Danger of using old air compressor

Discussion in 'Remodel Forum & Blog' started by Bratan, Jul 20, 2015.

  1. Bratan

    Bratan Member

    Joined:
    Feb 16, 2013
    Location:
    New York
    I never had an air compressor before but always wanted one for my garage. Couple of days ago I was passing a garage sale and guy had this Devilbiss 20 gallon 5HP compressor really cheap ($20). He said it ran great and only had little leak near regulator. He was selling it because he had 2 more already and was moving.
    Anyway I never owned one so I'm almost completely clueless. One thing that grabbed my attention after I got home is big warning on the tank to drain water daily or it might go Kaboom if it rusted thru.
    And indeed there's a lot of rust on the bottom (but it looks like it's external). I managed to unscrew the plug (took some effort) and there was water inside :( It's very muddy (like liquid cement) but not really brown or red...
    What do you guys think? Would it be crazy for me to start using it? Otherwise whole thing looks like in a great shape, just air filter is broken off, but I found replacement for about $15 online.
    Here are some pictures of the tank bottom.
    compressor_mud.jpg compressor01.jpg compressor02.jpg
    Also I own flexible inspection camera. If I manage to somehow unscrew that big drain plug (on 3rd pic), I can check inside, but is it a good idea to touch that plug? Besides I'm not sure I can unscrew it anyway....
     
    Last edited: Jul 20, 2015
  2. DonL

    DonL Jack of all trades Master of one

    Joined:
    Mar 30, 2011
    Occupation:
    Rocket Scientist
    Location:
    Houston, TX
    I would install a drain cock and fill the tank then open the valve to blow the crap out.

    Do not run it on a extension cord, unless it is a big one.


    Good Luck.
     
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  4. Bratan

    Bratan Member

    Joined:
    Feb 16, 2013
    Location:
    New York
    Thanks! I never heard of drain cock, so I just googled it. Looks like mine has a winged version and of course I broke that part, but it was pretty rusted. I'll get a new one at lowes and try blowing dirty sludge out. Maybe even fill it with fresh water a little few times...
     
  5. DonL

    DonL Jack of all trades Master of one

    Joined:
    Mar 30, 2011
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    Houston, TX
    You may want to change the oil in the pump unless it is oil-less.

    It gets water in it and gets milky looking.

    Standing it on end may let it leak out also.

    What kind of pump does it have ?
     
  6. Bratan

    Bratan Member

    Joined:
    Feb 16, 2013
    Location:
    New York
    It's oil-less. 5HP electric pump, other than this I have no idea :) It's DeVilbiss PRF5020-WK model from 90-s. I found a manual online (it's very generic) and tons of diagrams for replacement parts, but other than that not much info. For example doesn't say anything how to unscrew drain valve, it just says drain water after every use. I had no idea that valve's internal thread goes other way :)
    As I mentioned air filter a.k.a. "compressor muffler" is broken, but I found part that supposed to fit
    Craftsman KK-4981 Compressor Muffler
    Doesn't seem to have cover on top of the "foam" filter tho, is this normal? Also is it ok if I run for a short while without air filter? Want to make sure everything works before ordering one...
     
    Last edited by a moderator: Jul 28, 2015
  7. DonL

    DonL Jack of all trades Master of one

    Joined:
    Mar 30, 2011
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    Rocket Scientist
    Location:
    Houston, TX
    I would not run it with out a filter.

    Put a old sock or bra over the intake.
     
  8. Bratan

    Bratan Member

    Joined:
    Feb 16, 2013
    Location:
    New York
    One more question. What is Auto/Off setting? I cam move switch to either one but it never shuts off compressor...
     
  9. DonL

    DonL Jack of all trades Master of one

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    Location:
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    That is the pressure cut off, and should shut off the motor after the tank is full.
     
  10. Bratan

    Bratan Member

    Joined:
    Feb 16, 2013
    Location:
    New York
    Yup that's auto, what about "0" setting? Should it turn off compressor?
    BTW I got tank up to 125 psi and still alive :)
     
  11. DonL

    DonL Jack of all trades Master of one

    Joined:
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    Location:
    Houston, TX
    It sounds like the contacts in the switch may be welded together.

    It should turn off.
     
  12. Gary Swart

    Gary Swart In the Trades

    Joined:
    Sep 1, 2004
    Location:
    Yakima, WA
    Seems like a lot of unknowns here. Do you have an air compressor dealer in your area? I mean a business that specializes in compressors, not just Sears, HD or Lowe's that sell new ones. If you do, consider having them check this thing over. It would be like having a mechanic check a used car before buying. With this compressor, you're not in it so much, but safety should be a concern.
     
  13. dgold

    dgold Product R&D

    Joined:
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    Occupation:
    Product R&D - Swimming Pool Industry
    Location:
    Carlsbad, CA
    Pretty much all compressors are rusty in the tanks to some degree - the higher pressure causes the air to get hot. Then the moisture in the air condensates against the inside surface of the "cool" steel tank.

    There are compressor businesses in every town, and they can inspect the tank for you if you're really concerned and want to be extra cautious. You could also keep it outside in a shed and anchor it to a concrete slab - the main benefit being that you don't have to listen to it.

    FYI: DeVilbiss Air Power had some nice / reliable oil-free pumps. Eventually the piston ring will wear out, but it can take many years - especially if you're not using it to run air tools all day long, day in, day out, like an auto mechanic might.

    As for the tanks, I've never heard of one violently "exploding" from rust / erosion. The rust will more than likely eventually create a thin spot or two which would eventually fail, creating a irreparable leak. It might be loud and scare the hell out of you, but it's not like the whole tank will suddenly rupture into a thousand pieces of shrapnel in every direction.

    Use it. Enjoy it.

    FWIW, once upon a time, I did air compressor R&D. I don't know much about industrial / scroll compressors, but I'm quite familiar with portable / shop compressors with reciprocating pumps. I've seen a LOT of old, poorly maintained compressors go a long long time.
     
    Last edited: Jul 22, 2016
  14. Anthony Curtas

    Anthony Curtas Member

    Joined:
    Oct 13, 2011
    Occupation:
    Engineer
    Location:
    Northern Virginia
    I know this is a month old, but hopefully this helps.

    We have a compressor at work that is on its 3rd pressure sense switch. Sometimes they just go bad, especially when they are used and cycle a lot. My Porter Cable pancake at home has been running fine for 15 years now, albeit with a lot less use.

    We purge the work tank about once a week. Quarter turn valve on the bottom with a hose aimed out the shop door. Blasts a dirty water/mud mix for a few seconds, then we seal it up. Keeps the rust to a minimum. Ours is oiled though, so some of that is oil not rust, but a good practice anyway.

    The PC at home has a twist vent and when I drain it, it always has a little rust in the water. Nothing to worry about too much.

    Both have filters and water/oil separators at the source to let us use paint sprayers as well as air tools/nailers.

    Good luck.
     
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