Circular ring with an almost perfectly round cross section which is mainly used in fluids technology to seal machine parts when at rest (Figure O 11). Its sealing action is achieved through axial or radial compression of its cross section, which in terms of the initial sealing performance generates the necessary preload. It is made from elastomers based on very narrow tolerances and a very high surface quality. ISO 3601 and DIN 3771 define the main variables and characteristics for O-ring seals. DIN 65 202 and DIN 65 203 refer to O-ring seals used in aviation and space travel.
Figure O 11: O-ring seal