Cable tray, which is produced by cable tray making machine. In engineering design documents, cable trays are usually called “bridges” in general, and no specific structural features are pointed out. The prices of cable trays of different types and materials vary greatly.
How to buy cable trays has become one of the most concerned issues for consumers. This article will provide reasonable suggestions for purchasing cable trays through the following points.
1. Cable tray structure type selection
The confusion of the type of cable tray structure will bring about the problems of heat dissipation and mechanical protection at the work site. Therefore, in the design stage, the designer should be required to reasonably select the structural features of the cable tray according to the engineering environmental characteristics and technical requirements, and clearly express it in the model label of the floor plan and the material table.
2. Cable tray material selection
The material of cable tray is another common problem in cable tray engineering design. According to materials, cable trays are mainly made of steel, FRP and aluminum alloy.
The FRP cable tray is characterized by its light weight, and its specific gravity is only 1/4 of that of carbon steel, which has good water resistance for chemical plant. It is not easy to burn, and the oxygen index of the frame-retardant and fiberglass cable tray is ≥32. It has a long service life. The general design life is 20 years, but the price is three time that of steel cable trays.
The superiority of construction lies in the convenience of cutting. Flexible assembly, and no need for fire during installation. This is of great significance foe chemical plant projects in explosive hazardous environments and tight construction schedules.
3. Type selection of anti-corrosion layer on the surface of table tray
The third common problem in engineering design is that the cable tray model does not indicate the type of anti-corrosion layer, and there is no unified text description.
The surface anti-corrosion coatings if cable trays mainly include hot-dip galvanizing, galvanized nickel, cold galvanizing, powder electrostatic spraying, etc. The manufacturer's data show: the hot-dip galvanizing process life is not less than 40 years, and it is suitable for outdoor heavy corrosive environments.
4. Fire protection rating selection of cable tray
The overall fire resistance of the cable tray should meet the requirements of relevant national codes or standards. In places with high engineering fire protection requirements, aluminum alloy cable trays should not be used.
Under the same specifications, the flame-retardant cable tray is 2.2 times more expensive than the steel cable tray, the service life is more than 5 times that of the steel cable tray, and the weight is 30% heavier than the steel cable tray. Fireproof cable trays are slightly more expensive than steel cable trays, their service life is more than three times that of steel cable trays, and their weight is basically the same as steel cable trays.
5. Selection of filling rate of cable tray
The width and height of the cable ladder frame and tray should meet the requirements of the filling rate. In general, the filling rate of the cable ladder frame and tray can be 40%-40% for power cable, and 50%-70% for control cables. And it is advisable to reserve 10% to 20% of the project development margin.
6. Selection of load class of cable tray
When selecting the load level of the cable tray, 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 support and hanger of the cable tray is not equal to 2m, the working average the cloth load should meet the requirements. Under the condition that various components and meet the corresponding load conditions, their specifications and dimensions should match the straight sections and elbow series of pallets and ladders.