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LP vs HP tanks on doubles...

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

  1. ianr33

    ianr33 Solo Diver

    # of Dives: 200 - 499
    Location: Wah Wah Land
    5,166
    977
    Al 80 doubles are great for warm water. Cheap and light as a feather (compared to 104's )
    With a 3mm wetsuit I use 6 pounds of weight plus a 6 pound backplate,not much weight to carry.

    Using 2 deco gases they hold enough for 20 minutes at 200 feet,just an easy way to dive.
     
  2. Van Isle

    Van Isle Solo Diver

    # of Dives: 200 - 499
    Location: Victoria, BC, Canada
    270
    5
    I've just finished researching and buying a set of doubles and a wing; I feel your pain! The information one can get on the internet is incredibly biased and is based on a poster's geographic location, type of diving, air consumption, fills and mixes available.

    It is important to talk to the divers doing the diving you want to do in the area you want to do it.

    For me, PNW cold water deco dives with less than 30 minutes of deco, in a dry suit, one deco gas, led me to HP 100s. I'm not afraid of the weight of the bigger tanks, despite being 5'8", but I did want a doubles set that I could and would dive all the time to get bottom time in the rig on lots of recreational shore dives prior to fundies/tech training. If I ever get to bigger, badder dives, I'll get 130s. No big deal. If I move to cave country to do huge penetrations I'll get what works there, LP 104s or whatever is gospel. Getting trimix fills is easy here: there are boosters around, I can get partial pressure blends, 32% is banked for "standard" trimix mixes. If that's not the case where you are maybe LP tanks make it easier to get the right mixes, I don't know. Again, that's why you need to talk with divers doing your dives in your area. Good luck!

    VI
     
  3. iztok

    iztok PADI Pro

    # of Dives: 200 - 499
    Location: Charlotte, NC
    4,601
    393
     
  4. Van Isle

    Van Isle Solo Diver

    # of Dives: 200 - 499
    Location: Victoria, BC, Canada
    270
    5
    I haven't heard of this before this post, but I'm guessing it might be true in cases where there is neither a booster readily available nor large banks of high pressure helium and O2, so it would be therefore easier (i.e. have sufficient gas at sufficient pressure) to get partial pressure fills in an LP tank assuming final fill of 2400psi vs HP 3445psi.

    But this is just a guess.

    VI
     
  5. iztok

    iztok PADI Pro

    # of Dives: 200 - 499
    Location: Charlotte, NC
    4,601
    393
    As I said if we talk about filling to nominal pressure of LP vs nominal pressure of HP. However they are equal when it comes to same pressure fills.
     
  6. sean_nc

    sean_nc Solo Diver

    17
    0
    Not trying to pick on you Superlyte but this logic has never made sense to me.

    1. If you continuously overfill any tank and use up the safety margin you run a real risk of problems.

    2. Why not just get the same tank with a different steel that is rated to hold the pressure? Safer way to hold the same amount of gas.

    3. If your local shop wants to pump the tanks that high I don't want to be around. I know shops have been doing it for years but I see no reason to risk it when I can get the right tank and do it safely.

    4. If it's as safe as everyone says why not "Try that magic" with an HP and fill that 3442 up to 5163?
     
  7. UCFKnightDiver

    UCFKnightDiver ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Florida
    1,092
    145
    Find me an HP tank that holds in excess of 130 cuft of gas and I will, and it has been happening for years with no failures and tanks are still passing hydro's with no problem, not seeing the issue here.
     
  8. iztok

    iztok PADI Pro

    # of Dives: 200 - 499
    Location: Charlotte, NC
    4,601
    393
    HP 130 at 3860psi (pressure you mentioned) holds 147 cuft.
     
  9. elan

    elan DIR Practitioner

    # of Dives: 200 - 499
    Location: Toronto, Ontario, Canada
    3,316
    379
    I think there is a tank made by Faber which holds 146 cuf at 3500 if I'm not mistaken.
     
  10. UCFKnightDiver

    UCFKnightDiver ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Florida
    1,092
    145
    I don't believe I mentioned any pressure of 3860psi.
     

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