Aluminum alloy cable in China has not been applied for a long time but there have been cases showing that aluminum alloy cable applications in cities and factories and mines have huge hidden dangers and risks, the following two actual cases and the eight factors that lead to risky accidents of aluminum alloy cables are discussed.
Case 1
A steel plant bulk use of aluminum alloy cables, put into production one year time, two fires caused by half a month shutdown, the direct economic loss of 200 million.
This is the cable bridge after the fire has been repaired, the traces of the fire are still visible
Case 2
A city lighting distribution system in Hunan used aluminum alloy cables, and within a year of installation, strong corrosion of the aluminum alloy cables occurred, resulting in damage to the cable joints and conductors, and line outages.
Through these two cases can be seen in China's cities, factories and mines of aluminum alloy cable in the large-scale promotion of cities, factories and mines has left a hidden danger, the user of aluminum alloy cable of the basic performance of the lack of knowledge, and therefore suffered huge losses, if the user early understanding of aluminum alloy cable in the fire safety and reliability and corrosion resistance on the characteristics of the problem, so that the loss can be avoided in advance.
From the point of view of the characteristics of aluminum alloy cables, aluminum alloy cables have natural defects in fire prevention and corrosion resistance. It is manifested in the following 8 aspects:
1. Corrosion resistance, 8000 series aluminum alloy is not as good as general aluminum.
GB/T19292.2-2003 standard table 1 note 4 states that: aluminum alloy corrosion resistance is worse than aluminum worse than copper, this is because the aluminum alloy cable to join the magnesium, copper, zinc, iron elements, and therefore easy to localized corrosion such as stress corrosion fracture, layer corrosion, intergranular corrosion, and 8000 series of aluminum alloys belong to the easy to corrode formulations, aluminum alloy cables to increase the heat treatment process, prone to cause physical state Uneven, more prone to corrosion than aluminum cables. At present, the aluminum alloy used in our country is basically 8000 aluminum alloy series.
2. Temperature resistance, aluminum alloy than copper difference is large
The melting point of copper is 1080℃ while the melting point of aluminum and aluminum alloy is 660℃, so copper conductor is a better choice for fire-resistant cable. Now some aluminum alloy cable manufacturers claim to be able to produce fire-resistant aluminum alloy cable and passed the relevant national standards test, but aluminum alloy cable and aluminum cable in this regard, there is no difference, if in the center of the fire (above) that is, the temperature is higher than the melting point of aluminum alloy and aluminum cables, regardless of what kind of insulation measures taken by the cable, the cable will melt in a very short period of time, the loss of conductive function, so aluminum and aluminum alloy is not suitable to be used as a fire-resistant Therefore, aluminum and aluminum alloy should not be used as fire-resistant cable conductors, and should not be used in densely populated urban distribution networks, buildings, factories and mines.
3.The coefficient of thermal expansion of aluminum alloy is much higher than that of copper, and AA8030 aluminum alloy is even higher than ordinary aluminum.
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