The quality of a product is good or bad, and its first feature is reflected in the appearance quality of the product. No matter what kind of product or semi-finished product, the appearance quality must be paid attention to in production, and strict control and inspection must be implemented. The sheath is the appearance of the cable, and its appearance requirements are smooth and round, uniform in luster, no eccentricity (not exceeding the specified deviation), no mechanical damage, flattening, no visible sundries, bubbles, blisters, obvious particles, bamboo Section shape, twist shape, etc. In addition to meeting the above quality requirements, the thickness of the sheath also has a certain influence on the quality of the cable.
If the thickness of the sheath is lower than the standard requirements, it is of course unqualified, but if the thickness exceeds the standard requirements, it is also unqualified. For example: the cable model is ZR-KVVP 4*1.5mm2, and the average thickness of the sheath is measured to be 1.6mm. If this model refers to the GB9330-88 standard, the thickness should be 1.2mm. The reasons for disqualification are as follows:
(1) Reduce the service life. After the cable is laid, it will be energized for a long time, which will generate heat energy. The allowable working temperature of the conductor is 70 °C. The long-term use temperature of PVC should not exceed 65 °C. If it is in summer, the working temperature will rise, and these temperatures will pass through the external The sheath is emitted, the thickness of the sheath increases, and the heat energy is difficult to dissipate, which will affect the service life of the cable. Due to the action of heat, th