Composite ladder cable tray, as a complementary project for wiring engineering, currently lacks specialized guidelines, and the specifications of various manufacturers are lacking in universality. Therefore, the design and selection process should reasonably choose the appropriate tray based on the types and quantities of cables for each low-voltage system.

1. Selection of cable tray types and varieties

1. When there is a requirement for cable network shielding against electrical interference or protection against external influences (such as corrosive liquids, flammable dust, etc.), it is recommended to use (FB) type槽式 composite anti-corrosion shielding cable bridge (with cover).

2. For environments with high corrosiveness, use Class (F) composite epoxy resin flame-retardant cable bridge supports. The arm and brackets should also be made of the same material to extend the service life of the bridge supports and accessories. In areas prone to dust accumulation or other environments requiring cover, or outdoors, it is advisable to add a cover plate.

3. In addition to the aforementioned situations, tray-type, channel-type, ladder-type, glass-protected flame-retardant cable bridge supports, or steel ordinary-type bridge supports can be selected based on the on-site environment and technical requirements. In environments prone to accumulating dust or other areas requiring coverings, as well as outdoor settings, it is advisable to install a cover.

4. For public passages or road crossings outdoors, it is advisable to add a padding board at the bottom of the lower step or use a pallet in that section. When crossing a large span over a public passage, the load capacity of the bridge can be increased according to customer requirements or a walking frame can be selected.

5. For spans greater than 3 meters, select a composite bridge (FB).

6. Choose composite epoxy tree finger bridge (F) for outdoor use.

II. Cable Tray Specifications Selection

Composite epoxy resin cable trays should meet the requirements of the relevant standards and specifications for the cable filling rate, which should not exceed 40-50% for power cables, 50-70% for control cables, and an additional 10-25% for future expansion.

2. Various elbow and accessory specifications should comply with engineering layout conditions and be compatible with the bridge架.

3. Selection of support and hanger specifications should be configured according to the bridge channel specifications, number of layers, span, etc., and should meet the load requirements.

Section 3: Configuration of supports and hangers for cable trays

1. Indoor support and suspension spans typically range from 1.5 to 3 meters; outdoor pillar spans usually are 6 meters.

2. The support and suspension configuration for non-linear sections follows these principles: When the bridge width is less than 300mm, a support or suspension should be set on the straight section side, 300-600mm away from the junction of the non-linear section with the straight section. When the bridge width is greater than 300mm, an additional support or suspension should be added in the middle of the non-linear section, in addition to meeting the following conditions.

3. When installed in layers, the center distance between layers of pultruded fiberglass cable trays is set at 200, 250, 300, and 350mm.

4. The bridge channel should have expansion joints of 20-30mm every 50 meters (for metal bridge channels).

Section 4: Calculation Formulas for Cable Trays

Cable trays are made from thin steel plates. Their load-bearing capacity is limited. The load capacity of cable trays is a quantity related to the tray specifications and the support distance.

For the same support span and bending deformation, the bridge with a larger side height has a greater load-bearing capacity, while the one with a smaller height has a lower load-bearing capacity.

Additionally, when the load-bearing capacity is the same, the cable tray with a smaller support distance will have less bending deformation than one with a larger support distance for the same specification. Generally, support brackets are installed at intervals of 1.5 to 2.0 meters for cable trays.1. Actual Load Capacity Calculation for Cable Trays

In the formula G_total = n1*q1 + n2*q2 + n3*q3 + ... + nn*qn, G_total represents the total load, q1, q2, q3, ..., qn are the unit weights (kg/m) of each cable, and n1, n2, n3, ..., nn are the number of cables of the same type. (G_total < G_allowed, where G_allowed is the allowable load for the cable tray. This is because when the cable tray is installed outdoors with a protective cover, the impact of heavy snow and ice loads on the cable tray should also be considered.)

2. Calculation of Cable Tray Width

The determination of cable tray width varies depending on the working system of power cables and control cables. Since power cables are typically laid horizontally in a single layer within the tray, the installation width of the tray, b, is:

b=n1*(d1+k1)+n2*(d2+k2)+n3*(d3+k3)+…

nn*（dn+kn）

In the formula: d1, d2, d3...dn represent the outer diameters of various cables inside the bridge, in mm; n1, n2, n3...nn are the number of cables of the same type and specification mentioned above; K1, K2, K3...are the spacing values when placing the cables, which should be greater than 1/4 of the cable diameter.

Yunnan Ziyang Zongjiu Industrial & Trade Co., Ltd. is a cable tray manufacturer in Yunnan, specializing in tray production and processing for many years. We offer standard specifications at factory prices, featuring galvanized, fire-resistant, and easy-to-install channel trays. If you are in need of purchasing cable trays, please feel free to call for detailed discussions!!