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Followup on Quincy QR-25 unloaders

As I mentioned earlier, the rubber diaphragms on both unloader towers rotted so much, that I suspect that they actually were originals. As a result, unloaders did not work properly.

I bought replacement diaphragms (Quincy 1855 analog, aftermarket) and installed them and now unloaders work properly. It also unloads instantly.

In fact, the unloaders work so well that I may rewire this compressor for a choice of either run on demand, or "continuous run", which means that the motor would run constantly and the compressor pump would be loaded or unloaded by unloaders, based on pressure.

Continuous run seems more suitable for sandblasting. According to my calculations, my compressor does approximately 24 CFM as of now, and the sandblasting cabinet uses about 15 CFM based on some information that I gleaned from its manual. So continuous sandblasting starts and stops motor a little too often.

I believe, possibly incorrectly, that the control that came with my Quincy has a electrically operated unloader that I can use with the electric pressure switch, for continuous run. (the original pressure switch was damaged)

Does anyone here have their compressor wired for continuous run?

Reply to
Ignoramus4181
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I'd construct a control that would cause it to go into continous run if run on demand happened more than x times a period. If you don't cycle the unloaders after y minutes than drop back to run on demand.

It would be nice to the motor and not flicker the lights as much.

Hold on, it either pumps or does not pump. If it is like an IR air cube with double acting pistons then it can half pump so to say. Is your Quincy double acting?

I wasn't following the thread closely so I may have missed above detail.

Maybe you are just thinking along my original track of thought.

Wes

-- "Additionally as a security officer, I carry a gun to protect government officials but my life isn't worth protecting at home in their eyes." Dick Anthony Heller

Reply to
Wes

Well, running continuously, sometimes with load, and sometimes without, is very nice to the motor.

With the unloader, the compressor pump spins, but does not actually pump air.

Unloaders job is to open intake valves. With the unloader activated, the compressor moves pistons, but does not compress air/

I was just thinking about a SPDT switch. In one position, it would run the motor on demand. In another position, the motor would run continuously, but the compressor would sometimes actually pump and sometimes it would not pump, just spin idly.

Reply to
Ignoramus4181

Yep, those diaphragms are typically bad in older, unused Quincys. I DID warn you! The newer ones are nylon reinforced.

Reply to
Buerste

I do not mind replacing them every so many years. They are less than two dollars apiece. In fact, I bought four, used two, and kept two for future use.

Any thoughts on the continuous run concept?

Reply to
Ignoramus4181

With a VFD and a pressure sensor, the compressor could be throttled to

15CFM to match the demand and run continuously at a lower RPM and temp.
Reply to
Pete C.

I didn't do the study myself but Roger claims that we are ahead not continuously running them. We are currently under 50% duty cycle, depending on the current crop of air leaks.

Reply to
Buerste

My compressor was set up that way when I got it, with an entirely pneumatic unloader-pressure control. I upped the motor to 2 Hp, and built a dual-mode controller. You could actually set up a dual mode controller with a couple time delay relays. Whenever the switch says the tank pressure is high enough, the compressor unloads. If air is needed, the compressor loads. If the tank stays filled long enough, the motor is shut off. Mine is a bit more complicated, I used a microcontroller, and it monitors for loss of oil pressure, excessive run time and a broken belt, among other things. It also keeps the compressor unloaded while spinning down to avoid the clunk-clunk-clunk when it stops.

Jon

Reply to
Jon Elson

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