Tips for selecting expansion joints

An expansion joint or movement joint is an assembly designed to safely absorb the heat-induced expansion and contraction of construction materials, to absorb vibration, to hold parts together, or to allow movement due to ground settlement or earthquakes. They are commonly found between sections of buildings, bridges, sidewalks, railway tracks, piping systems, ships, and other structures.

An expansion joint consists of a bellows (a kind of elastic element), a bracket, a flange and connectors at both ends, which is also a kind of compensating component. An expansion joint uses effective deformation of its bellows to compensate expansion and contraction of a pipeline and a vessel caused by heat and cold due to temperature variation. An expansion joint can be used for compensating axial, lateral and angular displacement of a pipeline and a vessel, and it can also be used for reducing noise and vibration, which make an expansion joint widely used in modern industry. When temperature goes up in heat supply pipelines, the expansion joint should be installed on the pipeline in order to prevent the pipeline being deformed or destroyed due to expansion caused by heat or temperature stress.

The expansion joints can compensate expansion caused by heat so as to reduce stress of walls of pipes and acting force on valves and brackets. As an important part for pipework, the expansion joint plays an important role in ensuring the long-term normal operation of the pipeline.

Building faces, concrete slabs, and pipelines expand and contract due to warming and cooling from seasonal variation, or due to other heat sources. Before expansion joint gaps were built into these structures, they would crack under the stress induced.

Tips for selecting expansion joints

Expansion joints have rectangular sections and waveform with similar shape. A single expansion joint in the pipe bears two-dimensional displacement. The pipeline comprising two expansion joints can bear three-dimensional displacement. Metal expansion joints could be classified into full-height expansion joints and half-height expansion joints.

1. After the user pick the appropriate expansion joint in accordance with the thermal displacement of the piping system, they have to provide details about the medium from the pipe, design pressure of the duct, the greatest temperature during operation, the general dimension of sections of the duct, the chosen waveform and the quantity of the waveform to be able to design and manufacture structure of expansion joints.

2. The maximum allowable expansion of each waveform

Full-height type: △α = ± 24 mm  Half-height: △α = ± 12 mm.

3. The ash board: For pipes with less dust, the ash board doesn%u2019t need to be utilized for flue pipes with much dust, the ash board ought to be adopted.

4. In order to reduce the number of the waveform, we have to take into account the cold-drawn process for expansion joints.

5. Expansion joints are suitable for pipes whose cross-sectional areas are less than 4.6 square meters and one side of the overall dimension of the air and flue gas duct which is less than 1.5m but greater than 0.6 mm. Standard full-height expansion joints can be applied to all air and flue gas ducts.

Source: China expansion joints Manufacturer – Yaang Pipe Industry Co., Limited (

(Yaang Pipe Industry is a leading manufacturer and supplier of nickel alloy and stainless steel products, including Super Duplex Stainless Steel Flanges, Stainless Steel Flanges, Stainless Steel Pipe Fittings, Stainless Steel Pipe. Yaang products are widely used in Shipbuilding, Nuclear power, Marine engineering, Petroleum, Chemical, Mining, Sewage treatment, Natural gas and Pressure vessels and other industries.)

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