I Just Got a New Air Compressor

[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.