Speaking of cable trays, everyone is familiar with it. Some people who do n’t understand may often encounter troubles when choosing cable trays. Now Nanjing cable tray manufacturers will explain the selection methods and how to choose cable trays.
Selection of fire resistance grade of cable tray: 1. In the section with fire protection requirements for cable tray, you can add materials with fire or flame resistance to the cable ladder and tray to form a closed or semi-closed structure. Measures such as painting fire-resistant coatings on the surface of bridges and their hangers should meet the requirements of relevant national codes or standards. In places with high fire protection requirements, it is not suitable to use aluminum alloy cable trays. 2. 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. Fire-resistant cable tray is slightly more expensive than steel cable tray, its service life is more than 3 times that of steel cable tray, and its weight is basically the same as steel cable tray. Fifth, the selection of the filling rate of the cable bridge: The selection of the cable ladder frame, tray width and height should meet the requirements of the filling rate. The filling rate of the cable ladder frame and tray under normal circumstances, the power cable can take 40% to 50%, The control cable can take 50% to 70%, and 10% to 25% of the project development reserve should be reserved.
Material selection of cable tray: 1. The material of cable tray is another common problem in cable bridge engineering design. According to the material classification, cable bridges are mainly made of steel, glass fiber reinforced plastic and aluminum alloy. The characteristics of FRP cable tray are light weight, the specific gravity is only 1/4 of carbon steel; water resistance and corrosion resistance are good, suitable for chemical plants. 2. Non-combustible, flame retardant fiberglass cable tray with oxygen index ≥32. Long life, generally designed life is 20 years, but the price is three times that of steel cable trays. The advantage of construction is that the cutting is convenient, the assembly is flexible, and no fire is required for installation. This is particularly significant for chemical plant projects with explosive hazardous environments and tight construction schedules, because in explosive dangerous environments, the chemical plant must be shut down during the installation of engineering fires. Benefits will be affected. Aluminum alloy cable trays are also very light. Due to the different specific gravity of aluminum and steel (Al = 2.7, Fe = 7.86), the ratio of aluminum to steel is about 1: 3 by weight. 3. The external dimensions and load characteristics of aluminum alloy cable trays are basically similar to those of steel bridges. In terms of cost, the cost of aluminum alloy bridges is 20% higher than galvanized steel cable bridges, and the service life is more than 5 times that of steel cable bridges.
Selection of cable tray structure types: 1. In engineering design documents, cable trays are generally referred to as "bridge trays" without specifying specific structural characteristics. The price of cable trays of different types and different materials varies widely, and the structure types The confusion will cause problems in the field of heat dissipation and mechanical protection. 2. Therefore, in the design stage, designers should be required to reasonably select the structural characteristics of cable trays according to the characteristics of the engineering environment and technical requirements, and clearly expressed in the type designation and material table of the plan.
Selection of the type of anticorrosive layer on the surface of cable tray: 1. The third common problem in engineering design is that the type of cable tray does not indicate the type of anticorrosive layer, and there is no uniform text description. This problem has lessons in reality. For example, a certain Indonesian project undertaken by China as a general contractor did not carry out salt spray test on the surface anticorrosive treatment of steel cable trays. After the completion of the bridges, the bridges were quite rusted and had to be replaced. 2. The surface anticorrosive coatings of cable trays are mainly hot dip galvanized, galvanized nickel, cold galvanized, powder electrostatic spraying, etc. According to the manufacturer's information, the hot dip galvanization process life is not less than 40 years, which is suitable for outdoor heavy corrosive environments. , High cost; galvanized nickel process life is not less than 30 years, also suitable for outdoor heavy corrosion environment, high cost; cold galvanization process life is not less than 12 years, suitable for outdoor light corrosive environment, the general cost; powder electrostatic spraying process life Not less than 12 years, suitable for indoor normal temperature and dry environment, the price is average. 3. The designer should reasonably choose the type of surface anti-corrosion layer of the cable tray according to the engineering environmental conditions, and express it clearly in the design document.
Select the cable bridge according to the cable bending radius: When selecting the bend of the cable bridge or the device that leads up and down, it should not be less than the minimum allowable bending radius of the cable in the cable bridge.
Selection of the load level of the cable bridge: When selecting the load level of the cable bridge, the working uniform load of the cable bridge should not be greater than the rated uniform load of the selected load level of the cable bridge. If the actual span of the support and hanger of the cable bridge is not When it is equal to 2m, the working uniform load should meet the requirements. Under the conditions of corresponding loads, the specifications and dimensions of various components and supports should match the straight sections of the pallets, ladder frames, and bent series.
The selection of the size of the cable tray: In engineering practice, the problem in selecting the size of the cable tray is either too large or too tight. How to choose the reasonable size of the cable tray? The ratio of the total cross-sectional area of the cable to the cross-sectional area inside the tray. The power cable should not be greater than 40%; the control cable should not be greater than 50%.
The above information is the troubles you may encounter when choosing Nanjing cable trays . Nanjing cable tray manufacturer Ruiquan Electric has introduced the methods in the selection. I hope that the above can help you.