Metcar’s self-lubricating, carbon-graphite piston rings and guide rings are used extensively in reciprocating compressors, where oil-free gases, such as air, steam, refrigerants, hydrogen, hydrocarbons, chlorine, nitrogen and oxygen can be compressed to pressures greater than 55bar.
Guide rings can be either solid rings or segmented rings with butt joints. Metcar’s segmented, carbon-graphite, piston 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. At least two rings with off-set segment joints are needed to seal to pressures of 7bar. Extra sets of rings are needed to seal higher pressures.