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How to Disassemble Frozen Downstream Valves

Discussion in 'Repairing your own Gear' started by rsingler, Apr 1, 2020.

  1. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
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    The Aqualung ABS and many others like it employ a fixed orifice and a standard downstream poppet to provide reliable, if uninspiring performance. Many are touted for their small form factor and ability to be utilized "upside down" when handed off in an OOA emergency.

    What to do when you are presented with one that has not seen service in many moons?
    20181114_235243_1.jpg
    If you try to unscrew the outer half of the valve body using the case to hold the inner half, this frozen valve half will likely turn inside the case, distorting it permanently!
    20200331_151552.jpg
    From this point on, the valve may not be held straight, and changing hoses will likely result in a cocked valve, asymmetric lever, and degraded performance in an already marginal second stage.

    Bruce Howe at ScubaTools.com created a wonderful new tool ($17) introduced at DEMA this past November to address this challenge. It's called a 2nd Stage Valve Body Internal Retaining Nut Tool
    SKU: 20-228-100
    20200331_131248_1.jpg
    The feet of the tool are designed to fit in the groove occupied by the lever, enabling you to hold it steady while unscrewing the outer half, without damaging the case.

    That said, I've run into some problems with the Aqualung ABS. Those issues may apply to other regs, as the tool is listed for more than a dozen models and brands.

    First off, the feet that slip into the groove where the lever runs are slightly too thick.
    It was a quick matter with a grinder to thin them down <1mm.
    20200331_141812.jpg
    As you can see, there's a very helpful recess machined into the tool to accept the stem of the poppet, so that you can disassemble the valve assembly once you've unscrewed the nut and flipped out the lever. The tool does an excellent job of holding the inner half steady while you apply the substantial force required to unfreeze a green valve.

    However, upon reassembly, torquing the halves tight without similarly stressing the case is not possible because of the nut, which now displaces the feet outside the inner half.
    So my next mod was to Dremel a recess in the other end (after thinning the feet as above) so that the tool would fit around the assembled valve for torquing.
    20200331_141857.jpg
    20200331_141557.jpg
    At this point, the next challenge revealed itself: the curved lever, even when fully depressed, got in the way of engaging the feet. So I ground a bevel in the back side to accommodate the lever:
    20200331_141931.jpg
    ...and bingo! The tool fit perfectly for torquing upon final assembly:
    20200331_141707.jpg
    20200331_141630.jpg
    Torquing became a simple matter of mounting the tool in a vise.
    20200331_131504.jpg
     
    axxel57, Bigbella, couv and 3 others like this.
  2. Protondecay123

    Protondecay123 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 0 - 24
    Location: Apex of Moronia
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    Impressive machining! Great Job!
     
    Bigbella, Bob DBF and rsingler like this.
  3. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    4,909
    6,183
    113
    As an aside, the existing tools for adjusting the nut all require the lever to be depressed while adjusting. Aqualung specifies setting up the valve before you install it in the ABS case, since there's no access hole in the side opposite the nut.
    But what if you want to adjust once the valve is assembled inside?
    20200320_180212.jpg
    It's a PITA to turn off the air before every tweak, and really slows the process.
    Instead, I obtained a micro right angle socket handle and appropriate sized socket.
    20200320_180206_1.jpg
    By grinding down both length and diameter of the socket and a little length of the connector,
    20200320_180308.jpg
    you have a very low-profile tool that can fit inside the case under the lever, allowing on-air adjustment.
    20200320_180333.jpg
    Between these two tools, tuning a downstream reg is now a snap!
    20200320_180626.jpg
     
    Rarian, couv, Dark Wolf and 1 other person like this.
  4. Bigbella

    Bigbella ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: San Francisco
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    My main complaint with this current thread, is its thorough lack of detail, heh, heh, heh . . .
     
    axxel57, couv, Dark Wolf and 2 others like this.
  5. Protondecay123

    Protondecay123 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 0 - 24
    Location: Apex of Moronia
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    :rofl3::rofl3::rofl3::rofl3: Yeah. I want to know to the Ten Thousandth of an Inch how much he shaved off of that socket. o_O
     
    Dark Wolf and rsingler like this.
  6. Bigbella

    Bigbella ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: I'm a Fish!
    Location: San Francisco
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    You and me both. Yeah, what gives?
     
    Dark Wolf and Protondecay123 like this.

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