Design standards for cable trays

1. Selection of cable tray type and variety

1. When it is necessary to shield the cable network from electrical interference or to protect the external environment (such as: corrosive liquid, flammable dust, etc.), the (FB) type trough-type composite anti-corrosion shielding cable bridge (with cover) should be selected

2. (F) composite epoxy resin anti-corrosion and flame-retardant cable tray should be used in strong corrosive environment. The same material should also be used for the brackets and brackets to improve the service life of the bridge and accessories. It is advisable to add a cover plate in the environment or outdoor places that are easy to accumulate dust and need to be covered.

3. In addition to the above-mentioned conditions, tray-type, trough-type, step-type, glass anti-corrosion and flame-retardant cable bridges or ordinary steel bridges can be selected according to the site environment and technical requirements. It is advisable to add a cover plate in the environment or outdoor places that are easy to accumulate dust and need to be covered.

4. In public passages or outdoor crossing road sections, pads should be added to the bottom of the bottom steps or pallets should be used in this section. When the large span spans the public passage, the load capacity of the bridge frame can be increased or the row frame can be selected according to the user's requirements.

5. Composite bridges (FB) should be used for large spans (>3m).

6. Composite epoxy resin bridge (F) should be used outdoors.

2. Specification selection

1. The width and height of the bridge frame should be selected according to the table below, and should comply with the actual charging rate of the cable not exceeding the specified value of the relevant standards and specifications. The power cable can take 40-50%, and the control cable can take 50-70%. In addition, 10-25% of the program development margin should be reserved.

  2. The specifications of various bends and accessories should meet the project layout conditions and match the bridge frame.

3. The selection of support and hanger specifications should be configured according to the bridge specification, number of floors, span and other conditions. And should meet the load requirements.

4. The selection of bridge cross-sectional area is shown in the table

3. Configuration of supports and hangers

1. The short span of indoor support and suspension is generally 1.5-3m. The middle span of outdoor columns is generally 6m.

2. The support and hanger configuration of the non-linear section follows the following principles. When the width of the bridge frame is less than 300mm, a support and hanger should be installed on the side of the straight section 300-600m away from the junction of the non-straight section and the straight line. When the bridge width > 300mm, in addition to meeting the following conditions, a support and hanger should be added in the middle of the non-linear section.

3. When the bridge frame is set up in multiple layers, the center distance between layers is 200, 250, 300, 350mm.

4. Expansion joints of 20-30mm should be left every 50m in the straight section of the bridge (metal bridge).

4. Fire prevention

The section requiring fire protection of the bridge frame must be made of steel or non-combustible and flame-retardant materials. The BJⅢ series cable bridges produced by our company are all fireproof bridges.

5. Grounding

1. The bridge system should have a reliable electrical connection and be grounded (only for metal bridges).

2. When it is allowed to use the bridge system to form the grounding trunk circuit, the following requirements should be met. The connection resistance between the bridge ends should not be greater than 0.00033 ohms, and the insulating coating should be removed from the grounding holes. In the 1KV and below neutral point direct grounding system, the grounding of the powered equipment is connected to the system neutral line grounding. When equipped with a dynamic cut-off power supply device, the metal cross-sectional area of the bridge frame in the step direction should not be less than the specified value.

3. When another grounding trunk line is laid along the entire length of the bridge frame, at least one point of each bridge frame (including the non-linear section) should be reliably connected to the grounding trunk line.

4. For vibrating places, a spring ring should be installed at the connection of the grounding part.

Six, bridge system design content

The engineering design of the bridge system should cooperate closely with civil engineering, technology and related professions to determine the best layout. The design content may include:

1. Relevant sectional drawing of the bridge system.

2. The floor plan of the bridge system.

3. A detailed list of the specifications and quantities of straight sections, bends, supports and hangers required by the bridge system and necessary instructions.

4. Technical description or schematic diagram of non-standard parts with special requirements.