This AIR documents the methodologies used to calculate the dimensions and tolerances used in the following backup rings standards: • AS5781 • AS5782 • AS5860 • AS5861 In addition, an appendix is provided which provides details of gland and backup ring design practices.
Previous parts standards that were originally developed for backup rings used dimensions that were based only on the fit to hardware and O-ring dimensions at ambient. However, backup rings to AS5781, AS5782, AS5860, AS5861 were designed to suit practical operating conditions and machining capabilities of the material. Thus, there is a requirement for a document that provides the means to determine the dimensions for these backup rings. This document has been compiled to meet this need.