Sealing systems in which the sealing gap between two sealing surfaces is sealed to a greater or lesser extent by a sealing element that touches both surfaces. The related deformation is applied by screw force (metal rings) or by the pressure of the medium (elastomer seals).
These sealing elements are predominantly elastic in fluid technology and made of elastomers or thermoplastics (materials for seals). In addition metal seals are used for special application conditions; the sealing action on these seals is achieved by spring action or plastic deformation. The former include piston rings as well as grooved ring seals made of hard brass (for very high temperatures). These seals are also suitable for sealing moving surfaces. However this statement does not apply to soft metal seals with plastic deformation.