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How to improve the pass rate of refractory test
- May 18, 2017 -

Because the fire-resistant cables are now used more and more widely, so many manufacturers are in production, but often the quality is not guaranteed. So in general, enterprises in the development of fire-resistant cable products, are first-trial production of a product, testing the relevant national inspection agencies, testing reports, the bulk of production, a few manufacturers have established their own fire test testing room, as we all know, fire-resistant test is to test the production of cable process results, the same process plan, in different period of the production of cable performance has certain differences, for the production of refractory cable enterprises if the fire resistance test pass rate of 99 %, the fire-resistant cables are in danger of a 1% safety hazard, which is a 100% hazard for users. How to improve the passing rate of fire-resistant cables, from raw materials, conductor selection, production process control, etc.

1. Mica with three species, synthetic mica, Jin Yunmu, Muscovite, their respective quality performance is the best synthetic mica, Muscovite worst, for small specifications of the cable must be selected synthetic Mica tape wrap, Mica tape layering can not be used, long-term storage of mica tape easily hygroscopic, so in storing mica tape must consider the ambient temperature and humidity.

2. Use mica tape wrap equipment, should adopt stable performance good, wrap angle is best in 300--400 wrap wrap, its mica belt wrap wrap evenly tight, all with the equipment presses the guide pulley and rod must be smooth, the line neat, the tension is not too big, the receiving line tooling wheel side plate and the barrel body smooth.

3. For the circular core with axial symmetry, the mica tape is close in each direction after the package, so the conductor structure of the refractory cable should be circular pressing conductor. The reasons are as follows:

① Some users put forward a conductor as a bundle of soft structure conductor, which requires enterprises from the use of the reliability of the cable to communicate with the user to change the circular pressure conductor, soft structure bundle wire, complex twisted easily caused by mica tape damage, as a fireproof cable conductor is not desirable, but some manufacturers think that users need a kind of fire-resistant cables, manufacturers should meet the needs of users, I think users after all the relevant details of the cable is not very clear, cable is closely related to human life, Therefore, the cable manufacturing enterprises must clarify the relevant technical issues with the users.

② fan-shaped conductor also unsuitable to use, because of the fan-shaped conductor of mica tape wrapped pressure is uneven distribution, as shown in the figure, from the diagram can be seen that the fan-shaped core around the Bao Yunmu belt of its three sector corners of the pressure is the largest, because mica is flaky silicate polymer, the interlayer molecular attraction is far more than the key force of the s1-0 covalent bond in the crystal. Easily sliding between layers, bonded by silicon, but the adhesion strength is also low, in the external forces scraping, squeezing very easy to fall off, cracking, especially in the use of fan structure, wrap around the core through the guide wheel The Wire rod and the edge of the line to the side plate of the tooling wheel, and the rear road process squeeze insulation into the mould core, are easy to scratch and hurt so that the electrical performance decreases. In addition, from the cost point of view, the section perimeter of a fan-shaped conductor structure is larger than the circumference of circular conductor section, which increases the precious material mica tape, although the circular structure cable diameter increases. The amount of PVC sheath material increases, but the overall cost of the circular structure cable is still economical compared with the total Based on the above mentioned above, the conductor of fireproof power cable is the best of circular structure from technical and economical analysis.