This article is about the mechanical seal. For other uses, see Oring.
Typical O-ring and application
An O-ring, also known as a packing or a toric joint, is a mechanical gasket in the shape of a torus; it is a loop of elastomer with a round cross-section, designed to be seated in a groove and compressed during assembly between two or more parts, forming a seal at the interface.
The O-ring may be used in static applications or in dynamic applications where there is relative motion between the parts and the O-ring. Dynamic examples include rotating pump shafts and hydraulic cylinder pistons. Static applications of O-rings may include fluid or gas sealing applications in which:
(1) the O-ring is compressed resulting in zero clearance,
(2) the O-ring material is vulcanized solid such that it is impermeable to the fluid or gas, and
(3) the O-ring material is resistant to degradation by the fluid or gas.
The wide range of potential liquids and gases that need to be sealed has necessitated the development of a wide range of O-ring materials.[2]