ingersoll rand rotary screw compressor getting aerated

by herb elsner
(furlong pa)

hi,my compressor oil is getting airiated i changed the fluid and spin on filter with ingersoll parts and it still does it.i know its air because when i drained it and let it sit for a few days it went back to dark colored from white

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Nov 15, 2015
Second thought
by: Carl

Maybe ive missed the point.....

You say its airiated? Do you mean air is in the oil as in tiny air bubbles? If that's what you mean then that is exactly what it's supposed to do, like i said in my previous comment, air is mixed with the oil in the separator which causes air bubbles, looking in the sight glass it can look milky or white but these are just the tiny air bubbles and nothing to worry about.

Doug, it shouldn't be anything to do with the scavenger tube, all that does is scavenge any oil that may creep through the separator element and sucks it back into the system. If the sep element is new then it wont have any oil to suck so it wouldn't matter if there isn't any oil going through the scavenge tube.

The screw is lubricated by the oil going from the sep tank through the oil filter then into the screw, from there to the cooler (when the thermo valve opens) and back to the tank.

If there is a lack of oil going into the screw then it would overheat, hence one of the reasons why you replace the oil filter every 2000 running hours.

Hope that helps


Nov 14, 2015
by: Carl

I'm not exactly sure what you mean by "airiated"?

Do you mean emulsified by water in the oil? If so, then i am guessing that your compressor is used but doesn't run very frequently?

What i mean by that is, the compressor is run when you're using it but for what air you need, it runs for 10-20 minutes?

With screw compressors, the compressed air that is made by the screw is transferred into the vessel where the oil is (separator vessel) contains moisture. If the compressor isn't ran to temperature for a period of time then the oil gets emulsified and goes white in colour (the same as a car engine that is only used to go to the shops a few times a week).

What you can do is run your compressor every one or few weeks on full load (leave a few air guns on) then it should clear your oil of moisture.

Hope that helps.


Nov 13, 2015
by: Doug in

You refer to the screw's oil, yes?

Assuming it's the right oil, possibly the scavenger tube is not set right, causing a bit too little oil on the screws, allowing air to blow by, contaminating it.

Good luck.

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