Champion R15B Centrifugal Unloader Valve Won't Close
by Greg White
Champion R15B Centrifugal Unloader Valve
I've posted this on a few forums and so far I haven't been able to get any help at all. I'm hoping I've finally come to the right spot!
I have an air compressor that I bought used from the Army at a surplus sale. I only paid $200 for the whole unit and it was OD green and had some surface rust so I figured I'd take it apart, clean it up, paint everything, replace the rusty fasteners and fittings, then put it back together. I had to buy a single phase motor for it and I built a little sound enclosure shed for it behind my garage as well. I did all that and everything is great with the exception of my centrifugal unloader and what may be an oil leak.
The centrifugal unloader on the front of my pump has a breather that the Army TM (TM = Training Manual, or the tech manual. I've put the link below it in case anyone needs it since it covers Champion R15 pumps well) calls an unloader body. Looking at the old rusty one I think it's just a 3/8" NPT breather so I got a new one seeing how the old one was rusty and the felt screen was worn out. When I turn on the air compressor it starts just fine and doesn't draw too many amps. My understanding is that once the pump reaches a certain RPM that the weights move outward therefore taking pressure off the pin and allowing the little valve ball to seat and block off air from escaping through the breather I described earlier. The problem with my compressor is that when I start it and let it run the unloader valve never closes and therefore air is constantly shooting out the breather. As a result the tank never fills completely with air and the whole unit
just runs and runs. I put a 3/8" NPT plug in place of the breather, the tank pressure shot up to 175 psi in no time, and then the motor turned off like it should. I have included a picture of the unloader I bought that is installed and some overall photos of the whole air compressor unit as well. I'm thinking that for some reason the weights are not swinging out and therefore the valve can't close. I removed the little plug that holds the spring and ball, made sure they were clean, and then made sure the pin that pushes them was moving freely. Everything seems to be working fine, I just can't figure out why this valve won't close.
The other issue I'm having is with some oil leaks. I originally used Catoil (Link to tech specs: http://catoil.biz/CatOil%20Testing.pdf) as I was told it was a top notch air compressor oil. Based on those numbers it looks like it may not be heavy enough so I drained that out and replaced it with some regular 30W non-detergent oil. When I was using the Catoil the compressor leaked and slung oil everywhere like crazy. With the 30W ND I'm noticing some but the pump hasn't ran much so I'm hoping that it's just getting the rest of the Catoil out of it's system. I also had a thought that possibly the Catoil was so lite that it got into the piston and somehow affected the RPM of the pump. I've noticed the oil coming out of the manifolds but when I check them for leaks with soapy water I don't get any bubbles. Could oil in the pistons effect RPMs in a way that would cause the centrifugal unloader to not work properly?
Sorry for the long post, I just want to make sure I include as much detail as possible.
Link for PDF manual: http://compressors.tpub.com/TM-5-4310-373-14/index.htm