Back-Up Rings

Hard rubber molded contoured Back-Ups are routinely produced in a 90 durometer Nitrile and Viton. 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. Back-up Rings are used in conjunction with O-rings and seals for both static and dynamic sealing applications. They prevent extrusion of the O-ring or seal when it is subjected to high pressure, and/or larger extrusion gaps. The back-up ring should be used on the opposite pressure side of the seal. For seals that are exposed to pressure from both sides, two back-up rings should be used, one on each side of the O-ring or seal.