Discussion on process problems of producing fire-resistant cable
Because fire-resistant cables are now used more and more widely, many manufacturers are producing them, but often the quality is not guaranteed. Therefore, under normal circumstances, when enterprises develop fire-resistant cable products, they first trial-produce a section of products, send them to relevant national inspection agencies, and then produce them in batches after obtaining the inspection reports, A small number of cable manufacturers have set up their own fire resistance test rooms. As we all know, fire resistance tests are aimed at the inspection of cable process results produced, the same process scheme and the cable performance produced in different periods have certain differences, for enterprises that produce fire-resistant cables, if the passing rate of fire-resistant tests for fire-resistant cables is 99, there is a 1% danger of potential safety hazards for fire-resistant cables, which is 100% danger for users, in view of these problems, Chongqing Taishan Cable Co. , Ltd. explained how to improve the passing rate of fire-resistant cable fire-resistant experiment from the aspects of raw materials, conductor selection and production process control: 1. There are three kinds of Mica tapes: synthetic mica, phlogopite and muscovite. Their respective quality properties are the best for synthetic mica and the worst for Muscovite. For small-sized cables, synthetic mica tapes must be selected for wrapping, mica tape layering can not be used, long-term storage of Mica tape is easy to absorb moisture, so the temperature and humidity of the surrounding environment must be considered when storing Mica tape. 2. When selecting Mica tape wrapping equipment, it should adopt good stability, and the wrapping angle should be 300-- 400 winding, the mica belt is evenly and tightly wrapped, all the guide wheels and rods that touch the equipment must be smooth, the cable is neat, the tension is not too large, and the side plate and cylinder of the wire taking-up tool are smooth. 3. For the round wire core with axial symmetry, the direction after the mica tape is wrapped is tight, so the conductor structure of the fire-resistant cable should adopt the round compact conductor. The reasons are as follows: ① some users propose that the conductor is a bundle twisted soft structure conductor, which requires enterprises to change the communication with users from the reliability of cable use to a round compressed conductor, the soft-structure cable bundle and twist are easy to cause Mica tape damage, which is not desirable as a fire-resistant cable conductor. However, some manufacturers think that what kind of fire-resistant cable users need, manufacturers should meet the needs of users, I think the user is not very clear about the details of the cable after all. The cable is closely related to human life, so the cable manufacturing enterprise must explain the relevant technical issues to the user. (2) fan-shaped conductors should not be used either, because the winding pressure of Mica tape of fan-shaped conductors is unevenly distributed, as shown in the figure, it can be seen from the figure that the pressure at the three fan-shaped corners of the fan-shaped core around the wrapped Mica tape is the greatest. As Mica is a sheet silicate polymer, its interlayer molecular attraction is far greater than s1-in the crystal- 0 The Bond force of covalent bond is weak. the interlayer is easy to slide and is bonded by silicon, but the bonding strength is also low, and it is easy to fall off and crack when scraping and squeezing by external force, especially when fan-shaped structure is adopted, when the wire core after wrapping is passed through the guide wheel, the branch Rod and the cable to the edge of the side plate of the tooling wheel, and the extrusion insulation of the rear process enters the mold core, it is easy to scratch and bruise, resulting in a decline in electrical performance. In addition, from the perspective of cost, the cross-sectional circumference of the sector conductor structure is larger than that of the circular conductor, thus increasing the mica tape of valuable materials, although the outer diameter of the circular cable has increased. the amount of PVC sheath material increases, but compared with the total cost, the product material is still economical in terms of comprehensive cost. Based on the above description, from the technical and economic analysis, the conductor of the fire-resistant power cable adopts the circular structure as the best.