Sealing performance of metal seals under extreme conditions

Metal seals are widely used in extreme working conditions, such as aerospace, nuclear industry, petrochemical industry, and high-speed and high-temperature equipment, due to their excellent high-temperature resistance, high-pressure resistance, and corrosion resistance. The following is an analysis of the sealing performance of metal seals under these extreme conditions.

1. High-temperature resistance

Material selection: Metal seals are usually made of high-temperature alloys (such as nickel-based alloys, stainless steel, etc.) to ensure structural stability in high-temperature environments.

Thermal expansion: Materials expand at high temperatures, which requires a proper gap between the seal and the flange mating parts to avoid excessive tightening or deformation caused by high temperatures.

Sealing pressure: Under high temperature conditions, the compression of the seal usually increases, so it is necessary to calculate a reasonable compression amount during design to ensure sealing performance.

2. High-pressure resistance

Design pressure: The design of metal seals must take into account the working pressure. Finite element analysis (FEA) is usually used to simulate the behavior of the seal under high pressure to ensure that it does not fail under explosion or pulsating pressure.

Sealing geometry: The use of appropriate geometric shapes (such as "V" or other spiral shapes) can improve the ability to resist high pressure, thereby enhancing sealing performance.

Material strength: The material of the seal ring must have sufficient strength and toughness to withstand the high pressure applied externally without breakage or leakage.

3. Corrosion resistance

Chemical compatibility: Select materials that are compatible with the working medium to ensure that they will not be corroded in a corrosive environment. For example, use corrosion-resistant materials such as stainless steel or Hastelloy.

Coating protection: In some cases, the corrosion resistance of metal seals can be enhanced by coatings (such as PTFE coatings) to avoid direct contact with corrosive media.

Environmental monitoring: Regularly monitor the chemical composition in the working environment so that the seal design or material selection can be adjusted in time to ensure sealing performance.

4. Resistance to extreme temperature changes

Thermal cycle performance: Metal seals need to maintain performance under frequent thermal cycles, and thermal fatigue and thermal stress of the material need to be considered during design.

Dynamic performance: Under temperature changes and vibration conditions, the seal ring needs to maintain good dynamic sealing performance to avoid leakage caused by thermal expansion or contraction.

Long-term stability: Under extreme temperature changes, the physical and chemical properties of the material need to remain stable to prevent aging, brittleness or other performance degradation.

5. Dynamic sealing performance

Moving end seal: In dynamic applications, metal seals need to withstand the influence of relative motion (such as rotation and reciprocating motion), and appropriate friction characteristics and wear resistance should be considered during design.

Dynamic load: Under high-speed working conditions, the sealing effect of the seal may be affected by out-of-position loads and boundary sliding, so an appropriate sealing lubrication scheme needs to be specified.

Gas leakage: Under gas dynamic conditions, it is necessary to ensure that the metal seal exhibits good airtightness under working speed and medium conditions through testing and analysis.

6. Testing and verification

Under extreme conditions, the performance of metal seals needs to be rigorously tested and verified:

Pressure and temperature cycle test: Simulate actual working conditions and test the performance of the seal under pressure and temperature changes.

Leak detection: Use airtightness or liquid tightness test to evaluate the sealing performance.

Fatigue test: Repeated loading test of metal seals to evaluate their durability and fatigue performance.

Conclusion

The sealing performance of metal seals under extreme conditions depends on many factors such as material selection, design geometry, working pressure and temperature, and corrosion resistance. Through reasonable design, optimized materials and rigorous testing, the long-term reliability and excellent performance of metal seals in aerospace, nuclear industry and other fields can be ensured.

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