Oil Carryover in Screw Compressor

Oil carryover in screw compressor

What is oil carryover?
Oil carryover refers to the phenomenon of excessive lubricating oil mixed in compressed gas, which will cause a sharp drop in the amount of oil in the lubrication system and pollute the back-end equipment. In severe cases, it will damage the air compressor. In twin-screw compressors, the failure of the oil film seal in the meshing gap between the yin and yang rotors is the fundamental cause, which is specifically manifested as oil mist at the exhaust port. Long-term operation will cause bearing wear and decreased heat exchange efficiency.


Causes of oil carryover in screw compressors

1. Failure of the oil separation system
When the separator core is damaged, the oil-gas mixture directly passes through the exhaust pipe

After the separation core made of glass fiber is perforated, the separation efficiency drops by more than 60%

Typical symptoms: The exhaust oil content suddenly increases to more than 300ppm, which is hundreds of times higher than the normal value range.

2. Blockage of the oil return line
Blockage of the oil return line will cause the oil to be unable to flow back to the compressor, and it will be discharged with the gas after accumulation. It is necessary to check the patency of the pipeline, clean the blockage or replace the damaged parts.

3. Improper pressure control of air compressor system
If the system pressure is too low, the centrifugal force of the separator will be insufficient and the oil-gas separation will not be complete. The system pressure needs to be adjusted to the rated range and the minimum pressure valve needs to be ensured to work properly.


4. Lubricant quality
Aging, oxidation or impurities in lubricant will cause coking and emulsification, reduce the lubrication effect and cause oil entrainment. Qualified lubricants need to be replaced regularly to avoid using inferior oils.

5. Incorrect oil position
The oil level should be kept below the center line of the window. Excessive oil filling will increase the separation load by 35%.

Daily maintenance tips
Regularly clean up impurities in the oil circuit, check the sealing, replace aging parts filters, filter elements, etc., to ensure that the oil level is normal and there is no leakage. Doing these well will greatly avoid oil carryover in screw air compressor.