The application of electrical learning materials cable bridge in China is only more than 10 years, but in developed countries in Europe and America, it is only a few decades. In a machine room project, the bridge is very insignificant and rarely concerned with the expensive, high tech hardware and software, but it is also an indispensable part of the whole wiring project. How about the construction requirements and specifications of cable tray installation in construction?
1 General Provisions
1.1 this chapter applies to general industrial and civil building cables, bridge erection and cable laying in bridges within 10KV and below.
1.2 cable bridge installation and cable laying in the bridge shall be constructed according to the approved design documents.
1.3 is composed of a trays (grooves) supported by a support, a hanger and a bracket, or a straight line section of a ladder and a non straight line section, and the cable has a continuous rigid structure system, which is a cable bridge. See Figure 1.3
1.4 the metal cable tray and its bracket and the metal cable conduit introduced or drawn must be grounded (PE) or zero (PEN) reliable, and must meet the following requirements:
The length of the 1.4.1 metal cable tray and bracket shall be not less than 2, connected to the earthing (PE) or to the zero (PEN) trunk.
1.4.2 the copper conductor grounding line at the two ends of the connecting plate between the non galvanized cable bridge and the minimum allowable cross-sectional area of the grounding wire shall not be less than 4mm2.
1.4.3 between the two ends of the connecting plate of the galvanized cable bridge is not connected to the ground wire, but the connecting plate is not less than 2 fixed bolts with a loose screw cap or a looser washer.
1.1.5 cable installation is strictly prohibited from twisting, armour flattening, sheath fracture and serious scratch.
Where there are fire prevention requirements at the 1.4.6 cable tray, fire isolation measures should be taken.
2 construction preparation
2.1 technical preparation:
2.1.1 carries out technical and safety disclosure in accordance with approved construction organization design (construction plan).
2.1.2 construction execution process standard, Atlas, specifications are complete.
Before laying the 2.1.3 cable bridge, it should be checked that there is no place where the bridge is laid with other equipment, pipelines or overlaps. Before the construction, it should be negotiated with all kinds of work, supervision or construction unit and design unit, and make good records to ensure the smooth construction of the bridge.
2.1.4 the cable traction force shall be calculated according to the construction drawings or the cables used for construction.
1. the specification and type of cable tray must conform to the design requirements, and the accessories are complete; all types of steel for bridge and accessories, accessories and fasteners shall be galvanized standard parts.
2. line section, bend pass, bridge accessories and support, hanger column and type steel have product qualification certificate, and the bridge frame inside and outside should be smooth and smooth, without prickly, there should be no distortion and warping edge and other deformation phenomena.
3. the order or production of the bridge shall be carried out according to the design requirements, and should not be mistaken. It should be checked repeatedly so as not to cause waste.
4. the installation of the bridge installation should be selected to shield the electrical interference cable circuit. There are corrosive sites and flammable dust places. No cover and no hole closed tray should be selected. When it is necessary to adapt to local conditions, an assembly tray or a hole tray and a ladder should be selected. . When the low voltage power cable and the control cable share the same tray or ladder, the pallet or ladder should be selected in the middle, and the proper bending is set at the tray, the ladder branch, the lead and the lead. The soft connection plate, the articulated plate shall be selected and the expansion joint should be used when the space conditions are limited. Set up expansion plate; connect two sections with different width or height of pallet and ladder rack to configure widened or raised plates. However, during construction, the selection of supports, hangers and bridges should be chosen according to the design or engineering layout conditions.
5. the width and height of pallets and staircases should be chosen according to the following requirements:
(1) the filling rate of the cable in the bridge shall not exceed 40%, and the control cable should not exceed 50%. There should be reserved spare space for future cable addition.
(2) the carrying capacity of the selected pallets and Bridge specifications should meet the requirements. The uniformly distributed load should not be greater than the rated load of the selected pallet and ladder load rating.
(3) the relative deflection under uniform load should not be greater than 1/200.
The straight section of pallet and ladder can be selected according to the standard length of a single piece. The standard length of single piece is generally stipulated as 2, 3, 4 and 6m. The width and height of pallets and staircases are commonly used in specifications and sizes, as shown in table 2.4-1.
Note: the symbol delta represents the commonly used specifications.
All kinds of bending and accessories specifications should be suitable for engineering layout conditions and match with pallets and ladder frames.
The selection of specifications for hangers and hangers should be arranged according to the conditions of pallets, ladder specifications, storeys and span, and should meet the load requirements.
The surface treatment methods of steel bridge shall be selected according to factors such as engineering environmental conditions, importance, durability and technical economy. In general, it is advisable to choose the anticorrosive treatment method suitable for engineering environmental conditions according to table 2.4-2. When the "T" anticorrosion method used in the table for galvanized nickel alloy, high purification and other anticorrosion treatment bridge, should be tested and verified by the prescribed test, and should have clear technical quality indicators and testing methods.
Note: the symbol "0" indicates the recommended anticorrosion category.
Appearance check of 6. Bridge
There should be packing list, product qualification certificate and factory inspection report in the packing box of the bridge product. The thickness of pallets and ladder plates should meet the requirements of table 2.6. The surface anticorrosive coating materials should conform to the relevant national standards.
Hot dipped galvanized tray, bridge shelf surface should be uniform, no burr, burn, ash, scar, local non galvanized (more than 2mm diameter) and other defects, no impact on the installation of zinc tumor. The coating of the thread should be