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How to improve the pass rate of fire-resistant cable fire test
Since fire-resistant cables are now used more and more widely, many manufacturers are producing them, but the quality is often not guaranteed. Therefore, under normal circumstances, companies in the development of fire-resistant cable products, are trial production of a section of products, submitted to the relevant national testing agencies, after obtaining the test report, on the batch production, a few cable manufacturers have established their own fire test testing As we all know, the fire resistance test is aimed at the inspection of the results of the cable technology produced. There are certain differences in the same process plan and the performance of the cable produced at different times. For fire-retardant cables, the fire resistance test of the fire-retardant cable With a pass rate of 99%, there is a 1% risk of safety hazards for the fire-resistant cable, which is 100% dangerous to the user. So how to improve the pass rate of fire-resistant cable fire test, from raw materials, conductor selection, production process control, etc. do an explanation:
1. Mica comes with three types of synthetic mica, phlogopite, muscovite, their respective quality performance is synthetic mica, muscovite is the worst, for small size cable must choose synthetic mica tape to wrap, mica tape layering can not be used, The long-term storage of mica tape is easy to absorb moisture, so the temperature and humidity of the surrounding environment must be taken into account when storing the mica tape.
2. When using mica tape wrapping equipment, the stability performance should be good. The wrapping angle should preferably be 300-400, and the mica tape should be evenly packed around. All guide rollers and rods that touch the equipment must be smooth. Lines are neat and the tension is not too great. The side plates and cylinders of the tooling wheels are flat and smooth.
3. For circular cores with axial symmetry, their mica tapes are tight in all directions after wrapping. Therefore, for the fire-retardant cable conductor structure, a round compact conductor should be used. The reason is as follows:
1 Some users proposed that the conductor is a stranded flexible structure conductor, which requires the company to change from the reliability of the use of the cable to the user to a round compact conductor. The soft structure of the beam line, complex twisting can cause mica tape damage, as fire-resistant Cable conductor is not desirable, but some manufacturers think that users need what kind of fire-resistant cables, manufacturers should meet the needs of users, I think the user is not very clear about the relevant details of the cable, the cable is closely related to people's lives Therefore, cable manufacturers must clarify the relevant technical issues with users.
Two sector conductors should not be used, because the pressure distribution of the mica tape around the fan conductor is unevenly distributed. As shown in the figure, it can be seen from the figure that the pressure at the three fan corners of the fan-shaped core around the mica tape is the largest Because mica is a sheet-like silicate polymer, its interlayer attraction is far weaker than that of the s1-0 covalent bond in the crystal. The interlayers slide easily and are bonded by silicon, but the bonding strength is also Low, easily exfoliated and cracked during external force scraping and squeezing. Especially when fan-shaped structure is adopted, the wrapped core passes through the guide pulley, splitter bar and cable to the edge of the side plate of the tooling wheel, and the back channel When the process extrusion insulation enters the core, it is easily scratched and bumped, resulting in reduced electrical performance. In addition, from the perspective of cost, the perimeter of the sector conductor structure is greater than the perimeter of the circular conductor, thus increasing the valuable material mica. The belt, although the outer diameter of the circular structure cable has been increased, the amount of PVC sheathing material has increased, but the roundness of the structure cable is still saved compared to the total cost of the product material. Based on the above description, from the perspective of technical and economic analysis, the conductor of the fire-resistant power cable adopts a circular structure.