expansion joint

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I. Function of expansion joints Expansion joints are commonly used pipe connectors whose purpose is to compensate for the deformation of pipes caused by thermal expansion and contraction at different temperatures, thereby ensuring the proper operation of the piping system. In pipeline systems, due to temperature changes, the pipes expand when heated and contract when cooled; this can have a significant impact on the pipeline system and may even lead to its damage. The function of expansion joints is to absorb the expansion and deformation of the pipes through their own ability to stretch and contract, thereby ensuring the normal operation of the pipes. II. Placement locations of expansion joints: Expansion joints are generally installed at locations where the pipeline is bent, deformed, or subjected to rapid temperature changes. They are typically placed at elbows in horizontal pipelines and above vertical pipelines. When installing expansion joints, the following points should be taken into account: 1. The length of the expansion joint should be determined based on the designed expansion amount of the pipeline, with a certain margin generally reserved ； 2. The installation location of the expansion joint should avoid areas where the pipeline vibrates or is subject to external forces ； 3. The connection between the expansion joint and the pipeline should have a certain degree of adjustability, so that fine adjustments can be made during installation ； 4. When installing expansion joints, relevant specifications and standards should be followed to ensure the safe operation of the pipelines. III. Installation process of expansion joints When installing expansion joints, the following steps should be followed: 1. Leave sufficient installation space at the designated location on the pipeline ； 2. Before installing the expansion joint, it is necessary to inflate or fill it with water to ensure that it has a certain degree of flexibility after installation ； 3. Connect the expansion joint to the pipeline, ensuring the sealing and reliability of the connection ； 4. Adjust the position of the expansion joint so that it can expand and contract as the pipeline expands and contracts ； 5. Check the installation of expansion joints and pipelines to ensure their quality and reliability. IV. Precautions for expansion joints 1) Only one expansion joint (or one set of angular expansion joints) can be installed between two fixed pipe supports. 2) Compared to rigid pipes, corrugated expansion joints are much easier to install, as they can compensate for any deviations in the pipeline. However, this does not mean that there can be no requirements for pipeline installation. Because if a large amount of displacement has already occurred during installation, its service life will be affected during operation. Therefore, in principle, it is not recommended to use expansion joints to compensate for installation errors. 3) Generally, the expansion joints in their basic form mentioned above do not absorb torque; therefore, it is not allowed for the expansion joint to be twisted during installation. 4) The fixed support must have sufficient strength to ensure that the expansion joint is not damaged. The guide bracket must have sufficient guiding capability; otherwise, it will affect the transmission of pipeline displacement. 5) Pre-tensioning or cold straining of expansion joints: To ensure that the bellows expansion joints can compensate within the specified range of the structure and to reduce their deformation stiffness forces, the expansion joints in their supplied state should be pre-deformed according to the installation temperature at the site. Installation precautions: 1) The pipes must be well aligned; when other methods cannot ensure proper alignment, the method of laying straight pipes and then cutting a section to install an expansion joint can be used to achieve this. 2) During installation, the bellows should be protected to avoid any damage to it. 3) For expansion joints with guide sleeves, the direction of guidance should be consistent with the flow direction of the medium. 4) After installation, the pre-tensioning rods and transportation fixing rods should be removed to allow the pipeline to expand and contract in response to changes in ambient temperature. 5) The supports must meet the design requirements; it is strictly prohibited to conduct pressure testing in the pipelines before the supports are properly installed, to avoid damaging the expansion joints. 6) The insulation layer should be applied on the outer protective cover of the expansion joint, and must not be placed directly on the bellows. Insulation materials containing chlorine shall not be used. 7) The expansion joint permits a system pressure test at no more than 1.5 times the nominal pressure. 8) When operating pipelines equipped with expansion joints, valves should be opened and closed gradually to prevent sudden changes in temperature and pressure within the pipeline, which could cause damage to the supports or expansion joints.