Construction Method of Cable Tray: Construction Sequence Measurement and positioning → Production and installation of support hangers → Tray installation → Grounding treatment
Main Construction Methods and Technical Measures
Measurement and Positioning
Use the chalk line method to mark the installation position of the tray, determine the fixed position of the bracket, and make appropriate markings. For tray positioning inside vertical shafts, use the hanging steel wire method to establish the installation baseline. If the reserved hole is not suitable, adjust it promptly and make necessary repairs.
Production and Installation of Support Hangers
Based on the elevation and specifications provided in the construction drawings, position the support hangers and then fabricate them according to the measurement dimensions. The hangers should be factory-produced. Install the hangers along the bottom of beams or against walls in areas without suspended ceilings. In areas with suspended ceilings, install the hangers either inside the ceiling or against the walls. In public areas without suspended ceilings, integrate with structural components for aesthetics and maintenance convenience. Install against walls or column brackets, or under the lower chord members of trusses. The fixed installation of wall-mounted brackets should use expansion bolts, with a spacing not exceeding 2.5 meters. Additional support hangers should be added at the junctions of straight and non-straight sections, at building expansion joints, and in the middle of non-straight sections with a bend radius greater than 300mm. Ensure that the installation of support hangers maintains the required levelness or verticality of the tray.
Tray Installation
- For trays with special shapes, provide the field-measured dimensions to the material supplier, who will produce them accordingly to reduce on-site processing. The tray material, model, thickness, and accessories should meet design requirements.
- Before tray installation, coordinate with other disciplines to avoid conflicts with large-diameter firefighting pipes, sprinkler pipes, hot and cold water pipes, drainage pipes, air conditioning, and ventilation equipment.
- Lift the tray to the designated position, secure it with bolts to the supports, and carefully verify dimensions at bends. The tray should be aligned with the slope of the building. For trays against curved building walls, the curvature should match that of the building. Connect trays using connecting plates and semi-circular head bolts, with the semi-circular head on the inner side of the tray. Ensure that the gaps between trays meet design requirements to ensure that the entire system forms an integrated structure.
- Trays spanning building expansion joints should be treated with expansion joints according to the company standard “Steel Cable Tray Installation Technology.” When the straight section of a steel tray exceeds 30m, thermal expansion and contraction compensation devices should be installed.
- Tray installation should be horizontal, vertical, neat, and aesthetically pleasing, with consistent spacing and secure connections. The deviation in horizontal levelness within the same horizontal plane should not exceed 5mm/m, and the deviation in straightness should not exceed 5mm/m.
Grounding Treatment
Galvanized connecting plates can be used between galvanized trays as jumpers to connect trays into a whole. Install galvanized spring washers on both ends of the two connecting bolts on the connecting plate, and connect the trays with not less than 4mm2 soft copper wire. Then connect the trays to the grounding wire to form an electrical circuit. The tray system should have connections to the ground wire at no less than two locations.
Installation of Multi-level Trays
For multi-level tray installation, install the upper level first, followed by the lower level. Leave some space between the upper and lower levels to facilitate cable laying and maintenance. The clear distance between horizontally adjacent trays should not be less than 50mm, and the distance between levels should be based on the tray width, with a minimum of not less than 150mm, and the distance from the low-voltage cable tray should be not less than 0.5m.
