Installation sequence of cable tray: Measurement and positioning → fabrication and installation of supports and hangers → tray installation → grounding treatment
1. Measurement and positioning:
Mark the installation position of the bridge with the snap line method, determine the fixed position of the support and mark it. The installation datum line shall be determined by the hanging steel wire method for the positioning of the bridge in the shaft. If the reserved hole is inappropriate, it shall be adjusted in time and repaired.
2. Fabrication and installation of cable tray
We locate according to the design elevation of the construction drawing and the specification of the bridge, and then make the support according to the measured size for industrialized production. Where there is no ceiling, it shall be hoisted along the beam bottom or installed by the wall support, and where there is ceiling, it shall be hoisted in the ceiling or installed by the wall support. In public places without suspended ceiling, combined with structural components and considering the beauty of the building and convenient maintenance, it shall be installed against the wall, column support or on the lower chord components of roof truss. The support installed against the wall shall be fixed with expansion bolts, and the spacing between supports shall not exceed 2m. Supports and hangers shall be added at the connection of linear section and non-linear section, at the deformation joint of building and in the middle of non-linear section with bending radius greater than 300mm. The installation of supports and hangers shall ensure that the levelness or verticality of bridge meets the requirements.
3. Cable tray
a. For bridges with special shapes, the dimensions measured on site shall be handed over to the material supplier, who shall make them according to the dimensions to reduce on-site processing. The material, model, thickness and accessories of the bridge meet the design requirements.
b. Before the installation of the bridge, it is necessary to coordinate with various disciplines to avoid conflicts with large-diameter fire pipes, spray pipes, cold and hot water pipes, drainage pipes, air conditioning and exhaust equipment.
c. Lift the bridge to the predetermined position and fix it with the support with bolts. Carefully check the size at the turning. The bridge should be consistent with the slope of the building. For the bridge on the wall of the circular arc building, the arc should be consistent with the building. The bridge is connected with the bridge by connecting plate, and the connecting bolt adopts half round head bolt, and the half round head is on the inner side of the bridge. The gap between bridges must meet the design requirements to ensure that the bridges of a system are connected as a whole.
d. The expansion joint of the bridge crossing the deformation joint of the building shall be treated according to the enterprise standard installation process of steel cable bridge. When the straight section of the steel bridge exceeds 30m, a thermal expansion and cold contraction compensation device shall be set.
e. The bridge shall be installed horizontally and vertically, neat and beautiful, with the same distance and firm connection. The levelness deviation in the same horizontal plane shall not exceed 5mm / M and the straightness deviation shall not exceed 5mm / m.
4. Grounding treatment
The grounding treatment of cable tray can use galvanized connecting plate as jumper between galvanized trays to connect the trays into one. Galvanized spring washers shall be added to the two connecting bolts at both ends of the connecting plate. The bridge shall be bridged with soft copper wire of no less than 4mm2, and then the bridge shall be connected with the grounding wire to form an electrical path. There shall be at least two connections between the whole bridge and the grounding main line.
5. Multi layer bridge installation; Layered bridge installation
Install the upper layer first and then the lower layer. The distance between the upper and lower layers shall be reserved to facilitate cable laying and maintenance in the later stage. The clear distance between horizontal adjacent bridges shall not be less than 50mm, the distance between layers shall not be less than 150mm according to the bridge width, and the distance from weak current cable bridge shall not be less than 0.5m.
6. Determine the environmental conditions. There are generally three environmental conditions: corrosive environment, normal environment and special environment.
Determine the direction. According to the direction of most cables, it can go along, columns, beams and floors indoors and process pipes outdoors as much as possible. Calculate the load. Calculate the weight Q and total load of the unit length of cable on the strike section of the cable tray. Gtotal = n1q1 + n2q2... Nnqn, where Q1 · Q2 · Q3... QN is the unit weight of each cable (kg / M) N1 · N2 · N3... NN is the total allowable number of cables g (refer to the load curve chart for the allowable load of the cable frame). Select the cable tray according to the cable load and the environment where the cable tray is installed, Based on the load curve of the bridge, determine the type and specification of the, the spacing of the columns, the length of the supporting arm, the level of the bridge, the length of the columns, etc. Determine the fixing mode of the bridge according to the cable direction and installation environment; Hanging type, vertical type (both forms can adopt unilateral fixation or bilateral fixation), wall side type, etc.
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