Removing Moisture from Air Lines

Tips on getting good moisture removal from shop air lines using a filter/dryer. June 15, 2014

Question (WOODWEB Member) :
Now that I've made a decision on a compressor to install in my home wood shop (Porter-Cable C7510), the next question is what do I need in the way of an inline filter/dryer? I have four drops throughout the shop. I will not be spraying any finishes. The air will be used for simply blowing off dust and chips, and operating pneumatic tools. I'm looking for something that will keep the dirt and moisture out of my tools, without costing me a fortune. Either general or specific product recommendations are welcome.

Forum Responses
(Dust Collection and Safety Equipment Forum)
From Contributor G:
A simple five micron (or less) water filter should be enough for most tooling. Make sure to keep the filter at least 25' away from the compressor so the air has time to cool off - the farther the better. If you run pneumatic tooling you may want to think about an in line oiler on those outlets.

From contributor J:
I agree with Contributor G. It's important to have the 25' or so of pipe between the compressor and the first drop because typical filters/driers can only remove liquid water, not vapor. The air coming out of the compressor is warm, and can carry a lot of vapor. It needs time to cool so that the vapor can condense into a liquid before it gets to the filter. I used 3/4" copper (type L or K, not type M) for that run of pipe in my shop, and it works beautifully. My compressor is about twice the size of the PC you've chosen; if you're going to be running it at the typical 90 plus psi, you'll only need 1/2" pipe.

From Contributor G:
I run 1/2" copper in my shop. Iíve never had any issues with volume restriction with it. My spray room is 75' from the compressor and works great with the HVLP guns.

From contributor J:
Yeah, 1/2" can carry a lot of air. I ran 3/4" because I read several engineering articles on air system design before setting up my system, and the consensus seemed to be that one should design for the air to move through the pipes at no faster than 20 feet per second, to minimize pressure drop. The thinking goes like this: The smaller the pipe, the faster a given volume of air has to move to get through that pipe in a given amount of time. The faster the air moves the more pressure drop. The more pressure drop, the higher the pressure you need to compress the air to get the pressure you need at the end of the run. The higher the pressure at the compressor the less air your compressor will be able to compress, and the more electricity it will take to run that compressor. So, essentially undersized pipes cause reduced CFM capacity and higher electric bills.

From Contributor G:
Using my HVLP gun (10 CFM) at 43 PSI, I get a two PSI drop with the trigger pulled. Since my compressor can only output 11.4 CFM at 40 PSI I think I have it covered.

From the original questioner:
My shop is very small, basically a two car garage with a separate room for storage, the dust collector and the compressor. I don't have a single air drop in my shop that is more than 25' from the compressor. I would like to have the filter/separator/regulator near the compressor. Do you think that making a cooling coil out of 25' of 1/2" flexible copper tubing installed between the compressor and the filter would be an acceptable alternative?

From contributor J:
Something like that should be fine. You should probably use heavy-gauge tubing, which may be challenging to get in flexible stuff. Also, be sure to shape it so that water that condenses in the coil drains out naturally, either towards the filter or towards the compressor (don't create low points that will trap water).

From contributor O:
Rather than deal with a coil of soft copper tube you could buy a hand full of elbows and run a section of 25 to 50 foot of hard copper back and forth zig-zag fashion on the wall to make a condenser. The best method would include a bit of pitch in all the horizontal runs and drain back to the compressor tank. Second best would include a tee and a section to act as a water trap at where ever it drains to and a valve to open every so often to drain the condenser trap. An automatic water drain under your tank is also a good idea as a great deal of water condenses there.