The oil-free screw compressor element
No oil means that there is absolutely no essential oil for sealing the rotors and for cooling the Oil-free Screw Air Compressor china compressed air, elements and rotors. … The element can be cooled 
by cooling water that flows through particular pockets in the element casing.
In a lubricated screw compressor, the lubricant will come in direct in contact with the compressor inlet air and compressed air. … The oil contains anti-oxidants to attempt to reduce the breakdown of the lubrication properties because of internal conditions.