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why steel tanks? (and other steel tank questions)

Discussion in 'Tanks, Valves and Bands' started by jplacson, Feb 17, 2004.

  1. jplacson

    jplacson Photographer

    # of Dives: 100 - 199
    Location: Philippines
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    I was just wondering, why do freshwater divers choose steel over AL tanks? What's the advantage? Doesn't diving in freshwater require less weight than salt water? What's the big advantage of steel over AL? And why do steel tanks have round bottoms, why don't ALs have them as well?

    Sorry, these are purely out of curiosity...I've never done any freshwater dives so I was just intrigued by the differences. :)
     
  2. Genesis

    Genesis Great White

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    Steel tanks are more negative. Most freshwater divers are diving in drysuits, where more weight is required. Having the tanks be negative (instead of +4, as an AL80 is when empty) is a plus, as it allows you to carry less lead.

    Indeed, in a drysuit you really don't want any other part of your kit to be inherently positive, as that's simply going the "wrong way".

    Steel and AL tanks are made differently and this results in different shapes. The strongest pressure vessel is spherical; indeed, if you look INSIDE an aluminum tank you'll find that its not "flat" at the bottom.
     
  3. jplacson

    jplacson Photographer

    # of Dives: 100 - 199
    Location: Philippines
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    Oh! Thanks! I always thought that the reduced buoyancy you get in freshwater would compensate for the drysuit buoyancy.

    I've also never looked inside an AL tank, didn't realize that it was shaped similar to the steel tanks :p thanks for the info!!! :)
     
  4. Genesis

    Genesis Great White

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    Its "flatter" inside an AL tank, but its not "flat" :D

    Sharp corners are no-nos in pressure vessels.
     
  5. chrpai

    chrpai Great White

    # of Dives: I just don't log dives
    Location: Cedar Park, TX
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    Karl-

    Nice write up, but to be fair you should add in the O2 anaylizer costs for the nitrox fills. They do let you use theirs as part of the price.
     
  6. IndigoBlue

    IndigoBlue Manta Ray

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    You have brought up weighting directly and tank buoyancy indirectly.

    When people buy their first tanks, they usually are bargain shopping, so they go with price first, and that usually leads them to aluminum tanks, whether that is a good idea or not.

    So absent the pricing issue, you have asked a common question: Which tank is right for you?

    Almost all divers require about 4 to 10 lbs of weighting in order to be neutrally buoyant while breathing underwater. Then as you add a thermal suit, the need increases to 6 lbs or more. This pretty much allows you to choose either aluminum or steel tanks, if you please, and then make the balance of your weighting adjustment to the lead on your belt or integrated B/C.

    For really warm water, like The Red Sea, at 95F, you probably would be overweighted at the beginning of your dive with steel tanks. For moderately warm tropical water, at 82F, you could probably go either way, with steel or aluminum. For cold water, at 70F or less, steel is probably your best bet.

    That also brings up the wetsuit/drysuit issue. If you are wearing a thick wetsuit, you are probably unsafe at depths below 50 ft. However a lot of divers dive deeper than 50 ft with thick wetsuits. Therefore they sometimes try to compensate with an aluminum tank as a band aid. My advice is to avoid diving in a thick wetsuit. Thick wetsuits are cheaper to buy in the short term, although in the longer term you would be happier and better off financially in any drysuit rather than a thick wetsuit.

    All other things being equal, I would go with a steel tank, because they last forever, if you treat them right, and keep moisture out of them. But that is not always easy to do, especially on boat dives, where the tank monkey with the air hose is coming around filling the tanks between dives, and he does not do it properly, and he gets moisture into your tank. I have had a steel tank almost ruined that way.
     
  7. Jeddah Aquanaut

    Jeddah Aquanaut Divemaster

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  8. Jeddah Aquanaut

    Jeddah Aquanaut Divemaster

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    Now that I've been going thru a few tank threads here, I wonder...I just love Poseidon HP steel tanks. However, since the ones I used in Saudi lacked the D.O.T. Royal stamp of approval, I sold them. Has anyone seen Poseidon HP steel tanks made for use in the U.S.? I don't imaging they would be very common to begin with here, but they are nice. Their 8L tanks (300Bar) are sweet indeed.
     
  9. doole

    doole Instructor, Scuba

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    Well it does - until you start piling on the underwear.
     
  10. JS1scuba

    JS1scuba Dive Shop

    # of Dives: 5,000 - ∞
    Location: Arizona, SoCal, World
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    You will only find the Divator set up here in the Divator package, and then, it's rare. 300 bar fills are very rare here in the USA as well.


    Cheers
     

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