In the cross-linked insulated wire and cable, the main way of cross-linking is inert gas (nitrogen) cross-linking, warm water cross-linking, irradiation cross-linking three kinds, for the production of 10-500KV 70mm2 or more large cross-section, high voltage level of the cable, mainly using inert gas cross-linking (dry chemical cross-linking) to achieve. Inert gas crosslinking is made of polyethylene insulating material added with peroxy compound crosslinking agent. After the conductor shielding layer -- insulation layer -- insulation shielding layer is extruded through three layers of co-extrusion, the crosslinking process is completed continuously and uniformly through a sealed cross-linked pipe filled with high temperature and high pressure nitrogen. The heat transfer medium is nitrogen (inert gas), the crosslinked polyethylene has excellent electrical performance, and the production range can reach 500KV.

The test shows that nitrogen meets the technical requirements of GB3864 industrial nitrogen, and is used as the heating medium in the production of cross-linked cables, which can improve the quality of cross-linked cables, save investment and have a high degree of automation. It requires nitrogen purity ≥ 99.5%; Nitrogen pressure 1.2 ~ 1.6MPa; Dew point ≤-40 ℃.

In the past, most cross-linked production line manufacturers chose bottled nitrogen, but because most bottled nitrogen is the by-product gas of other manufacturers' cryogenic oxygen production devices, most bottled nitrogen is not pure enough, and oxygen and water indicators often exceed the standard. If the water content of the medium is too high and the temperature is too high, water vapor is generated and bubbles are formed to be contained in the PE in the plastic state, which will age the PE in advance. Therefore, the selection of nitrogen gas source required for dry cross-linking production line is very important.

Nitrogen making machine adopts pressure swing adsorption (PSA) nitrogen production principle, it has the characteristics of simple process flow, normal temperature production, low energy consumption, high degree of automation, easy to start and stop, less maintenance, product nitrogen purity can be adjusted with gas volume, etc., is an efficient on-site nitrogen making system.

Due to the special requirements of cross-linked cable production, the use pressure of nitrogen is 1.2 ~ 1.6MPa, and the instantaneous gas consumption of nitrogen is large, so the nitrogen maker has designed a medium pressure storage tank to balance the fluctuation of gas. The number of medium pressure storage tanks can be configured according to the number of user production lines and production conditions.

The actual operation of PSA nitrogen production device in the cross-linked cable production line shows that the technology is advanced, high degree of automation, ADAPTS to the nitrogen demand of the cross-linked cable production line, solves the problem of nitrogen self-production and supply, and the investment is quick, and basically can recover the investment in about one year. PSA nitrogen technology as a mature engineering technology in addition to the cable industry, can also be widely used in chemical, gold, food and other inert gas protection, replacement, compaction and other processes.