Analysis of cable skin characteristics
For a long time, the industry has been debating the characteristics of network data cable skin, such as whether the skin can meet the standard of flame retardant or low smoke?
Do you need halogens with high ignition points and resistance, but which release toxic gases in the fire?
Cabling professionals, the vast majority of network users, and even standards organizations in different regions are divided.
With the advent of the network era of integrated voice, data and image, multimedia broadband and fusion, network cabling will go deep into millions of households, and a correct understanding of the components and characteristics of network data cable skin is very important for future network builders and users' work and life.
As for the choice and standard of network data cable skin, the North American and European standard organizations and manufacturers have been arguing for a long time about whether to use UTP or FTP shielding products.
At present, North America, South America, Asia Pacific and China all adopt the North American cable fire prevention standard UL and NEC(National Electrical Code), while parts of Europe adopt the low halogen or low smoke halogen free green environmental protection cable standard.
Halogen controversy in the husk
Power and communications cables in most parts of the world contain halogens, which emit a toxic fog of chemicals when burned.
In the fire, halogen cables produce acidic gases that can damage workers' noses, mouths and throats. Smoke also makes it difficult for victims to get disoriented and escape the flames.
Recognizing this potential hazard, some European countries have adopted halogen-free cables as the standard for power and communications cables.
However, the US National Electrical Code specifies that the communications network must use ultra five - or six-class UTP(unshielded twisted pair) network cables with halogen cladding.
This is because, although halogen cables have important defects, halogen itself has a strong fire resistance and high ignition point. If the cable does not catch fire at all or is difficult to catch fire, it will not cause combustion, thus emitting toxic smoke.
In fact, some fires are caused by overheating when the cables themselves stay plugged in for too long.
Halogen-free cables are more likely to cause fire because of their low ignition points, while halogen-free cables are better protected from spontaneous combustion by halogen-free insulation.
However, if the cables are already on fire, the smoke they produce can lead to life poisoning.
These contradictions in the application of halogens have always been the focus of debate in the industry.
Today, cable halogens advocates, including Federal and Goodrich, dominate the technology.
Opponents of halogens expect to be able to persuade the NFPA(National Fire Protection Association) to change the current standard to stop halogens or allow halogen-free cables to be used in ventilation areas of buildings.
This is not the first time halogen-free cable advocates have tried to modify the standard, but so far have been unsuccessful.
The main reason is that the spontaneous combustion of cables in the trunk channel between layers makes it difficult for people to carry out regional fire control, thus causing the fire of the whole building, and the low-ignition point is easy to generate fire sources.
The other main reason is that there is no evidence that halogen-free cables actually save lives (because there are plenty of other decorations in the house that also contain halogens).
Under current U.S. building codes, the only halogen-free cable that can be legally installed is one that places the cable in a metal conduit, which doubles the cost of the entire wiring system.
As a result, most European countries, including France, Italy and the United Kingdom, have turned to halogen cables.
In Europe, halogen-free cables currently account for about 25% of the communications cable market, while halogen-free cables account for more than 98% of the market in North America and most of the world.
Cabling manufacturer Avaya company for different standards, different areas of users, launched a full range of data cable solutions to meet the needs of different users.
The advantage of being halogen-free
Halogen-free is characterized by low ignition point, easy combustion and low toxicity.
Current international standards for cables concern three main issues: fire resistance (how fast cables burn), the density of smoke (how much visible smoke they produce) and toxicity (how much damage they cause to humans).
The U.S. fire standards cover only the first two issues, but they are more widely and strictly applied. To meet the U.S. standards, halogens must be added to the polymers used to insulate cables. Their PVC cables contain chlorine, while FEP(Teflon Teflon) cables contain fluorine.
FEP is highly fireproof and can withstand temperatures of up to 800 ° C before combustion and smoke disassembly. It is several times higher than the maximum temperature of 150 ° C normally achieved by halogen-free cables. FEP is also an efficient insulator.
Therefore, FEP is very suitable for the production of high-speed data transmission cables, and is the key factor for the widespread adoption of UTP in ventilation areas.
FEP cables have largely replaced PVC cables in high-rise shafts and other ventilation areas.
V Some European countries have different standards. In order to comply with strict anti-toxicity regulations, cable manufacturers do not use halogens. Instead, metals are added to polyethylene and polyendene cable insulation layers.
When heated, the cable gives off only a small amount of visible steam.
However, the halogen-free cables are not as fireproof as halogenated cables, and their insulation burns quickly.
Therefore, halogen-free cables cannot meet the strict United States fire standards. To meet the fire requirements at the ventilation and ventilation level, excessive metal hydrides have to be added, thus affecting the performance and technical requirements of the cables.
Cable toxicity dispute
When PVC cables burn, they emit hydrogen fluoride and dioxide gases, which Greenpeace has identified as "scientifically known and toxic synthetic chemicals".
When the FEP cable burns, it releases hydrogen fluoride, which is colorless, odorless, but more toxic than hydrogen chloride.
Tests have shown the presence of another dangerous gas in FEP smoke.
The supertoxin has never been properly understood and is no longer being studied, but some believe it is an experimental product that does not exist in real life.
The Anderson laboratory in Europe used a method called the Pittsburgh test (published by the University of Pittsburgh) to measure the toxicity of the sheath.
In the test, a certain amount of insulation was burned and smoke was sent through a tube into the space of four mice until two died.
The weight of the burning insulation layer is a toxic unit of LC50, meaning that this amount of insulation layer will kill half of the animals in the study when burned.
In this test, it was found that FEP cables are 1.5 times more toxic than PVC cables and 5 times more toxic than halogen-free cables.
Supporters of FEP argue that the test is academic because the environment is not a real fire site, and that by the time the building reaches the temperature needed to release those toxic gases, anyone would be too hot (800 ° C) and already dead.