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Gavin M
12-12-2003 23:11:18
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Re: compressor in reply to Clete, 12-12-2003 08:17:21
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A real good tip for small compressors is to see if you can change the voltage to 220V if you are running on 110. Most "compressor-duty" motors (read light) pull a ton of amps on startup. My machine used to regularly flip a 20A breaker, especially when cold. It was a real effort to get it to run on those -30 mornings (Northern Alberta) when the shop was still cold. After rewiring to 220V the problem disappeared. The motor comes up to speed much faster and runs cooler. Usually there is a wiring diagram for either voltage by the strain relief (where the power wire enters the motor) and an access plate to get at the connections. If you're unsure, an electrician can do the job in less than an hour. My machine (5 HP) is connected to a 220V, 30A circuit, but I doubt it draws more than 10A even on cold starts. I built an air header out of 1" pipe around my shop, with connections at convenient points. I put a set of Wilkerson filters near the compressor (oil, particulates, charcoal), and a sub-header for painting in one bay. That has a Fisher 67 regulator and a silica-gel dryer for -50 dewpoint air. This runs a HVLP spray gun. I also built an oiler manifold that I can connect at any of the take-offs fir air tool oil. For running out to the yard, I have 2 100' foot sections of 3/4" rubber hose, with a lighter 25' 3/8" whip on the end. Lastly, I put a steam trap style autodump on the air compressor tank. This eliminates the hassle of blowing down the machine to get the water out (not as bad a problem here as in other places, the air is quite dry). I feel I have a good setup and was able to make it happen by picking up most of the stuff I have through dispersal auctions from finished industrial projects. Note for Kelvin: I think that the only reason Sch. 80 1/2" pipe was recommended for air service has to do with the thread depth allowance. The main run of 1/2" Sch. 40 pipe is good for much more than 150 psi, even with common ERW black pipe. Where trouble occurs is when the threads are cut for connections. If this is done sloppily it is possible to have very little material, unsupported, under the base of the thread roots. The problem is worse in vibrating service, such as a compressor discharge. If you've been running Sch. 40 pipe for 15 years, I wouldn't worry about it as if it was likely to fail, it would have done so by now. As an engineer, I typically specify Sch. 80 pipe for utility air, except for high vibration conditions, where I use Sch. 160. Good Luck.
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