Back-up rings in PTFE material are installed to prevent the extrusion of an rubber O-Ring in its housing groove under certain operating conditions. Two back-up rings one either side of the O-Ring in its housing are needed when the application is double acting.
Back-up rings are supplied as a spiral or endless ,Spiral are of two turns. This 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.
Single turn back-up rings are usually endless to ensure good support. However, they can be scarf split if required, although we do not recommend this because extrusion can occur at the split.
Back-up rings are manufactured in Polytetrafluoroethylene (PTFE) or filled PTFE, depending on the application.