Installation of a cable in wire trays
Trays for a cable (cable trays) – the electroassembly devices intended for laying in them of cables, power and low-current wires, construction of cable routes, suspended channels on industrial and other facilities. It is convenient to serve trays. Access to a cable and wires is at any time provided. Especially at such way of installation as laying of a cable in trays the esthetic type of electric wires at installation is provided indoors. Externally cable tray has an appearance of a metal profile or a box with the basis and a cover. The cable in a tray is completely environmentproofed. Length and width of trays can be various. Connection of trays is provided by connection of sections (input of one in another). In this case sections are fixed by screws or special connectors. Considering features of installation in these or those conditions, the angular sections, lateral branches, transitions, disconnectors, crosspieces providing crossings of a cable in one surface are provided in trays. Types of cable trays: continuous, punched, wire, ladder. Features of installation of cable trays. Laying of a cable in trays is made where laying of a cable in pipes is not obligatory according to installation conditions. In rooms with the increased temperature and dampness, and also chemically active environment installation of a cable in trays is allowed. The main document which regulates creation of cable system including such way of laying as installation of a cable in trays, - Rules of the Device Elektroustanovok. According to rules, the cable tray on which the cable made of the materials which are carrying out electric current is laid has to be surely grounded. Thus, if isolation of a cable is broken, the metal tray will not appear under tension and the possibility of defeat is excluded by electric current. Each section of a tray is not required to be grounded as the design already provided screw connection of sections. Cable trays need to be grounded in two or more places from different sides of the route and in addition, in places of branch. At installation of cable trays in their fastening not less than 2 meters from a floor have to be carried out. When crossing a tray with the pipeline the distance has to be not less than 5 cm and 10 cm in case of a parallel arrangement, and when passing in the next pipes of gas or hot liquid – 25 cm. In trays it is allowed to stack a cable up to 10 kV. The last tray has to be filled only for 50%. Other half of a tray remains free for ensuring cooling.