The extrusion process includes insulation and sheathing production. The insulation production methods are: coating, wrapping, extrusion, and their combination. At present, the main insulation production is coating (winding wire, no longer within the scope of production license management) and extrusion (wire and cable).

Second, the crosslinking method of crosslinking polyethylene materials: divided into chemical and physical two ways

1. Chemical cross-linking: peroxide cross-linking (1, steam cross-linking (SCP); 2, infrared crosslinking (RCP) and dry crosslinking; 3, long bearing mold (MDCV) cross-linked; 4, pressurized lava salt crosslinking (PLCV) process; 5, silicone oil crosslinking (FZCV) process. Cross-linked with silane grafting (one step, two step, copolymerization).

2. Physical crosslinking: high energy radiation crosslinking.

Third, crosslinked polyethylene material

Crosslinked polyethylene material is a mixture of low density polyethylene, peroxide crosslinking agent, antioxidant and so on. When heated, the peroxide is decomposed into highly chemically active free groups, which seize the hydrogen atoms in the polyethylene molecule, so that some carbon atoms of the polyethylene main chain are active free groups and combine with each other, that is, C-C crosslinking bond is generated, forming a network of macromolecular structure, and the insulation material uses diisopropyl benzene peroxide (DCP) as a crosslinking agent.

Since the decomposition of DCP requires high temperature, H2O, CH4 and other products produced in the reaction, the entire crosslinking process must be carried out at high temperature and pressure to increase the reaction rate and compress the residual by-product gas in the insulation.

Four, the basic requirements of the insulation process

1, no microporous insulation, the lowest water content

Full dry cross-linking and cooling system. The moisture content and micropores in the insulation are minimized. The cross-linked pipe heating system should ensure that the temperature of the heating pipe is uniform, and there is no "hot spot". The system should be easy to operate and have a short response time.

The air cooling blower of the all-dry cross-linked production line makes the nitrogen circulate quickly in the cooling tube and achieve heat exchange, so the cooling efficiency is high, and the air cooling is mostly used in the production process of high voltage and ultra-high voltage cables. Fully dry cross-linked production lines can also be equipped with water cooling, water cooling using closed-circuit circulation and heat exchange principles, most of which are used in the production of medium voltage cables. This all-dry cross-linking process can be applied to catenary and vertical cross-linking production lines.

2. Smooth interlayer interface

The smooth interface between the insulating layer and the semi-conductive layer of the cable is one of the important factors affecting the service life of the cable. Especially for the convex and embedded insulation layer of semi-conductive shielding layer at the interface of high-voltage and ultra-high-voltage cables, the local electric field strength will be too high, accelerate insulation aging, and increase the possibility of water tree phenomenon. In order to achieve smooth layer interfaces, ultra-smooth semi-conductive materials are used in the production of high-voltage and ultra-high-voltage cables.

3, cable insulation concentricity

Cable insulation concentricity is a guide to the position of each insulation layer, with good coaxial symmetry. Since the electric field distribution in the insulation is a key factor in the long-term operation of the cable, the circle makes the electric field strength of the conductor shield the lowest, which is the ideal and required shape, and the requirements for the concentricity of the cable are becoming more and more stringent. In addition, both vertical production lines and catenary production lines can produce thick insulated cables that meet the concentricity requirements. The roundness of the insulated cable depends on the various processes in the entire cross-linked production line, namely: extrusion, crosslinking and cooling, but absolute symmetry is not possible, especially in catenary cross-linked production lines.


Qingdao Tianxing Cable Co., Ltd. is a technology enterprise specializing in the production of wire and cable in Shandong Province, with more than 150 sets of domestic excellent cable production equipment and testing equipment, excellent production technology, modern testing equipment, to ensure stable product quality and timely supply. The company's main products are power cable, mineral cable, high life wire and cable, radiation crosslinked cable, control cable, computer cable, photovoltaic cable, communication cable, data cable, low smoke halogen free cable, flame retardant series wire and cable.