Recommendations for a portable air compressor?

Discussion in 'DIY' started by alloydog, Aug 13, 2012.

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  1. Wasn't sure where to put this, it's not really DIY, and it isn't "military", so here will have to do...
    I have done a webbysearchthing, but mostly found US stuff, and not many useful write-ups, just manufacturers sales pitches.

    The company I work for builds and maintains environmental monitoring equipment for mining companys, local government environmental agencies and so on. Many of the installations are in wells sunk into the ground or across small streams.

    One piece of kit that measures water quality, requires the sensor head to be cleaned at about 30 minute intervals with a blast compressed air.

    Currently, we use some awlful cheap crappy ones which were chosen due to time constraints and price. They are failing left, right and centre...

    The requirements we have are:
    Air pressure upto 6 bar
    Supply voltage 24 VDC
    Working temp as low as -30 °C
    Smallish - the ones we use are about 350 mm x 250 mm x 150 mm.
    Ideally available in Europe.
    The are in a enclosure, which will shelter them from the worst of the elements like rain, snow, direct sunshine and so on, but they will be subject to damp air, creepy-crawlies and other niceties of outdoor life.

    We use a system where an air reserviour is filled to about 6 bar - though we had to drop it to 5 - 5,5 bar because the current compressors can't handle it. This is controlled by a pressure-sensitive switch. When the air pressure in the reserviour drops to 4 bar (now 3 to 3,5), a relay opens and turns the compressor on.

    With regards to price, cheaper is nice, but since the value of gear in at the staitions can be in range of tens-of-thousands of Euros, a few extra hundred or so isn't going to make that much of a dent.

    The cleaning takes place every half hour, which means the air bottle needs topping up every couple of hours or so.

    Has anyone had any long term experience with anything suitable?

  2. Oil free? You didn't mention that, but oil would contaminate the sensor more than it would clean it. Oil free would greatly cut down the range of suitable compressors.
  3. A lot of smaller 12/ 24 volt compressors use a teflon piston ring and a sealed ball race big end bearing so no oil lubrication is req.

  4. Warn are generally seen as being the best of its type so you may have to get a specialist put one together for you ,is it 24 volt because it`s vehicle mounted or is it run off a solar power pack?
  5. Good point - that actually hasn't been mentioned, and we don't seem to have had a problem yet - the sensor in question measures things like total organic carbon, disolved organic carbon, NO2 and NO3 and other groovey stuff. The air blast is mainly to clear large bits of plant material. The sensor head gets a manual six-monthly clean with acetone as well.
  6. Jun-Air and Gast seem to ring some bells, but it is nearly a decade since I had an involvement with compressed air. Jun-Air are manufacturers and Gast distributors, ISTR. It would probably be sensible to get some advice from Gast or someone of that ilk since you may need some air treatment for filtration, water removal or automatic condensate drains.

    PS You may need oil-free; I've just remembered the condensate from a lubricated compressor cannot legally be discharged into a drain or water course without first passing through carbon filters and stuff to remove the emulsified oil. Jun-Air do small lubricated compressors for dentists' surgeries, so I don't know whether you'd need to remove the oil for a tiny thing like that. I was involved with industrial ones.
  7. Thanks for pointers - Matt Savage has recommended a compressor that meets the requirements.
    Now, since these beasties are used heavily by the off-road brigade, can any suggest a good forum where I can ask if anyone has used these long term? Yes, I can google "off road forum", but I don't know if I'll get a bunch of numpties who wouldn't knwo their arses from their elbows - which doens't say much for me, either...

    So, is there an ARRSE equivilent for off-roaders?
  8. Just a quicky. We've been using half a dozen Viair 325 compressors from Matt Savage. So far, they have lasted much longer than the pieces of crap we originally bought (though some of those are still going, after several repairs), surviving a Finnish winter at that. Thanks for the advise.
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