The structure and principle of expansion joints are different according to different materials. The following is a detailed introduction of metal expansion joints and non-metal expansion joints:
Structure and principle of metal expansion joint:
Metal expansion joints are mainly used to compensate the deformation of pipelines, containers and other equipment due to temperature changes or mechanical vibrations. Its main structures include bellows type, braided type, spherical type and hinged type, etc.
The bellows expansion joint consists of flanges at both ends, middle bellows and compensation shaft. When the pipe or container is subjected to thermal expansion and cold contraction deformation, the bellows absorbs the stress caused by the deformation by axial or transverse expansion and contraction, so as to achieve the compensation effect.
The braided expansion joint consists of flanges at both ends, braided bodies, guiding devices and the like. The woven body is woven from stainless steel wire and can absorb displacement and deformation in various directions.
The spherical expansion joint consists of two hemispheres and a flange that are capable of rotating and tilting to absorb the deformation when the pipe or vessel is deformed.
The hinge type expansion joint consists of two end flanges, hinges, inner sleeve, etc. The hinge causes the angle change at the end of the inner sleeve to absorb the deformation.
The working principle of metal expansion joint is mainly to utilize the expansion and contraction, elasticity and flexibility of metal materials. When the temperature in the piping system increases, the metal expansion joint is free to expand, absorbing the amount of thermal expansion; When the temperature drops, it can freely shrink, absorbing the amount of heat shrinkage. In addition, metal expansion joints can also absorb vibrations in the pipe system and change the direction of the pipe, thus protecting the proper operation of the pipe system.
Structure and principle of non-metallic expansion joint:
The non-metallic expansion joint is mainly used to compensate the axial, angular, lateral and combined displacements of pipelines caused by thermal deformation, mechanical deformation and mechanical vibration. Its main structure includes skin, stainless steel wire mesh, thermal insulation cotton and other parts.
As the main expansion body of non-metallic expansion joint, the skin is made of multi-layer composite of silicone rubber or high silicon oxide polytetrafluoroethylene and alkali-free glass silk, which is used to absorb the expansion amount and prevent air leakage and rainwater leakage.
Stainless steel wire mesh acts as an inner liner to prevent debris in the circulating medium from entering the expansion joint and prevent the insulation material from being lost.
Thermal insulation cotton takes into account both thermal insulation and air tightness, and is composed of glass fiber cloth, high silicon oxide cloth and various kinds of thermal insulation cotton felt.
The working principle of non-metallic expansion joint is mainly to utilize its own elastic deformation function. When thermal deformation, mechanical deformation or mechanical vibration occurs in the pipeline, the non-metallic expansion joint can compensate these displacements, which can reduce the deformation of the pipeline and improve the service life of the pipeline. At the same time, it also has the functions of sealing, not afraid of impact, vibration and noise reduction, etc.
In summary, the expansion joint plays an important compensation and protection role in the pipeline system through its unique structure and principle, ensuring the normal operation and prolonging the service life of the pipeline system.