What Causes Oil Carry-Over in Compressed Air Systems?

If you are having issues with your compressed air system, then it is likely due to excessive oil carry-over. Oil carry-over is a common problem in rotary screw air compressors. There are several causes of oil carry-over. Luckily, there are ways to fix these problems and prevent them in the future.

Key Takeaways

  • Oil carry-over occurs when the oil that is used to lubricate your air compressor makes it past the separator filter and into the pipes.
  • The main causes of oil carry-over are excess oil in the reservoir, low temperatures, faulty separator filters and scavenge lines, and oil degradation.
  • Issues can be prevented by monitoring your compressor’s temperature, checking the separator filter and scavenge line, and replacing the oil once a year.
  • C&B Equipment is the go-to company for air compressor repairs and maintenance. Take a look at our services page and contact us to receive a FREE quote.

What Is Oil Carry-Over?

Oil carry-over is when the oil that is used to lubricate compressors makes it past the separator filter and into the discharge piping. Problems related to oil-carry over have increased due to widespread use of electronic components in compressed air systems.

Excessive oil carry-over can be very expensive, especially when you consider the high cost of lubrication. In addition, carry-over can cause other issues within your rotary screw compressor. The oil can mix with any dirt, rust, or water that is present in your system. This sludge-like mixture has a tendency to clog the air compressor, which can lead to repairs and maintenance.

The Main Causes of Oil Carry-Over

There are five common causes of oil carry-over in compressed air systems.

  • There is too much oil in the reservoir
  • The temperature is too low
  • The separator filter is not working properly
  • The scavenge line is clogged
  • The oil has degraded over time

Too Much Oil in the Reservoir

If you or somebody else has been filling the oil reservoir too high, this could lead to oil carry-over. When there is too much oil in the reservoir, it has nowhere to go but downstream. Once the oil levels are back to normal, it will stop. Until then, this will cause oil to enter the discharge piping.

Temperature Is Too Low

If your rotary screw compressor is running too cold, then this could lead to oil carry-over. Ideally, your compressed air systems should always be running between 185 and 190 degrees Fahrenheit. Anything below these temperatures is too cold and will prevent your system from pulling the oil out.

Faulty Separator Filter

The separator filter is crucial to your compressed air system working properly. If your system has a faulty separator filter, then this can lead to oil carry-over. The purpose of the separator filter is to pull the oil from the compressed air and return it to the lubrication system.

Typically, the air that leaves the separator tank will have around two to three parts per million (PPM) of lubricant carry-over. If there is a significant increase in this oil carry-over, then you should have the separator filter replaced.

Clogged Scavenge Line

The scavenge line is located at the bottom of your air compressor’s separator filter. Its purpose is to recirculate the oil that has been pulled out of the air by the separator. Sometimes the scavenge line will become clogged, leaving the oil with no place to go but downstream. If this happens, it could lead to excessive oil carry-over.

Degradation of Oil

The degradation of oil over time can also cause problems within your air compressor. The oil in your compressed air system should not go more than a couple of years without being serviced. Oil that is very old will fail to lubricate properly and will lose its viscosity. This can lead to oil carry-over.

How You Can Prevent It

The most effective way to prevent oil carry-over in your air compressor is to address the aforementioned issues on a regular basis. In addition, only experienced personnel should handle the maintenance of your compressed air systems. This will prevent human errors like filling the reservoir too high.

Be sure to regularly check the temperature of your system and make sure it is within that sweet spot of 185 to 190 degrees Fahrenheit. Periodically check the separator filter and its scavenge line to make sure that both are in working order. Finally, you should replace the oil on an annual basis to ensure that it does not degrade and lose its viscosity.

Recommended Read A Complete Guide to Industrial Air Compressors

Schedule Repairs and Regular Maintenance with C&B Equipment

As an authorized repair facility for many brands, C&B Equipment can offer you top-notch air compressor repairs and maintenance. We work with any brand of compressor and offer regular preventive maintenance programs to ensure that your equipment is always in working order.

When checking your compressed air systems, we’ll make sure that the separator filter and scavenge line are working properly and check to make sure that your oil does not need to be replaced.

Take a look at our air compressor services page and contact us to receive a FREE quote!

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