Compressors and rust?

  1. julianf

    julianf Member

    Messages:
    5,061
    Location:
    devon, uk
    I've just been looking at drain valves, and having some trouble with the logic.

    Obviously water condensates on the inside of the tank, slips down the sides, and pools in the bottom.

    ...to then be let out of the drain eventually.

    What I can't see is how frequency of draining will make any difference at all to how quickly the tank rusts.

    If you drain the sump once every hour, the walls of the tank will be wet with condensation, running down to the sump, to be drained very soon.

    If you drain the sump once a month, the walls will still be just as wet or otherwise with condensation. The only difference is more water in the sump.

    Either way, every single cool surface inside that tank is going to be beading with water.

    So what's the thinking behind auto drain valves?

    Thank you.
     
  2. tigdlo Member

    Messages:
    88
    Location:
    UK
  3. optima21 Forum Supporter

    Messages:
    3,085
    Location:
    halifax, England
    I had one that rusted though, it wasn't catastorphic failure like those, just a pin hole, and then it took me ages to find out where it was coming from.

    Ive got an auto drain valve on mine when the pressure in the receiver drops to less than 5psi

    [​IMG]

    from the valve in clarke air filter

    https://www.machinemart.co.uk/p/clarke-cat152-14-mini-air-filter/
     
    MattF and Parm like this.
  4. Submariner1 Member

    Messages:
    96
    Location:
    Berkshire
    I wondered about that too.
    On mine the drain is near the end, but not at the end.
    5F3E8E6A-D7D0-45DE-83FE-21DC0AC3C0A1.jpeg
    If drained slowly little water came out.
    After the 3rd fill I drained it quickly and with a light shining on the gushing air you could see water droplets.

    my question is .... if drained fast, will it pull the water from the sloped end i.e. 60mm and throw it through the drain?
    Or will there always be some water in the end. I.e. should one tilt the tank as its nearing the end of the drain? ( that would be a pain)
     
  5. grim_d

    grim_d Unlikeable idiot.

    Messages:
    3,096
    Location:
    Scotland - Ayrshire
    I think I drain mine once a year.....if I remember.
     
  6. johnser

    johnser Member

    Messages:
    2,123
    Location:
    North Cornwall
    Without a drain valve, you'd eventually run out of capacity. Perhaps that's the main reason rather than to stop rust.
     
  7. daleyd

    daleyd Member

    Messages:
    7,101
    Location:
    Wrexham, North Wales
    I'd guess its as much to do with getting rid of any water in the tank so it doesn't come out in your airline as much as anything else. :dontknow:
     
  8. Morrisman

    Morrisman Forum Supporter

    Messages:
    2,702
    Location:
    Staffordshire, England
    If you don’t drain it, you will eventually have no air storage space, but different places will give different humidity, thus different amounts of condensate. Essentially you don’t want any water inside it, there’s no reason for it to be there.

    My old compressor was in the loft of my garage, hardly had a drop came out of it whenever I checked every few weeks, but it wasn’t in use all day every day.

    A general workshop ‘shop air’ compressor needs an auto drain because “I thought somebody else was doing that”....:whistle:

    I bought a big old twin cylinder unit off a mate of mine years ago, and couldn’t believe how heavy it was. After it had been in my garage a while i fired it up, drained the tank, and watch for half an hour while defrosted ice ran out the bottom.

    He had had it for years, but had no idea you had to drain the tank.:doh:
     
  9. Matchless

    Matchless I started with nothing, still have most of it left

    Messages:
    1,626
    Location:
    Essex UK
    the drain may have a tube to the bottom, would work if drained with a little pressure in the tank?
     
    Submariner1 likes this.
  10. grim_d

    grim_d Unlikeable idiot.

    Messages:
    3,096
    Location:
    Scotland - Ayrshire
    I've a nice big norgren reg that sorts that out for me.

    Just encouraging my laziness
     
  11. brightspark

    brightspark Member

    Messages:
    31,703
    Location:
    yarm stockton on tees
    in all my life of seeing leaky tanks theres no way they burst open like that :vsad:the rust pits just start leaking and pinhole in the odd spot when they get corroded on the bottom the large comp tank I have gets emptied possibly about every 6 month if I remember it gets used regular and id probably get a pint of water out of it when I do empty it
     
    the artfull-codger likes this.
  12. My Old Landy

    My Old Landy Melting Metal

    Messages:
    238
    Location:
    Buckinghamshire UK
    ooops! I haven't drained mine since I bought it two years ago :whistle: come to think of it, I didn't drain the last one and that lasted around 10 years before the motor died. Probably should take better care of them :clapping:
     
    Hopefuldave likes this.
  13. tigdlo Member

    Messages:
    88
    Location:
    UK
    At normal operating pressure I dont beleive they do, I think the ones in the photos have likely been over pressurised, but I think it shows the weakest point.
     
  14. skotl

    skotl Forum Supporter

    Messages:
    7,377
    Location:
    Edinburgh, UK
    I must be the only person on this forum to do so(!), but I open the drain valve every time I finish up for the day and then just leave it open. Then I tighten it up the next time I use it - seems pretty easy :dontknow:

    The five minutes it spits air out after I open the drain doesn't half worry the neighbours :D
     
    My Old Landy likes this.
  15. Submariner1 Member

    Messages:
    96
    Location:
    Berkshire
    I was going to do that, then realised the anti-vibration, sound proofing mat it sits on dents where the feet are and the drsin is close to the mat ... so spits wet air all over the feet brackets a d I guess would well in the dents of the mat.
    So I am looking for some Clear tubing to divert the released air.
     
    skotl likes this.
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