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hp tank fills

Discussion in 'Basic Scuba Discussions' started by salt h20, Feb 2, 2007.

  1. salt h20

    salt h20 Angel Fish

    # of Dives: 500 - 999
    Location: TEXAS GULF COAST
    has anyone bought a hp( 3442 psi) tank only to find your local dive shop cant fill it to the rated pressure? so in order for me to get 100cf or close i have to buy a hp 120

    and also am i more likely NOT to get a hot fill with 3000psi in my rated 3442 tank due to less heat buildup due to not packing as tight?
  2. loosebits

    loosebits Solo Diver

    # of Dives: 200 - 499
    Location: DFW, TX
    Yes,it's common for HP tanks not to be filled to rated pressure especially since to get it to 3450 they need to fill to around 3800 and let it cool.

    Just tell yourself you have an LP95 (95 cubes @ 2640) and you are getting an overfill.

    Yes, a fill to 3000psi will be a cooler fill all things being equal.
  3. LetterBoy

    LetterBoy he who lacks empathy ScubaBoard Supporter

    # of Dives: 100 - 199
    Location: The edge of the earth.
    Is this because there banks couldn't support it at the time or they can't pump that high?
  4. Warren_L

    Warren_L Instructor, Scuba

    # of Dives: 2,500 - 4,999
    Location: Toronto, Ontario, Canada
    I've been diving with PST HP tanks for a while (rated to 3442 psi - technically not high pressure, but certainly higher than the 3000 we typically see in AL tanks). The issues really depend on the shop you fill at.

    There are a handful of shops that I can fill at, depending where I am going and most of them (except one) keep their banks sufficient to fill to the rated pressure. Of course, if there is insufficient pressure to fill to 3442, you're going to end up short.

    The issue with the shops that do have sufficient pressure in their banks is the time required to do a proper fill. As already mentioned, you could fill it to 3800 psi and let it cool (though you're not really supposed to do that). So to get a proper fill to the rated pressure does require a bit of time which some shops may not be willing to spend, so you end up short of the rated pressure. How short depends on how quick they fill (and to how much) and let you go.
  5. JacobK

    JacobK Angel Fish

    # of Dives: 25 - 49
    Location: La Mirada, CA
    My LDS is able to fill my HP 100 without a problem.
  6. willardj

    willardj Solo Diver

    It's not that they can't it's that they want. Most compressure's are rated to 4000 or 5000 Psi
  7. Meng_Tze

    Meng_Tze Homo Bonae Voluntatis ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: 246 Bubbleless Cove
    No problems getting HP tanks filled. I am somewhat surprised your LDS can't do it...... most outfits can easily fill to 4K psi. Maybe he doesn't want to? Have you asked why he can not fill to the rated pressure?
  8. rookers

    rookers Tech Instructor

    I have not had a 'rated' fill on my Worthington HP 120s (3442psi) outside of cave country. I have seen as high as 3100 locally, but no more.
  9. willardj

    willardj Solo Diver

    This is why I went with lp 95's. You can get 95++ cubic feet
  10. spectrum

    spectrum Dive Bum Wannabe ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: The Atlantic Northeast (Maine)
    All of the shop around here have the capability. Willingness or ability of the fill person to pull it off is the big wild card. There are shops and especially boats that cannot do a pseudo HP or HP fill.

    If it's possible leaving the tank over night to get a fill, cool and top off will get you there. A careful fill (bleeding in over about 15 minutes) to about 200 PSI over will get you where you want to be. Lots of stuff can effect the results. Some shops don't bank HP or at times will top-off with hot gas right from the compressor. If you hit the shop early and they happen to have cold full banks you can get very nice results.

    Thats the bottom line. Technique can alleviate a lot of the difficulty but the physics are inescapable.


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