Dynamic O-ring sealing applications

Dynamic O-ring sealing applications are considerably more involved than static applications due to the implied motion against the O-ring seal interface. Resistance to fluids must be more carefully scrutinized than in conventional static seal designs since a volumetric increase in the O-ring in excess of approximately 20% may lead to friction and wear difficulties, and only a minimum of shrinkage (at most 4%), can be tolerated. The metal or other surface over which the O-ring will move also becomes critical. It must be hard and wear resistant. It also must be sufficiently smooth so that it will not abrade the rubber, and yet there must be small microfine “pockets” on the moving surfaces to hold lubricant. The greatest dynamic use of O-rings is in reciprocating hydraulic rod and piston seals. These are discussed first, but many of the ideas expressed are also applicable to other dynamic applications. Considerations applying only to other types of dynamic seals are discussed in greater detail later in the section.