ALEMITE Stewart-Warner Compressor

by Larry Jewett
(Leeds, Maine)

ALEMITE Stewart-Warner Compressor schematic

ALEMITE Stewart-Warner Compressor schematic

I just acquired an Alemite compressor that was manufactured in 1973. It is a UCD Series. I would like to find some information on how the compressor works.


It took over 10 minutes to build up 150# of pressure. I am trying to determine if this slow rate of pressure build up is correct for this compressor.

I am used to my Lowes compressor (both 60 gal tanks) building pressure in less than 5 minutes.

I am also trying to determine if the compressor needs any type of rebuilding. I would like to troubleshoot it myself, but am unsure of how it works. It is a lot more complex than my Lowes, because it has a centrifugal unloading circuit.

thanks

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Jan 09, 2019
Curtis
by: Larry

And this is a 2 stage, correct?

Jan 08, 2019
Curtis
by: Doug in s.d.ca.

Yes, they make good stuff.

First, you're sure you took all of the bolts out, right?

There all sorts of things that may work, depending on the machine.

For instance, you might try getting the bolts finger tight and running it a few seconds.

And/or a putty knife or similar to pry it loose.


Good luck.

Jan 08, 2019
Thank you...
by: Larry

Thank you Doug. I'm thinking that this is a pretty good compressor. The compressor unit was made by CURTIS of St. Louis. Looks more like a commercial unit than typical homeowner.

I have pulled the head bolts in order to check the valves, put the head doesn't want to come off. Not sure what the problem is. Maybe just stuck, but I don't want to break anything.

Jan 07, 2019
ALEMITE questions
by: Doug in s.d.ca.

Larry - good questions.

"Don't you need to know the cylinder displacement to multiply by the revs to determine the output?"

A:Yes, it's on the drawing, if I read it right - 4.5 bore by 3.5 stroke.

"And then how do measure the output to make sure that the rings are not worn?"

A:By seeing if the output goes significantly down with increasing pressure.

"Is there a quicker way to measure output than to measure when tank is full at a specific pressure?"

A:Yes, by checking at 1 bar gauge, which is absolute 2 bar. That should be under a minute, tops. probably closer to 30 seconds, unless the pump is way shot, or it's running way low RPMs.

Jan 06, 2019
Alemite
by: Larry Jewett

Don't you need to know the cylinder displacement to multiply by the revs to determine the output?

And then how do measure the output to make sure that the rings are not worn?

Is there a quicker way to measure output than to measure when tank is full at a specific pressure?

Jan 06, 2019
ALEMITE Stewart-Warner unloader
by: Doug in s.d.ca.

You can search for centrifugal unloader and look at some of the images - the weights force the valve closed when it's running fast enough, and the spring forces them back open when it slows or stops. The details vary, but that's the general idea.

As to the build time, it depends on the RPM of the pump. You can figure that out with the RPM of the motor and the pulley diameters. There are on-line calculators to make that easy.

4.5 x 3.5 ~ a bit less than a quarter gallon per rev. so your 60 gallon tank should go from empty to 1 bar (about 14.5 PSI) in about 420 revolutions.

The rate may or may not slow down at higher pressure.

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