Cable bridges have only been used in China for more than a decade, and they have only been developed in Europe and America for decades. In a computer room project, the bridge is very inconspicuous and less noticeable than the expensive and high-tech hardware and software, but it is also an indispensable part of the entire cabling project. However, as a supporting project of cable engineering, there is no specific normative guidance for cable bridges at present, and the manufacturer's specification programs lack generality. Therefore, the design selection process should be based on the types of weak cable system, the number of reasonable selection of suitable bridge.
First, the choice of cable tray type and variety
1. When it is required to shield the cable network of electrical interference or to protect the external (such as: corrosive liquid leakage, flammable dust, etc.), the type (FB) composite composite anti-corrosion shielded cable tray (with cover) shall be used. ).
2, strong corrosive environment should use (F) composite epoxy resin flame-retardant cable tray. The same material is used for the supporting arm and bracket to increase the service life of the bridge and accessories, and the cable tray. It is advisable to add cover plates in areas where there is a tendency to collect dust and other areas that need to be covered.
3. In addition to the above situations, the tray type, trough type, step type, glass anti-corrosion flame-retardant cable tray or steel ordinary type tray tray can be selected according to the site environment and technical requirements. It is advisable to add cover plates in areas where there is a tendency to collect dust and other areas that need to be covered.
4. In the public access road or outdoor crossing road section, the bottom of the bottom step should be padded or used in the section. When a large span spans a common pasغير مجاز مي باشدe, the load capacity of the bridge can be increased or a stand can be selected according to user requirements.
5, large span (> 3m) to use composite bridge (FB).
6, outdoor use composite epoxy resin finger bridge (F).
Second, the cable bridge specification selection
1. The width and height of the composite epoxy resin cable tray are selected according to the following table, and should comply with the actual charging rate of the cable not exceeding the specified value of the relevant standard specification. The power cable may take 40-50% and the control cable may take 50-70%. In addition, 10-25% of the development margin needs to be reserved.
2. The specifications of various bends and accessories should be in accordance with the conditions of project layout and be matched with the bridge.
3. The selection of support and hanger specifications shall be based on the specifications of the bridge frame, the number of layers, the span, and other conditions. And should meet the requirements of the load.
Third, the cable bridge support, hanger configuration
1. The indoor span and short span are usually taken to be 1.5-3m; the midspan of outdoor pillars is generally 6m.
2. The non-linear section support and hanger configuration shall follow the following principles: When the bridge width is less than 300mm, a support and hanger shall be installed on the side of the straight line between the non-linear section and the straight line at 300-600m; when the width of the bridge >300mm, in addition to meet the following conditions, in the middle of the non-linear section should also add a branch, hanger.
3, pultruded fiberglass cable bridge multi-layer setting when the center distance between the layers of 200,250,300,350 mm.
4. The bridge section should be left with expansion joint 20-30mm (metal bridge) every 50m straight line section.
Four, on the calculation of some of the cable tray:
Cable bridges are stamped from sheet steel. Its carrying capacity has a certain limit. The size of the load capacity of the cable tray is an amount related to the size of the tray and the support distance. Corresponding to the same support distance and bending deformation, the bridge with large side height has a large carrying capacity, while the bridge with small height has a small carrying capacity. In addition, when the load capacity is the same or different, for a cable bridge of the same specification, a small supporting distance is smaller than the supporting distance. Under normal circumstances, a set of support frames are installed every 1.5 to 2.0m in the cable tray.
1. Calculate the actual load of the cable tray G Total=n1*q1+n2*q2+n3*q3......nn*qn
In the formula: G is the total load, q1, q2, q3...qn is the unit weight of each cable (kg/m), n1, n2, n3... nn are the number of the same cable.
2. Calculation of Cable Bridge Width The determination of the width of the cable tray is different with the different working systems of power cables and control cables. Since the power cable is generally discharged horizontally in the bridge, the width b of the installed bridge is:
b=n1*(d1+k1)+n2*(d2+k2)+n3*(d3+k3)+......nn*(dn+kn)
In the formula: d1, d2, d3,... dn are the outer diameters of various cables in the bridge, the unit is mm; n1, n2, n3... nn are the same number of the same kind of specifications of the cable; K1, k2, k3... ... The spacing for the above cable placement should be a minimum of 1/4 of the cable diameter.
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