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Document Number: Tech. Argument _007 The impact of oil-lubricated versus oil-free lubrication on air valves. Whether the compressor cylinders are lubricated with oil or not is one of the important factors to consider when designing air valves. When selecting metal diaphragm air valves, for oil-lubricated applications we usually use valves with a center-guided design, while for oil-free lubrication we use valves with a center-fixed design (guided by guide arms). Valves with a center-guided structure cannot be used for oil-free lubrication due to friction between the metal valve disc and the guide ring. When selecting pneumatic valves with non-metallic valve discs, thanks to the self-lubricating properties of these materials, most valve types such as CS, CX, and CE can be used whether lubricated with oil or without it; however, the CT valve is only suitable for lubrication with oil. Furthermore, in addition to affecting the choice of valve type, the amount of lubricating oil also influences the selection of spring force. When there is an ample amount of lubricating oil, a stronger spring force is required to overcome the viscous resistance of the oil, which causes delayed closure of the gas valve. The lubrication condition of the compressor should not be changed arbitrarily; if a change is necessary, the valve design must be reviewed to make the appropriate adjustments to the valve structure and spring force as required. * Note: Oil-lubricated and oil-free lubrication also have a significant impact on piston rings and packing rings.