What are the requirements for installing cable trays?

You can refer to the cable tray standards JB-T10216-2000 and HG/T 21581-1995(HK09) – Installation Manual for Instrument Piping, Cables, and Trays!

Material Requirements 1.1 Cable trays and their accessories: The model and specifications of the cable trays must meet the design requirements. The interior and exterior surfaces of the trays should be smooth and flat, without any sharp edges; there should be no deformation such as twisting or warping. The accessories attached to the trays must be galvanized. 　　1.2 Copper core grounding wires shall be strung across both ends of the connection plates between ungalvanized cable trays, with a maximum allowable cross-sectional area of not less than 4 mm2. 2. Main tools: 2.1 Pencil, inkwell, tape measure, plumb bob. 　　2.2 Electrical tools, drill drivers, impact drills, ladders, etc. 3. Construction conditions: 3.1 Coordinate with the structural construction work of civil engineering, and complete all tasks such as preparing holes, embedding iron components, as well as installing hangers and suspension brackets. 　　3.2 All wet civil works in the vertical shafts of high-rise buildings have been completed. 4. Operating Procedures 　　4.1 Process Flow: Marking with string for positioning, Preparing holes, Preparing suspension rods and brackets, Installing metal expansion bolts, Embedding iron components, Constructing the steel structure, Installing the cable tray, Lifting the cable tray. 4.2 Marking with string for positioning: Determine the installation locations of electrical devices such as incoming wires, boxes, cabinets, etc., based on the design drawings. From the starting point to the ending point (starting with main lines and then branch lines), establish horizontal or vertical lines. Use a ink line to mark the center line of the wires along walls, ceilings, and floors. In accordance with the requirements of the design drawings and the construction acceptance standards, determine appropriate spacing and mark the exact positions with a pen. 　　4.3 Reserved holes: According to the axis positions indicated on the design drawings, fix the pre-fabricated wooden or iron frames in the marked locations and adjust them to be straight. Once the concrete has set and the formwork can be removed, take down the frames and smooth out the openings of the holes (filling in those openings). 　　4.4 Requirements for the installation of brackets and hangers, as well as embedded rods and hangers. 　　4.4.1 Requirements for the installation of supports and hangers 4.4.1.1 All steel materials used for supports and hangers must be straight, without any significant twisting; the length variation after cutting should be within 5 mm, and there should be no curling or burrs at the cut edges. 　　4.4.1.2 The steel supports and hangers shall be welded firmly without significant deformation; the welds shall be even and smooth, and their length shall meet the requirements. Defects such as cracks, undercuts, pores, depressions, incomplete welding, and missed welds are not allowed. 　　4.4.1.3 Brackets and hangers shall be installed firmly to ensure they are level and vertical; when installed on sloped buildings, the brackets and hangers shall have the same slope as the building. 　　4.4.1.4 When no specific requirements are specified in the design, the spacing between supports for horizontally installed cable trays should be 1.5 to 3 meters, while for vertically installed trays, this spacing should not exceed 2 meters. Fixed support points must be provided within 500 mm of the entrances and exits to junction boxes, cabinets, corners, bends, both ends of deformation joints, as well as at the three ends of T-joints. 　　4.4.1.5 It is strictly prohibited to use wood to fix brackets and hangers. 4.4.2 Embedded rods and hangers: Round steel with a diameter of not less than 8 mm is used, and these materials are processed through steps such as cutting, straightening, bending, and welding to create rods and hangers. Its ends should be modified with threads to facilitate adjustment. When integrating it with the civil structure, the hangers or suspension brackets should be anchored in the designated fixed positions simultaneously with the installation of the rebar. During concrete pouring, a dedicated person must be assigned to monitor to prevent the hangers or suspension brackets from shifting. When removing the formwork, be careful not to damage the threads at the end of the lifting rod. 　　4.5 The dimensions of the self-made embedded iron pieces should be no less than 120mm×6mm, and the diameter of the anchor round steel should be no less than 8mm. In close coordination with the construction of the civil structure, the surface of the embedded iron pieces should be placed beneath the rebar mesh, in close contact with the formwork. The anchor round bars can be fixed to the rebar mesh either by binding or welding. After the formwork is removed, the surface of the embedded iron pieces should be visible, or it should be recessed by a depth of approximately 10–20 mm. Supports and hangers made of flat steel or angle steel can then be welded to these pieces for fixation. 　　4.6 Steel structure: The brackets or hangers can be welded directly to the fixed positions on the steel structure, or universal lifting equipment can be used for installation. 　　4.7 Installation of metal expansion bolts: 4.7.1 Requirements for installing metal expansion bolts: 4.7.1.1 Suitable for concrete elements of grade C5 and above as well as solid brick walls; not suitable for hollow brick walls or prestressed slabs. 4.7.1.2 The error in drill diameter shall not exceed +0.5~－0.3mm ； The depth error must not exceed +3mm ； After drilling, the remaining debris inside should be thoroughly removed. 　　4.7.1.3 After the bolt is fixed, the deviation of its head shall not exceed 2 mm. 　　4.7.1.4 The quality of bolts and sleeves shall meet the technical specifications of the product. 　　4.7.2 Installation method of metal expansion bolts. 　　4.7.2.1 First, mark the positions of the fixing points by drawing lines along the wall or ceiling according to the design drawings. 　　4.7.2.2 Select the appropriate metal expansion bolts and drill bits based on the loads carried by the bracket or hanger; the length of the selected drill bit should be greater than the length of the sleeve. 　　4.7.2.3 The drilling depth should be such that, after the sleeve is fully embedded in the wall or ceiling, it appears level. 　　4.7.2.4 After the bolts are installed, the bracket or hanger can be directly fixed to the metal expansion bolts using nuts along with the appropriate washers. 　　4.8 Trunking installation: 4.8.1 Requirements for trunking installation: 4.8.1.1 The trunking should be flat, without any twisting or deformation, with no burrs on its inner surface, and all accessories should be present. 　　4.8.1.2 The interfaces of the cable tray should be smooth; the joints must be tight and straight. After the tray covers are installed, they should be flat, without any warping, and the positions of the outlet connections should be accurate. 　　4.8.1.3 It is not allowed to fill in the wire troughs that pass through walls together with the holes in the walls. 　　4.8.1.4 Metal cable trays, their supports, and the metal cable conduits that lead in or out must be grounded (PE) or connected to the neutral conductor (PEN) in a reliable manner, and they must comply with the following requirements: 1. The entire length of the metal cable trays and their supports must have at least 2 connection points to the grounding (PE) or neutral (PEN) main conductors. 　　2. Copper core grounding wires shall be strung across both ends of the connection plates between ungalvanized cable trays, and the minimum allowable cross-sectional area of such grounding wires shall be 4 mm2. 3. No grounding wire shall be bridged across both ends of the connection plate between galvanized cable trays, but there shall be no less than 2 connection and fixing bolts with locknuts or lockwashers at each end of the connection plate. 　　4.8.1.5 Expansion joints shall be provided for steel cable trays with a length of over 30 m, and for cable trays made of lead alloy or fiberglass reinforced plastic with a length of over 15 m; compensation devices shall be installed where the cable trays cross building deformation joints. 　　4.8.1.6 Trunking laid in shafts and passing through areas that are not fire-rated shall have fire separation measures in the locations specified by the design. 4.8.2 Installation of cable trays: 4.8.2.1 The connections between the straight sections of the cable tray should be made using connection plates, with washers and spring washers as well as nuts for fastening; the joints should be tight and even, and the nuts should be located on the outside of the cable tray. 4.8.2.2 When cable trays intersect, turn, or connect at right angles, single-way, two-way, three-way, four-way connections, or planar two-way and planar three-way connections should be used for such connections. 4.8.2.3 When the cable tray is connected to boxes, cabinets, etc., clamping connections should be used at the inlet and outlet points, and these connections should be secured with screws; seals should also be installed at the ends. 5. Quality Standards 5.1 Key Control Items 5.1.1 The specifications of the cable trays must meet the design requirements and relevant regulatory provisions. 　　Inspection methods: visual inspection, measurement inspection. 　　5.2 General items: 5.2.1 Cable tray installation: Brackets and hangers should be arranged reasonably, fixed firmly, and kept level ； The tray covers have no warping, the joints are tight and neat; corners, bends, T-joints, and turning connections are proper and secure, with no contamination inside or outside the tray. 　　5.2.2 Circuit protection: When the circuit passes through beams, walls, floor slabs, etc., the cable tray should not be fixed firmly to the building structure ； The tray bottom plates across the building deformation joints should be disconnected, and compensatory allowance should be provided for all protective ground wires. 　　5.2.3 For the straight sections of cable trays installed horizontally or vertically, the degree of straightness and the allowable vertical deviation shall not exceed 5 mm. 6. Protection of finished products 　6.1 When installing cable trays, care should be taken to keep the walls and ceilings clean, and the building’s walls, doors, and windows must not be damaged. 　　6.2 When the reserved holes deviate from the specified dimensions, it is not allowed to arbitrarily chisel or cut the reinforcement bars. 　　6.3 Drilling holes in the prestressed slab to install expansion screws is strictly prohibited. 　　6.4 Welding of supports and hangers is strictly prohibited at non-fixed positions on the steel structure. 7. Quality issues that require attention: 7.1 If the brackets and hangers are not securely fixed, this is usually due to nuts on the metal expansion bolts not being tightened properly, or to welding defects at those joints. It is necessary to tighten the nuts on the bolts promptly and re-weld any defective areas. If the metal expansion bolts are not fixed properly, if they penetrate the wall too deeply or protrude too much, or if there are significant deviations in the drilling, which lead to looseness, these issues must be repaired immediately. 　　7.2 If the welds of the brackets or hangers have not been treated for corrosion protection, rust preventive paint should be applied to those areas promptly. 　　7.3 The wire diameter of the protective ground wire and the diameter of the crimping screws do not meet the requirements; all must comply with the specified standards. 　　7.4 The cable tray did not undergo any treatment when passing through the building’s expansion joints; the tray that crosses such joints should have its bottom plate separated, and it should be secured at both ends of the expansion joint. 7.5 If the joints of the cable tray are not level, if the cover plates are damaged, or if the protective covers at the connections between the cable tray and pipes are broken or missing, these issues should be corrected and improved.

The installation of cable trays can follow the relevant provisions in the GB50303-2002 Code for Acceptance of Construction Quality of Electrical Installation Projects.