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Exploding pressure ?

Discussion in 'Tanks, Valves and Bands' started by Externet, Sep 3, 2019.

  1. Externet

    Externet Nassau Grouper

    If a healthy 3000psi aluminium cylinder is hydro tested pushed beyond recommended limits, at what pressure should it rupture ?
    If plain 2250psi steel, same question...
  2. Jonny Wishbone

    Jonny Wishbone Barracuda

    # of Dives: I just don't log dives
    Location: West Central Florida
    There is a few YouTube videos of alum and steel tanks exploding somewhere in the 8000+ range. There is also one where a steel blew at 4600ish. No details about the tanks so don’t know their ratings. They could have been already condemned for all We know.
  3. michael-fisch

    michael-fisch Manta Ray

    # of Dives: 2,500 - 4,999
    Location: Germany
    In Germany the minimum burst pressure of a new tank has to be highter than 4x the rated pressure.
    Since aluminum doesn't rust to any great extent and the T6 heat treatment isn't affected by temperatures much lower than 300°F it is probably safe to assume that a used S80 aluminum tank won't often blow below 12000psi or 828Bar.
    If it has been filled thousands of time the material could be damaged by work hardening which is why Bauer states that their P series aluminum filters should be (must if a fire department) replaced after a certain number of years.

  4. happy-diver

    happy-diver Skindiver Just feelin it ScubaBoard Sponsor

    # of Dives: 100 - 199
    Location: same ocean as you
    At 317 bar this is a bit low, even for a 2250 steel 72, the tank must have been broken

    I will overfill slightly steel tanks but never aluminium

    number of (years) do fibre wrapped tanks have a 15 year limit

    number of Cycles, or depressurisations, so every time the condensate drains activate
    michael-fisch likes this.
  5. OkByMe

    OkByMe Solo Diver

    # of Dives: 500 - 999
    Location: Collierville, Tennessee, United States
    Hydro's are usually at 5/3 the rated pressure. The expansion and subsequent retraction of the tank has to fall with a certain percetange. You would have to go well beyond this unless there is a problem with it and failure is imminent.
  6. JackD342

    JackD342 Dive Shop

    # of Dives: 500 - 999
    Location: Highland Park, IL
    Here is part of the prototype sample testing for 3AL. I don't find anything similar listed for 3AA - there are several other types of tests specified that I didn't notice in the 3AL document.

    (5) Each new design and any significant change to any acceptable design must be qualified for production by testing prototype samples as follows:

    (i) Three samples must be subjected to 100,000 pressure reversal cycles between zero and service pressure or 10,000 pressure reversal cycles between zero and
    test pressure, at a rate not in excess of 10 cycles per minute without failure.

    (ii) Three samples must be pressurized to destruction and failure may not occur at less than 2.5 times the marked
    cylinder service pressure. Each cylinder must remain in one piece. Failure must initiate in the cylinder sidewall in a longitudinal direction. Rate of pressurization may not exceed 200 psig per second.
    wnissen likes this.
  7. captain

    captain Captain

    Typical compressors are incapable of pressurizing a healthy cylinder to failure.
  8. Bob DBF

    Bob DBF Solo Diver

    # of Dives: I just don't log dives
    Location: NorCal
    Typical compressors seem to have a hard time even giving my tanks a proper fill.

    bmorescuba, captain and 2airishuman like this.
  9. 2airishuman

    2airishuman Solo Diver

    # of Dives: 100 - 199
    Location: Greater Minnesota
    The test pressure (5000 PSI) is, by design, 70% of the tensile strength of the metal. The tensile strength will typically be reached, therefore, at approximately 7100 PSI, and the cylinder will burst.

    Permanent damage to the cylinder will occur before that point, because the yield strength is lower than the tensile strength.

    If plain 2250psi steel, same question...[/QUOTE]

    3750 test pressure, tensile strength reached at 5300 PSI according to the math.

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