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.
This SAE Aerospace Recommended Practice (ARP) contains guidance regarding hardware design and installation procedures for seals in hydraulic components that utilize standard seal glands in accordance with AS4716, AS4832, AS4088, AS4052, AS5857, and AS6235.
This SAE Aerospace Standard (AS) specifies standardized gland design criteria and dimensions for static face seals for internal pressure and external pressure applications for aerospace hydraulic and pneumatic applications using the same size range as AS4716 and AS5857 where applicable. Some small diameter sizes are excluded because they are not practical. The glands have been specifically designed for applications using AS568 size elastomeric O-rings with related Class 2 tolerances at nominal system operating pressures up to 3,000 psi (20,680 kPa) utilizing no anti-extrusion (backup) rings. While the gland dimensions herein have been designed for pressures up to 3,000 psi (20,680 kPa) these glands may be used for higher pressures, but extra precautions need to be taken and testing should be performed to ensure integrity of performance.
The purpose of this report is to provide design, application and maintenance engineers with basic information on the use of metallic Spring Energized sealing devices when used as piston (OD) and rod (ID) seals in aircraft fluid power components such as actuators, valves, and swivel glands. The Spring Energized seal is defined and the basic types in current use are described. Guidelines for selecting the type of Spring Energized seal for a given design requirement are covered in terms of friction, leakage, service life, installation characteristics, and interchangeability. Spring Energized seals can also be made in various forms and types, including face seals (internal and external pressure sealing types), and rotary variants too. These further types will not be discussed in this document, but many of the same principles apply for them as well.
This SAE Aerospace Standard (AS) covers solid polytetrafluoroethylene (PTFE) retainers (back-up rings) for use in static glands in accordance with AS5857. They are for use in hydraulic and pneumatic system components as anti-extrusion devices in conjunction with O-rings, packings and other elastomeric seals. Because of the construction of groove dimensions, back-ups specific to rod applications are designated “R” - Rod (Female), back-ups specific to piston applications are designated “P” - Piston (Male). Retainers specified herein have been designed for a temperature range of −65 to 275 °F (−54 to 135 °C) and a nominal operating pressure of 3000 psi (20 684 kPa) for code 09 material and 5000 psi (34 474 kPa) for code 10 material. Material codes are based on AMS3678 material types.