U-Cup Backup Rings | Zatkoff

U-Cup Backup Rings

U-Cup Backup Rings


  • For 8400, 8500 & E4, E5 Series Rubber U-Cups & PolyPak Seals
  • Piston & Rod for Pressures Over 800 psi
  • Dynamic Extrusion resistance up to 7000 psi*

Backup rings are the most common anti-extrusion devices in dynamic sealing. They provide simple solutions to safely increase system pressure or solve an existing seal extrusion problem. Backup rings function by positioning a more robust material adjacent to the extrusion gap, taking the seal’s place and providing a barrier against high pressures. Backup rings can be used to offset the reduced pressure rating effects of wear rings or to improve seal life at increased pressures. They can also be used to protect seals against pressure spikes, or to ensure seal performance at higher temperatures.

*For U-Cup Backup Ring test results, ask for test report #LT428A


When to Use Backup Rings

  • System operating pressure exceeds the limitations of the seal’s extrusion resistance.
  • Pressure spikes in the system exceed normal operating conditions,risking damage to the seal.
  • The use of wear rings has increased the extrusion gap, reducing the seal’s pressure rating to an unacceptable level.
  • The system temperature is high enough to lower the seal’s extrusion resistance to an unacceptable level.

Backup Material Selection

  • T0125
    25% Glass Filled PTFE Alloy
    Stock Standard Solid
  • Z4651
    Premium Quality Elastoplastic Material
    Non-Standard Material


  • SO (SOLID)