This SAE Aerospace Recommended Practice (ARP) provides an overview of the various types of polytetrafluoroethylene (PTFE and TFE) back up rings for hydraulic and pneumatic fluid power applications, including their advantages and disadvantages.
The backup ring is defined. The various types designed for use with O-rings in MIL-G-5514 packing glands, and MS33566 and MS21344 universal fitting installations are described. Guidelines are included for selecting backup rings and backup ring materials. Backup ring installation procedures and precautions are described.
This document establishes standard gland dimensions for static radial O-ring seal applications and provides recommendations for modifying these glands in applications. No provisions are made in this document for anti- extrusion devices. SI unit conversions for U.S. customary units have been provided for reference purposes.