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  • Rubber


    Contoured Back-Ups are routinely produced in a 90 durometer Nitrile - Buna-N. This provides sufficient elasticity to permit stretching over the major diameter of a piston and then snapping back into the gland groove cut into the piston. 90 durometer has sufficient hardness to resist extrusion of the softer elastomeric O-Ring performing the actual sealing function against the high pressure liquid or gas.

    - 000 Series O-rings 0.070" ±0.003" - .045" Thick
    - 100 Series O-rings 0.103" ±0.003" - .045" Thick
    - 200 Series O-rings 0.139" ±0.004" - .040" Thick
    - 300 Series O-rings 0.210" ±0.005" - .060" Thick
    - 400 Series O-rings 0.275" ±0.006" - .096" Thick
    NOTE: Sizes (Dash No.) corresponds to standard O-ring numbers.

  • PTFE


    A back-up ring is a ring of hard, extrusion resistant material such as high durometer nitrile, nylon, Hytrel, or PTFE. They are not seals themselves but are usually used in conjunction with O-Rings in high-pressure applications for support or as spacers. 

    A back-up ring is designed to fit between the O-Ring and the extrusion gap and prevent the extrusion of the O-Ring. Back-up rings are installed with O-Rings and X-rings.  They prevent O-Rings from gap extrusion in static radial sealing. The hard back-up ring will keep the O-Ring material from flowing into the gap which will prevent premature failure. 

    NBR backup rings have one side concave to fit the O-Ring. PTFE comes in single turn scarf cut (with an angle cut), solid or a spiral of two turns. 

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