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Out of air incident.

Discussion in 'Near Misses & Lessons Learned' started by cbl, Feb 5, 2017.

  1. Dan

    Dan ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Lake Jackson, Texas
    7,522
    5,045
    Now you are comparing apple with orange. 50' line would give 7 x more volume than 90" line plus your big PVC air storage at 50 psi.
     
  2. BRT

    BRT not a soft touch

    16,593
    14,409
    Why don't you forget trying to think it through and attach your reg to a tank?
     
  3. Dan

    Dan ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Lake Jackson, Texas
    7,522
    5,045
    I'm not diving with hookah. I'm using the regular AL80 3000psi tank strapped on my back. When the tank pressure down to 150 psi, that's the minimum pressure drop that my Scubapro MK25 need to deliver intermediate pressure to my S600 2nd stage regulator. Basically the MK25 regulates the tank pressure from 3000 psi to 150 psi before going to the low pressure hose and to the 2nd stage regulator.

    Your compressor can only put up 50psi, so you don't need the 1st stage regulator, you just need the 2nd stage regulator that you use to breathe on.
     
  4. BRT

    BRT not a soft touch

    16,593
    14,409
    And you obviously don't own a tank full of air either.
     
  5. archer1960

    archer1960 Contributor

    # of Dives: 50 - 99
    Location: Southern New England, USA
    572
    137
    "Beginning" <> "OW Cert"
     
    KeithG likes this.
  6. archer1960

    archer1960 Contributor

    # of Dives: 50 - 99
    Location: Southern New England, USA
    572
    137
    Your description is correct as far as it goes, but it doesn't go far enough. Your 1st stage will continue to open until the IP reaches its 150psi set point. If it can't reach 150, it keeps trying, by simply going full open and staying there. Your 2nd stage works similarly. If it can't keep the downstream pressure it wants to, it simply opens all the way and stays there. So you can breathe your tank down until its internal pressure is equal to the ambient pressure at your 2nd stage.
     
  7. Dan

    Dan ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Lake Jackson, Texas
    7,522
    5,045
    What happen when the tank itself bleeds down & reaches 150psi? Can you get air in the lP hose, downstream of the 1st stage regulator? What is the minimum pressure in the tank required to be to open the 1st stage regulator? I thought there is a minimum of 150 psi to push open the piston & spring to vent the tank pressure to the IP hose. So if the tank pressure is less than the pressure required to push open the piston, then, there won't be any air bleed out of the 1st stage into the IP hose. Am I missing something?
     
    Last edited: Mar 3, 2017
  8. Dan

    Dan ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Lake Jackson, Texas
    7,522
    5,045
    Don't need to if I can rent one for $10.
     
  9. archer1960

    archer1960 Contributor

    # of Dives: 50 - 99
    Location: Southern New England, USA
    572
    137
    No, you have it backwards. It's the pressure downstream of the 1st stage regulator that CLOSES the valve. If the tank doesn't have at least 150 psi in it, a spring fully opens the valve, and your LP hose and 2nd stage receive whatever pressure is left in the tank. The 2nd stage works similarly, where it will deliver air until the pressure in the hose gets down to (almost) the ambient pressure in your mouth.
     
    Cowfish Aesthetic likes this.
  10. BRT

    BRT not a soft touch

    16,593
    14,409
    Thanks Archer. I hate for someone to sound like they know what they are talking about and teach things that are not true.
     

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