In the past 20 years of practice, the cable used in coal mines has undergone innovations from non-flame-retardant to fire-retardant, especially the test methods and determination rules for flame retardancy of coal-fired flame-retardant cables (MT 386-1995, MT 386-2011 Since its promulgation and implementation, the flame retardant performance of coal mine cables has been effectively controlled and improved.
However, the current fire-retardant cables for coal mines (mostly using chlorine-containing polymers as the sheath material) once burned by heat, the amount of smoke emitted by combustion is very large. Although the light transmittance measured by IEC 61034 or GB/T 17651--1998 is less than 10%, the amount of hydrogen chloride (HCl) gas released is very large, and its content exceeds 100 mg/g, even reaching 200 to 300 mg. /g. With such thick smog plus the irritating and toxic effects of toxic gases such as H2S and CO on the human respiratory system, in the narrow underground environment, the affected people could not escape the scene of the fire. According to foreign fire white paper records, this casualty in the "secondary disaster" accounted for 70% to 80% of the total number of casualties in the fire. In the number of casualties in coal mine fire accidents in China, the proportion of people who suffer from "secondary disasters" is also very large.
When a flame-retardant or non-flame-retardant material such as a cable is burned, it emits a large amount of smoke, CO, HC1 and other toxic gases. In order to avoid or reduce the "secondary disaster" of fire accidents, the International Electrotechnical Commission (IEC) successively took off in 1982 and 1989. IEC 60754-1 and IEC 60754-2 have been developed and revised to limit the amount of toxic gas released from the combustion of cables (specified HC1 content <5 mg/g, the pH of aqueous solutions of corrosive gases released by combustion is> 4.3, Conductivity <10 tts/ram). In 1991, IEC61034 was also established to limit the amount of smoke emitted when the cable is burned (specified smoke transmittance >60%). The United Kingdom has developed the naval engineering standards NES-718 and NES-713. U.S. Navy Standard MILS24643 directly uses the NES-713 standard to detect the amount of toxic gas released when the cable is burned (specified toxicity index <5).
All of these standards provide effective and reliable basis for limiting the smoke and toxic gases emitted by fire-retardant or non-fire-retardant materials such as cables. However, in the high-risk industries such as coal mines, our country's coal mining cables are low in smoke and low in toxicity (halogen ) The control is almost blank.
The low-smoke, low-halogen flame-retardant cable used in coal mines has less pollution to the environment when it is burned than when the flame retardant cable for coal mines is burned. That is, the low-halogen low-halogen flame-retardant cable for coal mines reduces or reduces the secondary disaster caused by the burning of cables. "; At the same time performance can meet the requirements of coal mine cable materials, is the main direction of the future.
It is very necessary and important to develop and apply low-smoke, low-toxic (halogen) flame retardant cables for coal mines.