Long span cable distance bridge can be divided into ladder, tray, trough. Cascade bridge with good ventilation performance, no dust, may disturb. The surface treatment of tray type cable bridge can be divided into three types according to the needs of users: galvanizing, electrostatic spraying and hot-dip galvanizing. Trough - type, tray - type bridge with dust - proof, anti - interference performance. Trough cable bridge is a fully closed cable bridge, with a cover plate, the use of quantitative connection bolts, it is suitable for laying computer cables, communications cables, thermocouple cables and other high sensitive system control cables, etc., it has a very good effect on the control of cable interference and cable protection in heavy corrosion environment. Long span cable tray is made of pultruded glass fiber reinforced plastic profiles, suitable for power cables, control cables, lighting cables and accessories. Compared with the iron bridge, it has the advantages of long service life (the general design life is 20 years), convenient installation and low cost (the proportion is only 1/4 of the carbon steel, no fire during construction, the length of a single bridge can reach 8 meters or even longer), convenient cutting and no maintenance. Installation and maintenance: 1. When the height of the bridge is 50 and 100, there are 6 connection holes at each end; when the height is 150 and 200, there are 12 connection holes at each end. 2. Support spacing: the support spacing shall be less than or equal to the allowable load and support span of the load curve. 3, bridge width: when choosing the width of cable bridge, there should be some spare space, so as to add cables in the future. 4. Separate laying: when there are fewer power cables and control cables, they can be installed on the same cable bridge, but the power cables and control cables must be separated and laid by partition. 5. Cable fixation: when the junction bridge is laid horizontally, the connection between the Bridges should be set at 1/4 of the span as far as possible. The horizontal cable is fixed every 2 meters or so, and the vertical cable is fixed every 1.5 meters or so.