What Are Cable Trays?

Cable trays are divided into trough, tray, ladder, and network formats, and are composed of brackets, supporting arms, and mounting accessories. The bridge in the building can be erected independently, or it can be laid on various structures (structures) and pipe racks. It should reflect the characteristics of simple structure, beautiful appearance, flexible configuration and convenient maintenance. All parts need to be galvanized , Installed in the open-air bridge outside the building.

It consists of trough, tray or stepped straight line sections, bends, tees, four-way components, and supporting arms (arm type brackets), hangers, etc.

Weak electrical systems in smart buildings usually have multiple information monitoring and communication facilities such as BA (building automation), OA (office automation), CA (communication automation), etc.

First, the choice of cable bridge type and variety

1. When the cable network that needs to be shielded from electrical interference or is required to be protected from external influences (such as corrosive liquids, flammable dust and other environments), the (FB) trough composite anti-corrosion shielded cable bridge (with cover) should be selected .

2. For severe corrosive environment, (F) composite epoxy resin anticorrosive and flame retardant cable trays should be used. Supporting arms and brackets should also be made of the same material to improve the service life of bridges and accessories and cable bridges. Covers should be added in the environment that is easy to accumulate dust and other areas that need to be covered or outdoor places.

3. In addition to the above situations, tray type, trough type, step type, glass anti-corrosion and flame retardant cable tray or steel ordinary bridge tray can be selected according to the on-site environment and technical requirements. Covers should be added in the environment that is easy to accumulate dust and other areas that need to be covered or outdoor places.

4. Cross the road section in the public passage or outdoors. The bottom of the bottom rung should be added with pads or trays in this section. When the long span spans the public passage, the load capacity of the bridge can be increased or the frame can be selected according to user requirements.

5. For large spans (> 3m), composite bridges (FB) should be selected.

6. Use composite epoxy bridge (F) outdoors.

Specification selection

1. The width and height of the bridge are selected according to the following table, and the cable fill rate should not exceed the value specified in the relevant standards. The power cable can be 40-50%, the control cable can be 50-70%, and the remaining 10- 25% formula development margin.

2. The specifications of various bends and accessories shall meet the project layout conditions and be matched with the bridge.

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

4.Bridge

Pay attention to the installation of cable tray

A few notes about cable bridge installation:

(1). Visual inspection

When the cable bridge enters the construction site, the following materials shall be submitted: the certificate of delivery of the product, the periodic inspection report of the provincial and municipal quality supervision station, and the relevant technical appraisal documents. The thickness of the cable bridge plate shall meet the relevant requirements. The coating surface of the hot-dip galvanized cable bridge should be uniform, without overheating, hanging ash, local non-galvanized defects. Electrostatic spraying should be flat, smooth, uniform, non-skinning, no bubbles, and blister. The bridge itself should be flat and free of distortion.The inner wall should be smooth and free of burrs. The weld surface of the bridge should be uniform without leakage, cracks, burn-through, etc defect.

(2). Installation position of cable tray

When the bridge is laid horizontally, the height from the ground should not be lower than 2.5m. In the multi-layer laying of the bridge, in order to dissipate heat, maintain and prevent interference, a certain distance should be left between the layers of the cable. When the cable bridge is laid in parallel with various pipes, its clear distance should meet the relevant regulations.

(3). Installation of support and hanger

The quality of the support and hanger of the cable bridge should meet the current relevant technical standards. When the cable bridge is laid horizontally, the support span is generally 1.5 ~ 3m. When trying to lay it vertically, the fixed distance should not be greater than 2m. It should not be greater than 10mm, and the vertical deviation of the vertical centerline of two adjacent bridge bracket arms should not be greater than 20mm.

1.Cable bridge as

1. Type selection of cable tray structure < br In engineering design documents, cable trays are generally referred to as "bridge trays" without specifying specific structural characteristics. The price of cable trays of different types and different materials varies widely and the structure The type of confusion will cause problems in the field of heat dissipation and mechanical protection. Therefore, in the design stage, designers should be required to reasonably select the structural characteristics of the cable tray according to the characteristics of the engineering environment and technical requirements, and clearly expressed in the model designation and material table of the plan.
2. Material selection of cable trays <br /> The material of cable trays is another common problem in cable tray engineering design. According to the material classification, cable bridges are mainly made of steel, glass fiber reinforced plastic and aluminum alloy. The characteristics of FRP cable tray are light weight, only 1/4 of the specific gravity of carbon steel; good water resistance and corrosion resistance, suitable for chemical plants. Non-combustible, flame retardant fiberglass cable tray with oxygen index 32. Long life, generally designed life is 20 years, but the price is three times that of steel cable trays. The advantage of construction is that the cutting is convenient, the assembly is flexible, and no fire is required for the installation. This is particularly significant for chemical plant projects with explosive hazardous environments and tight construction schedules, because in explosive dangerous environments, the chemical plant must be shut down during the installation of the project fire, which is economical. Benefits will be affected. The weight of aluminum alloy cable tray is also very light. Due to the different specific gravity of aluminum and steel (Al = 2.7, Fe = 7.86), the ratio of aluminum to steel is about 1: 3 by weight. The dimensions and load characteristics of aluminum alloy cable trays are basically similar to those of steel bridges. In terms of cost, the cost of aluminum alloy bridges is 20% higher than that of galvanized steel cable bridges, and the service life is more than 5 times that of steel cable bridges.
3 Selection of the type of anticorrosive layer on the surface of cable trays. <br /> The third common problem in engineering design is that the type of cable trays is not marked with the type of anticorrosive layer, and there is no uniform text description. This problem has lessons in reality. For example, a certain Indonesian project undertaken by China as a general contractor did not carry out salt spray test on the surface anticorrosive treatment of steel cable trays. After the completion of the bridges, the bridges were quite rusted and had to be replaced. The types of surface anticorrosive coatings for cable trays are mainly hot dip galvanized, galvanized nickel, cold galvanized, and powder electrostatic spraying. Manufacturers' data show that the hot dip galvanizing process has a service life of not less than 40 years, which is suitable for outdoor heavy corrosion environments and cost High; galvanized nickel process life is not less than 30 years, also suitable for outdoor heavy corrosion environment, high cost; cold galvanizing process life is not less than 12 years, suitable for outdoor light corrosive environment, the cost is average; powder electrostatic spraying process life is not less than 12 years, suitable for indoor normal temperature and dry environment, the price is average. The designer should reasonably choose the type of surface anticorrosive layer of the cable tray according to the engineering environmental conditions, and express it clearly in the design document.
4 Selection of fire resistance level of cable trays <br In the sections where fire resistance is required, cable trays and trays can be added with materials such as fire-resistant or flame-resistant boards and nets to form closed or semi-closed structures, and Measures such as applying a fire-resistant coating to the surface of the bridge and its support and hangers, and its overall fire resistance shall meet the requirements of relevant national codes or standards. In places with high fire protection requirements, it is not suitable to use aluminum alloy cable trays.
Under the same specifications, flame-retardant cable trays are 2.2 times more expensive than steel cable trays, their service life is more than 5 times that of steel cable trays, and their weight is 30% heavier than steel cable trays. Fire-resistant cable tray is slightly more expensive than steel cable tray, its service life is more than 3 times that of steel cable tray, and its weight is basically the same as steel cable tray.
5. Selection of cable bridge filling rate <br The selection of cable ladder frame, tray width and height should meet the requirements of filling rate. The filling rate of cable ladder frame and tray under normal circumstances, power cables can take 40% to 50% The control cable can take 50% to 70%, and 10% to 25% of the project development margin should be reserved.
6. Selection of load level of cable trays <br /> When selecting the load level of cable trays, the working uniform load of the cable trays should not be greater than the rated uniform load of the selected load level of the cable trays. When the span is not equal to 2m, the work uniform load should meet the requirements. Under the conditions of corresponding loads, the specifications and dimensions of various components and hangers should match the straight sections of the pallets, ladder frames, and bent series.
7. Selection of specifications and sizes of cable trays brIn engineering practice, the problem in the selection of specifications and sizes of cable trays is either too large or too tight. How to choose a reasonable size of cable tray? Articles 8, 10, and 7 of the Code for Electrical Design for Civil Buildings (JGJ16-2008) stipulate: "The ratio of the total cross-sectional area of the cable to the cross-sectional area inside the tray, the power cable should not be greater than 40%; the control cable should not be greater than 50%. "
8. Select the cable bridge according to the cable bending radius < br When selecting the bend of the cable bridge or the device that leads up and down, it should not be less than the minimum allowable bending radius of the cable in the cable bridge.
9. Problems with material statistics <br The main problems with material statistics in design drawings:
1) Missing items. Some statistics of the bracket materials are only for the through part, but not for the bent part; for some material tables, there is simply no support or hanger item. For engineering general contracting companies, the consequence of missing items is that the quotation is low during the project quotation stage, and the procurement department always signs supplementary contracts with suppliers during the project execution stage, which leads to a reduction in the general contractor's profit.
2) The wrong term. The reason is that many designers are not clear about some concepts, some consider elbows, supports and hangers as accessories, and some use the cover plate as the main material. In fact, the "bracket" of the cable tray includes both straight and bent through parts. The "accessories" of cable trays include various connecting plates, cover plates, partitions, pressure plates, terminal plates, lead-down pieces, fasteners, and so on. The accessories are not listed in the material table, and are supplied by the supplier with the package. The cost is entered in the unit price of the bracket. The project does not require a separate quotation by the supplier. The "support and hanger" includes supporting arms, columns, hangers, etc., which need to be listed separately. Suppliers in the project need to quote separately.
3) The statistical bias is large, usually the number is small. So how to accurately calculate the material of the cable tray in the project quotation? Generally speaking, a 1% to 2% margin can be considered for the through part of the bracket, and the quantity can be directly counted for the bent part. The total length of the bridge is divided by the average column spacing (the span of outdoor columns is generally 6m, and the span of indoor columns is generally 3m). The number of columns is increased by 2% to 4%. The total length of the bridge is divided by the average distance between the supports and hangers to get the number of supports and hangers, and then consider the 1% to 2% margin. As for the distance between the supports and hangers, the distance between the supports and hangers in the indoor straight section is generally 1.5 to 3m, and the distance between the vertically installed supports is not greater than 2m. The configuration of support and hangers for non-straight sections should comply with the specifications: when the bending radius of the bend is less than 300mm, a support and hanger should be provided on the side of the straight section 300 to 600mm away from the non-straight section and the straight line; When it is not less than 300mm, in addition to setting a support hanger on the side of the linear section 300 to 600mm away from the non-linear section and the straight line joint, an additional support hanger should be added in the middle of the non-linear section.

Selection and design of cable tray 1. Determine the environmental conditions There are generally three types of environmental conditions: corrosive environment, normal environment, and special environment.

2. According to the direction of most cables, you can walk along, columns, beams, and floors in the interior, and as far as possible along the process pipelines.
3. Calculate the load Calculate the weight q and total load G of the unit length cable in the section of the cable tray
G total = n1q1 + n2q2 ... nnqn where: q1 · q2 · q3 ... qn is the unit weight of each cable (kg / m)
n1 · n2 · n3 nn is the same cable number G total <G allowed (refer to the load curve chart for the allowable load of the cable tray)
4. Choosing the bridge type According to the cable load and the environment where the bridge is installed, based on the load curve of the bridge, determine the type and specifications of the bridge and the distance between the columns, the length of the support arm, the layer of the bridge, the length of the column, etc.
5. Determine the fixing method of the bridge frame according to the direction of the cable and the installation environment; hanging type, upright type (both types can be fixed on one side or both sides), wall side type, etc.
6. The layer arrangement and distance between various cables on the cable tray.
The cable bridge hierarchy is arranged as follows: the weak current control cable is at the top, and then the general control cable, low voltage power cable, and high voltage power cable are arranged below in order: the following table: this arrangement is good for shielding interference, ventilation, and heat dissipation.

Cable bridge parts name meaning and general terms

Main components of cable tray

The support of the cable tray when it is installed is completed by the column and the support arm. The post is the main component supporting the cable bridge; the load of the bridge is transmitted to the post through the supporting arm. Therefore, uprights and brackets are the two main components for cable tray installation.

Cable tray aluminum alloy frame

Abbreviation of aluminum alloy cable bridge device, which is made of aluminum alloy material, through-bent attachments of trays or ladder frames, support hangers, etc., constitute an overall device for supporting cables with a continuous rigid structure.

Cable tray trapezoidal bridge

Abbreviation for the component of the trapezoidal cable tray that directly supports the cable, a trapezoidal component composed of two longitudinal sides and a number of crossbars

Cable tray perforated tray

Perforated trough cable bridge is an abbreviation for the component that directly supports the cable. It is composed of a bottom plate with perforations and sides or is formed by punching a whole aluminum alloy plate and bending it to make a trough with a hole at the bottom.

Cable tray without hole tray

Abbreviation for the component of the non-porous trough cable bridge that directly supports the cable. It is a trough-shaped component made of a base plate and sides or made of a solid aluminum plate by bending.

Cable tray other series

LQJ series aluminum alloy cable tray is a kind of anti-corrosion bridge designed and manufactured by our factory. It has the characteristics of simple structure, novel style, corrosion resistance, convenient installation and maintenance, no maintenance, etc., and can be applied to a wide range of environmental conditions.

LQJ series aluminum alloy anti-corrosion bridge can be divided into LQJ-A, B, C type and LQJ-LPC type according to the structural form. The former uses aluminum alloy extruded profiles with different cross-section shapes to process the bridge board and ladder steps, which can be made into steps. Type, tray type, slot type structure to meet the needs of different occasions, the latter uses aluminum plate folding edge molding to make slot type wire trunking and various special bends to meet the needs of cable wiring. LQJ-A, B, C type aluminum alloy extruded profiles are processed by solution treatment and artificial aging treatment, which not only improves the corrosion resistance, but also increases the strength of aluminum alloy, thereby ensuring that the aluminum alloy bridge has a higher bearing capacity.

The surface of the LQJ series aluminum alloy anti-corrosion bridge is anodized, which makes it more excellent in corrosion resistance, has a long corrosion resistance, and does not require maintenance. It is especially suitable for high temperature, high humidity, and salt mist-rich environments. ^[1]