I Just Got a New Air Compressor

[dex3361]

I used an amp clamp to watch the amps as the air pressure built up to make sure I didnt take the pressure so high I would trip the motor overloads. I have a 2 stage Quincy with a 5HP single phase GE tri-clad capacitor start motor. I have it set up to kick on at 175 and off at 195 PSI. I put this compressor together about 15 years ago from stuff on its way to the scrap yard.

 

[BukitCase]

Wow, Randall - at pressures like that I hope your unloader works good; have you checked peak inrush on startup? Just curious.

Also, at those pressures you could probably get an air embolism with a blowgun almost a foot away from your skin !

Quincy's are a good unit though, not surprising it's still going strong after 15 years... Steve

 

[dex3361]

Peak inrush of that motor will hit over 60 amps. Full Load amps is 23 amps if I remember correctly.

I use a pressure regulator and adjust the pressure for the need. I always use a safety blow gun with the ports. I have a relief on the tank for safety of the ASME rated tank.

The Quincy compressor I have can be configured to pump up to 500 PSI with the right tank, motor and sheave combo.

 

[Iplayfarmer]

I got the pressure up to 120 psi with this switch, but then the safety valve popped. I'm guessing old, weak spring. I think I can adjust this switch even higher without a problem. I remembered wrong... it's labeled as a 70 - 90 psi switch. Right now after I adjusted it, the compressor cuts in at 100 psi and cuts out at 120 psi, and I still have lots of room to adjust further.

I timed the compressor to estimate CFM, and I'm a little disappointed. I get from 0 to 120 psi in 12 minutes with an 80 gallon tank. The numbers tell me that's about 7.25 CFM.

 

[Brad_Blazer]

If you use a lot of air I think running to very high pressure is an expensive way to add storage capacity unless you have tools or a process that can use the extra pressure. All of the energy used to increase pressure above the utilization pressure is wasted when you throttle it at the regulator or at the tool.

 

[Iplayfarmer]

I borrowed an optical tachometer. My motor is running at 1783 rpm and my pump is running at 956 rpm.

My trusty Harbor Freight amp clamp meter tells me that the motor is pulling about 5 amps when under load (pumping at ~120 PSI).

Looks like I could get a bigger pulley and be just fine.

 

[BukitCase]

Running amps on my 5 horse 80 gal. is just over 20 - does kinda look like you're leaving a few cards on the table, so to speak... Steve

 

[Iplayfarmer]

Running amps on my 5 horse 80 gal. is just over 20 - does kinda look like you're leaving a few cards on the table, so to speak... Steve

The good news is that I'm not spending a lot on power.

 

[BukitCase]

Kinda reminds me of the old airline joke - pilot - "folks, there's good news and bad news - the bad news is, we've hit some turbulence and gotten blown off course, and are completely lost. The good news - we're making EXCELLENT time... Steve

 

[Iplayfarmer]

Kinda reminds me of the old airline joke - pilot - "folks, there's good news and bad news - the bad news is, we've hit some turbulence and gotten blown off course, and are completely lost. The good news - we're making EXCELLENT time... Steve

Yeah. It's about like that.

I've spent enough time on this compressor for the time being, though, and it's working great for 95% of what I plan to do with it. I ordered a better relief valve and a different tank pressure gauge that should arrive tomorrow. I'll put them in sometime over the weekend and then use the compressor as-is for a while. At some point in the future I'll get the itch to sandblast or to paint something. When that happens I will shop for an 11 inch pulley that should give me closer to 15 CFM.

One thing I haven't mentioned is that the system is holding pressure nicely. I've been unplugging it when I'm done tinkering each night. The next night when I go to start tinkering again, the gauge is within a few PSI of where I left it.