Structure and design of metal bellows

Metal bellows is a flexible tubular structure, which is widely used in the fields of pipeline compensation, shock absorption, sealing and displacement absorption. Its structural design directly affects its performance and service life. The following is a detailed introduction to the structure and design points of metal bellows:

1. Structure of metal bellows

Waveform:

U-shaped bellows: The most common waveform, with good displacement compensation ability and small stress concentration.

V-shaped bellows: Used in occasions where large displacement compensation is required, but the stress concentration is large and the fatigue life is relatively low.

C-shaped bellows: Simple structure, suitable for small displacement compensation and low stress environment.

Geometric parameters:

Wave height (H): The vertical distance from the crest to the trough of the bellows, which directly affects the displacement capacity and stiffness of the bellows.

Wave pitch (P): The horizontal distance between two adjacent wave crests. The smaller the wave pitch, the better the flexibility of the bellows.

Wall thickness (t): The thickness of the bellows wall. The larger the wall thickness, the higher the bearing capacity and stiffness of the bellows.

Inner diameter (D): The inner diameter of the bellows, which directly affects the size of the pipe it adapts to.

2. Design points of metal bellows

Material selection:

Stainless steel (such as 304, 316L): has good corrosion resistance and mechanical properties, suitable for most industrial applications.

Alloy steel (such as Inconel, Hastelloy): suitable for high temperature, high pressure and strong corrosive environment.

Titanium alloy: has excellent corrosion resistance and high strength, suitable for marine engineering and chemical industry.

Stress analysis:

Elastic stress: The bellows will be subjected to axial, radial and bending stresses during use. Detailed stress analysis is required during design to ensure that it works within a safe range.

Fatigue life: The bellows are prone to fatigue failure in long-term reciprocating motion, and reasonable design parameters need to be determined through fatigue life analysis.

Seal design:

End connection: The connection method between the bellows and the pipeline (such as welding, flange connection) needs to ensure good sealing performance.

Crest and trough seal: The sealing design at the crest and trough needs to consider the preload and the performance of the sealing material to prevent leakage.

Displacement compensation capability:

Axial compensation: The design of the bellows needs to consider its axial displacement compensation capability to ensure its normal operation in the thermal expansion and contraction of the pipeline and mechanical vibration.

Radial compensation: In some applications, the bellows also need to have radial displacement compensation capability to adapt to the complex movement of the pipeline.

3. Design process

Demand analysis: Clarify the use environment, working conditions and performance requirements of the bellows.

Material selection: Select suitable metal materials according to the use environment and performance requirements.

Geometric design: Determine the geometric parameters of the bellows such as waveform, wave height, wave distance, wall thickness and inner diameter.

Stress analysis: Stress distribution and fatigue life analysis are performed through finite element analysis and other methods.

Seal design: Design the connection method and sealing structure between the bellows and the pipeline.

Manufacturing process: Determine the manufacturing process (such as spinning, hydraulic, roll forming) and heat treatment process of the bellows.

Performance test: Perform performance test on the manufactured bellows to verify the rationality of the design parameters.

4. Design tools and methods

Finite element analysis (FEA): used for stress distribution, deformation analysis and fatigue life prediction of bellows.

Computational fluid dynamics (CFD): used for fluid flow and pressure distribution analysis inside bellows.

Computer-aided design (CAD): used for 3D modeling and geometric parameter design of bellows.

5. Conclusion

The structure and design of metal bellows is a complex process involving material selection, geometric design, stress analysis, sealing design and manufacturing process. Through scientific and reasonable design, the performance and service life of bellows can be improved to meet the needs of various industrial and civil fields. In the future technological development, with the application of new materials and new manufacturing technologies, the design of metal bellows will continue to develop towards high performance, high reliability and intelligence.

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