During the bending and laying process, the risk of damage and breakage of the internal cores in integrated cables mainly stems from mechanical stress concentration, material fatigue, and improper laying techniques. To effectively prevent this problem, a comprehensive approach is needed, encompassing design optimization, material selection, process control, and auxiliary measures, to ensure the structural integrity and functional stability of the cable in complex laying environments.
The bending radius design of integrated cables is a crucial aspect in preventing core damage. During bending, the outer cores of the cable bear tensile stress, while the inner cores bear compressive stress. If the bending radius is too small, stress concentration will exceed the limits of the core material, leading to breakage or insulation damage. Therefore, the minimum bending radius specification must be strictly followed based on the cable's outer diameter, core structure, and material properties. For example, the minimum bending radius for multi-core integrated cables is typically 15-20 times the outer diameter, while single-core cables require a larger radius to distribute stress. The design can be optimized by altering the core arrangement, such as using a symmetrical layered structure, to reduce stress differences between core layers during bending, thereby lowering the risk of breakage.
Material selection directly affects the cable's bending resistance. The core material needs to possess both high strength and flexibility. Metals with excellent conductivity, such as copper or aluminum, are common choices, but annealing is necessary to reduce hardness and improve ductility during bending. The insulation material needs to balance flexibility and abrasion resistance. Cross-linked polyethylene (XLPE) is the preferred choice for integrated cable insulation due to its excellent mechanical properties and aging resistance. The sheath material needs to have tear and impact resistance. Polyvinyl chloride (PVC) or low-smoke halogen-free flame-retardant materials can effectively protect the core from external mechanical damage. Furthermore, adding filler structures, such as polypropylene tape or non-woven rope, to key areas can fill the gaps between the cores, enhancing the overall stability of the cable and reducing deformation during bending.
Laying process control is crucial to preventing core damage. During bending, sharp bends or forced pulling should be avoided. Pulleys or guide devices should be used to guide the cable to bend naturally, reducing localized stress concentration. For large-section integrated cables, anti-torsion frames or turntables can be used to release the cable's torsional stress during laying, preventing core breakage due to torsion. Simultaneously, the laying speed must be controlled to avoid rapid stretching that could cause relative displacement between the conductor and insulation layer, leading to internal friction damage. When laying in low-temperature environments, the cable must be preheated to improve material flexibility and reduce the risk of brittle fracture.
Auxiliary measures can further enhance the cable's bending resistance. For example, adding an elastic sheath or metal armor layer to the bending section can disperse stress through external support, protecting the conductor from direct compression. For dynamic applications with frequent bending, such as robot cables or elevator cables, tensile elements, such as aramid fibers or steel wire ropes, can be embedded in the cable structure to bear tensile force and reduce stress on the conductor. Furthermore, coating the conductor surface with talc powder or wrapping it with high-temperature resistant slip tape can reduce the coefficient of friction between conductors during bending, preventing insulation wear or conductor breakage due to relative sliding.
The treatment of integrated cable joints also requires attention. Joints near bending sections are stress concentration areas and require reinforced joint designs, such as increasing insulation thickness or adding stress cones, to disperse the electric and mechanical stress at the joint. When fabricating joints, ensure a secure connection of the conductors to prevent poor contact that could lead to localized overheating and accelerated material aging. Simultaneously, the joint's sealing must meet standards to prevent moisture intrusion, which could degrade insulation performance and indirectly cause conductor breakage.
Regular inspection and maintenance are crucial for ensuring the long-term safe operation of cables. Infrared thermal imaging or partial discharge detection technology can promptly detect potential insulation damage or conductor breakage at bends. Cables with minor damage should be repaired or replaced immediately to prevent further problems. Furthermore, establishing a digital archive of cable laying paths, recording the location and radius of bends, can provide a reference for subsequent maintenance and optimize laying plans.
Preventing internal conductor damage and breakage during bent laying of integrated cables requires a coordinated effort across the entire chain, including design, materials, processes, auxiliary measures, and maintenance. By scientifically designing the bending radius, selecting high-performance materials, standardizing laying processes, implementing auxiliary protection measures, and establishing a regular inspection mechanism, the cable's bending resistance can be significantly improved, ensuring reliable operation in complex application scenarios.
