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Question, vintage LP72 tank

Discussion in 'Vintage Equipment Diving' started by rnln, Feb 3, 2020.

  1. John C. Ratliff

    John C. Ratliff Instructor, Scuba

    # of Dives: I'm a Fish!
    Location: Beaverton, Oregon
    Your math is good, but your advise is not so good. It is not a good idea, especially for these ol' tanks, to overfill them on purpose. There is a reason they don't have the "+" on the hydro, as these are old tanks, and must have more testing before the plus can be added to the hydro. There is quite an extensive discussion about overfilling these tanks here:

    Overfilling LP Steel Tanks -- How bad is it?

    Sam Miller III and lowviz like this.
  2. halocline

    halocline Solo Diver

    The only reason hydro test facilities don't give LP72s plus rating is they either are too ignorant or lazy to do so, or they don't have access to the REE number for the tank. There is no additional testing required for the plus rating beyond the standard hydro test. I would think you would know that given your level of experience. The age of the tank has nothing to do with it.
    captain, couv, Luis H and 1 other person like this.
  3. rjack321

    rjack321 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Port Orchard, WA
    I dont think an 11 yr old thread proves your point. LP72s with or without +s are not failing from 2800psi fills. They didnt in 2009 and they haven't gotten any worse since then.
    tmassey likes this.
  4. Luis H

    Luis H Instructor, Scuba

    # of Dives: I'm a Fish!
    Location: Maine
    Age affects humans; (with very few exceptions) it does not affect steel. I realize that some humans may think that just because we decay with age, everything else must decay as well, but that is not the case.

    The only thing that age will do to a steel cylinder (or structure) is provide more opportunity for corrosion (rust) and other potential exposures to fire or other damage. All of this detrimental factors can be accounted for by inspection and testing.

    Like @halocline mentioned, there is no extra testing needed for the + stamping. It uses the same data from the same hydro test, but it compares different numbers.

    To obtain the number needed, the REE it requires just a little bit more effort and a little bit of knowledge.

    All of my steel 72's are stamped with the + stamp. The hydro's were done by my LDS and I calculated and provided the REE numbers.

    I can't remember ever seen a properly tested steel 72 fail hydro or fail the + stamp requirements. I didn't always checked for the + stamp requirements, but thinking back to the last 48 years and I can't remember a steel deciliter that passed without a large margin.

    To calculate an accurate REE for any particular cylinder, it is best to measure the actual wall thickness of that cylinder. I did my cylinders by using ultrasound equipment at work (with the assistance of a technician, etc.). To do it again, I would just buy an ultrasound measuring device for about $82 at Amazon.


    Once you have an average wall thickness (you want about 20 data points for the average), the calculations are relatively simple.
  5. John C. Ratliff

    John C. Ratliff Instructor, Scuba

    # of Dives: I'm a Fish!
    Location: Beaverton, Oregon
    Thanks Luis, I stand corrected.

    The "+" rating doesn't allow for overfilling a stamped 2250 psig tank, with a "+" rating, to be filled to 3000+ psi though. 'Glad to hear that my steel cylinders will be around for longer than me!

    Sam Miller III likes this.

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