||The choice of metal (grey cast iron", cast chromium alloy, steel, bronze,...) depends on the operating temperatures, specific pressures, operating environment, working life required.
||The rectangular cross-section fulfils all sealing functions. The K and HK cross-sections offer extended ring working life. The L form improves contact with the bottom edge of the cylinder in 2-stroke engines and offers a high level of protection against flutter.
||The type B optimises wearing in and favours correct dispersion of the oil film in the top section of the cylinder. The bevelled form (M) increases the specific contact pressure and thus accelerates wearing in and obtaining of adequate sealing. It also helps regulate oil consumption. In the case of combined wipers, the bevelled surface form enables extremely accurate control of oil film thickness in particular on compressors.
|Edges and lips
||Exterior chamfers (KA) facilitate passage of openings on 2-stroke engines, simplify assembly and increase the specific pressure by decreasing the support surface. Interior chamfers (Kl) must only be used for safety or assembly reason (groove base radius). The lips (IF or IW) modify the specific contact pressure at the top of the ring enabling a rectangular ring to act as a bevelled ring.
||Depending on the ring working life required and the friction difficulties encountered (1° groove), a hard chromium (CR) plating may be applied.
||The specific contact pressure (p) between a ring and the cylinder may be increased by inserting a spiral spring (SF) in the ring bore or by placing a steel blade between the ring bore and the base of the groove. This method is used for slit wiper regulators (S, G and D) and on compression rings for 2-stroke engines.
||The vertical cut (VER) is suitable for all thermal and compression applications. The oblique cuts (OBG and ÔBD) are intended to decrease possible wear on the cylinder by the ring ends. The bayonet (SV) and hook (SH) cuts are only used on hydraulic applications. They have practically no effect on sealing. The hooks are useful in the case of complex mechanical assembly. The notches (NE and NH) are used on rings for 2-stroke engines and enable indexing of the ring with a pin.
||Phosphating of the ring facilitates wearing in and offers excellent protection against oxidation.