The oil-free screw compressor element
No oil implies that there is no oil for sealing the rotors and for cooling the compressed air flow, elements and rotors. … The element is certainly cooled by cooling water that flows through unique pockets in the element casing.
In a lubricated screw compressor, the lubricant comes in direct in contact with the compressor inlet air and compressed air. … The oil contains anti-oxidants to Oil-free Screw Air Compressor attempt to reduce the break down of 
the lubrication properties because of internal conditions.