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.

 

[Iplayfarmer]

I don't know if I even dare ask this, but here goes...

Do I need to rebuild this compressor pump?

I'm thinking that at 956 RPM I should be getting a little more than the 7 1/4 CFM I calculated. It's consistently taking 11 - 12 minutes to fill my 80 gallon tank.

 

[BukitCase]

My DevAir 5 horse baldor, 80 gallon - I just ran a test - drained it all the way down, plugged back in, stopwatch -

120 psi in 4:30, shutoff @ 150 psi, 5:30. (I don't need 175 psi, and up to 160 my comp. is rated 24/7/365 operation so why tempt fate?)

My pump specs 635 rpm @ 19.8 cfm @ 150 psi, and lists displacement @ 23.4 cfm - I'm assuming that last figure is free air, but it doesn't say.

My motor pulley is just under 8", and the pump pulley is right at 20", it uses two belts and motor draws right at 22 amps running.

I would think that either your pump is designed to run quite a bit faster than mine (it is, according to that spec sheet), your belts are slipping, or you're about to find out how to rebuild an air pump

Wish I had better news; Personally, I'd make sure belt isn't slipping and try a larger motor sheave before I gave up and dug in further... Steve

 

[Iplayfarmer]

My DevAir 5 horse baldor, 80 gallon - I just ran a test - drained it all the way down, plugged back in, stopwatch -

120 psi in 4:30, shutoff @ 150 psi, 5:30. (I don't need 175 psi, and up to 160 my comp. is rated 24/7/365 operation so why tempt fate?)

My pump specs 635 rpm @ 19.8 cfm @ 150 psi, and lists displacement @ 23.4 cfm - I'm assuming that last figure is free air, but it doesn't say.

My motor pulley is just under 8", and the pump pulley is right at 20", it uses two belts and motor draws right at 22 amps running.

I would think that either your pump is designed to run quite a bit faster than mine (it is, according to that spec sheet), your belts are slipping, or you're about to find out how to rebuild an air pump

Wish I had better news; Personally, I'd make sure belt isn't slipping and try a larger motor sheave before I gave up and dug in further... Steve

Thanks for doing that test. I wish I could find a displacement specification for my compressor head. That would tell me a lot.

 

[BukitCase]

That spec sheet I linked on page 2 STILL doesn't make any sense to me - if you do the math based on a 1725 rpm motor, the pump speed is only HALF what the spec sheet says it is - makes me wonder if that compressor actually comes with a 3450 rpm motor. That would make the pump speed what's listed on the sheet.

I wouldn't expect your pump to put out quite as much as mine, it's listed as 15 cfm @ 175 and mine's listed as 19.1 @175.

Still, with it taking so long to come up to 120, it HAS to be either belt slippage, rpm, bad pump, or a combination. I'd probably try at least half again the diameter sheave if you can find one - you might not want to go to the full rated rpm of that pump, but I'd consider at least 3/4 of rating and see what happens... Steve

 

[unfinished]

Pistons are 3" and 1.75" with 2.75" stroke.

 

[Iplayfarmer]

Pistons are 3" and 1.75" with 2.75" stroke.

Awesome. How did you find that?

 

[Iplayfarmer]

Awesome. How did you find that?

Wait... I figured out where you got it from...

INGERSOLL-RAND Air Compressor Pump, 2 Stage - Air Compressor Pumps - 4KR37|2340 - Grainger Industrial Supply

BukitCase's link on page 2

A theoretical CFM at 1575 rpm with a 3" X 2.75" cylinder is 17.7 CFM and the spec puts it at 15 CFM. 85% efficiency

My 956 RPM should theoretically produce 10.74 CFM and my actual is about 7.25. 68% efficiency.

There are two take home messages...
1) I need a bigger pulley on the motor to get up to 1575 RPM. (or keep my eyes out for a 3520 rpm motor)
2) This pump is not as efficient as it should be indicating that a rebuild will likely improve performance.

How big of a deal is it to rebuild a pump?

 

[BukitCase]

Ingersoll Rand 234: Type 30 Model 234 Parts & Kits

Google is yer friend - I typed in Ingersol-Rand 234 pump repair kit and this was on the first page :thumbsup:

To save money, I would probably try the "two part compression test" I always use on engines - part 1, normal compression test - part two, repeat immediately after squirting 2-3 healthy squirts of oil into the cylinders - in this case, it might not be quite as easy as removing the "spark plugs" :laughing:

The first test gives you a baseline, the second one (usually) tells you either (a) compression did NOT get better, so it's likely the valves, or (b) compression DID get better, so it's likely the rings.

Although, from past experience, if the piston pins had circlips and were floated, and the circlips in one cylinder had gone away, and the result was a 1/4" deep groove in front and back wall of the cylinder that was suspiciously the same width as the piston pins, then this test won't help (DAMHIKT)

hth... Steve

Oh, forgot to mention - Nooo, I've not rebuilt an air pump yet - but keep in mind, that's basically all an internal combustion engine is - in fact, you can buy kits (or used to be able to) to convert a small block V8 into a 4 cylinder (self-contained) air compressor...

 

[Iplayfarmer]

Ingersoll Rand 234: Type 30 Model 234 Parts & Kits

Google is yer friend - I typed in Ingersol-Rand 234 pump repair kit and this was on the first page :thumbsup:

To save money, I would probably try the "two part compression test" I always use on engines - part 1, normal compression test - part two, repeat immediately after squirting 2-3 healthy squirts of oil into the cylinders - in this case, it might not be quite as easy as removing the "spark plugs" :laughing:

The first test gives you a baseline, the second one (usually) tells you either (a) compression did NOT get better, so it's likely the valves, or (b) compression DID get better, so it's likely the rings.

Although, from past experience, if the piston pins had circlips and were floated, and the circlips in one cylinder had gone away, and the result was a 1/4" deep groove in front and back wall of the cylinder that was suspiciously the same width as the piston pins, then this test won't help (DAMHIKT)

hth... Steve

Oh, forgot to mention - Nooo, I've not rebuilt an air pump yet - but keep in mind, that's basically all an internal combustion engine is - in fact, you can buy kits (or used to be able to) to convert a small block V8 into a 4 cylinder (self-contained) air compressor...

Nice visual on the piston pin grooves in the cylinder wall.

In pondering your 2 part compression test and your comparison to an internal combustion engine I wonder if "Mechanic in a Can" or "Marvel Mystery Oil" would work in a compressor to boost compression.

 

[unfinished]

My pump (234c2) had the displacement stamped on the dataplate. They've stopped doing that on the newer ones. It matches the grainger info.

That link at grainger, says 15 CFM free air. So CFM would be less @120 or @175psi.

My pump was on a 60 gallon tank, and I remember it being slow to fill up from empty. But to go from 120 to 150psi, where the pressure switch was set to, was not bad at all.

I would not tear the pump apart. Try sandblasting with it first, 80 gallons is a fair amount of air. Might have to stop for a little bit every so often to let the pump catch up. For hobby use, it might be okay.