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Valves & Fittings

Back-up Rings

Reliably Prevent Gap Extrusion

Back-up rings do not have a sealing function but are used to prevent gap extrusion. They can be used in combination with O-rings or X-rings, both for static and dynamic loads. Back-up rings prevent the seal from extruding into the sealing gap and thus enable sealing of higher media pressures. They are often used in applications with pulsating or varying pressures, such as hydraulic valves and pumps, cylinder bases and heads.

Benefits at a Glance

  • Prevent gap extrusion
  • Combinable with O-rings or X-rings
  • Different product variants to fit your application
  • Good lifetime
  • Very good price-performance ratio
  • Suitable for many industrial applications

Important note: Dichtomatik products comply with common industrial standards and therefore are suitable for many applications excluding safety-critical ones like Automotive. Premium Freudenberg products are the right choice for all applications ensuring highest quality and safety standards and therefore optimal total cost of ownership.

Backup Rings

Choose the Right Product

Out of a Three Types

  • STR END (endless) and STR GS (30° slotted) made of POM
    (temp.: -50 to +90 °C) for use in mineral oils, fats and pressure media HFA, HFB, HFC
  • STR END (endless) STR GS (30° slotted) made of PTFE
    (temp.: -200 to +260 °C) shows broad resistance to acids, bases, alcohols, oils and pressure fluids 
  • STU (endless with concave molding) made of NBR
    (temp.: -30 to +100 °C) for use in hydraulic oils, mineral-oil based lubricants, non-flammable hydraulic pressure fluids (max. +50 °C) and water (max. +80 °C)

Please note that resistances, pressures and temperatures are mutually influenced by various parameters.

    Related Documents

  • Brochures 66-plus 67-minus


    Product Overview - Dichtomatik Brand

    Tailor-Made Seals and Service Portfolio

    English | PDF | 4228 KB

  • Solutions Sheets 66-plus 67-minus


    Backup Rings

    STU-type backup rings are used in combination with radial-sealing O-rings to prevent gap extrusion (extrusion of seals into the sealing gap).

    English | PDF | 97 KB

Product Portfolio

Sealing products setting benchmarks

Premium products and individual sealing solutions of the Freudenberg brand are the perfect choice for any application. Uncompromising quality (0-defect strategy) and excellent performance ensure full safety and optimized total cost of ownership (TCO).

Freudenberg Product Portfolio 70-external-link