What is mineral insulated cable? Overview of mineral insulated cables

Release time:

2021-05-20 17:39

Source:

Mineral insulated cable is also called Mi cable. In the standard GB 50016-2014 jointly issued by China's housing, urban and rural areas and China's General Administration of quality supervision, inspection and Quarantine on May 1, 2015, page 377 clearly stipulates that mineral insulated non combustible cable is composed of copper core, mineral insulating material, copper and other metal sheath.
Development and current situation: Mi cable originated in Switzerland in 1896, spread to France in 1934, and developed in Britain and America in 1936. Because of its different fireproof characteristics, it is widely used, including the domestic testing standard bs6387 for various mineral cables, which is also the British standard.
Up to now, what we are talking about is rigid cable. After MI cable was introduced into China, because of its high production cost, there were few manufacturers and users in the initial stage. It was not until GB / t50016 was implemented in 2015 that it was explicitly required to use Mi cable for fire protection lines. So far, MI cable has ushered in the spring in China.
According to the structure, it can be divided into rigid and flexible. According to the standard, it can be divided into national standard cable (rigid) and enterprise standard cable (flexible). Only the rigid mineral cable has the old national standard, as the name suggests, it is extremely difficult to bend, and the transportation and installation has great limitations. The flexible mineral cable has the standards set by various enterprises, and the standards of various manufacturers are different, and the quality is uneven.
There are only six types of GB cables: bttq mineral insulated cable with light load of 500V, bttvq mineral insulated cable, wd-bttyq mineral insulated cable, and bttz, bttvz, wd-bttyz with heavy load of 750V. The types of flexible cables are named by each manufacturer, including btwtz mineral insulated cable, gan-btgyz mineral insulated cable, btly mineral insulated cable, ng-a mineral insulated cable, etc.
Article 2.0.1 of jgj232-2011 technical specification for laying mineral insulated cables indicates that mineral insulated cables are cables with ordinary annealed copper as conductor, dense magnesium oxide as insulating material and ordinary annealed copper or copper alloy material as sheath. The basis for testing mineral cables in China mainly includes C (simple combustion), w (spray) and Z (impact) tests in bs6387 "fire resistance test method for cable to maintain line integrity under flame conditions"; And GB / t19216.21 "line integrity test of cables or optical cables under flame conditions", "GB / T 13033-2007 mineral insulated cables and terminals with rated voltage of 750V and below". Classification and difference, in addition to the national standard cable (rigid), all other flexible mineral cables are enterprise standard.
Relatively speaking, the national standard cable technology is high, the construction is complex and rigorous, because the metal sheath is very difficult to bend, the installation is very difficult, and expensive special accessories are needed, and the fire resistance performance is also very high bs6387; The installation of flexible cable is similar to that of ordinary cable, and the construction threshold is low, but the fire performance reaches bs6387. In the application, the matching products are mainly selected according to the building fire rating and importance.,
Most of the rigid mineral cables in China can not be produced for a long time due to the limitation of technology, and the installation can reach (6D) by using special accessories and special tools such as baking gun and bending runner. Flexible mineral cable can be produced continuously, and different metal sheath structures have different bending properties. Domestic processes mainly include copper tube (rigid), aluminum tube, cross welded corrugated copper tube and interlocking armored metal sheath, and the allowable bending radius decreases in turn to 7d (D is the outer diameter of cable, and the bending radius of ordinary cable is about 10d), However, a small number of domestic mineral cable manufacturers break through the bottleneck of domestic mineral cable production and use the third generation mineral cable production technology to produce mineral insulated cables with large cross section and large length. In terms of design and construction, the actual site and cable tray restrictions should be considered, and appropriate products should be selected- Generally speaking, the smaller the allowable bending radius is, the less difficult the installation is. The rigid mineral cable itself is relatively hard, and its anti-collision ability is also very strong. The flexible mineral cable has strong flexibility, and the anti-collision ability depends on the specific structure of the corresponding cable. However, except for interlocking armored type, all mineral cables are difficult to be laid through curved pipes, especially large-size cables.

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