O-rings and back-up rings

O-rings are one of the most common sealing solutions. SKF supplies O-rings in a wide range of sizes and different materials, which make them appropriate for a wide variety of operating conditions and applications. They are easy to install and they enable a simple and cost-effective seal housing design.
O-rings maintain sealing contact force by radial or axial deformation in the seal housing between two machine components. The most important criteria that influence the maximum operating pressure at which O-rings in static radial sealing can be used are the following:
  • extrusion gap (fig. 1)
  • material (→ Materials)
  • sealed fluid
  • temperature
Under specific conditions, there is a risk for gap extrusion (→ Extrusion gaps and back-up rings). Back-up rings prevent O-rings from gap extrusion in static radial sealing (fig. 1).
O-rings are used in a wide variety of applications sealing various media. This section focuses on sealing systems for hydraulic cylinders. Therefore, this section and provided recommendations apply to static sealing of common mineral-based hydraulic fluids (→ Hydraulic fluids).
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