Difference between fire resistant cable and flame retardant cable
On the basis of improving the manufacturing process of refractory layer and adding refractory layer, a kind of refractory cable is developed.
1、 Fire resistant cable
On the basis of improving the manufacturing process of refractory layer and adding refractory layer, a kind of refractory cable is developed. It can withstand combustion for at least 90 min in 950 ℃ - 1000 ℃ flame and rated voltage without cable breakdown (i.e. 3A fuse does not blow).
2、 Flame retardant cable
Flame retardant cable is a kind of fire-resistant cable with better neutral performance. It is made of copper core, copper sheath and magnesium oxide insulation material. It is called mi (minimum insulated cables) cable for short.
The fire resistant layer of the cable is composed of inorganic materials, while the fire resistant layer of ordinary fire resistant cable is composed of inorganic materials and ordinary organic materials. Therefore, the fire resistance performance of MI cable is better than that of ordinary fire resistant cable, and it will not decompose to produce corrosive gas due to combustion.
Mi cable has good fire resistance and can work at 250 ℃ for a long time. At the same time, it has the characteristics of explosion-proof, strong corrosion resistance, large current carrying capacity, radiation resistance, high mechanical strength, small volume, light weight, long service life and smoke-free.
But the price is expensive, the process is complex, and the construction is difficult. In the oil irrigation area, important wood structure public buildings, high temperature places and other places with high fire resistance requirements and acceptable economy, this kind of cable with good fire resistance performance can be used.
Note: fire resistant cable can maintain normal power supply for a period of time in case of fire, but flame retardant cable does not have this feature
3、 Problems in design and Application
1. When the fire-resistant cable is used in cable tunnel, cable interlayer with dense cables, or in flammable places such as oil pipe and oil depot, class a fire-resistant cable should be selected first. In addition to the above conditions, class B fire-resistant cables can be used when the number of cables is small.
2. Fire resistant cable is mostly used as the power supply circuit of emergency power supply, which requires normal operation in case of fire. Due to the rapid rise of ambient temperature in case of fire, in order to ensure the transmission capacity of the line and reduce the voltage drop, for the circuit with long power supply line and strictly limited allowable voltage drop, the section of fire-resistant cable should be enlarged at least one gear.
3. Fire resistant cable cannot be used as high temperature resistant cable.
4. In order to reduce the failure probability of cable joints in fire accidents, the number of joints should be reduced as much as possible in the installation, so as to ensure that the line can work normally in the fire. If it is necessary to make branch wiring, the joint shall be fireproof.