O-ring is a kind of rubber seal ring with rounded section. Because of the O section, it is called O seal ring or O-ring. It appeared in the 19th century and was used as sealing component of steam engine cylinder at that time.
O-ring is suitable for a variety of machineries and equipments and plays the role of sealing under specified temperature and pressure in different liquids and gases under stationary or motion state. There are a variety of potted components used in machine tools, shipping, automobile, aerospace equipment, metallurgical machinery, chemical machinery, engineering machinery, construction machinery, mining machinery, petroleum machinery, plastic machinery, agricultural machinery and kinds of instruments. O-ring is mainly used in static seal and reciprocating seal. In rotating movement seal, it is only for low speed rotary sealing arrangement. O-ring is usually installed in the rectangular section of excircle or inner circle. It has good sealing and cushion function in oily, acidic, alkaline, frictional, chemical attacking environments. So O-ring is a widely used sealing element in hydraulic pressure and pneumatic transmission system.