Basic introduction to fire-resistant cables

Fire-resistant cables in China, ordinary fire-resistant cables are divided into categories A and B categories: B type cable to the 750 ? ~ 800 ? and rated voltage of the flames burning under the tolerance of the cable is not at least 90min breakdown (ie, 3A fuse is not blown) . Fire-resistant layer in improving the manufacturing process and increase the refractory layer, based on the method and developed a class A fire-resistant cable , it can at 950 ? ~ 1 000 ? and rated voltage of the flames burning under the tolerance of the cable is not at least 90min Breakdown (ie 3A fuse is not blown). Class A fire-resistant cable is better than B class of fire.
In addition, the mineral insulated cable is fire-resistant cables in a better performance, it is a copper core, copper jacket, made ??of magnesium oxide insulation material processing, referred to as MI (minerl insulated cables) cable. The cable is fully constituted by the inorganic fire-resistant layer, while the ordinary fire-resistant cable is fire-resistant layer is made ??of inorganic and organic compound from the general, the MI cables fire resistance than ordinary fire-resistant cable is better and will not be burning and decomposition of corrosive gas. MI cable has a good fire-resistant properties and can be long-term work at 250 ? under high temperature, as well as explosion-proof, corrosion resistance, large carrying capacity, radiation-resistant, high mechanical strength, small size, light weight, long life, no smoke characteristics. But the price is expensive, complex process, difficult construction, irrigation in the oil, the important public buildings, wood, fire and other places that require high temperature and an acceptable economic situation, fire resistance can be such a good cable.
Fire-resistant cable and flame retardant cable of the main differences are: fire-resistant cables in the fire for some time when the normal power supply, and flame retardant cable does not have this feature.
Designers should pay attention to the design chosen the following questions:
(1) When the fire-resistant cable for cable-intensive cable tunnel, cable sandwich, or in the pipeline, oil tanks and other flammable nearby places should be first choice class A fire-resistant cables . Notwithstanding the above, the number of cable configurations and low, can be B class fire-resistant cables .
(2) fire-resistant cables are mostly used for emergency power supply circuit, requiring fire work. The sharp rise in temperature during the fire, in order to ensure the transmission line capacity, lower pressure drop, for the for the cable road is long and strictly limited to allow the voltage drop of the loop, should be fire-resistant cable cross-section at least one file to enlarge.
(3) fire-resistant cable is not as resistant to high temperature cables to use.
(4) to reduce the cable joint failure in the probability of fire in the installation should minimize the number of joints to ensure the line can work in the fire. If you need to do branch connection, coping joints in fire prevention treatment.