Also known as pipeline expansion joint, expansion joint, compensator, expansion joint. Expansion joints are divided into several types: corrugated expansion joints, sleeve expansion joints, square natural compensation expansion joints, etc. Among them, corrugated expansion joints are more commonly used, mainly for pipeline operation.
Expansion joints are mainly used to compensate for the expansion deformation caused by temperature changes in pipelines, as well as for length compensation required for pipeline installation and adjustment. They are mainly divided into three structural forms: bent pipe expansion joints, corrugated pipe expansion joints, and sleeve expansion joints.
Bend type expansion joint is a type of expansion joint that bends a pipe into a U-shape or other shape (Figure 1 [Bend type expansion joint]) and compensates for it using the elastic deformation ability of the shape. Its advantages are good strength, long service life, and can be made on site, but its disadvantages are large space occupation, high steel consumption, and high frictional resistance. This type of expansion joint is widely used in various steam pipelines and long pipelines.
A bellows expansion joint is an expansion joint made of metal bellows. It can expand and contract along the axis direction, and also allows for a small amount of bending. Bellows expansion joint is a common axial type bellows expansion joint used for axial length compensation on pipelines. In order to prevent exceeding the allowable compensation amount, protective rods or rings are installed at both ends of the corrugated pipe, and guide brackets are installed on the pipes connected to it at both ends. In addition, there are corner and transverse expansion joints that can be used to compensate for the corner and transverse deformations of pipelines. The advantages of this type of expansion joint are space saving, material saving, easy standardization and mass production, but the disadvantage is a shorter lifespan. Bellows expansion joints are generally used on pipelines with low temperature and pressure, and short lengths. With the improvement of corrugated pipe production technology, the application scope of such expansion joints is expanding.
The sleeve expansion joint is composed of inner and outer sleeves that can move axially relative to each other. The inner and outer sleeves are sealed with stuffing boxes. Keep both ends of the pipe moving along the same axis during use. Install guide brackets at both ends of the expansion joint. Its advantages are low frictional resistance to fluid flow and compact structure; The disadvantage is poor sealing and high thrust on the fixed bracket. Sleeve expansion joints are mainly used for water pipelines and low-pressure steam pipelines.