What are the requirements for the sealing rings used in aircraft?

The sealing rings used in aircraft need to meet multiple requirements including extreme environment adaptability, material performance optimization, reasonable sealing structure design, strict manufacturing and inspection, as well as standardized installation and maintenance. The specific details are as follows:

I. Adaptability to Extreme Environments

1. High Temperature Tolerance: During the launch and re-entry stages, the aircraft will experience extreme high temperatures, such as up to 300°C during the launch phase and over 1000°C for the cabin skin during re-entry. Therefore, the sealing ring must have excellent high-temperature tolerance to ensure it does not fail under high temperatures.

2. Low Temperature Tolerance: When facing the sun away, the external temperature can drop to -120°C. The sealing ring must be able to maintain elasticity at low temperatures to prevent hardening, brittleness, and cracking.

3. High Vacuum Tolerance: In the near-Earth orbit and other high-vacuum environments, the sealing ring must prevent gas volatiles from contaminating the cabin environment, ensuring the normal operation of key components such as optical systems.

4. Radiation Tolerance: The aircraft will be exposed to particle penetration radiation in space. The sealing ring must have anti-radiation properties to prevent material performance degradation.

II. Material Performance Requirements

1. High-temperature-resistant materials: Such as silicone rubber, fluorine rubber, and perfluorinated ether rubber. These materials can maintain stable performance at high temperatures and have good chemical corrosion resistance and low gas permeability.

2. Low-volatile materials: To meet the requirements of high vacuum environments, the sealing ring material must have low volatility to prevent gas volatiles from contaminating the cabin environment. For example, developing "clean" silicone rubber to solve the volatilization pollution problem of silicone rubber in high vacuum.

3. Metal sealing materials: Such as copper and soft aluminum, which have gas volatiles thousands of times smaller than vacuum rubber and are suitable for scenarios with extremely high requirements for gas volatiles.

III. Sealing Structure Design

1. Removable Sealing Structure: Many sealing areas in manned spacecraft use removable sealing connections. This sealing can be end-face sealing or radial sealing, and the sealing ring can be axially or radially compressed.

2. Sealing Ring Cross-Section Shape and Groove Design: The cross-sectional shape and groove shape of the sealing ring can be different. The simplest shape is a circular ring or rectangular cross-section. In two对接flanges， one can be made into a stepped， circular， or rectangular cross-section. The elastic deformation force of the sealing ring is designed to allow it to return to its initial state， maintaining pressure at the connection point and generating sufficient sealing performance on the sealing surface when the height or cross-sectional width of the gasket is compressed to 30% - 40%.

3. Flange Connection Design： Flange connections are usually tightened until the shell or joint parts are in contact. The cross-sectional dimensions of the connecting flange need to be designed according to certain principles， that is， when the pressure difference between the inner and outer sides increases by 0.1 MPa， the increase in the gap between the sealing surfaces should be within the range of 0.1 - 0.2 mm.

IV. Manufacturing and Testing Requirements

1. Manufacturing Tolerance Control： During the manufacturing of the sealing ring， the size tolerance and surface quality must be strictly controlled to ensure reliable assembly.

2. Reliability Verification： The finished product must undergo reliability verification such as air tightness testing， low pressure testing， and ozone aging tests to ensure the maintenance of sealing integrity throughout the entire life cycle.

V. Installation and Maintenance Requirements

1. Correct Installation： During installation， ensure that the size and shape of the sealing ring meet the requirements， avoiding damage during the installation process. Before installation， clean the sealing surface to ensure it is free of impurities and scratches. Use appropriate tools during installation to avoid excessive compression or stretching of the sealing ring.

2. Regular Inspection and Replacement： During use， regularly inspect the performance of the sealing ring. If any aging， deformation， or wear is found， replace the sealing ring promptly.

3. Use Special Cleaning Agents and Lubricants： During maintenance， use special cleaning agents and lubricants to avoid using chemical substances that corrode the sealing material.

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