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Safely diving with heavy tanks

Discussion in 'Basic Scuba' started by Nathan Doty, Jul 16, 2019.

  1. Rooster59

    Rooster59 Solo Diver

    If you're not using much air at depth, you're still ongassing nitrogen. You might hit the NDL (time) and still have lots of air in your tank. If you're hauling around a big tank but not using a significant amount of the air in it, you may decide your tank is too big.
    NAUI Wowie likes this.
  2. NAUI Wowie

    NAUI Wowie Contributor

    # of Dives: 50 - 99
    Location: Silicon Valley northern CA

    lol not sure what you are saying. are you saying that with weights you can drop you dont need redundant lift? I dont understand how you fixed my sentence.

    Do you agree with helodriver that all divers should carry redundant separate lift apart from the bcd and weight belt? because thats what hes saying.
  3. melanie.

    melanie. Contributor

    # of Dives: 200 - 499
    Location: Ontario, Canada
    OP hasn't decided on tank. Therefore a very real possibility that he wont need weight in the future.

    The question was what happens when you have no ditcheable weight - the answer is get redundant lift. I dont understand why you think that is such an odd thing. I do not dive with weight....
    helodriver87 likes this.
  4. RayfromTX

    RayfromTX Student Of Gas Mixology Staff Member ScubaBoard Sponsor

    # of Dives: 200 - 499
    Location: Cozumel while the cruise ships are gone
    This is incorrect. The difference in negative buoyancy between a steel 72 and a steel 100 or 120 is 6 or 8 pounds respectively. Large steel tanks often create a need for redundant lift in case of bcd failure. The failure can be managed in other ways depending on the nature of the failure but as has been the case in the past, you are stating things as fact that are demonstrably false and potentially dangerous.

    Readers should be cautious and informed when diving large steel tanks. They are not dangerous in and of themselves but they do introduce factors that need to be considered in your gear configuration and managing the weight of them in a wing failure is one. The bottom line I suppose is to avoid being overweighted and when that occurs, recognize the need for redundant lift strategies.
  5. johndiver999

    johndiver999 Solo Diver

    # of Dives: 500 - 999
    Location: Gainesville FL
    You seem to be very opinionated on this topic. Your strong recommendation to use 100 cu-ft aluminum tanks is NOT something I would repeat - and I used those tanks for a long time before selling them - they suck compared to a nice steel tank. but the above topics are primarily opinions.

    However, your comment about a steel 120 being no different than a steel 72 (other than 1-2 lbs) with respect to buoyancy is not factual. It is a potentially dangerous piece of mis-information. Even if the two tanks had identical buoyancy characteristics (which they don't) the differences in their volumetric capacity translates to a large buoyancy swing between full and empty.

    Edit.. post above was written when I was writing mine..
    Caveeagle and RayfromTX like this.
  6. Caveeagle

    Caveeagle Rebreather Pilot

    # of Dives: 500 - 999
    Location: High Springs, FL
    This is a silly claim. I own and dive many steel tanks, there is much more than a 2# delta between a LP72 (slightly positive when below 500psi) and a hp100 (neg 7# empty).

    There ARE. Very good reasons for redundant lift when diving over-neg rigs. Just a few examples: blue water, where there is no “safe bottom”, cave, silty or sensitive bottom, or places where you cannot climb out with a blown wing. I know of one diver who had a real problem trying to exit Friedman sink with a wing that would not hold air when in a vertical position. Thankfully gas reserves allowed for an alternate exit, or it might have been a fatality. **nobody carries a SMB in caves.
    Colliam7, kafkaland and melanie. like this.
  7. Rechno

    Rechno Contributor

    # of Dives: 200 - 499
    Location: Germany
    You absolutely need redundant lift in case of BCD failure.
    One means to compensate can be the ability to swim your gear up. You can easily test it. Descend, empty your wing completely and try to swim it up. If you can do it comfortably and controlled, you got your redundant lift (called FINS/FLIPPERS).
    If you cant do it, you can try to change weighting, use ditchable weights.
    Alternatively or if you cant use droppable weights you will need another lift source (drysuit, liftbag, double-bladder).

    One other thing to keep in mind is, that you might have to spend some time floating, so in case you dont have ditchable weights, you should be sure to get out of your BCD quick.
  8. EireDiver606

    EireDiver606 Public Safety Diver

    Forget 90% of the comments on here and research what a balanced rig is. And do yourself a favour and get a free 3 day trial to GUEtv so you can learn even more.
    chillyinCanada likes this.
  9. EireDiver606

    EireDiver606 Public Safety Diver

    Diving is safer than driving your car. It’s only dangerous if you or others make it dangerous. Diving isn’t a bungee jumping substitute that’s (DANGEROUS)....
  10. Diving Dubai

    Diving Dubai Instructor, Scuba

    # of Dives: 1,000 - 2,499
    Location: Dubai UAE
    I'll throw this out there..

    I dive 15l 232 bar Steels (Hp120 @3300psi?) I choose to do so not because I need the gas, but I prefer the additional gas as a contingency - after a hard 1 hr dive I'll generally be up with 100 bar, but have been up with only 30 bar after 35 mins in "difficult" conditions

    I have proved I can swim my rig up form 20m (60') because I have had a wing failure.

    I carry little extra weight, in a 3mm I'm generally over at the SS, but then I'm generally not at minimum. I also plan my weighting to be enough to maintain a SS with absolute min gas (20bar) and while stressed (so more buoyant) - worst case.

    So to say steels aren't suitable for tropical diving is just wrong, although I accept I only have a limited experience of 5 years/800 dives with them.

    With the exception of my SM I would choose steels every day of the week. My wife and I have 28 of them between us.
    NAUI Wowie likes this.

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