Quincy 310 unloader plumbing

[gummycarbs]

Hi,

I picked up a Quincy 310 (ROC 21, L version) compressor pump awhile back and have been slowly getting it back into shape. It was the bare pump, so I'm assembling the rest of the compressor from Craigslist and Surplus Center.

My question is how to plumb the unloader. My understanding is that the Quincy hydraulic unloader provides two functions: 1) it relieves pressure on startup so that the motor isn't fighting tank pressure and 2) it prevents the compressor from building more than 40-ish PSI pressure in the event that the oil level is low. It's also my understanding that the design of the valves means that a check valve isn't needed between the output and the receiver tank.

I bought a Sunny 140-175 PSI pressure switch (4-1823-H4) with an unloader port. I also have a 3/4 check valve with a side port for the unloader.

Is there any reason not to use the check valve and the unloader port on the pressure switch? My thinking is to simply tee the check valve's side port and run it to both the pressure switch and the Quincy 310's hydraulic unloader. Any problem with that?

 

[gummycarbs]

bump

 

[The Tool Tyrant]

What is your reasoning for adding items not needed? The check valve does add additional resistance for the pump to overcome, so why add more work for the pump? Why do you want / need redundantsy for pump unloading?
It's not necessary to utilize the unloading port on your pressure switch.

 

[yelchevelle]

I have a 310, and not that I would go out of my way to install a check valve, I personally don’t think that it hinders that much. My 310 doesn’t have one. When I first rebuilt it, it would go probably 1.5-2 days between kicking on if nothing else was plugged into it. Now it’s probably 6-8 hrs.

I rebuilt it probably 8-9 years ago. Only maintenance I have done is oil changes. Valves probably need lapping, but I haven’t stopped to do it. Also, it’s been taken apart and put back together 3 times since I rebuilt it for moving. It could be leaking around a copper line


Right now, I probably only have mine on 1-2 days a week( average). I might go 5 days straight using it, but then it might sit turned off a week or so. I only run mine up to 120-130 psi, kicks on around 95-100. I don’t see a need for more psi for the way I use it.

how fast are you going to run it. I run mine between 800-900 rpm with a 3hp motor. It runs good, only down side is mine is an oil slinger, and it seeps a little oil through the crankcase vent now. When I ran it with a 1.5hp motor, It really didn’t leak, but the cfm couldn’t Keep up with my demand. Now I am in the process of finalizing one of my 240’s (somehow 3 of them followed me home). I am interested to see how I like it compared to the 310.

 

[gummycarbs]

The reasons I was planning on running a check valve are:
1) I already had one from my Surplus Center order.
2) I've never before used a compressor pump that didn't use one.
3) I don't know how reliably the Quincy 310 valves seal. Do you get a bit of carbon build-up and start leaking air?
4) I'm having a surprising amount of trouble locating a suitable fitting for the 3/4" NPT on the tank/receiver that provides a 1/8" NPT port that *isn't* a check valve.

@yelchevelle I think the pulley and motor combination I'm using should put it at around 825 RPM.

I'll be running the pump's output through a B&M 70274 after-cooler, which has 1/2 NPT fittings, so I kind of figured that would be my bottleneck anyway. I'm not really finding any information on how much a 3/4" check valve is going to reduce flow.

 

[yelchevelle]

I think the valves develop small leaks just from wear. Best I can tell, most carbon built up in the compressors I have seen is because someone ran detergent oil in them. I could be wrong about that, but one of the 240's I have was nasty inside. Came from an auto mechanic shop. I bet anything, they ran engine oil in it. It should primarily just be the output valve on the high pressure side (small piston) that causes leaking.

I choose not to loose sleep about it because the compressor seeping down, it just is not that big of a deal to me. I disconnect power to it over night. It takes a few minutes to build up if its been a few days or longer. I feel like the best thing for these industrial compressors is to run them. One of these days, I am going to figure out how to run a relay off my light switch in my garage to automatically cut the power to my heavier electrical equipment.

As far as the 3/4" to 1/8", I would run a T, with the air output running straight through, and the 1/8"reduced coming off the center leg of the T.

I haven't checked flow numbers, but I would be willing to bet 1/2" flows plenty of cfm for the output of the pump.

 

[The Tool Tyrant]

Sounds like you're on a mission. I've never heard of anyone having two sources of head unloading (kind'a like having two wives) so go for it and let us know how it all works out for you. I don't see how it could hurt anything.

After re-reading your original post, perhaps I misunderstood your question. Are you asking how to plumb the hydraulic unloader or the pressure switch unloader?
If you are asking the former, install your check valve and run a 1/4" copper line from the side port to the hydraulic unloader.

 

[Iron Beaver]

I would run a line direct from tank pressure (whether you do that with a port on a check valve or whatever) directly to the unloader. Less to go wrong.

 

[vwpieces]

4) I'm having a surprising amount of trouble locating a suitable fitting for the 3/4" NPT on the tank/receiver that provides a 1/8" NPT port that *isn't* a check valve.

The disc and spring can easily be removed. Should only be an internal snap ring holding that in from the bottom.
Then it's what you need to plumb and you already have it.