Another Air Compressor Question


I plan on the purchase of an air compressor mainly for use with a finish spray gun. Hobby usage, HVLP gun that takes lots of CFM.
I am thinking about an electric belt driven oil-lube compressor single stage. The problem seems to be my mis-understanding of oil lube .vs. oil-less. Since I want the primary usage to be finish spray, I don't want oil residue in the air lines. But I learn that one maker of a belt driven compressor, you have to change the oil every so often. But if belt driven, what is using the oil for lubrication? The electric motor? and how is the (or what is the method for) oil getting in the air tank?
And so my next question: if I do go with an belt driven compressor, there must be a gizmo that will filter the oil out of the line for applying a finish, so what do they call that gizmo? Any link? And if anyone can spare the time, is water condensation any problem to worry about with a HVLP spay gun?
TIA
Phil
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Not lots of CFM at all. Spray guns are on the low side of tools that demand lots of air. 10-12 CFM is usually more than adequate.

The oil is for the compressor head. It's a cylinder and piston just like your car engine, except it's turned by the motor instead of firing gasoline. The oil lubes the piston in the cylinder and the bearings. There is a fill plug on the base of the compressor head and a drain plug as well. Some compressors have a small window to monitor the condition and the level of the oil, and others do not. You would simply change the oil based on the number of hours of use, or top it off as it is consumed (if your compressor consumes a bit of oil).
The oil does not get into the tank, or the air lines. Make sure not to put an oiler in the lines like a lot of people do. Oilers are only for air tools and aren't necessary even in working shops. Oilers contaminate the air lines. If you run air tools, put a drop of oil into the air inlet of the tool before every couple of uses and it will be fine. Oil and spray guns just don't go together.

Like I say - the oil never gets in the lines. It merely lubricates the compressor head. You will want to put a water trap in your line downstream from the compressor, and you'll want a water trap that screws into the inlet of your gun as well. Drain your compressor tank of all accumulated water (all compressors accumulate water in the tank) before every spray session. Together these will keep moisture problems at bay.
Here's a link to the water trap that screws on the gun...
<http://www.eastwoodco.com/shopping/product/detailmain.jsp?itemType=PRODUCT & RS=1&itemID00&keyword4066>
Here's an example of a downstream moisture trap...
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber261
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In reality, as the seaks start to wear, oil does get into the lines. For air powered tools that's a benefit, not a drawback. For airbrushing or painting, I'd put a filter on the line.
Mike Marlow wrote:

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You are quite right Mike - in fact it really does get in even when the compressor is brand new - to a lessor degree. I should have thought through my wording below better. I was trying to distinguish between oiling the head and oil intentionally being in the tank as I understood the OP to be confused about.
As well, you are quite correct about line filtering, which is something I suggested to the OP as well.
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Huh?
You need to go to the store and look at these compressors to get a better grasp.
Belt driven does not mean that the pump is oiless although every one that I have seen is. The oil lubricates the compressor pump. the oil gets into the tank as the compressor pump piston rings begin to wear out. So, if doing this for a hobby a quality oil type compressor should last you a very long time before it starts to leak oil into the tank. Typically oil lubed compressors enjoy a life about 10 times longer than oil-less compressors.

Yes there are oil filters to add to compressors to guard against this when it eventually happens. You also want to for certain have a water trap/filter as close to you spray gun as possible. A lot of water condenses in side the tank with the heated compressed air going into the tank. As that hot air goes through your cool air line moisture condenses and contaminates the air coming out of the hose.
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The others have answered your questions quite well. I would just like to add a comment about filters.
I found a filter at an auto paint supplier that really helps and it only cost about $20. Whenever I'm painting I add it in the air line about 15 feet before my spray gun and it stops everything except the air. The filter media is a roll of cheap toilet paper (not even Charmin). You just replace the roll before each spray session and you never have to worry about moisture or oil contamination.
If you don't collect too much moisture in it during the painting job you might even still be able to use it for the other job that it was made for. :-)
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Charley


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I didn't know they still made those. Used to use one on the air operated bar feed for a CNC lathe. Kept the feeder from dripping.

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BTW, amazon is having a killer deal on porter cable compressors at the moment. You can get $150 off a big one that's normally around $900.
brian
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On Fri, 27 Jan 2006 01:03:08 GMT, "Phil-in-MI" <NO Spam &

Couple points...
Oil lube compressors, as a rule, not only out last "oil less" compressors but are much quieter..
While you're at Harbor Freight, (or online there), consider their "remote" tank drain system... it's a replacement spigot for the tank drain, at the end of a hose... In my experience, it's much easier to "get around" to draining the tank if you don't have to get on your knees and find the spigot... and NOT draining the tank with each use will put more water in the hose/spray gun or fill your separator quickly, in addition to reducing the life of your tank.. YMWV Mac https://home.comcast.net/~mac.davis/wood_stuff.htm
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mac davis wrote:

On the downside however, they're a LOT harder to start when cold. For those of us with shops that only get heated when we're in it, this is a factor.
Chris
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I have not found this to be true but I guess that depends on what oil you put into it.
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What I'd put on is the automatic drain. It plumbs in quite easily and blows off a small amount of air every time the compressor cycles. Does an excellent job of keeping water from building up in the tank.
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Thanks everyone for your responses. Bridger and both Mikes, thanks for the education.
As you could tell I am not too experienced with Air Compressors. But I hope I am now better able to purchase the product that will suit my needs.
And Brian, thanks for the Amazon price heads up.
Phil
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