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.

Purpose:

The purpose of this document is to provide information that will aid design engineers and maintenance personnel in the selection and use of TFE backup rings (retainers) and backup ring materials for aircraft and aerospace hydraulic and pneumatic fluid power applications.