Metcar Piston Rings

Our self-lubricating, carbon graphite piston rings and guide rings are used when there is a need for compressed gases that do not contain oil or grease. In a reciprocating compressor, oil-free gases such as air, steam, refrigerants, hydrogen, hydrocarbons, chlorine, nitrogen and oxygen can be compressed to pressures of over 800 psi. Segmented Metcar carbon graphite rings with overlapped joints are placed in a radial groove in the reciprocating piston with little clearance between the width of the groove and the width of the piston ring. A metal leaf spring expander ring in the ID of the segmented piston ring is used to exert outward force to hold the piston ring OD against the cylinder bore. Wear life up to 10,000 hours is possible when the compressor and piston rings are correctly designed. Carbon graphite piston rings are usually used in conjunction with carbon graphite guide rings or carrier rings. The function of the piston rings is to seal the high-pressure gas, and the function of the guide rings is to hold the piston centered with respect of the cylinder bore. Therefore, the guide ring must be in close contact with the piston and the housing bore. Guide rings can be either solid rings or segmented rings with butt joints.