An expansion joint is a flexible component that effectively compensates for axial deformation. For instance, the expansion joint with a high axial flexibility, which is welded onto a fixed tube sheet heat exchanger shell, can easily deform and compensate for the thermal expansion difference caused by different wall temperatures in the tubes and shell, reducing their axial loads. This, in turn, minimizes the temperature difference stress on the tubes, tube sheets, and shell, thus preventing strength failure, instability failure, and tube pull-out failure. There are various types of expansion joints, commonly including bellows, ring plate welding, and cladded types, among which the bellows type is widely used, while the ring plate welding type is only suitable for atmospheric or low-pressure conditions.