDiver likes this.
  6. bug catcher

    bug catcher Solo Diver

    # of Dives: 200 - 499
    Location: Wisconsin
    46
    10
    0
    Okay, thanks for the input!! I just wanted to make sure it was common practice.
     
  7. j yaeger

    j yaeger PADI Pro

    # of Dives:
    Location: Canton, New York, United States
    1,501
    310
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    old school lp 72's to 3000???
    anyone besides me that hasn't "put an eye out" yet?

    remember the burst discs,however.....
     
  8. BabyDuck

    BabyDuck Rebreather Pilot

    # of Dives: 500 - 999
    Location: Winterville, NC
    5,614
    430
    83
    baby, 3000 ain't even full yet...
     
    FinnMom, kelemvor, DogDiver and 6 others like this.
  9. Superlyte27

    Superlyte27 Cave Instructor

    # of Dives: 5,000 - ∞
    Location: Florida
    4,022
    3,133
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    First of all, the hydro for an LP120 is 4000psi, not 4400. 2400 x 5 / 3.
    Secondly, a 120 at 3000 is not 170cu' it's 136cu'
    Thirdly, i'd put 4k in that tank without blinking an eye, too...
     
    kelemvor and cmulvaney like this.
  10. Jim Lapenta

    Jim Lapenta Dive Shop

    # of Dives: 500 - 999
    Location: Canonsburg, Pa
    17,056
    9,009
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