Why Most Sleeve Expansion Joints Adopt Welded Connection
author: LIUNA
2025-05-13
Welded connection is the mainstream installation method for sleeve expansion joints, especially for high-temperature, high-pressure steam heating pipelines and buried long-distance piping systems. Flange connection is only used for low-pressure pipelines requiring frequent disassembly. The core reasons are summarized as follows:
1. Superior Pressure and Temperature Resistance
Sleeve compensators are commonly applied in working conditions of 0.6–4.0 MPa pressure and up to 600 °C high temperature.
Flange connections rely on gaskets for sealing. Under long-term high temperature, gaskets will age, creep and lose elasticity; under high pressure, flange bolts tend to stretch and loosen, easily causing medium leakage.
In contrast, welded joints form an integrated metal fusion structure without vulnerable gasket components. They maintain stable sealing performance under extreme temperature and pressure for a long time, achieving the same service life as the pipeline.
Flange connections rely on gaskets for sealing. Under long-term high temperature, gaskets will age, creep and lose elasticity; under high pressure, flange bolts tend to stretch and loosen, easily causing medium leakage.
In contrast, welded joints form an integrated metal fusion structure without vulnerable gasket components. They maintain stable sealing performance under extreme temperature and pressure for a long time, achieving the same service life as the pipeline.
2. Higher Structural Rigidity to Resist Axial Thrust
Thermal expansion of pipelines generates huge axial thrust during operation.
Flange connections bear force only through bolts. Under large axial load, flange faces are prone to deformation and opening gaps, which damages the sealing effect.
Welded ends integrate the sleeve compensator with the whole pipeline. The weld seam uniformly bears axial stress with high overall rigidity. It effectively avoids core tube eccentricity and friction abrasion, ensuring smooth telescopic movement of the sleeve structure.
Flange connections bear force only through bolts. Under large axial load, flange faces are prone to deformation and opening gaps, which damages the sealing effect.
Welded ends integrate the sleeve compensator with the whole pipeline. The weld seam uniformly bears axial stress with high overall rigidity. It effectively avoids core tube eccentricity and friction abrasion, ensuring smooth telescopic movement of the sleeve structure.
3. Perfect Adaptability for Buried Pipeline Engineering
Most municipal heating sleeve compensators are installed underground.
Buried pipelines face long-term soil pressure, foundation settlement and groundwater corrosion. Flange gaskets usually fail within 3–5 years, leading to frequent leakage and high maintenance excavation costs.
Welded joints can be fully protected by anti-corrosion and insulation treatment after welding, with no exposed wearing parts. They realize maintenance-free service for decades and meet the pre-expansion fixation requirements of direct-buried pipeline standards.
Buried pipelines face long-term soil pressure, foundation settlement and groundwater corrosion. Flange gaskets usually fail within 3–5 years, leading to frequent leakage and high maintenance excavation costs.
Welded joints can be fully protected by anti-corrosion and insulation treatment after welding, with no exposed wearing parts. They realize maintenance-free service for decades and meet the pre-expansion fixation requirements of direct-buried pipeline standards.
4. Lower Comprehensive Cost and Simplified Structure
Welded-type sleeve joints omit flanges, high-strength bolts and special sealing gaskets, greatly reducing manufacturing and material costs, especially for large-diameter pipelines.
Welded construction is more efficient for long-distance pipeline projects. Meanwhile, the internal packing sealing structure of the sleeve compensator is completely independent of the end connection mode. Welded installation does not affect later packing replacement and routine maintenance.
Welded construction is more efficient for long-distance pipeline projects. Meanwhile, the internal packing sealing structure of the sleeve compensator is completely independent of the end connection mode. Welded installation does not affect later packing replacement and routine maintenance.
5. Higher Operational Safety
The medium of thermal pipelines is mostly high-temperature hot water or steam. Flange connections have multiple leakage risks including gaskets, bolt holes and sealing surfaces, which may cause scalding accidents and pipeline damage.
Qualified welded seams form an integral metal seal with only one connecting interface, which greatly reduces leakage risks and improves the overall safety and stability of the piping system.
Qualified welded seams form an integral metal seal with only one connecting interface, which greatly reduces leakage risks and improves the overall safety and stability of the piping system.
Difference Between Full face Rubber Expansion Joint and Grooved Rubber Expansion Joint (Performance & Application)
Standard No. CJ/T 487-2015 Fabricated Sleeve Compensators for Urban Heating Pipelines
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When selecting pipeline expansion components, many engineering purchasers and designers notice a common phenomenon: stock sleeve expansion joints on the market mostly adopt 200 mm as the basic axial compensation stroke, while the single-unit compensation capacity of conventional bellows expansion joints generally ranges from 50 mm to 120 mm. This difference is jointly determined by product principles, application scenarios and production economy.
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