How to distinguish fire-resistant cables and flame-retardant cables

How to distinguish fire-resistant cables and flame-retardant cables

Fire-resistant wires and cables are usually divided into two types: fire-resistant wires and cables and flame-retardant wires and cables. They are the general term for wires and cables with fire-resistant properties. The following describes how to distinguish between these two types of cables!

First, talk about fire-resistant wires and cables

Fire-resistant cables can be divided into two grades according to the national experimental standard (GB12666): NHA and NHB; in general product naming, NHA is usually represented by GNH, commonly known as Class A fire-resistant cables. NHB is expressed as NH in general refractory products.

Fire resistance refers to the ability to maintain a certain period of time under the condition of flame burning, that is, to maintain the integrity of the circuit. This type of cable has a certain period of power supply capacity in the flame.

Fire-resistant cables are actually another type of fire-resistant cables. It is made of copper as the conductive core, seamless copper tube as the sheath, and inorganic mineral magnesium oxide as the insulating material!

Since the whole is made of inorganic materials, the entire fireproof cable neither burns nor prolongs burning. And can withstand fire. Tests have shown that the cable has been energized and operated normally after being burned in a flame of 800-900°C for 2 hours, and it is still intact after burning under a flame of 1000°C for 30 minutes and continues normal operation. Generally, the normal working temperature is 250℃, which can operate safely and reliably.

The fire-resistant cable can continue to work (transmit current and signal) when a fire occurs, and whether the fire-resistant cable itself continues to burn is not included in the assessment. The flame-retardant cable stops working quickly when a fire occurs, and its function is to be non-flammable and self-extinguishing without spreading. The fire-resistant cable maintains normal operation for 90 minutes while the flame is burning at 750～800℃.

Second, flame-retardant wire and cable

Flame-retardant cables can be divided into three grades according to the national test standard (GB12666): ZRA, ZRB, ZRC. In general product naming, ZRA is commonly known as high flame retardant cable or oxygen barrier cable or high flame retardant oxygen barrier cable. ZRC means ZR in general flame retardant products.

Flame retardant refers to retarding and delaying the spread of flames along wires and cables, so that the fire does not expand. This type of cable has self-extinguishing performance after it catches fire.

 The oxygen barrier flame retardant technology is mainly to fill a layer of inorganic metal hydrate between the cable insulated core and the cable outer sheath. It is a non-toxic, odorless, and halogen-free white glue. The oxygen barrier flame-retardant cable can be applied to low, medium and high-voltage power cables, control cables and communication cables without changing the cable structure and the original parameters of the material, and makes the cable flame-retardant Class A.

Compared with halogen-containing flame-retardant cables, halogen-free flame-retardant cables have the advantages of low toxicity, low smoke and halogen-free. The flame retardant level is not high, basically it is C class. The reason is that the energy efficiency of oxygen swallowing fire extinguishing by halogen free radicals is greater than the energy efficiency of non-halogen flame retardant degradation temperature.

Flame-retardant cables are self-extinguishing while maintaining the electrical and physical and chemical properties of ordinary cables, that is, they are not easy to burn, or when the cable ignites itself or an external source of fire ignites, the cable will not continue after the fire is extinguished. Burning, or the burning time is very short, or the extended burning length is very short.