Piston rings are used for sealing cylinders. They can work at higher temperatures than elastomeric, fabric, or polymer seals.
Piston ring seals are very important for the efficient performance of combustion engines. Damaged or leaking piston rings can lead to hot exhaust escaping the cylinder and entering the crankcase of the engine, contaminating the engine oil and causing carbon to build up on the pistons. This decreases engine efficiency and can ultimately lead to damage of engine components.
Two main types of piston rings are used in combustion engines: compression rings and oil control rings. Both types of piston rings are available from suppliers in North America and around the world. Compression rings and oil control rings that bear the CE Mark or meet specifications from the Society of Automotive Engineers (SAE) are also available.
Different engines require different piston ring design. Piston rings are installed in special grooves that are cut around the circumference of the piston. Compression rings are typically fitted in the upper part of the piston with the oil control ring groove below the compression rings. The oil control ring groove is wider than the compression ring grooves and has holes cuts in the bottom of the groove for oil to drain to the interior of the piston.
An industrial piston ring may be constructed of a high performance material such as graphite or special high temperature polymers. Industrial piston rings include rings for many kinds of engines, including the large bore, two-stroke engines used in cargo ships. Piston rings developed for these large engines are typically cast in a foundry and made of cast iron. A foundry piston ring may also be made of graphite iron or other iron alloys.
DIN 34110 - Piston rings for general engineering.
GOST 621 - Piston rings for internal combustion engines.
ISO 6621-4 - Piston rings for internal combustion engines.