Piston Ring Museum

Technologies that Assure Ring Function

C-2 Gas Sealability (2)Ring Side Face Flatness

In addition to requiring excellent roundness, the ring must also be designed such that there is the right gap or contact between the piston groove and the piston ring to assure proper gas sealing.

Gas Sealability (2)Ring Side Face Flatness

At the figure to the right, piston ring seals tightly against the cylinder and the piston to prevent combustion gas leak.Combustion gases leak only from open joints of piston rings.
It is important that the piston ring seal tightly against the piston during piston movement or else combustion gases will leak . For this reason, the top and bottom surfaces of the piston ring are precision ground to a smooth surface roughness of approximately 1 micrometer. This "flatness" ensures tight seating in the piston groove and good sealing characteristics.