The oil-free screw compressor element
No oil implies that there is no oil for sealing 
the rotors and for Oil-free Screw Air Compressor china cooling the compressed air flow, elements and rotors. … The element is usually cooled by cooling drinking water that flows through special pockets in the component 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 due to internal conditions.