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Questions about LP72 tanks

Discussion in 'Tanks, Valves and Bands' started by elgoog, Aug 25, 2015.

  1. tbone1004

    tbone1004 ScubaBoard Supporter ScubaBoard Supporter

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    no, the 3aa tanks don't need it. just the ones with the DOT exemption permit.
     
  2. guruboy

    guruboy Divemaster ScubaBoard Supporter

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    Edit- So I saw in another thread that the round-out procedure is recommended for all PST Hot Dip Galvanized tanks. Are all Hot Dip Galvanized tanks tanks with exemptions?

    From what I can tell from other posts by Luis, non-exemption tanks can also be Hot Dip Galvanized and he has all of his PST steel tanks tested using the round-out procedure.

    Not sure if my WK is Hot Dip Galvanized though.
     
    Last edited: Feb 17, 2016
  3. Luis H

    Luis H Instructor, Scuba

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    On post number 31 I put a copy of:

    “PST Technical Bulletin D100-E

    Procedure for Hydrostatic Retesting of Hot Dip Galvanized Scuba Cylinder Revised 1/01/03”

    That bulleting is referring to:

    “All PST scuba cylinders made starting in 1952 are protected from corrosion by a hot dip galvanized coating.”


    The procedure applies to all PST galvanized tanks, including 3AA cylinders.

    The document is from PST, but there is a similar document for Worthington cylinders and it should be done for any hot-dipped galvanized cylinder, independent of the manufacturer. The same (bimetallic) physical properties applies to all.

    I have done many hydro tests and the results are very different when the procedure is followed. I would never allow a hydro-tester touch my cylinders if they are not performing the proper procedure.

    Many 3AA cylinders will pass without doing the proper procedure, but I have seen plenty of cylinders that were incorrectly failed because they were not following the procedure as required by the manufacturer.


    If the cylinder was not stamped “condemned” or the numbers were not stamped with “XXX” over them, the cylinder can be re-tested using the specific CFR procedure for “test equipment failure during testing”. The CFR has some allowance for retesting a cylinder when the original test was messed-up due to equipment or operator error, but there is a specific procedure for it.
     
    Last edited: Feb 17, 2016
  4. Luis H

    Luis H Instructor, Scuba

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    Here is the text from the PST bulletin:


    P r e s s e d S t e e l T a n k C o . , I n c .

    1445 South 66th St.

    Milwaukee WI 53214

    Ph: (414) 476-0500, Fax: (414) 476-9881

    www.pstscuba.com

    PST Technical Bulletin D100-E

    Procedure for Hydrostatic Retesting of Hot Dip Galvanized Scuba Cylinder Revised 1/01/03

    Steel scuba cylinders manufactured by PST must be re-inspected and retested at least every five years in accordance with the Code of Federal regulations

    Title 49 CFR 173.34 (US) or CSA B339 (Canada).

    This bulletin describes procedures that must be performed prior to retesting each cylinder. The cylinder must be prepared and test system checked in order

    to obtain accurate results in the hydrostatic expansion retest for galvanized steel cylinders. All PST scuba cylinders made starting in 1952 are protected

    from corrosion by a hot dip galvanized coating. This hot dip galvanized coating may affect the readings from the hydrostatic test, therefore failure to

    prepare the cylinder and perform the test system check in accordance with this procedure may result in rejection of a perfectly acceptable cylinder.

    Cylinder Preparation Procedure:

    1. Remove the plastic boot.

    2. Remove any crusty white corrosion deposits. Crusty deposits are most likely to form inside the removable plastic boot if the owner has not

    routinely rinsed saltwater residue from this area.

    3. Do not use aggressive acidic or caustic metal cleaners on the galvanized surface. The mottled gray-white appearance of used galvanized

    cylinders is normal.

    Test System Check Procedure :


    1. Visually inspect the cylinder, fill it with water and place in the water jacket, as in your normal practice for any testing.

    2. Zero the burette or expansion measuring system and pressurize the cylinder to 85% to 90% of the prescribed test pressure. Warning: DO NOT

    EXCEED 90% [49 CFR 173.34(e)(4)(v)] of test pressure.

    3. Hold the pressure and determine that the system is free of leaks.

    4. Release the pressure to zero.

    5. Zero the burette if necessary.

    6. Proceed to retest the cylinder at the required test pressure.

    7. Repeat this procedure with each hot dip galvanized cylinder to be tested.

    This test system check procedure is specifically authorized under the provisions of 49 CFR 173.34 (e)(4)(v) and CGA C-1, Methods for

    Hydrostatic Retesting, 1.4.

    This procedure is necessary to obtain accurate test results. The provision of the PST Warranty therefore requires that the cylinders are prepared for

    test and the system check is performed in accordance with these procedures. If these procedures are not followed in the retesting of hot dip

    galvanized cylinders, the owner should be given prior notice by the retester that the warranty may be invalidated by the retester.

    Related test bulletin PST Bulletin D101-E, Retesting DOT-E9791 or TC-SU 4349 Advanced Technology Cylinders. PST high-pressure (3442-psi)

    cylinders have a special test requirement based on their design and the DOT/TC requirements. This bulletin provides the necessary information.

    Following this procedure will assure an accurate retest for PST scuba cylinders. If you experience any difficulty in obtaining acceptable readings,

    please contact PST customer service at 414-476-0500.

    PST TECHNICAL BULLETIN D101-E


    Retesting DOT-E9791 or TC-SU4349-230 Advanced Technology Cylinders. Revised 01/01/03

    High-pressure steel scuba cylinders manufactured by PST must be re-inspected and retested at least every five years in accordance with the Code of

    Federal Regulations Title 49 CFR 173.34(US) or CSA B339 (Canada).

    PST high-pressure (3442 psi) cylinders must be retested in accordance with DOT –E9791 or TC-SU4349-230 and have special test requirements based on

    their design and the DOT/TC requirements. This bulletin provides the necessary information.

    1. The retester must have a current copy either DOT-E9791 or TC-SU4349-230.

    2. The test pressure is 5250 psi.

    3. The wall calculations of CGA-C6 are not applicable to these high-strength steel cylinders. For the purpose of inspection criteria, the minimum

    wall for a new E7 cylinder is .179 inch, and E8 is .197.

    4. Almost all PST high-pressure scuba cylinders are hot dip galvanized for protection from corrosion. Specific procedures must be followed for

    cylinder preparation and retest checks to obtain accurate results in retesting hot-dip galvanized cylinders. These are described in PST Bulletin

    D100-E, Procedures for Hydrostatic Retesting for Hot Dip Galvanized Scuba Cylinders .

    Following these procedures will ensure an accurate retest for PST scuba cylinders. If you experience any difficulty in obtaining an acceptable reading,

    please contact PST customer service at 414-476-0500.

    These bulletins are provided free to all retesters approved by the US DOT or Transport Canada.
     
    JamesBon92007 and lowviz like this.
  5. lowviz

    lowviz Solo Diver ScubaBoard Supporter

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    Thanks Luis!

    I'll share too.
    I'm still working on alkaline coating. It works. Now trying to "minimalize" it. Somewhere along the line, I finally realized that I'm not making tanks for production, I'm just keeping mine sweet. So a room temp, felt wand applicator, spot treatment is now what I'm focused on. A super thin coating that can be easily re-applied as needed looks like the way to go. A lot of goodies in here: Some problems with Process of Zinc-Nickel Plating

    I'm saying nothing until I get it right, but I think that I'm close.
     
  6. guruboy

    guruboy Divemaster ScubaBoard Supporter

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    Mine is a WK tank though. How do I tell if it is hot dipped galvanized? It looks like it is but I would like to make sure before taking the tank back.

    They put a condemned sticker on it and coated it with some sort of clear coating. Nothing was stamped on the tank though. How do I get the information on the CFR procedure? Will the hydro facility already have it?

    TIA.
     
    Last edited: Feb 17, 2016
  7. Luis H

    Luis H Instructor, Scuba

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    The WK cylinders that I am familiar with are galvanized with black paint finish over the galvanizing. There most be a scratch somewhere that will show the galvanizing (grey finish).

    The hydro station is required by law to have the most recent copies of the applicable CFR and CGA documents. The fines for not having current documents are significant. That doesn't necessarily means that they have read them or know where to actually find the information.

    The CFR are on line and you can Google them and find them. If you are not used to reading this type of document, they can be difficult.
     
  8. Luis H

    Luis H Instructor, Scuba

    # of Dives: I'm a Fish!
    Location: Maine
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    I have had very good success with high zinc galvanizing paint. The best is ZRC brand name, but I have used several others and they all seem to work extremely well.

    Hot-dipped galvanizing is the absolute best. I have cylinders that look great that are over 50 years old.

    Galvanizing paint on the other hand will scratch, but the zinc will not allow any rust to progress below the paint, as it will with all other paints that I have seen. It will only rust on the visible scratch if it is wide. The scratch can be easily sanded and re-painted.

    The zinc will protect the steel.
     
    lowviz likes this.
  9. lowviz

    lowviz Solo Diver ScubaBoard Supporter

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    So have I. It works just fine for Hydro stamps. Looks like sh!t on the body.

    The problem (for me) is, that tinsel spray-painting a really old 72 just seems to be something like abusing your own "girl/woman" (respect).

    No longer the same thing...
     
  10. guruboy

    guruboy Divemaster ScubaBoard Supporter

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    Thank you for the extra info. My tank is just the standard dull grey metal color of most steel tanks, no signs of paint anymore. It looks like any other galvanized steel tank I've seen in the past, but I'm not an expert.

    What do you suggest I do with my tank now, since there is nothing physical that prevents the tank from being retested (all they did was slap a condemned sticker on it, no stamping of the metal).

    If I take it back and ask they repeat the test, does it have to be using the CFR procedures for retesting a tank after "test equipment failure during testing"?

    Are the test results invalid if I take it to a different facility and have them perform a regular hydro test?
     
    Last edited: Feb 18, 2016

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