Flame-retardant cable: refers to the test specimen under the conditions of the test, the flame is burned, after the removal of the test source of fire, the flame spread only within a limited range, the residual flame or residual light within a limited time can extinguish the cable. Its fundamental characteristic is that in the event of a fire, it may be burned out and cannot be operated, but it can prevent the spread of fire. In layman's terms, if the cable is misfiring, it can limit the burning within a certain range, and it will not create sprawl, keep other equipment, and avoid causing greater losses.
According to the different flame-retardant materials of cables, flame-retardant cables are divided into halogen-containing flame-retardant cables and halogen-free low-smoke flame-retardant cables. The halogen-containing flame-retardant cable's insulation layer, sheath, outer sheath, and auxiliary materials (bags and filling) are all or part of halogen-containing polyethylene (PVC) flame-retardant materials, and therefore have good flame-retardant properties. However, when the cable is burned, a large amount of smoke and halogen acid gas will be released. The halogen acid gas will cause corrosive damage to the surrounding electrical equipment. Rescue workers must wear gas masks to get close to the site to extinguish the fire. When the cable is burned, it will cause damage to the surrounding electrical equipment and rescue workers, which is not conducive to the fire-fighting and rescue work, resulting in serious "secondary hazards." The halogen-free, low-smoke flame-retardant cable has all or part of the insulating layer, sheath, outer sheath, and auxiliary materials (bags and fillers) made of Halogen-free, cross-linked polyethylene (XLPE) flame retardant material. Better flame-retardant properties, and no halogen acid gas is emitted when the cable is burned, the cable emits less smoke, and the amount of smoke is also close to the recognized "low smoke" level.
According to the national standard GB12666.5-90 "bundle wire and cable combustion test method" in the provisions - intercepted samples from the finished wire and cable, the length of each sample is 3.5m, the number of specimens in bunched wire and cable The different volumes of non-metallic materials contained per meter of length are divided into three categories:
Class A: The number of test specimens shall be such that the total volume of non-metallic material contained per metre is 7 liters (liters).
Class B: The number of test specimens shall be such that the total volume of non-metallic material per meter is 3.5L.
Class C: The number of test specimens shall be such that the total volume of non-metallic material per meter is 1.5L.
With the burner flame burning sample, the time for class A and B samples is 40 minutes (minutes), the time for class C samples is 20 minutes, if the height of the carbonized part of the sample does not exceed 2.5 meters, the test result is determined as qualified.
Class A flame retardant is the most stringent, Class B flame retardant requirements are higher, and both are suitable for applications where flame retardant requirements are more stringent. Class C flame retardants are generally flame retardant and are suitable for most flame retardant applications. When ordering flame-retardant cables, the user shall specify the category code “(A)†or “(B)†after the type “ZR†specified in 7.2. Precautions when choosing:
(1) As the halogen-containing flame-retardant cables (including flame-retardant cables and low-halogen low-smoke flame-retardant cables) emit corrosive halogen acid gases when they are burned, they greatly impede the firefighting work, delay the time for firefighting and aggravate the spread of fire. In low-density public places, halogen-free low-smoke flame-retardant cables should be designed and used as much as possible.
(2) Any kind of flame retardant cable can be used in the work area with a small population density.
(3) Flame-retardant cables are classified into categories A, B, and C3. Among them, the performance of category A flame-retardant cables is better than that of categories B and C, and the price is also the most expensive. Designers should indicate the type of flame-retardant cable when ordering.
(4) From the appearance, it is impossible to distinguish the category A, B, and C of the flame-retardant cable. Only the manufacturer guarantees the supply. Therefore, the cable manufacturer should be carefully selected when designing.
(5) Halogen-free and low-smoke flame-retardant cables have the advantages of low corrosion and low smoke compared with halogen-containing flame-retardant cables, but their electrical and mechanical properties are significantly reduced. Therefore, halogen-free low-smoke flame retardant is used during cable laying. The cable should have a larger bending radius than the halogen-containing flame-retardant cable.
(6) In the cable laying design, the non-flame-retardant cable and the flame-retardant cable should not be laid side by side. It is not appropriate to lay the flame-retardant cable of different flame-retardant types in parallel.
According to the different flame-retardant materials of cables, flame-retardant cables are divided into halogen-containing flame-retardant cables and halogen-free low-smoke flame-retardant cables. The halogen-containing flame-retardant cable's insulation layer, sheath, outer sheath, and auxiliary materials (bags and filling) are all or part of halogen-containing polyethylene (PVC) flame-retardant materials, and therefore have good flame-retardant properties. However, when the cable is burned, a large amount of smoke and halogen acid gas will be released. The halogen acid gas will cause corrosive damage to the surrounding electrical equipment. Rescue workers must wear gas masks to get close to the site to extinguish the fire. When the cable is burned, it will cause damage to the surrounding electrical equipment and rescue workers, which is not conducive to the fire-fighting and rescue work, resulting in serious "secondary hazards." The halogen-free, low-smoke flame-retardant cable has all or part of the insulating layer, sheath, outer sheath, and auxiliary materials (bags and fillers) made of Halogen-free, cross-linked polyethylene (XLPE) flame retardant material. Better flame-retardant properties, and no halogen acid gas is emitted when the cable is burned, the cable emits less smoke, and the amount of smoke is also close to the recognized "low smoke" level.
According to the national standard GB12666.5-90 "bundle wire and cable combustion test method" in the provisions - intercepted samples from the finished wire and cable, the length of each sample is 3.5m, the number of specimens in bunched wire and cable The different volumes of non-metallic materials contained per meter of length are divided into three categories:
Class A: The number of test specimens shall be such that the total volume of non-metallic material contained per metre is 7 liters (liters).
Class B: The number of test specimens shall be such that the total volume of non-metallic material per meter is 3.5L.
Class C: The number of test specimens shall be such that the total volume of non-metallic material per meter is 1.5L.
With the burner flame burning sample, the time for class A and B samples is 40 minutes (minutes), the time for class C samples is 20 minutes, if the height of the carbonized part of the sample does not exceed 2.5 meters, the test result is determined as qualified.
Class A flame retardant is the most stringent, Class B flame retardant requirements are higher, and both are suitable for applications where flame retardant requirements are more stringent. Class C flame retardants are generally flame retardant and are suitable for most flame retardant applications. When ordering flame-retardant cables, the user shall specify the category code “(A)†or “(B)†after the type “ZR†specified in 7.2. Precautions when choosing:
(1) As the halogen-containing flame-retardant cables (including flame-retardant cables and low-halogen low-smoke flame-retardant cables) emit corrosive halogen acid gases when they are burned, they greatly impede the firefighting work, delay the time for firefighting and aggravate the spread of fire. In low-density public places, halogen-free low-smoke flame-retardant cables should be designed and used as much as possible.
(2) Any kind of flame retardant cable can be used in the work area with a small population density.
(3) Flame-retardant cables are classified into categories A, B, and C3. Among them, the performance of category A flame-retardant cables is better than that of categories B and C, and the price is also the most expensive. Designers should indicate the type of flame-retardant cable when ordering.
(4) From the appearance, it is impossible to distinguish the category A, B, and C of the flame-retardant cable. Only the manufacturer guarantees the supply. Therefore, the cable manufacturer should be carefully selected when designing.
(5) Halogen-free and low-smoke flame-retardant cables have the advantages of low corrosion and low smoke compared with halogen-containing flame-retardant cables, but their electrical and mechanical properties are significantly reduced. Therefore, halogen-free low-smoke flame retardant is used during cable laying. The cable should have a larger bending radius than the halogen-containing flame-retardant cable.
(6) In the cable laying design, the non-flame-retardant cable and the flame-retardant cable should not be laid side by side. It is not appropriate to lay the flame-retardant cable of different flame-retardant types in parallel.
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