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H.P Steel tanks in Florida

Discussion in 'Tanks, Valves and Bands' started by Boston Breakwater, Oct 13, 2020.

  1. Barnaby'sDad

    Barnaby'sDad ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 50 - 99
    Location: Virginia
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    Same here. I unloaded my previous set of HP100’s thinking I wanted HP120’s. After doing a few more dives with HP100’s, I bought another pair of them (same make and model).:popcorn:

    Another reason someone might want HP tanks is that they don’t want to roll around with tanks filled ~1,000 psi above their service rating. I get that it’s a thing, but I’ll pass on that.
     
    Boston Breakwater likes this.
  2. uncfnp

    uncfnp ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: North Carolina
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    I don’t know at what point it’s an official “cave fill” but my local shop typical fills to about 3600 to 3700. My shop in Florida fills to about 3800. I have picked them up with 4000.

    They are 3442’s
     
    BRT likes this.
  3. tbone1004

    tbone1004 Technical Instructor ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Greenville, South Carolina, United States
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    The threads are not nominal, they are different thread standards. Standard scuba tanks are 3/4 NPS-National Pipe Straight.
    The 3500psi HP bottles a 7/8 UNF-Unified National Fine

    UNF calls out the size as the major diameter, or the OD of the threads.
    NPS is a pipe thread standard and it is actually calling out the size of the "pipe" so it's the ID of what the pipe would be if you screwed it into the thread. NPS and NPT are very similar in terms of how they are defined, so similarly a 1/4" NPT that we're all familiar with has a 1/4" pipe diameter, but the major OD is actually just over half an inch.
     
    James79, Boston Breakwater and Ana like this.
  4. kelemvor

    kelemvor Big Fleshy Monster ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Largo, FL USA
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    I'd call that a cave fill. In an HP120 rated for 3442 but filled to 4k you should have 139cuft of gas in there. In an LP108 (2640 rated) filled to 3600 you have 147. Little more gas with the 108, and none of that counts for Ideal gas or whatever, but the general idea is the same. If I had HP120's I'd definitely use them, but if I were shopping, I'd prefer to use LP108's (or 104 as Worthington is gone). I have had mine filled to 3800 once but that makes me uncomfortable for some reason so I usually ask for 3600.

    Now that HP tank is only overfilled by 600psi where the LP tank is overfilled by 1k so the HP should be safer. However, I don't think there's a single story of a cave fill causing anything other than the occasional blown disc so I don't really worry about it much.

    My wife has a couple HP tanks. HP80's. We have them because the form factor fits her body much better than the taller al80's.
     
    Boston Breakwater likes this.
  5. tbone1004

    tbone1004 Technical Instructor ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Greenville, South Carolina, United States
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    cave fills as a general "rule" are considered to be 3600psi. That is an overfill for any of the MP or HP tanks, though a marginal one at best. Many shops fill to 4000 and let them cool to 3600 ish and depending on time of year and the fill rate, it may end up at 37/38. We want our bottles in increments of 300psi though to make thirds easy to handle. The way thirds are calculated is you round down to the next increment, so if you have a 3500psi fill, you round down to 3300 and use a third of that for an 1100psi third. If they had overfilled by 100psi and we had 3600, then you get a 1200psi third. It's not huge, but it is there.
     
    Boston Breakwater and kelemvor like this.
  6. Barnaby'sDad

    Barnaby'sDad ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 50 - 99
    Location: Virginia
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    Are you talking “hot” fills or fills to 3,600+. I’ve gotten a few of the latter, but generally the fill is hot enough that I’m lucky to be at 3,400 when it cools.

    3,500 here.
     
  7. tbone1004

    tbone1004 Technical Instructor ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Greenville, South Carolina, United States
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    A proper cave fill is 3600psi at 70f
     
  8. Squirm88

    Squirm88 Angel Fish

    # of Dives: I just don't log dives
    Location: Tallahassee, FL
    57
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    To me the Faber LP 85's are slightly smaller and lighter than the HP 100's yet they hold more gas with a proper fill. On a single tank dive with an aluminum backplate and wing I need no additional weight with an LP 85. It's about the perfect tank for my single tank dives. Even on my cave dives my go to set of doubles is a set of doubled up LP 85s.
     
    Dark Wolf and Boston Breakwater like this.
  9. Barnaby'sDad

    Barnaby'sDad ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 50 - 99
    Location: Virginia
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    The person I quoted was talking local to them (North Carolina) for some of their figures. I’m just curious if they actually manage to get their tanks filled to the full rated pressure, or if they get their tanks back piping hot at ~3,600 psi...in which case it cools down and you lose a good amount of pressure.

    I’ve probably gotten more 3,100-3,200psi fills in my 3,442-3,500 tanks than legit ~3,500psi fills. If that’s my own doing (getting an on the spot fill) that’s one thing. If it’s on a tank that was left for a fill, it’s not cool. Well...it’s clearly not cool, but not appreciated, I mean, lol.
     
    TooManyHobbies likes this.
  10. tbone1004

    tbone1004 Technical Instructor ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: Greenville, South Carolina, United States
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    I know the shops that @uncfnp goes to, they'll give 3600 cold if you ask nicely and can leave it over night. Now, the issue with that is they have double labor bringing them back onto the whips, so some shops will charge more for it *only fair*, but the shops in her region will fill them really slowly to about 3700-3800 and they'll cool to 3600 or so

    Also of note is that the working pressures at standard temperature, so if the tank is rated at 3442 and is filled to 3800 and cools to 3442, then it hasn't been overfilled because with temperature correction it was still holding the same volume of gas so that's nice.
     
    Bob DBF and Barnaby'sDad like this.

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