... how long do the rings on the pistons last?
Good question Dan.
The pump is 2-stage so air is first compressed by the larger 2.50" piston & then compressed again by the 1.75" piston. Ring wear in any recip engine, whether an air compressor pump or an automotive motor, is a function of linear feet of piston travel, peak piston speed, condition of oil, operating temperature, etc. 15-20 years is a reasonable expectation for a low speed pump that's in service 8 hours each day - about 30k-40k hours.
Rotary screw compressors run a lot longer with Quincy having a 130k hour design. That's 65 years at 8 hours a day but the majority of screw compressors run 16-24 hours/day & that results in far fewer years. Either way a Quincy rotary screw has a 10-year guarantee & that indicates life expectancy beyond that.
The pump on my compressor is splash lube:
Some pumps use an automotive style oil filter & pressure lube - they last even longer.
This old pump is going on 85 years (more or less). Quincy records indicate it was first sold to a service station, back when service stations added air to the tires, checked the oil, cleaned the windshield, etc. Goodness knows how many places it landed between then & 1980 when the prior owner bought it to use in his small business. He sold it to me in 2002 & it was the dirtiest piece of equipment I ever bought, cannot remember how many cans of engine cleaner it took before the pump was degreased. Since then it's seen light use as the "house garage" compressor ... filling bicycle tires, blowing off the mower, etc. The three compressors in my shop run a lot more.
Synthetic 15W-50 motor oil is my lubricant of choice & it gets changed whenever it stops looking clear & clean. There is certainly blow by past the rings & water vapor condenses in the bottom of the crankcase. Watery oil sucks as a lubricant.
I'm thinking this compressor will outlive me & get passed on to my son.
