Fire-resistant cables can maintain normal operation for a certain period of time even when exposed to flames, and they can also preserve the integrity of the circuit. During combustion, these cables produce only a small amount of acidic gas and smoke, significantly enhancing their performance. In particular, under conditions involving water spray or mechanical impact during combustion, fire-resistant cables can still ensure the continued integrity and operation of the circuit. Now, let’s take a closer look at the structure and functions of fire-resistant cables.

　　Another special type of fire-resistant cable is known as fire-rated wire and cable. It features a seamless copper sheath and uses magnesium oxide as its insulating material. Due to the unique properties of its materials, fire-rated wire and cable neither burns nor supports combustion.

　　I. Structure of Fire-Resistant Cables:

　　1. The conductors in single-layer cables are typically made of copper, a metal material with high electrical conductivity. Therefore, when selecting a cable, you should check whether its conductor is indeed copper, what type of copper it is, and its overall quality—because these factors determine the cable’s fire resistance, which is a key indicator of the cable’s overall quality.

　　2. The secondary jacket uses heat-resistant, non-combustible materials as the insulation layer material.

　　3. The third layer is the isolation layer.

　　4. Fourth, the outer layer is primarily composed of smoke-free, halogen-free, and plastic-modified materials. This material exhibits excellent corrosion resistance.

　　The thermal resistance of fire-resistant cables depends on the allowable operating temperatures of both the conductor and the cable jacket during operation. At high temperatures, neither the conductor nor the copper jacket will oxidize, because the oxygen content in the cable insulation is very low. While oxidation of the conductor itself is not severe, the cable jacket suffers significant oxidation when exposed to the atmospheric environment. The higher the temperature, the more severe the oxidation becomes. When the temperature of the copper jacket exceeds 250°C, rapid oxidation begins, forming an oxide layer of CuO that causes the jacket thickness to decrease.

　　II. What is the function of fire-resistant cables?

　　It primarily serves to transmit electricity, but it is more fire-resistant than ordinary cables. In the event of a fire, it can maintain power transmission for a longer duration than conventional cables, giving people more time to escape the blaze.

　　For example, when a fire breaks out in an elevator, ordinary cables can easily be burned through. The elevator immediately shuts down, leaving people unable to evacuate quickly. In contrast, fire-resistant cables can hold out and continue functioning for a much longer period.

　　III. Applications of Fire-Resistant Cables

　　1. Power and control circuits for fire pumps, sprinkler pumps, and fire elevators.

　　2. Power control circuits for fire-resistant rolling shutters, electric fire doors, smoke exhaust system fans, smoke exhaust dampers, and fire dampers.

　　3. Manual alarm circuits for the fire alarm system, fire broadcast system, and telephone lines.

　　4. Security CCTV lines for high-rise buildings or critical facilities such as airports and subways.

　　5. Emergency lighting circuit that centrally supplies power to and controls and protects the power supply circuit.

　　6. Important relay protection circuits and operating power supply circuits for medium- and large-sized substations and switchgear.

　　7. Computer monitoring circuit.

　　Fire-resistant cable designation letter: N. Fire-resistant control cable models: NH-KVV, NH-KVVP, NH-RVV, NH-RVVP, NH-RVS, NH-RVSP.

　　The above is an introduction to the structure and functions of fire-resistant cables. If you’d like to learn more, feel free to contact us anytime! Our company has many years of experience and looks forward to having you join us at any time.

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qinshan@qinshancable.com

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