A piston ring is a metal ring used to be embedded inside the piston groove. There are two types of piston rings: compression rings and oil rings. The compression ring can be used to seal the combustible mixture gas inside the combustion chamber; The oil ring is used to scrape off excess oil from the cylinder.

A piston ring is a metal elastic ring with significant outward expansion deformation, which is assembled into the corresponding annular groove of the cross-section. A piston ring that undergoes reciprocating and rotating motion, relying on the pressure difference of gas or liquid, forms a seal between the outer surface of the ring and the cylinder, as well as between the ring and one side of the ring groove.

Piston rings are widely used in various power machinery, such as steam engines, diesel engines, gasoline engines, compressors, hydraulic presses, etc., and are widely used in automobiles, trains, ships, yachts, etc. Generally, the piston ring is installed in the ring groove of the piston, and it forms a chamber with the piston, cylinder liner, cylinder head and other components to do work

The working surface of the piston ring shall not have scratches, abrasions, or peeling. The outer cylindrical surface and upper and lower end faces shall have a certain degree of smoothness, and the curvature deviation shall not exceed 0.02-0.04 millimeters. The standard sinking amount of the ring in the groove shall not exceed 0.15-0.25 millimeters. The elasticity and clearance of the piston ring shall comply with the regulations. In addition, the light leakage of the piston ring should be checked by placing it flat inside the cylinder, placing a small light bulb under the piston ring, and a light shielding plate on top. Then, observe the light leakage gap between the piston ring and the cylinder wall to determine whether the contact between the piston ring and the cylinder wall is good. In general, the leakage gap of the piston ring measured with a thickness gauge should not exceed 0.03 millimeters. The length of continuous light leakage gaps should not exceed one-third of the cylinder diameter, the length of several light leakage gaps should not exceed one-third of the cylinder diameter, and the total length of several light leakage gaps should not exceed half of the cylinder diameter. Otherwise, they should be replaced.