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Automatuc Compressor Drain Valve Kit

Discussion in 'The Tool Shed' started by Focker, Feb 7, 2018.

  1. Feb 7, 2018
    Focker

    Focker That's a terrible idea...What time? Staff Member

    WA
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    Is anyone using one of these on their air compressor?

    Is it designed to have your air compressor always full of air? I've always been in the habit of emptying my air compressor after use.

    I was looking at the Harbor Freight kit...
    Automatic Compressor Drain Kit

    I've seen some nice (expensive) powered ones that you can set to go off every 30 minutes for 10 seconds at a time etc...
     
  2. Feb 8, 2018
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    It looks like some sort of equalizing setup? If so it would probably have to have pressure to operate.
     
  3. Feb 8, 2018
    ITLKSEZ

    ITLKSEZ Hope for the best, prepare for the worst

    Liberty Lake, WA
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    Those reviews are hilarious. Five people said it's best use is a paperweight. :D

    Every shop I've ever worked at had one, but they were set up on some sort of timed interval, like you said. Every four hours or so, it would blast a shot of air out the bottom drain. It would scare the bejeezus out of you if you happened to be walking past.

    You really drain your tank every time you use it? (Not judging, I've just never heard that before.)
     
  4. Feb 8, 2018
    Focker

    Focker That's a terrible idea...What time? Staff Member

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    Yes I do.
     
  5. Feb 8, 2018
    garage gnome

    garage gnome ECJ5 welder

    Western MA
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    I've installed lots of automatic drains and the best one is ingersoll rand. They last the longest. The timer can be adjusted for how often it blows off and for how long.
     
  6. Feb 8, 2018
    radshooter

    radshooter Member

    Northwest Kansas
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    Don't feel bad Focker, I do to. At least until I find the slow leak! :D
     
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  7. Feb 8, 2018
    Rick Whitson

    Rick Whitson Detroit Area 2024 Sponsor 2022 Sponsor

    I live South of...
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    I have a Champion gas station compressor, when they close a lot Service Stations, and made pumpers and food stores out of them, a lot of the garage equipment became available. I bought the compressor for cheap, it has an auto drain system on it, not sure how it works, but it blows air out every time it shuts off, and yes it scares the "Bejeezus" out me.
     
  8. Feb 8, 2018
    scoutpilot

    scoutpilot Member

    Asheboro, NC
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    I have one of those HF units on a CH 60gal. It's designed to open at a certain low pressure and close at a certain low pressure. I upgraded the tubing to heavy truck air brake line and rearranged the switch/wiring and tubing orientation so I have all straight connections and it has worked flawlessly since then. Except for the one time I forgot and left it on overnight in single digit temps and it froze open.
     
  9. Feb 8, 2018
    TIm E

    TIm E Aggressively average

    NW Arkansas
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    Amen brother. Mine has a slow leak too and I am anal about fixing such things, but decided to leave it. I takes a day or two to loose all pressure and certainly isn't enough to affect anything while in use. So yeah, set it and forget it.

    I drain the water out of the bottom of the tank every handful of uses. I have a copper pipe extension to make it easier to get to the drain valve, so the small amount of water that accumulates is only in the copper pipe anyway.

    That being said, an automatic drain would be nice if you wanted to leave pressure in there long term or use it daily.
     
  10. Feb 8, 2018
    Focker

    Focker That's a terrible idea...What time? Staff Member

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    I don't. I have piece of mind that my tank isn't rusting and rotting inside.
     
  11. Feb 8, 2018
    OzFin

    OzFin Vintage Jeep Guy

    Michigan
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    This doesn't answer Brad's question but "for what its worth"...
    There is the old school method of putting non- diluted automotive anti-freeze in the tank, how much depends on the size of the tank. When the condensate migrates to the bottom of the tank it mixes with the antifreeze. The anti freeze had corrosion inhibiters in it and it protects the steel tank in a similar manor that it protects against corrosion in a motor block & radiator. The anti-freeze/ condensate mixture is drained off and replenished periodically as needed. If you measure the amount of anti-freeze put into the compressor tank and measure again when its drained off a timeline can be established as to how often it should be drained. Of course the timeline is based upon the previous usage being consistent with future activities.
     
  12. Feb 8, 2018
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    Good habit. You compressor will thank you for it.
    Keep in mind when the air is compressed it heats up and draws/suspends moisture. When it cools back down from sitting it then releases the moisture. Might try draining it like you normally do and then try draining it after all is thoroughly cooled down and see if you get any more moisture out. May not be an issue being as you are in drier country but I know it makes a difference in my area. Tank/compressor size can play into this also.
     
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  13. Feb 8, 2018
    Focker

    Focker That's a terrible idea...What time? Staff Member

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    I was just going to ask the group if it's too hard on the motor to fill up the tank every time? My particular tank is 80 gal.

    Keep in mind I probably go up to 7 or more days in between uses.
     
  14. Feb 8, 2018
    Focker

    Focker That's a terrible idea...What time? Staff Member

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    I always start my compressor with the drain valve open to release any possible moisture, there's usually a little when that happens.
     
  15. Feb 8, 2018
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    One can't help but wonder if the cost of what you do outweighs the intended benefit? Cost being wear on the motor and pump plus electricity. Intended benefit being less rusting possibility. Personal opinion is that you will never truly get all of the moisture out.
     
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  16. Feb 8, 2018
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    Can it be objectively proven that draining the tank leaves it any less rust-prone? Enough moisture to cause rust is going to remain, and be constantly reintroduced, I suspect.

    On the other hand, to remove moisture for painting or sandblasting, etc, requires coolers AND traps at the extreme far end of the line to be effective. For SCUBA and SCBA air we even use chemical desicant as well.
     
    Last edited: Feb 8, 2018
  17. Feb 8, 2018
    Focker

    Focker That's a terrible idea...What time? Staff Member

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    FF to 4:55.

     
  18. Feb 8, 2018
    PeteL

    PeteL If it wasn't for physics, and law enforcement... 2024 Sponsor 2023 Sponsor 2022 Sponsor

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    • Yup. But as he says, that compressor might be 35 years old.

      How long would it have lasted if he drained it every day? We don't know.
      Possibly introducing fresh oxygen and 'hungry' water vapor might conceivably even have shortened it's life.
    Rust is oxidation, and it removes oxygen from the air. Keeping stale air in the tank might actually slow the process. :shrug:
     
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  19. Feb 8, 2018
    Glenn

    Glenn Kinda grumpy old man Staff Member

    Apopka, Fl
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    I've held this thought for years myself. No proof, just one of those feelings. I do think the electronically timed drain would be a good investment.
     
  20. Feb 8, 2018
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

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    Pfft. You guys are reaching. Water in the tank will rust it. I drain mine after every use. Not difficult.

    I leave my tank pressurized, but I drain it of water when I turn it off. IMO there's no reason to bleed off the pressure, and the tank will hold pressure for months if you fit a ball valve at the outlet, and shut it off.

    Let's crunch the numbers.

    The more the compressor is used, the more water will accumulate in the tank. There is a finite amount of air above the tank, but it's compressed to say 150 psi above atmospheric. Atmospheric is about 15 psi, so that's actually about 165 psi. p1 v1 = p2 v2, so that's about 660 gallons of air at STP (standard temperature and pressure, that is atmospheric at room temperature). Air is about 20% O2, so that's 132 gallons of O2 at STP. There are 5.92 gallons per mole of O2 at STP, so that's 22.3 moles of O2 in each tank of compressed air. The molecular formula of rust is Fe2O3 plus some bound water, so we have 3 moles of oxygen for each 2 moles of iron, or 3 moles of O2 for each 4 moles of iron. A mole of iron is about 56 grams, so that's 29.7 moles of iron times 56 grams per mole, or 1.7 kilograms of iron that can be oxidized from the air in a single 60 gallon compressed air tank. At roughly 2.2 lb per kilogram, that's 3.74 lbs of iron to oxidize before the compressed air tank is depleted of oxygen.

    Clearly, the tank can't take many cycles of rust at that amount of oxidation. The rate of oxidation is the limiting factor, not the availability of oxygen.
     
    Last edited: Feb 8, 2018
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