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Trough type cable tray is a trough type component made by bending a whole steel plate. Conceptually, its difference from a tray is the different height-to-width ratio. The tray is shallow and wide, while the trough type cable tray has a certain depth and closure.
Cable tray (cable bracket) is the general term for a rigid structural system with closely supported cables, composed of straight sections, bends, components of trays or ladders, as well as support arms (arm type brackets), hangers, etc.
Trough type cable tray can be used for fully enclosed cable laying. It is most suitable for laying computer cables, communication cables, thermocouple cables and other control cables of high-sensitivity systems. It has good effects on shielding interference of control cables and protection of cables in heavy corrosion environments.
Selection points
1) When trough type cable trays and their supports and hangers are used in corrosive environments, they should be made of corrosion-resistant rigid materials, or anti-corrosion treatment should be applied. The anti-corrosion treatment method should meet the requirements of engineering environment and durability.
2) In sections with fire protection requirements, cable trays can add boards, nets and other materials with fire-resistant or flame-retardant properties in cable ladders and trays to form closed or semi-closed structures, and take measures such as painting fire-resistant coatings on the surface of the tray and its supports and hangers. Its overall fire resistance should meet the requirements of relevant national specifications or standards.
3) In places with high engineering fire protection requirements, aluminum alloy cable trays should not be used.
4) The selection of width and height of trough type cable trays should meet the requirements of filling rate. Generally, the filling rate in cable ladders and trays can be 40%～50% for power cables, 50%～70% for control cables, and 10%～25% engineering development margin should be reserved.
5) When selecting the load grade of cable tray, the working uniform load of cable tray should not be greater than the rated uniform load of the selected cable tray load grade. If the actual span of the cable tray supports and hangers is not equal to 2m, the working uniform load should meet the requirements.
6) Under the condition of meeting the corresponding load, the specifications and dimensions of various components and supports and hangers should match the straight sections and bend series of trays and ladders.
7) When selecting bends or lead-up and lead-down devices of trough type cable tray, they should not be less than the minimum allowable bending radius of cables in the cable tray.
8) For steel cable trays with span greater than 6m and aluminum alloy cable trays with span greater than 2m or load bearing requirements greater than load grade D, strength, stiffness and stability calculation or test verification should be carried out according to engineering conditions.
9) When several groups of cable trays are laid in parallel at the same height, maintenance and inspection distances should be considered between adjacent cable trays.
12) The standard length of straight single pieces of trough type cable trays can be 2, 3, 4, 6m.
Installation points
1. The laying direction of trough type cable tray should be short and direct, and should be laid along walls, columns or beams as much as possible.
2. According to the laying direction of trough type cable trays, propose to the civil engineering specialty and structural specialty the position and load of pre-embedded steel plates required for reserved wall holes, floor holes and hanger installation. And it should be coordinated with the technology specialty, plumbing specialty and power specialty.
3. For concealed metal trunking wiring in the ground, close cooperation with the civil engineering specialty is required during design, so as to reasonably determine the line path and equipment selection according to different structural types and building layouts.
4. Cables of different voltages and different uses should not be laid in the same layer of cable tray:
(1) Cables above 1kV and cables of 1kV and below;
(2) Double-circuit cables supplying power to first-level loads in the same path;
(3) Cables for emergency lighting and other lighting;
(4) Power, control and telecommunication cables. If cables of different grades are laid in the same cable tray, a partition should be added in the middle for isolation.
5. When installation or maintenance under engineering conditions does not need to consider additional concentrated loads, the working uniform load of trough type cable trays is calculated according to the uniform distribution of cable self-weight.
6. Trough type cable trays should not be laid in parallel with the following pipes. When unavoidable, the position of the cable tray should meet the following regulations, or corresponding protective measures should be taken.
(1) Trough type cable trays should be above pipes with corrosive liquids.
(2) Trough type cable trays should be below thermal pipes.
(3) When flammable and explosive gases are heavier than air, trough type cable trays should be above the pipes.
(4) When flammable and explosive gases are lighter than air, trough type cable trays should be below the pipes.
7. The minimum distance between trough type cable trays and pipes should comply with regulations.
8. Necessary spacing should be maintained between generic cabling cables and electrical equipment such as motors and power transformers nearby that may generate high-level electromagnetic interference.
9. The spacing between generic cabling cables, optical cables and pipelines laid on walls and other pipelines should comply with regulations.
10. When trough type cable trays are laid horizontally, the best span should be selected according to the load curve for support, and the span is generally 1.5～3.0m. When cable trays are laid vertically, metal cover protection should be added to the part below 1.8m from the ground, except when laid in electrical equipment rooms.
11. When cable trays are laid in multiple layers, the interlayer distance is generally:
(1) The distance from the top plate of the layout on the tray or other obstacles should not be less than 0.3m.
(2) The spacing of power cable trays should not be less than 0.3m.
(3) The spacing between control cable trays should not be less than 0.2m
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