Backup Rings
Back-up rings are installed to prevent the extrusion of an elastomeric O-ring in its housing groove under certain operating conditions.
Materials
Back-up rings are usually manufactured in virgin PTFE. Other filled PTFE and Plastics are also available depending on the application.
Back up rings are also available in NBR and Viton 90.
Spirals
Spiral back-up rings enables the back-up ring to be opened with ease for fitting over a shaft, and ensures the 'O' ring is supported around its entire diameter.
Solid/Solid splits
Solid single turn back-up rings can also be supplied, and these are usually endless to ensure good support. However, they can be scarf split if required.
Contoured Rubber/Par Backs
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.