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My Rix SA-6 Diesel

Discussion in 'Compressors, Boosters & Blending Systems' started by rob.mwpropane, Nov 11, 2020.

  1. tbone1004

    tbone1004 Technical Instructor ScubaBoard Supporter

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    Location: Greenville, South Carolina, United States
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    sort of?

    if you have a gauge after the PMV it will read whatever is in the line. What the PMV does is not allow any gas to pass until the set pressure is reached. Once it is reached, it still has to equalize.

    So. If your PMV is set to 2000psi and you have a gauge right before and right after the PMV, you just changed the filter cartridges and are about to fill an AL80 that is just back from hydro and completely empty

    You start the pump and the gauge before the PMV starts climbing to 2000 psi but the gauge after the PMV stays at 0.
    Once the filter towers reach 2000psi, the PMV allows gas to pass and you will see 2000psi on the gauge prior to the PMV, and then the gauge after will start to increase slowly as the tank is filled.
    Once the tank pressure exceeds 2000psi, both gauges will increase together.

    If you have an empty filter tower, and you hook up a full tank to the fill whip and open it, it will not allow gas to go backwards through the PMV and fill the towers.
     
    Miyaru and rob.mwpropane like this.
  2. rjack321

    rjack321 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Port Orchard, Washington State
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    Its a PMV, and yes it doubles as a check valve
    back-pressure-regulator-1-to-10-cfm

    A PMV is just a check valve with a 2000psi spring holding the ball back from opening until there's lots of pressure. A check valve by itself would open at ~1psi

    @rob.mwpropane you can just leave it there to act as a check valve or move it downstream of your tower. You need to add whatever you are missing (check valve or PMV)
     
    rob.mwpropane likes this.
  3. rob.mwpropane

    rob.mwpropane Contributor

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    This is why I asked. To know what the gauge would do. I assumed that, but don't like to assume. Thanks.

    It would be better to remove the check valve and install a PMV after the coalescers...correct? Especially if I plan to disconnect the quick connect from the filter tower?

    (can anyone verify it's a check valve or PMV based on the attached pic?)
     

    Attached Files:

  4. rob.mwpropane

    rob.mwpropane Contributor

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    Somehow I missed your link my first read. Thank you, do you know what they are set to? There is no literature on that site that states what it is.
     
  5. rjack321

    rjack321 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Port Orchard, Washington State
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    about 1900-2100psi usually, unless its leaking

    Its super easy to test:

    close the whip valve (or connect it to a closed tank)
    turn on compressor
    pressure at the whip should be 0 for awhile then jump up to "something"
    the something value is the PMV opening pressure

    If its old and leaking the pressure will just gradually rise almost as soon as you start the pump.
     
    rob.mwpropane likes this.
  6. couv

    couv Instructor, Scuba

    # of Dives: 1,000 - 2,499
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    Rob, I have a PMV that looks (almost exactly) like that. But let's remove doubt and verify. Remove the outlet fitting and allow a little low pressure (100-200 psi) up to the valve. Does air escape the outlet side? If yes it's either just a check valve or a defective PMV. Either way you should test it.

    Next step will be to hook up a pressure gauge to the outlet side and see where the PMV breaks open. If it's too high or low you'll want to replace it. I'll leave it to the experts to advise you what too high or low is for you system.

    Edit: There's three of us typing all over each other. I also see @rjack321 has already sorted out the answer and given a link to the exact same valve and vendor I used.
    back-pressure-regulator-1-to-10-cfm
     
    rob.mwpropane likes this.
  7. rjack321

    rjack321 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
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    You don't want to be disconnecting the tower, leave it pressurized, that's what the check valve before and the PMV after will do.
     
    rob.mwpropane likes this.
  8. rob.mwpropane

    rob.mwpropane Contributor

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    I still plan to have a check valve before the tower.

    PMV - check valve - tower - PMV
     
  9. rob.mwpropane

    rob.mwpropane Contributor

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    P.S. - you all rock, thanks.
     
  10. rjack321

    rjack321 ScubaBoard Supporter ScubaBoard Supporter

    # of Dives: 1,000 - 2,499
    Location: Port Orchard, Washington State
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    A PMV *is* a check valve, you don't need 2 before
     
    couv likes this.

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