Filter setup for a portable compressor?
by Pat
(Floyds Knobs, IN, USA)
Most of the information I've seen on filter placement involves larger "shop air" systems, where the compressor and piping are all fixed. I'm trying to sort out what makes sense for a smaller, portable unit I just got.
This unit is a 2HP, 4 gallon "twin-tank" design that's rated for 5cfm at 90psi. I plan to use for pneumatic air tools and light spraying. Tools will be connected through a 25ft, 3/8" air hose. Right now the unit just has a pressure regulator and a couple of quick connects at the output. No filter. My main concern is where to place the filter(s), particularly in regard to moisture removal for spraying and mobility. I know it's recommended, in general, to have one at the compressor outlet, but that seems like the worst place with regard water removal. I imagine much of the water might still be vapor at that point. On the other hand, most of the filters/moisture separators I've seen look like fairly bulky items, and many need to be vertical to function correctly, which makes putting one at the end of an unfixed air hose problematic. Either way, I plan to use a desiccant filter (along with a regulator) when spaying, as recommended. But without something else before that, I might go through a lot of (expensive) desiccant! Any advice? Thanks!
Pat
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Bill says...
Pat, excellent question and research.
Your compressor tank will have water generated into it and that water will flow to the bottom of the tank. Use a lot of compressed air, and the turbulence in the tank as the air flows out will, inevitably, entrain some of the liquid water and deliver it to your air line. Hence the recommendation for a general purpose (you can find mini-filters for smaller compressors) filter at the egress point of the tank, and before the regulator.
Depending on the ambient temperature, you will likely get moisture condensation in the air line. The desiccant dryer will remove that at the air tool, but if there is too much, it will overwhelm the dryer.
In your case, I would put the desiccant dryer after the filter and before the regulator. Depending on the type of desiccant dryer you use, it will provide air that has a dew point below the ambient temperature in your shop, and if the ambient temperature in your shop stays above that dew point, you should expect not to get any water vapor condensation in the 25' air line.
Cheers,
Bill
