The oil-free 
screw compressor element
No oil means that there is no Oil-free Screw Air Compressor china essential oil for sealing the rotors and for cooling the compressed air flow, components and rotors. … The element is definitely cooled by cooling water that flows through particular pockets in the component casing.
In a lubricated screw compressor, the lubricant will come in direct in touch with the compressor inlet air and compressed air. … The essential oil contains anti-oxidants to try to reduce the break down of the lubrication properties due to internal conditions.