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When the cable tray is laid horizontally, the optimal span should be selected according to the load curve for support, and the span is generally 1.5 to 3.0m. When laid vertically, the fixed spacing should not be greater than 2m.
1. Product Definition
Cable tray (cable bracket is the full name of a rigid structural system that is composed of straight sections, bends, components and brackets (arm-type brackets, hangers, etc. of trays or ladders) with close support cables.
2. Key points for product selection
Cable trays, wire ducts and their supports and hangers are used in corrosive environments and should be made of corrosion-resistant rigid materials or anti-corrosion treatment. The anti-corrosion treatment method should meet the requirements of the engineering environment and durability.
In sections with fire protection requirements, cable trays can be added with fire-resistant or flame-retardant plates, nets and other materials in cable ladders and trays to form a closed or semi-closed structure, and the surface of the cable tray and its supports and hangers should be Measures such as applying fire-retardant coating on the surface should be taken, and its overall fire resistance should meet the requirements of relevant national specifications or standards.
In places where the engineering fire protection requirements are high, aluminum alloy cable trays should not be used.
The selection of cable ladder width and height should meet the requirements of filling rate. Under normal circumstances, the filling rate of the cable ladder can be 40% to 50% for power cables and 50% to 70% for control cables, and 10% to 25% engineering development margin should be reserved.
When selecting the load level of the cable ladder, the working uniform load of the cable tray should not be greater than the rated uniform load of the selected cable tray load level. If the actual span of the cable tray support bracket is not equal to 2m , the working uniformly distributed load should meet the requirements.
The specifications and dimensions of various components and supports and hangers should match the straight sections and bend series of trays and ladder racks under the condition of meeting the corresponding loads.
When selecting the bends or up-lead and down-lead devices of the cable tray, it should not be less than the minimum allowable bending radius of the cable in the cable tray. 8 For steel cable trays with a span greater than 6m and aluminum alloy cable trays with a span greater than 2m or a load requirement greater than load grade D, the strength, stiffness and stability should be calculated or tested according to the engineering conditions.
When several groups of cable trays are laid in parallel at the same height, the maintenance and inspection distance between adjacent cable trays should be considered.
For the commonly used specifications and dimensions of the width and height of the ladder rack, please refer to Article 2.2.2 of CESC31∶91 "Design Specifications for Steel Cable Tray Engineering".
For the commonly used specifications and dimensions of the width and height of the ladder rack, please refer to Article 3.1.2 of CECS106∶2000 "Technical Regulations for Aluminum Alloy Cable Trays" Article.
The standard length of a single straight-through ladder rack and aluminum alloy tray and ladder rack can be 2, 3, 4, and 6 meters.
For the surface anti-corrosion treatment method of steel cable tray, please refer to Article 3.4.2 of CECS31∶91 "Design Specifications for Steel Cable Tray Engineering".
For the surface anti-corrosion treatment method of aluminum alloy cable tray, please refer to Article 4.4.1 of CECS 106∶2000 "Technical Regulations for Aluminum Alloy Cable Tray".
Installation points
The laying direction of ladder-type cable tray and cable duct should be short and should be laid along the wall, column or beam as much as possible.
According to the laying direction of cable tray and cable duct, the required embedded steel plate position and load when the reserved wall hole, floor hole and hanger are installed should be proposed to the civil engineering and structural professionals. And it should be coordinated with the process, plumbing and power professionals.
When designing the concealed metal cable duct wiring in the ground, close cooperation with the civil engineering professionals should be carried out so as to reasonably determine the line path and equipment selection according to different structural types and building layouts.
Cables of different voltages and different uses should not be laid in the same cable tray:
1. Cables above 1kV and 1kV and below;
2. Double-circuit cables supplying power to the primary load along the same path;
3. Cables for emergency lighting and other lighting;
4. Power, control and telecommunication cables. If cables of different levels are laid in the same cable tray, partitions should be added in the middle for isolation.
When installation or maintenance under engineering conditions does not require additional concentrated loads, the working uniform load of cable ladders and trays is calculated based on the uniform distribution of the cable's dead weight.
Cable trays should not be laid parallel to the following pipelines. When this cannot be avoided, the location of the cable tray should comply with the following regulations, or appropriate protective measures should be taken.
1. The cable tray should be above the pipeline with corrosive liquids.
2. The cable tray should be below the thermal pipeline.
3. When flammable and explosive gases are heavier than air, the cable tray should be above the pipeline.
4. When flammable and explosive gases are lighter than air, the cable tray should be below the pipeline.
The minimum distance between cable trays and pipelines is shown in relevant standards.
The necessary distance should be maintained between the integrated wiring cables and nearby electrical equipment such as motors and power transformers that may generate high-level electromagnetic interference. The distance between the integrated wiring cables and power cables should comply with the provisions of Article 11.0.2 of GB/T 50311-2000.
The distance between the integrated wiring cables, optical cables and pipelines laid on the wall and other pipelines should comply with the provisions of Article 11.0.2 of GB/T 50311-2000.
