PAB Profile Positively-Actuated Back-Up

PAB Profile Positively-Actuated Back-Up

PAB Profile Positively-Actuated Back-Up


Description

While modular back-ups require an increase in groove width to be incorporated into the sealing system, because they are integrated with the seal positively-actuated back-ups do not change the required axial groove width. For many profiles, these back-ups can provide the ultimate extrusion resistance while retaining the seal’s original groove dimensions. While the most common material used to manufactured positivelyactuated back-ups is nylon, it is not uncommon to see applications that require materials such as UltraCOMP, PTFE or polyacetal.

Due to the nature of this product line and the design relationship between the back-up and the seal, parts are sold only as part of an assembly that includes the seal design best suited to the application.

Positively-actuated back-ups can be incorporated into profiles such as the BPP and BD. Tooling may be required.

Back-up 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. Back-up 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. Back-ups 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.

When to Use Back-Up 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.

Standard Materials

  • Rod
    • R0 (Virgin PTFE)
    • R1 (Nylatron)
    • R12 (PEEK)
  • Piston
    • P0 (Virgin PTFE)
    • P1 (Nylatron)
    • P12 (PEEK)
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