The double-layer structure design of metal expansion joint mainly considers its compensation ability, pressure resistance, sealing performance and service life. Here are some basic design takeaways for double-layer metal expansion joints:
Material selection：
The inner layer is usually made of materials with good corrosion resistance and high temperature stability, such as stainless steel, to adapt to the erosion and temperature change of the internal medium.
The selection of outer material takes more into account external environmental factors, such as atmospheric corrosion, mechanical damage, etc. Stainless steel or other special alloys may also be used.
Bellows design：
The core of a double-layer expansion joint is its bellows part, which generally consists of two layers of bellows, inner and outer. The inner bellows is in direct contact with the working medium and is responsible for withstanding the pressure and temperature changes of the medium; The outer bellows provides additional support and protection while also sharing a portion of the pressure.
The design of corrugations (such as wave height and wave pitch) will affect the flexibility and strength of the expansion joint, and the designer will adjust these parameters according to the specific application requirements.
Connection mode：
The double-layer bellows can be connected by welding or flanging to ensure the close fit and overall stability between the inner and outer layers.
For some application scenarios, it is also possible to add reinforcing rings or other support structures between the inner and outer layers to increase the rigidity and load-bearing capacity of the expansion joint.
Seal design：
In order to prevent leakage, there are usually special sealing measures in the double-layer structure. This may include the use of high-quality sealing rings, packing, or achieving a self-sealing effect by precisely controlling the manufacturing accuracy of the bellows.
Safety considerations：
Failure modes and their consequences, such as setting appropriate fatigue lives and performing pressure tests, should also be considered during design to ensure safe operation even under extreme conditions.
To sum up, the design of double-layer metal expansion joint is a process that comprehensively considers many factors, aiming at improving its functional performance while ensuring the safety and reliability of use. The actual design will also be adjusted and optimized according to specific application scenarios and user needs.