Oil at Unloader Valve ?

by David
(Sacramento)

Hello,
Compressor airs up fine however at restart it trips the electrical breaker.

I examined the unloader valve.

Oil was found seeping from the tube that runs from the head into the valve.

Is this common ?

Is this problem ?

Cleaned the valve but compressor still trips the electrical breaker at restart.

Cleaned again and found more oil.

Is the compressor in need of rings or a filter or something ?

Any advise is appreciated.

David

___________________________
Bill says...

David, many interesting questions. Regarding the oil from the unloader valve...

Is this common ? NO

Is this problem ? YES

Is the compressor in need of rings or a filter or something ? LIKELY

It seems to me that this oil is interfering with the normal function of your unloader valve. If the compressor doesn't unload, a too great amperage draw on start up commonly blows breakers.

This oil is migrating out of your compressor head, into the tank, into the unloader valve and unloader valve line, and ultimately it's getting out of the tank, downstream to your applications.

By and large, compressor oil is detrimental to other air components. It is compressor oil, not air valve oil, or air tool oil. They are different animals.

In a reciprocating compressor, oil is used to lubricate the running of the crank, piston rod and piston as the piston cycles in the cylinder. A lack of lubrication can cause failure.

It's the piston rings (seals) that keeps the oil below them, and if these seals are failing, oil migrates past them and into the air stream.

Even new compressors have some wicking of compressor oil past the seals, as some oil remains on the surface of the cylinder to be exposed to the air being compressed into the tank.

In your compressor, the amount of oil getting into the compressed air suggests a significant seal failure, in my opinion. It's likely time to tear the compressor pump down to see what's what.

Cheers,

Bill










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Oil at Unloader Valve ?

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Oct 07, 2010
 Hillbilly Ring Test
by: David

Thanks Bill,
I took the head apart and found one broken valve flapper.
Then I took the compressor into the middle of the yard and fired it up with the head off. I wanted to see how much oil was getting past the rings. To my surprise there was no noticeable oil flinging everywhere. Everything stayed really clean. Last night I ordered new valve flappers and gaskets.

I was thinking of ordering a new pressure switch and unloader valve.
The unloader valve I have doesn't have a side hole for the air to escape. When I manually push the small wire pin and blow into the valve there it doesn't allow air through. I'm thinking the unloader valve is bad. To be safe I was thinking of throwing a new pressure switch on it too.

Any thoughts to my assumption ?


_____________________
Bill says...

Since I don't know how much oil is wicking by, it may not be "flinging", simply building up on the wrong side of the piston and leaking from the reed valve.

Your unloader valve must unload when the pressure switch turns the compressor off, or you may have problems on start up. So, if it's not unloading, and cleaning it doesn't solve the problem, change it.

As to the switch, if the one you have is working, I wouldn't change it on my compressor. Good to have one as a spare though.

Cheers,

Bill

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