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Apeks DS4 - IP creeps then holds

Discussion in 'Repairing your own Gear' started by jgttrey, Nov 7, 2019.

  1. jgttrey

    jgttrey ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Houston
    610
    751
    93
    I've been servicing my Apeks DS4 first stages for a while with no problems.

    I bought a used one just to have around as a spare and because the deal was good. I recently O2 cleaned and serviced it. Here's my question:

    IP locks up reliably but then creeps up about 10 psi and then stays there. This 10 psi creep takes about minute. It stops there and holds indefinitely. It happens wherever I set the IP - if I start at 125, it will go to 135. If I start at 135, it will go to 145. Purge the regulator and it will start over again - lock at 125 and slowly creep up to 135 and stay there, or 135-145, or whatever.

    If it was 2-3 psi, that would not be a concern, but 10 seems excessive. My other DS4s do not do this.

    Any thoughts as to why, whether it matters, and if so, the fix?

    Many thanks.
     
  2. runsongas

    runsongas Great White

    # of Dives: 500 - 999
    Location: California - Bay Area
    3,424
    1,289
    113
    check the valve seat. order some magic mesh and try giving it a polish.
     
    jgttrey likes this.
  3. inka

    inka Barracuda

    # of Dives: I just don't log dives
    Location: Lima- Peru
    283
    76
    28
    there is an Apeks polish tool to "repair" the non removable seat
    Apeks Polishing tool
    Try with an pencil eraser , it could works too.
     
    jgttrey likes this.
  4. rsingler

    rsingler Scuba Instructor, Tinkerer in Brass Staff Member ScubaBoard Sponsor

    # of Dives: 500 - 999
    Location: Napa, California
    3,335
    3,709
    113
    If you serviced it, I will presume that your technique was good and the replacement seat was new.
    Therefore, any IP creep is leak at either the orifice/seat interface, or the balance chamber. In either case, the leak disappears when the parts deform and match whatever irregularity allows a leak.
    Typically, leaks along oring lands disappear very quickly (10 sec - 1 min), because the orings are flexible, or don't disappear at all, because the scratch is too deep.
    Typically, leaks at the orifice/seat interface stop much more slowly (1 min- 1 hour), because the hard plastic of the seat takes longer to deform and fill the irregularity.
    Your timing suggests it could be either.
    However, from experience, unless inspection reveals a scratch in the balance chamber, your problem is almost certainly due to sandblasting of the orifice volcano or knife edge, where high pressure air cuts around the corner. Alternatively, a reg that's gotten wet can see corrosion where moisture sat at that tiny gap between orifice and seat:
    20140821_115315.jpg
    As suggested above, some careful polishing with Micromesh wrapped around a pencil can restore the smooth surface needed to seal against the HP seat.
    20140821_120317.jpg
    My favorite diaphragms allow replacement of the entire orifice itself. Other volcanos are machined into the body. The DS4, unless I'm mistaken, has its volcano machined into the body. Any nick may or may not be repairable.

    If you choose the pencil eraser trick, be very careful of the grit you choose. Some ink erasers will really scratch the brass.
     
    Scubagaskets and jgttrey like this.
  5. jgttrey

    jgttrey ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Houston
    610
    751
    93
    Great information. Thanks everyone.

    I'm pretty confident the problem isn't on the balance chamber side. I inspected that closely under magnification and it looked great. Mirror smooth.

    I'd like to think my technique was good and I used all new OEM parts, except for the balance chamber orings, which I swapped for Viton (same batch as I've used before with no problems).

    You're correct, the orifice on the DS4 is machined into the body. I'll take a look and try giving it a little buffing with a pencil eraser. I'll reinspect the balance chamber while I'm at it just to make sure.

    Thanks again.
     
  6. jgttrey

    jgttrey ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 200 - 499
    Location: Houston
    610
    751
    93
    Update:

    Much better now. I confirmed the balance chamber had no scratches. I couldn't find any corrosion on the orifice, but there may have been some very, very slight sandblasting -- it was much more like the second picture in the post by @rsingler than the first, but maybe just an ever-so-slight "glitter" as I turned the body around under illumination, suggesting a very slight roughness.

    I polished with a pencil eraser and it looked better. Reassembled with a new seat and diaphragm.

    It now locks up and creeps maybe 2 psi before stopping, then holds that pressure overnight.
     

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