This specification and part standard covers polytetrafluoroethylene (PTFE) resin material and the dimensional requirements for retainers (back-up rings) previously covered by MIL-R-8791 and MIL-R-8791/1. The retainers are intended for use in hydraulic and pneumatic system components as anti-extrusion devices in conjunction with packings and O-rings.

Use

Retainers to the dimensions in this specification are for use in glands to MIL-G-5514 (formerly MIL-P-5514C, D and E Revisions) (Cancelled). They may also be used in glands to AS4716, however, please refer to the Caution and Important Note below.

Caution: Parts standard AS5781 for back-up rings for use in glands to AS4716 has been published. For new design, backup rings to AS8791 should not be used in AS4716 glands.

Important Note: The dimensional requirements of this specification are the same as former Military Specification MIL-R-8791/1*. As such, no attempt has been made to ensure the lap of the scarf-cut ends is adequately designed to be functionally satisfactory at low temperatures or to cater for cylinder expansion (breathing) due to pressure effects. Users should ensure satisfactory performance by testing at the appropriate low temperature for each application.

* With the exception of dash sizes 004, 005, 006 where the angle of the scarf-cut has been changed for reasons of manufacturability.

MIL-R-8791 (cancelled) and AS8791 (original issue) were used for the material specification for back-up rings to MIL-R-8791/1 (cancelled) and the following military standards that are inactive for new design: MS27595, MS28773, MS28774, MS28782, MS28783. This specification (AS8791) should be used as the material call-out for the standards listed above.