An expansion joint is an important pipeline fitting. Its primary purpose is to absorb dimensional changes in pipelines, conduits, vessels, etc., caused by factors such as thermal expansion and contraction, or to compensate for axial, lateral, and angular displacements of pipelines, conduits, vessels, etc.

The use of expansion joints can prevent deformation or damage to pipelines due to thermal expansion and contraction, and reduce the stress on pipe walls as well as the forces acting on valves or support structures. In addition, expansion joints can also be used for noise and vibration reduction, facilitating the installation and disassembly of valves and pipelines, absorbing equipment vibrations to minimize their impact on pipelines, and accommodating deformations of pipelines caused by earthquakes and ground subsidence.