The cable tray construction sequence is as follows: measurement positioning → support hanger installation → bridge installation → grounding treatment
Cable tray selection design: Strong and weak electric lines should be laid in separate slots. Strong and weak electricity must be separated by metal separation plates when the junction boxes (boxes) are crossed. Strong and weak electric wires must not be in direct contact in the line slots. The various wirings in the ground trunking are only allowed to be connected at the outlet of the junction box. In the construction and installation of the ground trunking, all the trunking pipes are required to be connected into a reliable grounding whole.
1. Measurement positioning:
Use the elastic method to identify the installation position of the bridge, determine the fixed position of the bracket, and mark it. The positioning of the bridge in the shaft should first determine the installation baseline by the suspension wire method. If the reserved hole is not suitable, it should be adjusted in time and repaired.
2, cable tray production and installation
We design the elevation and bridge specifications according to the construction drawing, and then make the bracket according to the measured size, and the bracket is factory-produced. It is erected along the bottom of the beam or mounted on the wall bracket without a ceiling, and is installed in the ceiling or suspended by the wall bracket. In the public place without ceiling, combined with structural members and considering the aesthetics of the building and convenient maintenance, it is installed on the wall, column bracket or the chord member of the roof truss. The fixing brackets against the wall are fixed by expansion bolts, and the spacing of the brackets is not more than 2 meters. In the middle of the line connecting the straight section and the non-linear section, over the deformation joint of the building and in the middle of the non-linear section with a bending radius greater than 300mm, the supporting hanger shall be added. The installation of the supporting hanger shall ensure that the horizontalness or verticality of the bridge meets the requirements.
3, cable tray
a. For special shape bridges, the size of the on-site measurement shall be handed over to the material supplier, and the supplier shall make the size according to the size to reduce on-site processing. The bridge material, model, thickness and accessories meet the design requirements.
b. Before the bridge is installed, it must be coordinated with various professions to avoid conflicts with large-diameter fire pipes, spray pipes, hot and cold water pipes, drain pipes, air conditioners and air exhaust equipment.
c. Lift the bridge to the predetermined position, bolted to the bracket, carefully check the size at the corner, the bridge should be consistent with the slope of the building, the bridge in the arc-shaped building wall, the arc should be with the building Consistent. The bridge frame and the bridge frame are connected by a connecting plate, the connecting bolt adopts a semi-circular head bolt, and the semicircular head is inside the bridge frame. The gap between the bridges must meet the design requirements to ensure that the bridges of one system are integrated.
d. The bridge spanning the deformation joint of the building shall be treated with expansion joints according to the enterprise standard “Installation Process of Steel Cable Tray”. When the straight section of the steel bridge exceeds 30m, a thermal expansion and contraction compensation device shall be provided.
e. The bridge frame is horizontal and vertical, neat and tidy, the distance is consistent, and the connection is firm. The horizontal deviation in the same horizontal plane does not exceed 5mm/m, and the straightness deviation does not exceed 5mm/m.
4, grounding treatment
Grounding treatment of cable trays Galvanized connecting plates can be used as jumper cables between the galvanized bridges to connect the bridges. A galvanized spring washer is added to the two connecting bolts at both ends of the connecting plate, and the bridge is connected by a soft copper wire of not less than 4 mm2, and then the bridge is connected with the grounding wire to form an electrical path. There should be no less than two connections between the bridge and the grounding trunk.
5, multi-layer bridge installation; layered bridge installation
First install the upper layer, then install the lower layer, leaving a margin between the upper and lower layers, which is conducive to the later cable laying and maintenance. The horizontal distance of horizontal adjacent bridges should not be less than 50mm, the distance between layers should be no less than 150mm according to the width of the bridge, and the distance between the bridges of weak electric cables is not less than 0.5m.
6, determine the environmental conditions There are generally three environmental conditions: corrosive environment, normal environment, special environment.
Determine the direction according to the majority of cable runs, indoors along the columns, beams, slabs, and as far as possible along the process pipeline. Calculate the weight of the cable and the total load G of the unit length cable on the striker section of the cable tray. Total = n1q1 + n2q2... nnqn where: q1·q2·q3...qn is the weight per cable (kg/m) N1·n2·n3...nn is the same cable number G total (the allowable load reference load curve chart of the cable grid). The selection of the bridge is based on the cable load and the environment of the bridge installation, based on the load curve of the bridge. Type and specifications and the spacing of the columns, the length of the arm, the level of the bridge, the length of the column, etc. According to the cable orientation and the installation environment, the fixing method of the bridge is determined; the hanging type, the vertical type, (the two forms can be fixed by one side or both sides), the wall side type, and the like. The hierarchical arrangement of the various cables on the cable tray and the distance between the layers. The arrangement of the cable tray level is: the weak electric control cable is at the uppermost layer, and then the general control cable, the low-voltage power cable, and the high-voltage power cable are arranged in sequence below, so that the arrangement is favorable for shielding interference ventilation, heat dissipation, and the like.