Precise Preparation Before Installation:
- Strict Quality Control: Before installation, ensure the rubber expansion joint's model, specifications, length, working pressure, temperature range, and media compatibility fully match the design drawings and site conditions. Inspect the rubber body and flanges (or flanges) for scratches, cracks, bulges, aging, or other manufacturing or transportation damage. The flange sealing surface should be smooth and flat.
- Thorough Cleaning of Interfaces: Remove rust, welding slag, oil, and burrs from the flange surfaces of the pipes to be connected. Ensure the contact surfaces are clean and free of foreign objects; this is a crucial step to prevent leaks and avoid damaging the rubber.
- Pipe Alignment: Before connecting the rubber expansion joint, adjust the pipe supports and routing to ensure the flanges at both ends are parallel and coaxial, reducing forced deformation stress during installation. Allow for the correct offset and angle compensation as required by the design.
Precise Positioning and Axial Alignment:
- Stretch/Compression Installation Prohibited: During installation, the rubber expansion joint should be in its natural (unstretched or uncompressed) state (unless the design or manufacturer specifies special pre-deformation requirements). It is forbidden to use the elasticity of the expansion joint to forcibly stretch or compress it to compensate for pipeline installation errors.
- Ensuring Axial Freedom: After installation, it must be ensured that the rubber expansion joint can freely expand and contract axially between its two fixed supports. Any structure restricting its axial displacement (such as supports placed too close together, clamps too tight) or lateral forces generated by the pipeline will significantly reduce its lifespan.
- Precise Concentricity Control: When connecting flanges, bolts should easily pass through all bolt holes without forcibly prying or pulling the flange to align with the holes. This is a direct standard for verifying whether the pipelines at both ends are truly aligned. Prioritize tightening the bolts on the fixed flange connected to the rubber expansion joint body.
Bolt Tightening Principles: Balance and Moderation
- Diagonal Synchronous Principle: When tightening the bolts connecting the flanges, strictly adopt a cross-shaped, symmetrical, phased, and gradual tightening method. Never tighten one side completely at once.
- Moderate Torque: The final tightening torque should meet the design requirements or refer to the flange standard to avoid over-tightening, which could lead to flange deformation, bolt elongation, or excessive compression of the rubber, damaging the sealing layer. A torque wrench is recommended to ensure accuracy and consistency.
- Accessory Installation Notes: If equipped with a limit lever (control lever), after the bolts are finally tightened, the outer nut must be completely loosened (keeping the inner locking nut of the limit lever in the same position) to ensure the free movement of the rubber expansion joint.
Protection Strategies for Special Environments
- High Temperature/Surface Protection: When the rubber expansion joint is installed near a high-temperature source (such as steam pipes, hot equipment) or its own operating temperature is high, a heat insulation cover (such as high-temperature glass wool, aluminum silicate, etc., which must be fire-retardant) must be installed to prevent external high temperatures from accelerating rubber aging or internal medium temperatures from affecting performance.
- Corrosive Media Protection: For corrosive media such as acids, alkalis, and oils, or in environments with strong ultraviolet radiation (outdoors), rubber expansion joints with appropriate corrosion-resistant coatings (such as PTFE coating) or weather-resistant properties should be preferred. Avoid splashing corrosive liquids on its surface after installation.
- Mechanical Protection: In locations where accidental collisions or friction may occur (such as pedestrian walkways, equipment operating areas), metal protective covers or isolation fences should be added.
Avoiding Fatal Mistakes: Common Installation Errors
Rough Installation and Misalignment: Forcibly stretching/compressing the installation, or severe pipe misalignment, subjects the expansion joint to excessive stress over a long period-leading to rubber tearing, wire mesh detachment, and premature failure.
Uneven Bolt Tightening: Incorrect tightening sequence or uneven force-leading to flange misalignment, localized leaks, or damage to the rubber sealing surface.
Ignoring the Limiting Rod: Failure to loosen the outer nut of the limiting rod-severely restricts the displacement of the rubber expansion joint, rendering it ineffective and prone to damage.
Failure to Remove the Transport Rod: Failure to remove the factory-installed fixed-length transport rod after installation-completely disables the expansion joint's expansion capacity, rendering it a rigid connection, highly susceptible to damage under pressure or thermal expansion.
Lack of Protective Measures: Lack of insulation near high-temperature sources-accelerates rubber aging, cracking, and carbonization; lack of protection in corrosive environments-results in rubber swelling, delamination, and a sharp decline in physical properties.
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