Parker Back-Up Rings

Rubber Back-Up Rings

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. 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. 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.

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MB Profile, Modular Back-up for PolyPak® and U-cup Seals

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Modular back-ups, MB profile, are specifically designed to complement the PolyPak® profiles. To help make the selection and ordering of the correct part number for the MB profile easy and efficient, the part numbering system used is very similar to that of the PolyPak. By formulating high modulus blends of Molythane® (4617) and Polymyte® (4652), Parker has ensured that MB back-ups can be used with either type of base sealing material while maintaining the expected temperature range and fluid compatibility. The robust design ensures pressure ratings up to 10,000 psi are met.

Technical Data

Alternate Materials: For applications that may require an alternate material, please consult ESP.

**7,000 psi (482 bar) with tight-tolerance wear rings.

5,000 psi (344 bar) with standard-tolerance wear rings.

8700 Profile, Low Profile Modular Back-up for PolyPak® and U-cup Seals

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8700 profile back-up rings provide added extrusion resistance to u-cups and PolyPak® seals with only minimal increase in gland width. The 8700 profile back-up was originally designed to dramatically increase the pressure rating of rubber u-cups in situations where temperature or fluid compatibility prevent the use of urethane seals. As such, 8700 profile back-ups share a part numbering system very similar to our 8400 and 8500 profile rubber u-cups for easy matching of components. Additionally, they are perfect for adding heavy duty pressure capabilities to medium duty urethane sealing systems.

Technical Data

Alternate Materials: For applications that may require an alternate material, please consult ESP.

**4,900 psi (337 bar) with tight-tolerance wear rings.

3,500 psi (241 bar) with standard-tolerance wear rings.

5100 Profile (5100 Series), O-ring Groove Back-up

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Parker 5100 profile back-up rings offer extrusion resistance up to 7,000 psi for dynamic applications and up to 20,000 psi for static applications. They are physically interchangeable with most existing o-ring back-ups. Our easy to identify orange colored 4651 Polymyte® material used with this profile, provides outstanding extrusion resistance when compared to hard nitrile back-ups plus offers extended fluid compatibility. 5100 profile back-ups are designed to meet standard industrial o-ring groove dimensions for single or dual back-up o-ring groove designs and will always install in the proper direction.

Technical Data

Alternate Materials: For applications that may require an alternate material, please consult ESP.

**4,900 psi (337 bar) with tight-tolerance wear rings.

3,500 psi (241 bar) with standard-tolerance wear rings.

PAB Profile, Positively-Actuated Back-up

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While modular back-ups require an increase in groove width to be incorporated into the sealing system, PAB profile back-ups do not change the required axial groove width because they are integrated with the seal. 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 manufacture positively-actuated back-ups is nylon, it is not uncommon to see applications that require materials such as PEEK or PTFE.

Technical Data

Alternate Materials: For applications that may require an alternate material, please consult ESP.

**7,000 psi (482 bar) with tight-tolerance wear rings.

5,000 psi (344 bar) with standard-tolerance wear rings.

PDB Profile, PTFE O-Ring Back-up

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PDB profile back-up rings are PTFE anti-extrusion rings. The PDBA and PDBB profiles are designed to retrofit MIL Spec grooves used in commercial applications. PDBA styles are split rings retrofitting MS28774 designs, while PDBB styles are solid rings retrofitting MS27595 designs. Due to the fact that these profiles are designed to commercial grooves, MIL Spec certifications are not available. Although the standard material is virgin PTFE, any of Parker’s available PTFE blends can be used.

Technical Data

Alternate Materials: For applications that may require an alternate material, please consult ESP.

WB Profile, HPHT Back-up

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Parker’s wedged back-up rings extend seal life by preventing extrusion of elastomeric seals in high pressure, high temperature environments. WB profile back-up rings are custom made-to-order and available in a variety of materials depending upon operating conditions. Under high system pressure, the elastomer seal applies an axial force on to the wedged back-up set. This axial force allows the wedged halves of the back-up set to slide apart along their common angle and bridge the metal gland clearance gaps; preventing extrusion of the primary sealing elastomer.

Technical Data

Assumes max. radial e-gap of 0.005″ (13mm), typical gland dimensions without wear rings.

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