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  1. #1
    User tdukes's Avatar
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    Water in compressed air

    Was thinking about a HVLP sprayer but we have a lot of moisture in our compressed air. Could go with a unit that has its own compressor which probably use a desiccant like my plasma cutter.

    Just wondering what some are doing to 'dry' their shop air. Have seen some expensive air dryers but not wanting to spend that.

    TIA

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    Re: Water in compressed air

    I have been using a water/oil separator and an inline desiccant filter. I have been reading up on this, and it seems that Campbell Hausfield makes an inline one with replaceable cartridges.

    I also am wanting to set up an automatic drain thingy (tech term) on the compressor drain that turns on and off every so often when the compressor is on. My thoughts are draining the water regularly should help. Harbor freight sells one, but I am thinking more of one that works on a timer, and tying it in to my remote control for turning my compressor on and off.

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  5. #3
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    Re: Water in compressed air

    There are several things you can do to address the wet air from your compressor.

    First, if you have a very large compressor and tank that stores enough air to reasonably complete a modest sized spraying operation in one go then you can just charge the tank and then let it sit to cool off for an hour, or so, which will condense most of the moisture out of the compressed air (leaving it on the bottom of your tank). I have often used this approach with my 80 gallon air compressor as the tank has enough air to sustain a good deal of spray finishing before it runs low, I then recharge it while killing time waiting for enough time to pass to tackle the next coat, by which time things have cooled down again. Most of the condensing moisture is made possible because the air in your tank is very hot immediately after compression and this added heat increases the moisture capacity of the air and as the air cools, such as in your hose, or at your spraygun due to the sudden pressure drop, that moisture begins condensing where it can then get into the airstream and cause issues (especially if a lot gets spit out at once). So anything that cools the air prior to it entering your hose will help to condense excess moisture out of the compressed air, and water on the bottom of your tank is water that willl not end up in your tool (or finish).

    Second, it is always a good idea to install a water and oil separator to help strip liquified water and oil droplets from the air stream (they function on a similar principle to cyclone DCs) -- especially if your compressor is not oilless. They work best if at the end of a length of pipe so that the air has had a chance to cool some before reaching the trap, but even if you have to install it directly before (or after if necessary) the regulator at the tank that is still better than nothing, just realize that some additional moisture may condense in your air hose due to both the pressure drop and the cooling of the airstream.

    And finally, install either a moisture trap (essentially a filter packed with toilet paper like material) or an inline desiccant cartridge within the last couple of feet just before your HVLP spraygun.

    You could also install a much larger desiccant drier at the tank if you wish IR even install a refrigerated drier, but those only make sense if you will be doing a great deal of spraying. And at the spraygun you will want your final pressure regulator to ensure you always have the optimal air pressure for your soraygun regardless of the pressure drop in your length of hose -- doing it this way, I find I can get away with using 1/4" polyurethane hose for the final length of hose at the spraygun and still have more than adequate air pressure and flow (the poly hose is both far lighter and more flexible, a great combo when spray finishing). Another option is installing an intercooler (basically a radiator) between the compressor and tank with a fan blowing over the intercooler, this dramatically cools the compressed air quickly and causes much of the excess water to condense out of the airstream.

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  7. #4
    User Pop Golden's Avatar
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    Re: Water in compressed air

    I have 2 compressors and turbine HVLP. The HVLP doesn't seem to have any problem with moisture. This may be because of the heated air it provides. I also shoot mostly shellac. My larger compressor (an Emglo) is used only for nailing & blowing. My other compressor is a Senco "Hotdog" this is used for airbrushing. As I shoot mainly water based paint Here's my moisture problem. I have a high quality moisture collector at the compressor and an additional in line filer at the brush. This doesn't completely solve the problem, but it goes a long way. I also keep an eye on the humidity and try not to air brush when it is high. I have also given thought to adding an additional collector at the compressor. Don't really know if this would help, but maybe it's worth a try. North Carolina is a sloppy wet environment. I understand that places like Arizona drys lacquer before it gets were it's going. SO! considering maybe our problem is the better of the two.

    Pop
    ​With Enough Thrust Pigs Fly Just Fine.

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    Re: Water in compressed air

    I use a water/oil separator in the line near the compressor which has a drain in the bottom. I also use a disposable inline filter just before the gun.

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    Re: Water in compressed air

    I have a 5 hp 80 gallon tank compressor. I don't usually use much air for my shop work so just have a filter drier in the line to the shop, but when sand blasting or spraying, I have a refrigerated drier that the compressed air goes through on it's way to the sand blaster or spray gun. This unit cools the air to about 35 deg F and condenses out the moisture. After it the air goes through a filter that uses a roll of toilet paper and it lets only very clean and very dry air reach the sand blaster or spray gun.

    Cooling the air somehow after it is compressed will take a lot of the moisture out of the compressed air. Doing it doesn't have to be as involved as my system. Warm compressed air rises in the tank and cooler air settles to the lower part of the tank. Pumping hot wet compressed air into the tank and then drawing it back out at the top of the tank will guarantee moisture getting to your paint sprayer. If there is a way to connect your air line and sprayer to a connection in the tank that is half way down the dimension of the tank the air going to the spray gun will be drier. Put a good filter in the air line to the sprayer and it will have a better chance of working if the air comes out of the middle of the tank.

    Another way is to add a cooling coil between the compressor and the tank. Removing the heat here before the air enters the tank will cause the condensation to fall to the bottom of the tank. I did this on a previous 2 hp air compressor by adding an auto air conditioner condenser coil between the compressor and the tank and mounted the coil so that the fan in the compressor pulley pulled air through this coil. It will cool the air and condense out a lot of the moisture before it ever reaches the tank. I used this compressor with the cooling coil for years befor getting my big compressor.

    Oh, those automatic drains from Harbor Freight work, for a while, and then stick part way open, keeping your compressor running non stop. I've had several and all failed, so I have piped my tank drain out from under the tank, and have a ball valve on it, so I can easily drain the condensate from the tank every time that I think about doing it.

    Charley

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  13. #7
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    Re: Water in compressed air

    I run a 80 gallon 15 cfm compressor and use a setup like this http://www.tptools.com/1and2-Moistur....html?b=d*8092.

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  15. #8
    User tdukes's Avatar
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    Re: Water in compressed air

    Not sure of the size of the compressor at work. The tank is about shoulder height and I could maybe wrap my arms around half the diameter.. We use some heavy duty snap-on impacts that require massive amounts of air. I have blown out numerous regulators for my plasma cutter and nail guns, brad nailers, staplers, etc. as my port is just right off the compressor.

    I may need to look into a separate compressor and set it up for low volume, low pressure, 90 or so psi. Always have been concerned about ruining a $1200 plasma cutter.

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    Re: Water in compressed air

    Another option is getting a used refrigerated air drier and that will lower the air below the dew point and that could be used for your plasma cutter as well.
    They work well and can be found on Craiglist or FleaBay for a couple hundred.
    Desiccant air driers work well but you either need to renew or replace the cartridge when they have reached saturation which can be a PIA.

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  18. #10
    User Pop Golden's Avatar
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    Re: Water in compressed air

    Lowlander has a great idea. I have seen an improvement on this idea. It consist of a series of horizontal pipes with a slight tilt between the compressor and the filters.

    Pop

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  20. #11
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    Re: Water in compressed air

    That's also an excellent idea. If I used a blast cabinet or sprayed all the time I would definitely install a moisture manifold

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  22. #12
    User tdukes's Avatar
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    Re: Water in compressed air

    Quote Originally Posted by Lowlander View Post
    I run a 80 gallon 15 cfm compressor and use a setup like this http://www.tptools.com/1and2-Moistur....html?b=d*8092.
    I took a look at that. I can't go to the big box stores and buy the parts to make that for that price.

    One thing, I was wondering is would it be more efficient if it were made with copper tubing? I believe copper is a better conductor of heat but not sure the pressure rating.

  23. #13
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    Re: Water in compressed air

    https://www.copper.org/applications/...ect_recom.html
    Yes, I believe it does conduct heat better than the black pipe. Looks better in my opinion too.
    Bottom of page should tell you what pipe to use.

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    Re: Water in compressed air

    Quote Originally Posted by tdukes View Post
    I took a look at that. I can't go to the big box stores and buy the parts to make that for that price.

    One thing, I was wondering is would it be more efficient if it were made with copper tubing? I believe copper is a better conductor of heat but not sure the pressure rating.
    You would typically choose type L (avoid the cheaper and thinner type M) copper pipe for compressed air distribution and you may use sweated fittings at the pressures used in a typical shop compressor (typically in the 100-190PSI range).

    But before you go to the trouble to build such you may want to talk to whomever handles your HVAC work to see if them may have any used condenser or evaporated coils for cheap (even a pinhole leak would not really matter here if it is placed between the compressor and the unloader valve since the check valve will prevent draining down your tank) that you might be able to adapt to your purpose -- such combined with a fan will remove far more heat far more quickly and can be placed inline between the compressor head and the tank so as to precook the air before it reaches the tank and quickly condense out most of that excess moisture. Plus you will find that all of that copper, and especially the fittings, are absurdly expensive these days (hence all the copper thefts in recent years) -- not that there is anything wrong with building it all from copper, it will just be expensive.

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