Back-Up Rings Overview
Back-up rings, also known as anti-extrusion rings, are used in sealing applications for rods or pistons to prevent the extrusion of sealing elements like O-rings or X-rings under high pressure. They are applicable in both dynamic and static settings.

Advantages
Back-up rings enhance the lifespan of O-rings and X-rings by protecting them from impurities and expanding their application range. They are cost-effective solutions for conditions involving pressures over 50 bars, large tolerances, high speeds, pressure changes, and wide temperature variations.

Types of Back-Up Rings
There are three standard profiles:

• AES: Spiral form, made of PTFE, suitable for static and dynamic use, and can be adjusted for non-standard diameters.
• AEM: Rectangular cross-section, available in virgin or filled PTFE-PU-PA-NBR90, suitable for reciprocating and rotating movements.
• AEC: Concave cross-section, made of NBR90–FPM 90-virgin or filled PTFE-PU, designed for reciprocating movements and high pulsating pressures.

Installation Recommendations
Installation guidelines are similar to those for O-rings. Non-cut back-up rings require special tools for installation in closed grooves, involving expansion with a cone and recalibration.

Materials and Pressure Ratings
Back-up rings are made from various materials like virgin PTFE, glass-filled PTFE, carbon-filled PTFE, bronze-filled PTFE, NBR 90 SH, and FPM 90 SH. Each material has specific pressure ratings, with PTFE variants supporting up to 400 bars.

Installation Dimensions
Dimensions for installation are provided as guidelines and should be validated through testing. The document includes detailed tables with dimensions for different back-up ring types and their corresponding O-ring sizes according to AS568A standards.

Specifications
The document provides detailed specifications for a series of back-up rings and O-rings, including their dimensions and corresponding item numbers. The data is organized in a tabular format, listing dimensions for each item.

Procedures
The document does not explicitly outline procedures but provides a comprehensive list of dimensions for various back-up rings and O-rings, which can be used for selection and application in relevant engineering tasks.

Standards
The O-ring dimensions are specified according to the AS568 A standard, ensuring compatibility and standardization across applications.

Key Data
The document includes a series of item numbers (e.g., AEC00318, AEC00319) with corresponding dimensions. For example, AEC00318 has dimensions 25.73 x 35.03 x 1.52 mm for the back-up ring and 24.77 x 5.33 mm for the O-ring.

Recommendations
Users should refer to the item numbers and dimensions to select the appropriate back-up rings and O-rings for their specific applications, ensuring they meet the required standards and specifications.