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Is the cable sheath really thicker and then better?
Nov 06, 2017

There are many methods to inspect the cable quality, and the thickness of the sheath is one of its standards, although the cable sheath and cable quality is not like copper, aluminum and other raw materials have a direct relationship, but the thickness of the cable sheath is often the most able to reflect the production level of a cable manufacturer, there is currently a saying is "cable sheath thicker, the better the quality of products" Is that true?


     To figure this out, first we need to know the relationship between the thickness of the sheath and the quality of the cable:

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Sheath Thickness Determines cable life

It's good to understand, the cable needs to run for a long time, and the laying environment is more special, especially some need to be buried, immersed in the water or exposed to the open air, easy to be corroded in the environment, the cable due to the corrosion of the external media, the thinnest point of insulation and mechanical level will be reduced, Coupled with the routine testing of the sheath test or the occurrence of grounding fault, the thinnest point will be not low probability of breakdown. and the protection of cable sheath has a direct relationship with its thickness, and the thin point of the sheath often loses its protective effect first. In addition, we can not ignore the internal consumption of cables, wire and cable long-term power, will produce a lot of heat (conductor allowed to work temperature of 70 ℃, PVC long-term use temperature should not exceed 65 ℃), because the cable this in the "external and external" situation, the sheath will play a very good protective role, Therefore, the thickness of the sheath determines the service life of the cables to a certain extent.

Thickness of sheath determines the difficulty of laying

With the development of global industry, more and more environments require high-voltage cable products to be small in diameter, in the process of laying the need to consider leaving a gap, so as to emit the wire and cable power generated after the heat, and the thickness of the sheath will increase the difficulty of laying, so the thickness of the sheath requirements to strictly comply with the relevant standards, Otherwise can not play the role of protecting the wire and cable. So the sheath also can not blindly pursue its thickness.

    According to the above two kinds of analysis, we can get the answer: 

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Cable products, like other products, quality, good or bad, the first feature is reflected in the appearance of products, no matter what kind of product, or semi-finished products, in the production must pay attention to the appearance of quality, the implementation of strict control and inspection. Sheath is the appearance of the cable, then how to check the appearance of the sheath?


Visually, a good sheath looks smooth and rounded, gloss uniformity, non-eccentric core (not exceeding the specified deviation), no mechanical damage, compressed, no visible debris, bubbles, sand holes, obvious particles, bamboo shape, twist shape, etc. from the thickness, the thickness of the sheath has an effect on the cable quality, It is known that the role of cable sheath is to protect the cable insulation core in the external force without damage, thus playing a protective role. If the thinnest point of the cable sheath is not up to the requirement, the cable sheath will be damaged when it has not reached the normal maximum outside destructive effect.


As described above, the cable in the production of the thickness of the sheath below the standard requirements are unqualified, the thickness exceeds the standard requirements are not qualified. We take this model for example: The cable model is dld-kyjv22 $number. 5mm2, the average thickness of the sheath thickness is 1.7mm, such as the reference gb9330-88 standard requirements, the thickness should be 1.2mm, exceeding or below all are unqualified. So how can we control the thickness of the cable sheath?


                                      blob.png                  blob.png

                 Control sheath thickness according to standard calculation

                                    Calculation formula: D (outside diameter of extrusion) x0.035+1》

                                                                          blob.png

                                             On-line measurement of sheath thickness          

              《Sheath thickness = (perimeter of the extruded sheath-perimeter of the front of the sleeve)/2π

                                       OR

            Sheath thickness = (perimeter of the extruded sheath-perimeter of the front of the sheath) x0.1592

                                      blob.png  

                         The thinnest point of a single core sheath  

                                 《Nominal value x85%-0.1

                                                                         blob.png

                                               The thinnest point of the multi-core sheath    

                                                   《Nominal value x85%-0.1》

                                                                        blob.png

   《 Improve the temperature of low density polyethylene sheath extruder, improve the stress cracking strength, because the extrusion temperature is too high, it is easy to make the plastic Coke burning, or "skid" phenomenon; In addition, the shape stability of the squeeze layer is poor, the shrinkage rate increases, and even the plastic layer changes and bubbles appear.》

                                                                        blob.png

Do a good job extrusion body and screw cooling system to eliminate the friction overheating, in order to maintain the heat balance in the extrusion process, stable extrusion pressure, so that the plastic stirring evenly, improve the quality of plasticizing.



                  The cable sheath is not more  thicker and then the better! 


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