The most complete expansion joint classification knowledge points

An expansion joint is a flexible element that can effectively compensate for axial deformation. For example, the expansion joint welded on the fixed tube plate radiator shell has large axial flexibility and is easy to deform. It can compensate for the thermal expansion difference between the tube and the shell due to different wall temperatures, reduce their axial load, and reduce the pipe, The temperature difference stress between the tube sheet and the shell can avoid strength damage, instability damage and pipe pull-off damage. There are many types of expansion joints. The commonly used structures are corrugated, ring-to-plate welding and sandwich type. Among them, corrugated expansion joints are the most widely used, and ring-to-plate welded expansion joints are only suitable for normal pressure or low pressure occasions.

Material and classification of expansion joints:

Metal expansion joint

① Elbow expansion joint

Bend the tube into a U shape or other shape, also known as a tension bend. It is an expansion joint that uses the elastic deformation ability of the body to compensate. Its advantages are good strength, long life, and can be made on site, but its disadvantages are large space occupation, high consumption of steel and high frictional resistance. This kind of expansion joint is widely used in various steam pipelines and long pipelines.

② Bellows expansion joint

Bellows expansion joint is an expansion joint made of metal bellows. It can expand and contract along the axis of the pipe and also allow a small amount of bending. Bellows expansion joint shows a common axial bellows expansion joint used for axial length compensation on the pipeline. In order to prevent exceeding the allowable compensation amount, protective rods or protective rings are arranged at both ends of the bellows, and guide brackets are arranged on the pipes at both ends connected with it. In addition, there are corner and lateral expansion joints, which can be used to compensate the corner deformation and lateral deformation of the pipeline. The advantages of this type of expansion joint are space saving, material saving, easy standardization and mass production, but the disadvantage is that the service life is short. Bellows expansion joints are generally used on pipelines with low temperature and pressure and short lengths. With the improvement of the production technology level of bellows, the application scope of such expansion joints is expanding. At present, bellows expansion joints can be used in piping systems with a maximum pressure of 6.0 MPa.

③ Sleeve expansion joint

The casing expansion joint is composed of inner and outer casings capable of relative axial movement. A stuffing box is used to seal between the inner and outer casings. When in use, keep both ends of the tube moving on an axis. The product is mainly composed of sleeve (core tube), shell, sealing material, etc. It is used to compensate the axial expansion and contraction of the pipeline and the axial rotation of any angle. It has the characteristics of small volume and large compensation amount. It is suitable for hot water, steam and grease. The medium, through the sliding movement of the sliding sleeve to the outer sleeve, achieves thermal expansion compensation.

The inner sleeve of the sleeve-type compensator is connected to the pipeline, and adopts the principle and structure of high-performance self-pressure dynamic seal. It can slide freely in the casing with the expansion and contraction of the pipeline, and can meet the sealing requirements of any pipeline. The inner sleeve is sealed with a new type of synthetic material, which can withstand high temperature, anti-corrosion and anti-aging. The applicable temperature is -40 to 150, and can reach 350 in special cases. It can not only ensure axial sliding, but also ensure that the medium in the pipe does not leak.

Non-metallic expansion joints

① Rubber air duct expansion joint

The air duct compensator is divided into four types: FDZ, FVB, FUB and XB. It is composed of rubber and rubber-fiber fabric composite materials, steel flanges, sleeves, and thermal insulation materials. It is mainly used for various fans and air ducts. The functions of the flexible connection between them are shock absorption, noise reduction, sealing, medium resistance, easy displacement and installation.

② Fiber fabric expansion joint

The fabric compensator is mainly made of fiber fabric, rubber, and other high temperature resistant materials. It can compensate the vibration of fans and air ducts and the deformation of pipes. Fiber fabric expansion joints can compensate axial, lateral, angular and other products, and have the characteristics of no thrust, simplified bearing design, corrosion resistance, high temperature resistance, noise reduction and vibration reduction, etc., especially suitable for hot air ducts and smoke and dust ducts in power plants. The fiber fabric and thermal insulation cotton body in the non-metal compensator have the functions of sound absorption and vibration isolation, which can effectively reduce the noise and vibration of boilers, fans and other systems. Simple structure, light body and easy maintenance.