Backup Rings
Backup Rings are contoured to fit around o-rings in a groove. In high pressure situations, this can be helpful if there is a pressure differential between the two sides of the seal. This is normally done to make up for an o-ring without a high enough durometer or hardness. Softer o-rings will extrude more quickly than harder ones. High pressure differential can cause the o-ring to extrude and eventually cause the seal to fail.
Pressure applied evenly to both sides of a seal normally has no effect on sealing performance. Substantial improvement in extrusion resistance is attainable by 1) using harder O-rings, 2) decreasing the diametral clearance, or 3) using contoured hard rubber or plastic back-up rings. O-rings with high modulus and hardness are better able to resist extrusion. The higher the modulus of a material, the greater the force required to stretch it. Similarly, the harder the material, the greater its resistance is to indentation.
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Backup rings are available in:
- Rubber(buna, viton)
- Teflon
- Urethane
- Peek or Polyether ether ketone
- Leather
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