Expansion joint is a kind of flexible element which can effectively compensate the axial deformation. For example, the expansion joint welded on the shell of fixed tubesheet heat exchanger has large axial flexibility and is easy to deform, which can compensate the thermal expansion difference between the tube and shell due to different wall temperature, reduce their axial load, reduce the temperature difference stress of the tube, tubesheet and shell, and avoid strength failure, instability failure and tube pull-out failure. There are many kinds of expansion joints, such as wave, ring plate welding and shell clamp structure. Among them, wave expansion joint is the most widely used, and ring plate welding expansion joint is only suitable for atmospheric pressure or low pressure.
