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LP vs HP tanks on doubles...

Discussion in 'Advanced Scuba' started by DC53, Mar 26, 2010.

  1. SkimFisher

    SkimFisher Contributor

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    I have been told on more than one occasion that in Europe our LP tanks are considered HP tanks. Can anyone confirm or deny? Anyone heard something similar?
     
  2. Scared Silly

    Scared Silly Regular of the Pub

    # of Dives: 500 - 999
    Location: on the path to perdition
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    You are correct that CGA sets standards but those standards are referenced in the CFRs so in affect they are laws.

    Here is a good example,look at the section:
    http://edocket.access.gpo.gov/cfr_2007/octqtr/pdf/49cfr173.301.pdf

    As for OSHA I would have do some searching but they are all inter-rated. When it comes to overfilling - OSHA would probably cite for creating a hazardous situation by not following prescribed DOT rules.
     
  3. Meng_Tze

    Meng_Tze Homo Bonae Voluntatis ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: 246 Bubbleless Cove
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    I look forward to your search details around OSHA and DOT regulations around filling of recreational SCUBA tanks. There was a change around the filling of 6351-T6 Alloy tanks. As we know there have been some issues with that.

    DOT 3AL cylinders manufactured of 6351-T6 aluminum alloy. Suitable safeguards should be provided to protect personnel and facilities should failure occur while filling cylinders manufactured of aluminum alloy 6351-T6 used in self-contained underwater breathing apparatus (SCUBA), self-contained breathing apparatus (SCBA) or oxygen service. The cylinder filler should allow only those individuals essential to the filling process to be in the vicinity of the cylinder during the filling process.

    But that is the only reference to filling SCUBA tanks. The DOT does reference SCUBA in the following sections:

    §173.302 Filling of cylinders with nonliquefied (permanent) compressed gases.
    §180.205 General requirements for requalification of specification cylinders.
    §180.209 Requirements for requalification of specification cylinders.

    Again, this is to deal with the tanks themselves as safe vessels for gas. But they do not prescribe filling of recreational scuba tanks outside of above quoted section (part of §173.302).

    Recreational SCUBA is unregulated, self regulated at the most.
     
  4. iztok

    iztok PADI Pro

    # of Dives: 200 - 499
    Location: Charlotte, NC
    4,601
    393
    So DOT requirements are not law?
     
  5. DA Aquamaster

    DA Aquamaster Directional Toast ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
    Location: NC
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    DOT regs only apply to tanks used in interstate commerce. At various times that has been applied to tanks that could *potentially* be used in interstate commerce, but the DOT generally speaking will not go after a shop for overfilling scuba tanks, at least in the last couple administrations.

    ------

    All things being equal, it makres sense to go with a HP tank rather than an LP tank of the same size and weight. The Worthington LP95 and Worthington X8-119 are a good example. Both are 8inches in diameter, 24 inces tall and weight 42 pounds. At 3600 psi the X8-119 would hold 128.6 cu ft and the LP 95 at the same 3600 psi would hold 127.2 cu ft. The X8-119 is the hands down smart choice. The real decision would be whether you go with the X8-119 or the X8-130. The 130 is 1.5" taller, only a pound heavier and holds 131.4 cu ft at 3442 psi and 137.4 cu ft at 3600 psi. Of the three tanks, the X8-130 would be my choice.

    However, in comparision to a Faber LP 95 it is less clear. The Faber LP 95 is the same size but weighs only 38 pounds and holds a honest 95.1 cu ft at 2640 psi and 129.7 cu ft at 3600 psi. So it has X8-119 capacity and near X8-130 capacity when filled to 3600 psi but weighs 4 and 5 pounds less respectively. That saves 8 to 10 pounds per set of doubles.

    ----

    Someone mentioned not buying more tank than you'll use most of the time and I agree. A pair of X7-100s will weigh about 91 pounds full with manifold and bands and will hold 199 cu ft of gas. In comparison, double X8-130s will weigh 116 pounds when full with manifolds and bands and hold 262.8 cu ft.

    So with 130's you are carrying an extra 25 pounds to get the extra 63 cu ft of gas whether you need it or not. If 199 cu ft is enough for most of your diving, then you are needlessly carrying significantly more weight.

    If you are using X7-100s instead, on the few dives where you need more gas, you can carry, for example, an AL 72 as a stage. It will weigh about 36 pounds when full with reg, and bring your total gas to 271 cu ft. So in effect you will be carrying 11 more pounds, but only on the small number of dives where you really need the extra gas.
     
  6. Superlyte27

    Superlyte27 Cave Instructor

    # of Dives: 5,000 - ∞
    Location: Florida
    4,101
    3,218
    I dive double Faber 95's. Recently a cave shop asked us what we wanted filled in the tanks. My new dive buddy said "pump em up to 4k" (I thought he was joking, the shop didn't). Which the shop did. When we got in the water, my computer read 3860psi. Hmmm. 3860psi = 139cu' of air each tank. That's alotta stinkin air in a set of LP tanks. Try that magic with HP tanks. Now granted, I wouldn't ask for 4k fills. But a cold 3600 is very common.
     
  7. Meng_Tze

    Meng_Tze Homo Bonae Voluntatis ScubaBoard Supporter

    # of Dives: 500 - 999
    Location: 246 Bubbleless Cove
    2,309
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    Yes they are, never contradicted that. They do not apply to fill pressures used in recreational SCUBA. That is my point.
     
  8. Scott L

    Scott L Solo Diver

    # of Dives:
    Location: North Palm Beach, FL
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    3900 is common here for HP...
     
  9. Colliam7

    Colliam7 Tech Instructor Staff Member ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
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    Not at all surprised. Nothing wrong with the advice. I just don't see a strong reason for absolutism, either way.
    YES!!!
     
  10. iztok

    iztok PADI Pro

    # of Dives: 200 - 499
    Location: Charlotte, NC
    4,601
    393
    My first set of doubles is AL80s. Granted I put it together as I had 6 AL80s and got manifold and bands cheap. But then I started to think and read more and came to realization that double AL80s have place in diving when diving wet just fine. With drysuit steel tanks make sense (well should be the other way around with steel doubles drysuit makes sense).
     

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