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LDS Won't + 10% Fill Plus Rated Tank?

Discussion in 'Tanks, Valves and Bands' started by Dubious, Jul 10, 2020.

  1. Kharon

    Kharon Solo Diver

    # of Dives: 200 - 499
    Location: Upstate NY
    He's blowing smoke. Steel tanks can be plus rated on any hydro as long as the tank had a plus rating on manufacture and the plus test is done.

    And you also are blowing smoke. If the tank had a plus rating on manufacture it can be plus tested at any point and if it passes the plus test will have a plus rating. Prior tests matter not a bit. The rating at maufacture and current test is the only thing that matters. There is no requirement to "maintain" a plus rating on every hydro. Some testing sites can't do the plus test. Having a tanki tested there does nothing to prevent another site from doing a plus test on a subsequent test.

    Another bushwah tale you will hear is that if the tank is plus tested and doesn't pass at the plus level it has to be condemned. Total crap. It will at that point not be given the plus rating. That's all. You can continue to use it as LP without the additional 10%. But you can still have it plus tested at a later date. If it passes it will get the plus rating - very unlikely that having failed once it will pass at a later date. But you can have it tested. And it can continue to be used as a LP without 10%+ as long as it passes a regular hydro. Should it somehow pass a later plus test it will get the plus rating.

    Dive shops make crap up all the time depending on what they are trying to sell or what they are pretending to know. One owner of a LDS announced at a local club meeting that if he didn't pass a tank on a vis he would drill holes in it. Absolutely illegal and he would be liable. The only thing he can legally do is give the tank back withou a visual inspection sticker. Same for a hydro that isn't passed. They can only X out - not drill holes. So many people blow smoke - they think that because they think it, it must be so. You have to look at the actual regulations ans applicable laws to find out what is true.
    Bob DBF and James79 like this.
  2. Johnoly

    Johnoly ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 2,500 - 4,999
    Yaa, a shop drilled a hole in my tank once. I had a friend make me a handful of stainless steel bolts on his garage lathe. They are self tapping threads and to make them stronger they are made in metric and with Torx driver heads. He said to use a torque wrench and set the foot pounds to the same as what the tank PSI is rated to so it equals out. So far so good and I saved the tank.
  3. boulderjohn

    boulderjohn Technical Instructor ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Boulder, CO
    A friend of mine bought some used tanks, used them for two years, and took them in for hydro. The shop decided that the tanks did not pass, so they destroyed the threads so that they could not be used again. My friend did not know they had to use special procedures when testing Worthington tanks, and it turned out the shop did not know that, either.
  4. captain

    captain Captain

    There is no such thing as a plus test. The hydro test is performed as it normally is. The plus is determined by simple arithmetic using the results of the hydro test and the REE of the tank,. If the tank REE is not stamped on the tank by the manufacturer the hydro shop must have documentation from the manufacturer what it is, otherwise the shop must perform ultrasonic testing of the tank wall thickness and calculate the REE per the procedure in the CFR. Good luck finding any shop to do that, it ain't going to happen.
    Luis here on the forum is a mechanical enginer and has performed the ultrasonic testing on his personal tanks and determined the REE's and can determine if his tanks qualify for the plus but he cannot legally stamp a plus on his tanks, It must be done by a federally licensed testing facility. If you search you can find his post about it.

    Page 6
    Question, vintage LP72 tank
  5. Wookie

    Wookie Secret Field Agent ScubaBoard Business Sponsor

    No. I was wrong in my knowledge. I said I was wrong and thanked the person who upgraded my knowledge.

    What part of be kind don’t you understand? Big internet tough guy?

    Edit. You didn’t even read what I wrote. Although I was wrong, you weren’t even close.
    rjack321 likes this.
  6. halocline

    halocline Solo Diver

    As Captain said in a later post, there's no additional test for the plus rating. The way hydro test works (sorry if you personally know this, but obviously not all readers do) is that the tank displacement is carefully measured, then the tank is pressurized to test pressure and the displacement is again measured. Then the pressure is released and it is measured again. So the tester now has three numbers, which allow him to measure A) the amount of expansion under pressure, and B) the amount, if any, of permanent expansion by comparing the first and last numbers. For the tank to pass hydro, it must exhibit 90% elasticity, which I believe basically means that if it were to expand 100 cc under test pressure, it must contract at least 90 cc when depressurized and measured a final time. For the Plus rating, there is a maximum amount of initial expansion allowed, that's what the REE number is. If the tank expands less or equal to that number, it qualifies for the plus.

    The reason for this lengthy explanation is because it is very possible for tanks to not qualify for the plus rating depending on how the tester initially pressurizes the tank. For example, worthington (I think it was them) had this memo about pre-pressurizing or "rounding out" galvanized tanks prior to hydro by partially pressurizing them to 90% of the test pressure. This was to counteract any effects that the hot galvanizing might have had on the initial shape of the tank. Some testers perform this pre-pressurizing, some don't. It definitely has an effect. Another variable is the accuracy to which testers pressurize tanks. I think there is a 5-10% margin they can work within, and who knows how accurate their gauges are.

    I bring this up because I had a pair of pst galvanized LP72s fail the plus rating on the first hydro after I bought them. They had been sitting for decades. I'm sure that the tester did not use the pre-rounding procedure, and they had not been subjected to test pressure in at least 30 years. So they measured slightly higher total expansion than the REE number and were rejected by the tester for the plus rating. On the next hydro, the tester did do the pre-rounding procedure, and they passed easily.

    Interestingly, the first tester was a bit of a zealot about passing tanks, and illegally stamped the words "no plus" in my tanks. Needless to say, I went looking for a different tester next time around. There is a wide range of knowledge and personalities regarding scuba tanks in the hydro testing world, I have found out. It's not surprising; they don't make much money and probably 90% of their business is testing and filling fire extinguishers.
    Bob DBF, couv and captain like this.
  7. boulderjohn

    boulderjohn Technical Instructor ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Boulder, CO
    That has been my experience, but I admit I was surprised to experience it.

    The first time I ever had tanks hydroed, I took them to a hydro facility while I was vacationing in Florida. I paid to have them oxygen cleaned and put back together as doubles as well. The shop was filled with tanks that had nothing to do with scuba. Mine were the only scuba tanks in sight. Not only did they not give me the +, they did not have O2 Vis stickers and gave me a certificate to carry around with me saying the tanks had been O2 cleaned. I later found that they had screwed all the valves--the stems were bent.

    Well, it turns out that all the tanks I take with me to Florida annually require their hydros during the months I am there. I learned my lesson and found a shop that does nothing but scuba tanks, and everything has been hunky dory ever since.
  8. Boiler_81

    Boiler_81 Solo Diver

    I am in the same position with a couple of my tanks. Where in FL do you take your tanks for hydro?

  9. greeniguana

    greeniguana ScubaBoard Supporter ScubaBoard Supporter

    Question was not directed at me, but I'll contribute.....

    Services - Deep Six Divers Service Inc.

    In Lakeland. They one of few shops I know of that is DOT certified hydro tester. Tanks never leave their shop, they know what REE is, they know what rounding out is.....
    Boiler_81, couv and captain like this.
  10. boulderjohn

    boulderjohn Technical Instructor ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Boulder, CO
    Boiler_81 and captain like this.

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