PCL Dropout Autodrain valve

  1. MattH

    MattH Member

    Messages:
    3,019
    Location:
    Bristol
    I recently bought a PCL Dropout to remove any water from an airline that feeds one of my Laser cutters:

    https://www.pclairtechnology.com/pr...ing_wp_cron=1539248371.4563210010528564453125

    Seems like a good unit and a cheaper and easier solution over a desiccant filter.

    It has a standard autodrain on the bottom i.e. a small spring loaded valve that shuts with air pressure.

    My question is, my compressor and air line that run the laser cutter is tight with no leaks. I turn it off after cutting and when I turn it back on the next day there is still plenty of pressure.
    This means that the autodrain will never function and the Dropout will fill up with water.
    How do I get this thing to drain?

    The reg next to the unit has a manual drain which I was opening each morning, but there's no way to open the Dropouts drain with out venting the system.

    (the brass pushfit fitting on the autodrain is something I added on so I can run a poly line to a container to catch any discharge).

    2018-10-11 10.03.47.jpg
     
  2. rtbcomp

    rtbcomp Moderator Staff Member

    Messages:
    17,770
    Location:
    Sheffield UK
    Can you manually override the auto function by pushing the whole lot upwards?

    If not put a 3 way ball valve on the inlet side of the drain and a non-return valve on the outlet then release pressure by switching the ball valve so the unit vents to atmosphere.

    As you say, the drain valve closes with pressure, so you need to de-pressurise the unit to empty it.
     
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  3. MattH

    MattH Member

    Messages:
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    No, unfortunately you can't. The outlet is a 1/8" BSP (?) fitting molded into the plastic bowl protector.

    Looks like I'll have to create a vent with valves as you say, just seems an oversight on an "AutoDrain".
     
  4. rtbcomp

    rtbcomp Moderator Staff Member

    Messages:
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    Location:
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    I think they assume you're going to empty all the air from the system at the end of day, which is the recommended practice. Bit of a pain if it fills up half way through the day.
     
  5. CKJDJK

    CKJDJK Member

    Messages:
    276
    Location:
    Northumberland
    Can you put a three way valve between the regulator and drop out. shutting off the dropout from the rest of the system. fit a drain to the tap to discharge air in drop out circuit.
     
  6. waddycall

    waddycall Member

    Messages:
    731
    United Kingdom
    You need a leak
     
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  7. rtbcomp

    rtbcomp Moderator Staff Member

    Messages:
    17,770
    Location:
    Sheffield UK
    It needs to go between the compressor and the drop-out. See Post #2

    Edit - I've assumed his air is coming from left to right in the picture.
     
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  8. MattH

    MattH Member

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    Location:
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    Yes, left to right.

    As Waddycall says, maybe i'll loosen one of the fittings a bit!
     
  9. 500e

    500e Always buy fire insurance a flood is hard to start

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    Last edited: Oct 11, 2018
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  10. WorkshopChris Forum Supporter

    Messages:
    3,880
    Location:
    South East Essex
    As above i would expect this to have a float to drain.
    Info in the link mentions >Maintenance free with built-in auto-drain.
     
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  11. knighty Member

    Messages:
    1,252
    Location:
    Sunderland
    guessing it's important for your air to be nice and dry?

    I'd fit a solenoid to the drain valve on the compressor... so when you turn the compressor off on a night you can flick a switch and vent/drain the compressor too.... compressor tank will drain / drop any water out of it and pressure will drop so your auto drain opens too

    (or fit a tap and do it manually of course)
     
  12. Fintray

    Fintray Forum Supporter

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  13. MattH

    MattH Member

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    3,019
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    Great spot, thanks Fintray.
     
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  14. knighty Member

    Messages:
    1,252
    Location:
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    watched the youtube vid and was impressed... thought I should buy one... but the 'cheap' nylon one is £155 and 10cfm max (I have a machine coming which needs 30cfm)

    this one... https://www.ebay.co.uk/itm/272768195108 is £80 as suposed to be good for 203cfm? - but I don't think it's the same thing (struggling to find info)
     
  15. MattH

    MattH Member

    Messages:
    3,019
    Location:
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    They’re not pennies but look at the cost of a desiccant dryer and then a 1um filter setup.
    The Dropout is loads cheaper.
     
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  16. timgunn1962 Member

    Messages:
    14
    Location:
    Lancashire UK
    That looks to be a float-type autodrain to automatically drain the dropout in-line units: it's an accessory for the main units.

    The dropout bumph makes a big thing about being maintenance-free (apart from draining) and having no filter to clog. Coalescing filters will do the same job and can be found for less money. Many have float-operated autodrains.

    At work, we need instrument-quality dry air 24/7 for instrumentation on unmanned sites and have always found that running full receiver pressure to an autodrain coalescing filter near the point-of-use, then immediately to a regulator reducing the pressure to that actually required, normally gives dry enough air for our purposes. The basic principle is that the coalescing filter is at the coolest point in the system and at high pressure. The coalescer takes out all the condensed water (mist) and reducing the pressure then effectively dries the air further (the partial pressure of the water vapour reduces in proportion to the pressure reduction).

    Where we need to run the airlines to equipment outside in winter, we usually use a membrane dryer after the regulator (they can only take about 8.5 bar, not the 10 bar maximum receiver pressure) and keep the whole air prep system indoors where there's no chance of freezing the autodrain. The membrane dryers give dryer air than refrigerant dryers (pressure dewpoints can be as low as -30 degC), so we don't need to worry about condensation downstream even in the harshest UK winters.

    It's worth sketching/photographing your system and talking to a good pneumatics supplier for advice.

    For the OPs problem, there are 2 things that spring to mind. First (and temporary), many semi-auto drains can be drained under pressure by pushing a probe up the outlet to lift the poppet. I usually use the pen from my Swiss Army Knife because I always have it with me, but there are better things to use. Check to see if this is the case with yours. Expect a wet sleeve.

    Second is to fit a 3-port isolating valve between the reg and the Dropout. Something like http://www.farnell.com/datasheets/3...301.1762612078.1539381454-95735438.1531657139

    When you switch it off, it will release the downstream pressure and let the Dropout drain do its thing.
     
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