Views:103 Author:Site Editor Publish Time: 2019-09-13 Origin:Site
Cables include electric cables, control cables, compensation cables, shielded cables, high temperature cables, computer cables, signal cables, coaxial cables, fire resistant cables, marine cables, mining cables, aluminum alloy cables, earth cables and the like. They are composed of single or multi-strand wires and insulating layers for connecting circuits, electrical appliances, etc.
1) When the cables cross each other, the high voltage cable should be below the low voltage cable. If one of the cables is protected by a pipe or separated by a partition within 1 m before and after the intersection , the minimum allowable distance is 0.25 m.
2) When the cable is close to or intersects with the heat pipe, if there is insulation, the minimum distance between parallel and cross is 0.5m and 0.25m respectively.
3) When the cable crosses the railway or the road, it should be protected by a pipe. The protection pipe should extend beyond the track or road surface by 2m.
4) The distance between the cable and the foundation of the building should allow that the cable is buried outside the building's scattered water. When the cable is introduced into the building, it should be protected by a pipe, and the protective pipe shall be outside the building's scattered water.
5) The distance between the cable directly buried in the ground and the grounding of the general earthing device should be 0.25~0.5m. The buried depth of the cable buried directly in the ground should not be less than 0.7m, and should be buried under the frozen soil layer.
With the rapid development of the power cable buried laying project, there is a higher requirement for cable protection, the cable protective pipe is made of polyethylene PE and high quality steel which are processed with pre-treated sand blasting, dipping or coating, heating and solidifying. It is the most commonly used electrical insulation tube for protecting wires and cables. Because it has good insulation performance, high chemical stability, no rust, no aging, and can adapt to harsh environments.
Protecting the cable with a cable protection pipe has the following advantages:
1) Good corrosion resistance and long service life, it can be used in wet salt and alkali area.
2) Flame retardant and heat resistance, it can be used for a long time at 130 °C without deformation, and does not burn in case of fire.
3) High strength and high rigidity, it can be used directly under the carriageway without the need to add a concrete protective layer.
4) The cable protection pipe has certain flexibility whether it is a pipe or pipe fitting, and it can resist the damage caused by external heavy pressure and foundation settlement.
5) It has good resistance to external signal interference.
6) The inner wall is smooth and does not scratch the cable. The design adopts a socket type connection for easy installation and connection. The rubber sealing ring seal at the joint not only adapts to thermal expansion and contraction, but also prevents mud sand from entering.
If the cable need to be stored for a long time, the following things should be considered according to the location of the cable:
1) Under the eaves. The standard LAN cable can be used only when the cable is not directly exposed to sunlight or high temperature. It is recommended to use the pipe.
2) The outer wall. Avoid direct sunlight on the wall and human damage.
3) In the pipe (plastic or metal). For example, in the pipeline, pay attention to the damage of the plastic pipe and the heat conduction of the metal pipe.
4) Suspended application / overhead cable. Considering the sagging and pressure of the cable, which bundle is intended to be used, whether the cable is directly exposed to sunlight.
5) Laying directly in the underground Cable trench. Cable trench installation should be checked regularly for dryness or humidity.
6) Underground pipelines. In order to facilitate future upgrades, cable replacement and isolation from surface pressure and surrounding environment, auxiliary piping is a better method. But don't expect the pipeline to remain dry forever, which will affect the choice of cable type.
The main raw materials for the production of electric wires are electrolytic copper, insulating materials and sheathing materials. In the raw material market, electrolytic copper is about 50,000 yuan per ton, and the recovered copper is only about 40,000 yuan per ton; the price of high-quality insulating materials and sheathing materials is 8,000 yuan to 10,000 yuan per ton, and the defective products is only 4,000 yuan to 5,000 yuan per ton, and the difference is even more disparity. In addition, the length is insufficient and the amount of glue contained in the insulator is insufficient, which is also an important cause of price difference. The length of each line is 100 meters, and the defective product is only about 90 meters; the insulation containing rubber is 35%~40%, and the defective product is only 15%. By contrast, it is not difficult for the consumer to see that there is a difference in the sales price of the finished wire.