【 Weak current College 】 mine electric fire causes and prevention

As China's coal mining mechanization and electrification level increases, external causes of fire-on-year increase of the share. Low voltage cable is on fire, transformer fire, trolley tram arc ignition ignition wooden supporting shed, electric fires have also occurred frequently, and mine complex environment, electrical equipment, in the event of fire, the consequences will be dire consequences, it is very dangerous.

In recent years repeatedly occur in the mine electrical fires, mine safety production bring significant threats, and causing significant losses. Under the 1949 to 1995 statistics, China's coal mine total 58 times once killed more than 3 people, fire accidents in which fire had caused by electrical equipment, 27% of the total number of 46.55 per cent. Author on mine electric fire cause and prevention measures and countermeasures.

1. main characteristics of electrical fires

1) concealment. As a result of leakage current and short circuit usually occur in electrical equipment and wiring of electrical cross-site, so the first part of the fire is not seen, only when the fire has been formed and developed into the fire before it can be seen, but the fire has been great, and fighting is very difficult.

2) randomness. Mine electrical equipment layout, combustion location is hard to predict, and the time of the fire and probability are difficult to quantify. It is this abrupt and acutely accidentally poisoned to mine electric fire management and prevention are to a certain degree of difficulty, and accidents happen easily become malignant.

3) burning speed. Cable fire, short-circuit or overcurrent in the wire temperature is particularly high, causing flame burning along the wire is very fast and with tunnel airflow and other combustion, the combustion speed is much faster.

4) Suppression difficult. Wires or electrical equipment fire in General is in its interior, fire point is not visible and cannot be used water to fight, so live wire is not easy to fight the fire. In addition, the large mine shaft, electrical circuit complexity, the brought to fire suppression is difficult.

5) losses. Electrical fire, usually not only simple cause damage to electrical equipment, but also of affecting underground numerous production equipment. In addition, the electric fire also raises other a series of mine accident, more significant losses.

2, electric fire hazard

Mine electrical fires, the event may be caused by the underground "chain reaction", flame with cables, electrical equipment, air flow, gas and coal mine dust and so raises other accident, not only causing property damage, resulting in casualties. Present the main findings are:

1) caused mine electrical equipment, production of material losses and damage.

2) fire may be burned or damaged equipment on site working conditions, to have a serious impact on the mine production.

3) raises other accidents. Fire tend to change the status of the original work of fan, led underground ventilation system disorder, fire smoke filled the roadway, burning of roadway and shaft, and sometimes can cause gas or coal dust explosions, and other accidents, resulting in greater loss.

4) caused mine internal environmental pollution. Mine cable, wire and electrical equipment for insulation materials are combustible, combustion will produce a variety of toxic gases, causing the entire mine internal or local air pollution.

5) causing bodily harm. Toxic gas fire will spread through the air, the larger the scope of the disaster area or the affected area staff by toxic gas attack and poisoning, asphyxia or death.

3. electrical fire cause

In the use of electric energy, the fire may be the source of the arc, spark and glow with heat conductive parts of high temperature.

At first may cause electrical equipment insulation material combustion, flame spread to roadway bracket, coal dust, gas and other combustible materials, this happened mine electrical fire. Electrical fires caused by Wells was varied, as the overload, short-circuit, bad, arc Sparks, leakage, etc.
1) short circuit. Conductor short-circuit, because there are a large number of current flowing through the conductor of heat quickly, in a few seconds, sometimes faster, the conductor is hot, and can burn attached insulated, wood frame, coal dust and nearby combustible materials, resulting in a fire. In methane and coal mine dust dangerous mine conditions, the vigor of the conductor and contains methane or coal dust explosive mixture with air, arrival explosion that touch on condition that could cause an explosion.

2) overload. When a load is shorted results occurs, the conductor of the fever is usually a slower, but long accumulation, the device will reach himself in danger of losing the insulation properties of temperature, the last often brings in electrical equipment and circuitry shorted.

3) earth fault. Middle earth leakage, especially mine cable line two-phase shorted, leakage will spark fires.

4) poor contact. Line in individual parts of contact resistance of the increase was mainly the result of poor contact. Proven, underground cables and cable or cables and devices part (header) is not well, often leaving a current mine roadway to produce the most common cause of fire.

5) leakage. Leakage is caused by electrical one of the main causes of fire and, more generally, more subtle. Use electrical dielectric strength is insufficient or wire insulation performance is not good, and so on, are prone to leakage. Because the insulation performance degradation is irreversible, so leakage currents will gradually increase, causing the spark ignition of combustible and formation around an electrical fire.

6) static electricity. In the underground, the generation of static electricity may be due to: gravel or other containing a mixture of the compressed air and rubber pipe, metal wall friction, tape and with the wheel friction, rubber band in the belt conveyor rollers friction to arcing and sparking. Static voltage can reach very high value (about tens of thousands or even hundreds of thousands of volts), easily lead to gas explosion and fire.BR>
7) electrical lighting fires. Well if you do not handle lighting lamp housing is covered in dust, and sometimes can cause a fire. Tiny lights stacked in coal dust as the lights in the neck or glass, hindering light gun proliferation of internal heat, when the temperature rise to a certain extent it is possible to cause combustion of coal dust.

4, electric fire prevention measures

Mine electric fire still adhere to the "precautionary principle" fire main, strict safety regulations for the coal mine "requirements. The author believes do mine electric fire prevention work of basic strategies has the following several aspects.

4.1 strict safety rules for the implementation of the mine in the electrical design and fire protection requirements

1) underground electrical equipment selection and installation to be strictly in accordance with the statutes. In a particular workplace, such as the existence in the underground methane, coal dust and other flammable, explosive, must follow the safety rules for selection of professionally-crafted electrical devices, such as explosion-proof electrical equipment, to ensure that the use of security. In order to prevent cable, fire-retardant cables must be selected mine, cable connection and installation should strictly follow the spec, disallows coil piles or buried transmission, use the procedure in preventing overload of the lines, to avoid short circuit, fire, etc.

2) strengthen the underground electrical equipment management, make daily inspection and maintenance work. Underground of various electrical equipment, to forbid overload, ensure that the electrical equipment in normal use. At the same time to prevent equipment failure, such as internal to the cause of fire equipment. To periodically check the cable insulation level and devices running the intact condition, and do the appropriate records. In addition, you should always enhance the safety of mine workers, electricity education to prevent man-made electrical equipment and wiring of mechanical damage caused by a short circuit causing leakage phenomena such as fire.

3) mine electrical equipment have overcurrent, overvoltage, leakage and ground protection measures. Underground high-voltage motors, power transformer high voltage control devices, should have a short circuit, overload, grounding and undervoltage release protection. In the mining area of substation and power point mobile substation or raises feeder, should be installed in short circuit, overload and earth leakage protection device. Low-voltage motor control equipment, should have a short circuit, overload, single-phase breakage, leakage locking protection device and a remote control device. Underground distribution network road are should be installed overcurrent and short circuit protection device. Electricity too in 36V above and as insulation damage can carry dangerous voltage of electrical equipment for metal shell, architecture, armored cable Strip (or steel), lead-sheathed leather or shielding, and so must have a protective earth.

4.2 strengthen mine electrical management, improving awareness

1) establish and improve mine all rules and regulations. Underground electrical workers to carry out their duties, so that each electrical equipment is the specialist is responsible for. The establishment of various electrical equipment operating procedures, establishment of mine electrical equipment repair and maintenance of the system, the establishment of the mine electrical accident investigations and treatment system, the system of mine workers certificates and so on, use the system to regulate prevention requirements of electrical fires.

2) do the miners ' safety education, raising awareness of fire prevention. On the General safety of mine workers ' education, electricity is the implementation of the "safety first, the prevention first," an important measure is to avoid electrical fire accident of a reliable guarantee. On the need for new workers, three-level safety education to acquire knowledge of the safe use of electricity, electrical fire approach, the practice of electrical equipment, so that its thinking on electrical fires.

3) for the special regulation, fire electric fire accident. Mine should be kept within business organizations of the underground fire, fire special management measures and devices are complete, security duties are in place, whether there are other dangers, such as problem identification and timely rectification, effectively reducing the probability of electrical fires.

4) mine electric fire emergency plan, and make the necessary accident simulation exercise. Each mine should establish electrical fire emergency plan, and electrical equipment preventive pilot drills and analog electrical accident handling drills to ensure that in the event of fire, with the appropriate extinguishing, refuge, rescue, and other specific prevention measures.

4.3 application of new technologies and new equipment to improve the fire-fighting capability

1) application of the automatic fire alarm installations. The present application in electrical fire protection products mainly have the leakage alarm system, anti overload alarm system, cable type, such as the temperature alarm system, its characteristics are able to accurately detect cable line of abnormal status, by handling will provide information to the maintenance personnel, so that you can set the electric fire danger and proactively.

2) actively developing on the mine electrical fire, developing mechanisms and regularity, continuous research and development of mine fire alarm equipment, fire-fighting equipment and evacuation equipment; the mine electrical fire in the prevention, detection and putting out three areas to achieve solid control measures.

5. concluding remarks

To sum up, in order to effectively prevent the occurrence of the mine electrical fire, reduce mine fire caused a great loss, should do well in the following areas of work; a focus on prevention, in strict accordance with the specifications for electrical equipment for use, inspection and maintenance; fully enhance the underground electrical equipment management, employee education, raising awareness; and establishing emergency plan, application of new technologies and new equipment to improve the fire-fighting strain and control capabilities.