Oil appearing at the point of use is a serious problem for product quality and can indicate a failing air/oil separation system. The solution is to identify whether the oil is being carried through the system or introduced elsewhere.

Check the Oil Separator First

• A damaged or collapsed separator element allows oil mist to pass downstream.
• A saturated or clogged separator can also increase differential pressure and oil carryover.
• Replace the separator at the recommended interval or when pressure drop exceeds the limit.
• Inspect the separator housing and sealing surfaces during replacement.

Inspect the Scavenge Line and Check Valve

• The scavenge line returns separated oil from the separator to the airend.
• A blocked line or failed check valve can prevent oil from returning, forcing it downstream.
• Confirm the small orifice or strainer in the line is clean.
• Check for cracked or loose tubing connections.

Other Common Causes

• Overfilled oil creates excessive carryover because the separation space is reduced.
• Incorrect oil grade may foam and increase oil mist generation.
• Operating temperature that is too high reduces separation efficiency.
• Excessive intake restriction or low load can disturb normal separation.

If oil is present only at one machine, inspect the local piping and filter rather than assuming the compressor is at fault. When the problem is confirmed at the compressor discharge, a qualified service provider for oil injected screw air compressor systems should inspect the separator and scavenge circuit.

For applications that cannot tolerate any oil carryover, an oil free rotary screw air compressor may be the correct long-term solution.