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Anti fire of cable

2016/8/10 17:02:57

The industries have always been arguing the problems of cable fire retardant characteristics, such as the difference between different fire retardant standards and if low smoke halogen free and fire retardant are against each other and so on. There are different opinions between professionals and even the standard organizations in different parts of the region.

In view of all above sorts of questions, we should first avoid a very serious mistake. In abroad it will divided into the whole cable (known as flame resistant cable) and the outer sheath; and in mainland, we generally refer only to the outer sheath of the cable. The flame resistant cable part we will be discussed separately.

The main technical indicators of the fire safety of cables are the flame retardant, the density of smoke and the toxicity of the gas. North America and Europe have different ideas about the choice and standard of this technical index.

North American fire retardant standards pay more attention to the first two problems. Traditional concept is that the root of fire lies in the gas of carbon monoxide (CO) and subsequent combustion process in CO conversion of CO2 heat release. Therefore, improving items of ignition and combustion control in the process of heat release can reduce fire hazards.

In view of this, the North American UL certification orgnization proposed standard based on the North American cable fire protection standard. To meet UL standards  halogen addition must be added to the cable insulation layer of polymer, including chlorine, Teflon PTFE material.

UL fire retardant cable standards are divided into the following grades:

CMP-UL910, is the highest level of flame retardant cable of UL standards. Test requires environment ventilation and flame wont spread. It is generally believed that such cable burning point is over 800; Generally it is applicable to the ventilation duct or air treatment equipment used in pressurized air return system, which is regarded applicable by Canada and the United States.

As CMR-UL1666 standard, test requirements are that the beam cable should be vertical combustion, similar to the IEC60332-3 standard; generally it is used for vertical and horizontal wiring.

As CM-UL1581 standard, test requirements are equivalent to CMR, only the flame spread is different; generally it is applicable to the use of horizontal wiring.

As CMX-UL1581-VW-1, test requires a single cable vertical combustion, similar to the standard of IEC60332-1; generally it is applicable in horizontal wiring to use.

The European concept is that:the halogen acid (HCL) emissions, gas corrosion, smoke concentration and gas toxicity in the burning determine whether people can safely out of the fire scene . At present, most of the world's power and communication cables are equipped with halogen. The cable in the combustion will emit toxic fog like chemicals. During the fire, halogen cable will produce acid gas, which damages the nose, throat and other organs. Smoke is also easy to make people lose direction and makes it difficult to escape the fire scene. Therefore, most of the European regions are using low halogen or low smoke halogen free green as cable standard.

Europe for the cable fire retardant as well as low smoke and no halogen has the corresponding standard division:

IEC60754-1/BS6425-1, halogen gas content test

IEC60754-2, gas acidity test. These two standards are set for the cable if it has halogen and one of the essential test of a low smoke halogen free cable.

IEC61034-1/ASTM E662 standard, smoke density test. After cable burning,if  the smoke leakage rate is higher, he release of smoke is less. It is one of the essential tests for low smoke halogen cable.

 

IEC60332-1/BS4066-1, single cable vertical burning test, similar to UL CMX grade cable.Generally it is applicable in horizontal wiring use.

IEC60332-3/BS4066-3, beam cable vertical burning test, similar to UL CMR level cable. According to the different level of the flame-retardant cable capacity, it can be divided into A/B/C/D4 grades. It usually adopts cable IEC60332-3C grade, suitable for use in vertical and horizontal wiring .

These are just flame retardant cable standards. In a word, integrated wiring is just a subsystem of the building. The overall resistance capability of building is not only determined by integrated wiring cable flame retardant ability. So we should take comprehensive consideration of different sub system of cables and piping material of flame retardant ability. According to the actual demand and the scene then we decide to use low smoke zero halogen cable or other types of cable.