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Thread: Best approach for drying air from air compressor

  1. #1
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    Best approach for drying air from air compressor

    I have a California Air Tools 10020AC compressor (2HP, 5.30 CFM @ 90psi) that I use mainly for blowing off stuff, and supply to my wide belt sander, and occasionally for a staple gun. I don't use other air tools.

    Despite having an automatic drain valve on it, it still spits water on occasion. I'm looking for the best way to dry the air from it. I'm sure living in Florida doesn't help.

    Is the best approach a desiccant in line filter (with dessicant beads https://www.amazon.com/gp/product/B0...6WMF7DIH&psc=1), or something like this PneumaticPlus 3-stage air drying system https://www.amazon.com/gp/product/B0...HTFH4QLV&psc=1 , or something else?
    - "Only two things are infinite, the universe and human stupidity, and I'm not sure about the former." - Albert Einstein
    - The difference between an amateur and professional is that the amateur practices until he gets it right. The professional practices until he can't get it wrong

  2. #2
    The answer is going to depend a lot on both how much air you use, and what your budget is. In my shop I run the air through a filter/dryer similar to the PneumaticPlus one you linked. That gets the oil and big water and "junk" out of the air. Then I run it through two big desiccant dryers (each holds about a gallon of desiccant granules). That _should_ get all the moisture, but if I'm not really on schedule about recharging the desiccant I'll get water past it in the lines. I'm about to add a "cheap" refrigerant dryer (I found an as-new one like the $400 harbor freight units for $100) right after the tank to trap as much moisture as possible before it even gets to the filter/dryer stuff. That'll prolong the desiccant's life.

    If you're using air in any kind of volume (painting / sanding) and you want really dry air, and you're in Florida you've got a task ahead of you. If you're running the occasional air nailer you can get by with a lower volume setup.

  3. #3
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    Best approach is a refrigerated dryer. I bought one capable of 54 cfm off CL for $125, and it's working fine on a 10 hp compressor.

  4. #4
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    Quote Originally Posted by Ben Mitchell View Post
    The answer is going to depend a lot on both how much air you use, and what your budget is. In my shop I run the air through a filter/dryer similar to the PneumaticPlus one you linked. That gets the oil and big water and "junk" out of the air. Then I run it through two big desiccant dryers (each holds about a gallon of desiccant granules). That _should_ get all the moisture, but if I'm not really on schedule about recharging the desiccant I'll get water past it in the lines. I'm about to add a "cheap" refrigerant dryer (I found an as-new one like the $400 harbor freight units for $100) right after the tank to trap as much moisture as possible before it even gets to the filter/dryer stuff. That'll prolong the desiccant's life.

    If you're using air in any kind of volume (painting / sanding) and you want really dry air, and you're in Florida you've got a task ahead of you. If you're running the occasional air nailer you can get by with a lower volume setup.
    Really looking for a relatively low cost solution. Unless I happen to get lucky and snag a good value for a refrigerated dryer from CL, I think big desiccant dryers might be the best approach. Any good links for them? The ones I keep finding are small, not nearly the 1 gallon size you were describing.
    - "Only two things are infinite, the universe and human stupidity, and I'm not sure about the former." - Albert Einstein
    - The difference between an amateur and professional is that the amateur practices until he gets it right. The professional practices until he can't get it wrong

  5. #5
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    I had one similar to this in my shop decades ago. https://www.amazon.com/Plews-56-081-...758881&sr=8-22
    For these to work the best, it has to be located as far away from the compressor as possible. It's easier for the water to drop out of the air when it has cooled a bit. After the desiccant filter, I had a "toilet paper" filter. These have a roll of brown paper in them and really grabs the last bit of water. You have to buy their filters, don't expect real toilet paper to work. Besides toilet paper is too precious of a commodity these days anyway.

  6. #6
    Quote Originally Posted by Alan Lightstone View Post
    ... the best approach a desiccant in line filter (with dessicant beads https://www.amazon.com/gp/product/B0...6WMF7DIH&psc=1), or something like this PneumaticPlus 3-stage air drying system https://www.amazon.com/gp/product/B0...HTFH4QLV&psc=1 , ...
    Quote Originally Posted by Richard Coers View Post
    I had one similar to this in my shop decades ago. https://www.amazon.com/Plews-56-081-...758881&sr=8-22
    For these to work the best, it has to be located as far away from the compressor as possible. It's easier for the water to drop out of the air when it has cooled a bit. After the desiccant filter, I had a "toilet paper" filter. These have a roll of brown paper in them and really grabs the last bit of water. You have to buy their filters, don't expect real toilet paper to work. Besides toilet paper is too precious of a commodity these days anyway.
    Mr. Lightstone, the '3-stage' FR (filter regulator) will give you very clean air, and maybe remove any water particulate (already condensed). It will do virtually nothing to reduce the dew point of the air passing thru it. In FL humidity, with a big pressure drop across the regulator, the filter will swamp - quickly!

    A refrigerated dryer is the gold standard, if you can swing the cost. Only down side is they typically perform better in continuous operation; not the intermittent use found find in the average home shop.

    Failing a screaming deal on a reefer, Mr. Coers is correct on several counts: 1) A desiccant dryer will be your best bet in your (assumed) price range; 2) pre-cool the air if possible (Maybe a 2nd receiver in series with the primary? Even an old car radiator? ::lots of surface area.); 3) locate the dryer as far from the compressor as reasonable; 4) place a FR close to point of use. (Use a FRL, on air motors/cylinders/impacts - needing oil).

    I have fought this water battle for years. I poke at our Process Engineers that they sometimes 'get air in our instrument water', and so ruin our actuators and my ability to control and automate systems. BTDT, got scars.

  7. #7
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    To help the filter dryers is to install drip legs and to also have p-traps. Keep your compressor drain all the time will also help. I have water separators at each of my hose connections with a drip leg.

  8. #8
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    I had a moisture problem years ago and purchased an after cooler from Grainger. It looks like a car radiator with a fan blowing through it. Works like a champ.
    Steve Jenkins, McKinney, TX. 469 742-9694
    Always use the word "impossible" with extreme caution

  9. #9
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    Quote Originally Posted by Steve Jenkins View Post
    I had a moisture problem years ago and purchased an after cooler from Grainger. It looks like a car radiator with a fan blowing through it. Works like a champ.
    I took a look at those. How do they drain?

    Also, a little fuzzy on how/where to install drip legs.
    Last edited by Alan Lightstone; 12-24-2020 at 11:50 AM.
    - "Only two things are infinite, the universe and human stupidity, and I'm not sure about the former." - Albert Einstein
    - The difference between an amateur and professional is that the amateur practices until he gets it right. The professional practices until he can't get it wrong

  10. #10
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    I put a drip leg and moisture trap right after it
    Steve Jenkins, McKinney, TX. 469 742-9694
    Always use the word "impossible" with extreme caution

  11. #11
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    I'd recommend a standard filter and a dessicant dryer. You can also purchase filters that go right before the tool, but I believe those are more so for small debris.

  12. #12
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    The posters above are right, the best approach is a refrigerated dryer to condense out and remove the moisture from your compressed air before you feed it into the lines in your shop. You will never have moisture problems at the air nozzles or spray guns, or air powered tools in your shop if you go this way, but refrigerated air dryers are not cheap, and the cost to run them can add to this.

    When your air compressor runs, it squeezes the air together, leaving less room between the air molecules for the moisture molecules, but the compressing effort also heats up the air, so most of these moisture molecules can stay in the air, until the air cools off in your compressor tank. As it cools, the compressed air can no longer hold this moisture and it begins falling inside the tank, much like rain does from a cloud. If you can cool this air to the room temperature or below before you use it, you will not have air line moisture problems.

    The air compressor manufacturers have put no effort into the design of your air compressor to make it more effective at removing moisture from the compressed air. They haven't even taken into account the fact that hot air rises and cool air falls in their design. They take the very hot compressed air directly from the compressor output and dump it directly into the top of the air storage tank. Then, right next to where that very hot compressed air enters the tank they provide the air outlet to your tools. The hot moist air from the compressor then just floats across the top of the tank like a hot air balloon floats above the cooler air and moves across the top of the tank and into your air lines, where it then gradually cools and the moisture in it begins to form water droplets that make it to your air tools and nozzles. It wouldn't be difficult at all for them to change their designs and make significant improvements to this problem.

    If they had just added a finned radiator to the compressor outlet to fully cool the air to room temperature before it reaches the tank, the moisture would fall to the bottom of the tank. If they provided a tank connection for your air lines and tools that was about 1/2 way down the height of the tank, the air reaching it would already be cooler to at least to room temperature, and the air coming out of this outlet would be relatively free of the condensing moisture. You want cooled air to reach your tools and nozzles, not the very hot moist air as it comes directly out of the compressor. I have a repurposed small car air conditioner condenser coil (the one from in front of the car radiator) piped in between my small 2 hp air compressor and it's 20 gallon tank. This coil is also positioned so the fan in the center of the compressor pulley is drawing air through This coil. The bottom outlet of this condenser coil is piped to the original inlet on the top of the 20 gallon air compressor tank. The cooled air and it's condensed moisture enter the tank at the original location, but since the air is already cool the moisture quickly falls to the bottom of the tank, so it freely mixes with the cooled air in the tank and the condensed moisture falls to the bottom of the tank. When in use, I can drain as mush as 1/2 gallon of water from the bottom of the tank after each full day that I run this compressor, and I never have moisture problems at the tools or nozzles.

    For added protection when using this air compressor for painting, etc. I bought a filter from the local auto paint supplier that uses a roll of toilet paper as it's filter cartridge. They sell a better version for this for about $1.50, but just one from the bathroom will work for several hours. It does indeed do a great job of removing any remaining moisture and debris from the lines when doing work that requires this. A refrigerated dryer is even better, but this is the best if you can't afford the refrigerated dryer.

    I hope I have helped you all to understand the problems of getting dryer compressed air. A few relatively simple design changes can make a big difference to the dryness of your compressed air system. They are well worth doing, even if you end up getting a refrigerated system some day.

    Charley
    Last edited by Charles Lent; 12-24-2020 at 6:57 PM.

  13. #13
    Quote Originally Posted by Steve Jenkins View Post
    I put a drip leg and moisture trap right after it
    Multiple drip legs, so to speak. I hesitated to respond to this, because the OP seems to be seeking a mobile solution. The easiest solution, and the only one I know of, is to have a passive piping system of some length, with repeated drops (and vertical takeoffs to the next leg.) Thatís cheap and effective, but not mobile. Dessicants are useless when theyíre saturated, FWIW.

  14. #14
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    What pressure is an AC condenser coil good for? I've been contemplating putting in some kind of heat exchanger between the compressor and tank.

  15. #15
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    Quote Originally Posted by Doug Dawson View Post
    Multiple drip legs, so to speak. I hesitated to respond to this, because the OP seems to be seeking a mobile solution. The easiest solution, and the only one I know of, is to have a passive piping system of some length, with repeated drops (and vertical takeoffs to the next leg.) Thatís cheap and effective, but not mobile. Dessicants are useless when theyíre saturated, FWIW.
    I did similar to this. I have 3 drops with a drain valve in each, the first one gets some moisture, the other 2 donít. After the drops, I did a filter and regulator. I think they are Pneumatic Plus.

    The radiator is interesting and I thought about that. I wasnít sure on the pressure rating and I would prefer a separate fan instead of using the compressor cooling fan. The pipes were simpler for me.

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