What is an expansion joint?

Release time:

2021-03-22

Expansion joints are commonly referred to as compensators or expansion bellows. They consist of a corrugated tube—a flexible element—that forms the core working component, along with end pipes, supports, flanges, guide tubes, and other accessories. An expansion joint is a flexible structure installed on vessel shells or pipelines to compensate for additional stresses caused by temperature differences and mechanical vibrations. By utilizing the effective expansion and contraction deformation of its main component—the corrugated tube—it can absorb dimensional changes in pipelines, conduits, vessels, and other components resulting from thermal expansion and contraction, or compensate for axial, lateral, and angular displacements in these systems.

　　Expansion joints are commonly referred to as compensators or expansion bellows. They consist of a corrugated tube—a flexible element—that serves as the primary working component, along with end pipes, supports, flanges, guide tubes, and other associated accessories. An expansion joint is a flexible structure installed on vessel shells or pipelines to compensate for additional stresses caused by temperature differences and mechanical vibrations. By utilizing the effective expansion and contraction deformation of its main component—the corrugated tube—it can absorb dimensional changes in pipelines, conduits, vessels, and other components resulting from thermal expansion and contraction, or compensate for axial, lateral, and angular displacements in these systems.

　　It can also be used for noise reduction, vibration damping, and heating systems. To minimize pipe deformation or damage caused by thermal expansion or temperature stresses when heating pipelines, compensators need to be installed on the pipelines to accommodate thermal expansion, thereby reducing stress on the pipe walls and the forces acting on valves and support structures.

　　As an elastic compensation element capable of free expansion and contraction, expansion joints boast excellent operational performance and a compact structure, and have thus been widely adopted in sectors such as chemical engineering, metallurgy, and nuclear energy. Expansion joints used on vessels come in various forms; among them, U-shaped expansion joints are the most commonly employed, followed by Ω-shaped and C-shaped joints. As for expansion joints used on pipelines, from the perspective of structural compensation, they can be categorized into universal-type, pressure-balanced type, hinge-type, and universal joint-type expansion joints.

　　An expansion joint is a flexible component designed to accommodate axial deformation. For example, an expansion joint welded onto the shell of a fixed-tube-sheet heat exchanger has high axial flexibility and is easily deformable, enabling it to compensate for the thermal expansion differential between the tubes and the shell caused by differences in wall temperatures. This reduces the axial loads on both the tubes and the shell, thereby minimizing thermal stress differences and decreasing the likelihood of strength failure, instability, or tube pull-out failures. There are various types of expansion joints; commonly used ones include bellows-type, ring-plate welded, and clamp-shell types. Among these, bellows-type expansion joints are the most widely applied, while ring-plate welded expansion joints are suitable for applications involving atmospheric or low-pressure conditions.

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