Jason, I agree with the book you mention. A 3/8" ID hose is the minimum you should consider for a full sized gun. Or other air tools for that matter. A 1/4" really is too small. That said, I do use a 6 ft length of 1/4" ID hose as a "whip" at the end of my 3/8" hose when I use my spot gun and other small tools like a 1/4" drive air ratchet or die grinder. Plus the inlet pressure to the die grinder is not as important as that to the spray gun. The whip improves the manuverability in tight places like an engine compartment. I don't use it when I use my full sized gun. Hoses are a pain, especially when you carry around two of 'em. One for the gun and one for supplied air (I use a 3/8" ID hose for that also). There's really only so much you can do. One thing is to use a high quality, very flexible hose. Parker #831 hose is excellent but quite expensive. Once purchased though, it will last for many, many years. It coils just as easily at zero deg as it does at 90 deg. Try that with PVC hose. Remember also that the pressure drop with flowing air is inversely proportional to the fifth power of the line inside diameter, all other things being equal. That means the pressure drop with 1/4" hose would be several times that using a 3/8" hose. I think you would find running 1/4" hose from your wall station all the way to your gun would simply not permit you to achieve the proper gun inlet pressure. That Cobalt uses about 14 cfm at a gun inlet pressure of 50 psig per the Sharp website. That's a rather high inlet pressure for an HVLP gun. It's also typically what I use with my non-HVLP DeVilbiss gun. If your arrangement is anything like mine (50' hose + some quick couplers) I don't think you could even make it work at all with 1/4" hose - you'd be starving the gun for air. Using 50 ft of 3/8" hose and three quick couplers, I will get 30 or so psig pressure drop between my wall regulator and my full sized gun (using about 14 cfm as I recall). That shows the need to check your working pressure right at the gun inlet with the trigger pulled. I don't use swivels. I have never found them to be needed. I do use a quick coupler at the gun. They provide a type of swivel action, at least in one plane. I never use a regulator or throttle valve at the gun although I do install a pressure gage there for setting the air pressure. As far as air drying, the ideal setup would be an air cooled aftercooler at the compressor, followed by a refridgerated air dryer. Most home shops don't have that however and make do with a length of metallic piping to cool the air some and condense out moisture that gets past the storage tank. Filters are terms used rather loosely when it comes to moisture removal. By their nature, they do not remove moisture in the vapor form - only in the liquid form. In any event, a moisture separator or "filter" should be installed as far downstream as possible prior to your hose connection to permit as much condensation upstream as possible. I use a moisture separator, followed by a standard prefilter, followed by a coalescing oil removal filter, followed by a fine final filter, followed by a station regulator. Other arrangements will work also. Just make sure that each component is rated for the necessary pressure and flow capacity at a reasonably small pressure drop.
|