water lubricated air compressor
The general mechanism of an air compressor is a piston or rotary element (e.g. rotary screw or vane) that draws in air, which is compressed into a storage tank. Naturally, since the piston or rotary element needs to move consistently and smoothly for this to work, it generally needs to be lubricated.
In a lubricated air compressor, there is lubricating oil which keeps the piston or rotary element running smoothly without damaging the mechanism. The lubricant also helps to dissipate heat and maintain air compression efficiency.
Oil-free air compressors also use a piston or rotary element, but they get around the lubrication problem by coating the compression element with a pre-lubricating material like Teflon. Some oil-free compressors may also use water in place of oil for the lubricating and cooling process. These alternate materials protect the pump and allow the mechanism to move smoothly without the need for any oil-based or synthetic lubrication.