In low-temperature environments, piping systems are prone to shrinkage and deformation due to the thermal expansion and contraction properties of their materials. If the design of pipeline seismic supports fails to adequately account for shrinkage compensation, this can lead to excessive support stress, uncontrolled pipeline displacement, and even leaks or structural damage at joints. Therefore, reliable shrinkage compensation for pipeline seismic supports in low-temperature conditions is essential through material selection, structural optimization, and compensation device design.
The impact of low-temperature environments on pipeline materials is a primary consideration for shrinkage compensation. Metals such as austenitic stainless steel have significant linear expansion coefficients at low temperatures, and shrinkage increases with decreasing temperature. For example, austenitic stainless steel used in cryogenic pipelines typically shrinks more than carbon steel. If the support and pipeline materials are different, gaps must be reserved or elastic connectors must be used to compensate for the difference. For dissimilar metal combinations, the impact of thermal stress on the support structure must also be evaluated to prevent deformation or failure due to uneven shrinkage.
The sliding support structure is the core design for shrinkage compensation in low-temperature pipeline seismic supports. Installing low-friction sliding plates on the sliding surfaces of pipe racks can reduce resistance during pipe contraction and prevent localized stress concentrations caused by bracket jamming. In low-temperature environments, the sliding plate material must be both cold-resistant and wear-resistant to avoid malfunction due to embrittlement or increased wear. Furthermore, the sliding surface must be kept clean to prevent the intrusion of frost and impurities, ensuring free sliding during pipe contraction.
Adjustable brackets use mechanical structures to dynamically compensate for shrinkage. Low-temperature vertical pump pipe supports often feature adjustable height adjustments using bolts or hydraulic devices to compensate for dimensional changes caused by shrinkage of the insulation layer. These brackets must have ample adjustment range and be equipped with locking devices to prevent vibration-induced displacement during operation. Furthermore, the adjustable brackets must be installed away from the direction of thermal expansion of the pipe to avoid interference with thermal displacement.
The coordinated design of compensators and seismic supports is critical for low-temperature piping systems. Devices such as square compensators and corrugated compensators absorb pipe contraction through their own deformation, reducing tensile stress on the brackets. During design, ensure a reasonable spacing between the compensator and bracket to prevent excessive bracket stress due to compensator deformation. For example, square compensators are typically placed at the midpoint between two fixed supports, with deviation no greater than 0.6 times the span to ensure a balance between compensation and support stability.
The connection design between cryogenic valves and pipelines requires special consideration. Cryogenic valves feature long bonnets to prevent packing from freezing, and upward-facing valve stems prevent direct contact between the packing seal and the cryogenic fluid. When arranging valves, consider the operating space for the handles to prevent pipe contraction from preventing the valves from opening and closing properly. Furthermore, flexible joints or expansion joints should be used at the connection between the valve and the pipeline to compensate for differential contraction at low temperatures and avoid leaks caused by rigid connections.
Preventing cold bridges is a key aspect of cryogenic pipeline supports. Thermal insulation gaskets or non-metallic supports should be installed at the interface between the pipe support and the insulation layer to prevent cold air from being transferred through the support to the structure, leading to localized condensation or frost heave. For example, when aluminum heat exchangers are located close to insulated pipelines, space should be reserved between them or an additional insulation layer should be installed to prevent cold bridges that could hinder pipe contraction or abnormal support stress.
Regular inspection and maintenance are essential for ensuring the long-term stable operation of cryogenic pipeline seismic supports. Vibration monitoring and displacement measurement are necessary to assess changes in bracket performance under low-temperature conditions. If bracket deformation, sliding surface wear, or compensator leakage are detected, timely adjustment or replacement of the component is necessary. Furthermore, establishing a bracket lifespan profile and developing a preventive maintenance plan based on operating time and operating conditions can significantly improve the safety and reliability of cryogenic piping systems.
