Model and selection of fire-resistant wires and cables
Model and selection of fire-resistant wires and cables
Fire-resistant cables are divided into Type A and Type B. Common models of fire-resistant wires and cables: NA-YJV/NB-YJV, NA-YJV22/NB-YJV22, WDNA-YJY/WDNB-YJY, WDNA-YJY23/WDNB-YJY23.
Common models of fire-resistant cables
Model meaning
1. Model composition
Types of flame-retardant and fire-resistant wires and cables: the product combustion characteristic code and the related wire and cable models are composed of two parts.
2. Code table of combustion characteristics
Classification of fire-resistant cables
Ordinary fire-resistant cables are divided into Type A and Type B: Class B cables can withstand combustion for at least 90 minutes in a flame at 750℃～800℃ and at rated voltage without the cable being broken down (that is, the 3A fuse will not blow). On the basis of improving the manufacturing process of the refractory layer and adding the refractory layer and other methods, the Class A refractory cable was developed. It can withstand combustion for at least 90 minutes in a flame of 950℃～1 000℃ and rated voltage without the cable being broken down (that is, the 3A fuse will not blow). The fire resistance of Class A fire-resistant cable is better than that of Class B. In addition, mineral insulated cables are one of the best performance among fire-resistant cables. It is made of copper core, copper sheath, and magnesium oxide insulating materials, called MI (minerl insulated cables) for short. The cable is entirely composed of inorganic substances as the refractory layer, while the refractory layer of the ordinary refractory cable is composed of inorganic substances and general organic substances. Therefore, the fire resistance of MI cable is better than that of ordinary fire-resistant cable and will not decompose and generate corrosive gas due to combustion. MI cable has good fire resistance characteristics and can work at a high temperature of 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 size, light weight, long life and no smoke. But the price is expensive, the process is complicated, and the construction is difficult. This kind of cable with good fire resistance can be used in oil tank farms, important wooden public buildings, high temperature places and other occasions with high fire resistance requirements.
Selection of fire-resistant cables
According to the specific characteristics of fire-resistant cables, designers should pay attention to the following issues when designing and selecting:
(1) When fire-resistant cables are used in cable tunnels, cable interlayers with dense cables, or in flammable places such as oil pipes, oil depots, etc., Class A fire-resistant cables should be selected first. In addition to the above cases and when the number of cables is small, Class B fire-resistant cables can be used.
(2) Fire-resistant cables are mostly used as power supply circuits for emergency power supplies and require normal operation in case of fire. As the ambient temperature rises sharply during a fire, in order to ensure the transmission capacity of the line, the pressure drop is reduced. For circuits with long power supply lines and strictly limited allowable voltage drops, the cross section of the fire-resistant cable should be enlarged by at least one level.
(3) Fire-resistant cables cannot be used as high-temperature cables.
(4) In order to reduce the failure rate of cable joints in fire accidents, the number of joints should be reduced as much as possible during installation to ensure that the lines can work normally in a fire. If branch wiring is needed, fire-proof the joints should be done.
Fire-resistant cables are divided into Type A and Type B. Common models of fire-resistant wires and cables: NA-YJV/NB-YJV, NA-YJV22/NB-YJV22, WDNA-YJY/WDNB-YJY, WDNA-YJY23/WDNB-YJY23.
Common models of fire-resistant cables
|
model
|
name
|
Remarks |
|
NA-YJV/NB-YJV
|
XLPE insulated, PVC sheathed Class A, (B) fire-resistant power cables
|
It can be installed indoors, tunnels and pipelines that require fire resistance.
|
|
NA-YJV22/NB-YJV22
|
XLPE insulated, steel tape armored PVC sheathed Class A, (B) fire-resistant power cablesA(B)
|
It is suitable for laying in the ground when fire resistance is required, but not suitable for laying in pipelines.
|
|
WDNA-YJY/WDNB-YJY
|
XLPE insulated, polyolefin sheathed A, (B) halogen-free low-smoke fire-resistant power cable
|
It can be installed in indoors, tunnels and pipelines that require halogen-free, low-smoke and fire resistance.
|
|
WDNA-YJY23/WDNB-YJY23
|
XLPE insulated, steel tape armored polyolefin sheathed A, (B) halogen-free low-smoke fire-resistant power cable
|
It is suitable for laying in the ground when halogen-free, low-smoke and fire resistance are required, but not suitable for laying in pipelines.
|
Model meaning
1. Model composition
Types of flame-retardant and fire-resistant wires and cables: the product combustion characteristic code and the related wire and cable models are composed of two parts.
2. Code table of combustion characteristics
|
Codename
|
name
|
|
Za
|
Flame retardant
|
|
ZA
|
Flame Retardant Class A
|
|
ZB
|
Flame Retardant Class B
|
|
ZC
|
Flame Retardant Class C
|
|
ZDb
|
Flame retardant class D
|
|
Omit
|
Halogenated
|
|
W
|
Halogen free
|
|
D
|
Low smoke
|
|
U
|
Low toxicity
|
|
N
|
refractory
|
|
NJ
|
Fire-resistant plus impact
|
|
NS
|
Refractory and water spray
|
|
a Z is a single flame retardant and is only used for products whose base material does not contain halogen. If the base material contains halogen, Z is omitted. b ZD is Class D for bundle combustion, suitable for outer diameter not greater than 12mm. That is, the product of small cables. |
Classification of fire-resistant cables
Ordinary fire-resistant cables are divided into Type A and Type B: Class B cables can withstand combustion for at least 90 minutes in a flame at 750℃～800℃ and at rated voltage without the cable being broken down (that is, the 3A fuse will not blow). On the basis of improving the manufacturing process of the refractory layer and adding the refractory layer and other methods, the Class A refractory cable was developed. It can withstand combustion for at least 90 minutes in a flame of 950℃～1 000℃ and rated voltage without the cable being broken down (that is, the 3A fuse will not blow). The fire resistance of Class A fire-resistant cable is better than that of Class B. In addition, mineral insulated cables are one of the best performance among fire-resistant cables. It is made of copper core, copper sheath, and magnesium oxide insulating materials, called MI (minerl insulated cables) for short. The cable is entirely composed of inorganic substances as the refractory layer, while the refractory layer of the ordinary refractory cable is composed of inorganic substances and general organic substances. Therefore, the fire resistance of MI cable is better than that of ordinary fire-resistant cable and will not decompose and generate corrosive gas due to combustion. MI cable has good fire resistance characteristics and can work at a high temperature of 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 size, light weight, long life and no smoke. But the price is expensive, the process is complicated, and the construction is difficult. This kind of cable with good fire resistance can be used in oil tank farms, important wooden public buildings, high temperature places and other occasions with high fire resistance requirements.
Selection of fire-resistant cables
According to the specific characteristics of fire-resistant cables, designers should pay attention to the following issues when designing and selecting:
(1) When fire-resistant cables are used in cable tunnels, cable interlayers with dense cables, or in flammable places such as oil pipes, oil depots, etc., Class A fire-resistant cables should be selected first. In addition to the above cases and when the number of cables is small, Class B fire-resistant cables can be used.
(2) Fire-resistant cables are mostly used as power supply circuits for emergency power supplies and require normal operation in case of fire. As the ambient temperature rises sharply during a fire, in order to ensure the transmission capacity of the line, the pressure drop is reduced. For circuits with long power supply lines and strictly limited allowable voltage drops, the cross section of the fire-resistant cable should be enlarged by at least one level.
(3) Fire-resistant cables cannot be used as high-temperature cables.
(4) In order to reduce the failure rate of cable joints in fire accidents, the number of joints should be reduced as much as possible during installation to ensure that the lines can work normally in a fire. If branch wiring is needed, fire-proof the joints should be done.
