At present, coal mine in our country mostly to upward angle of forward tunneling, making this kind of coal mine with partial or full tilt of the top of the tunnel, the reason is to by gravity is transported out of the mining of coal. As the edge of a mass of coal mine roadway in the overflow of gas is lighter than air, so that gas in the air by buoyancy will be along the inclined roadway flow to the top, gathering in the tunnel at the top of the highest point (the coal mining face and near, volume ratio of 5% ~ 15% of the gas - air explosive gas mixture formation. Therefore, the "self deterioration effect of the top of the coal mine dump" has the gas concentration ". At present our country coal mine uses the ventilation method can not completely eliminate this kind of can explode the mixed gas to form, this is this kind of coal mine gas explosion one of main reasons.
It should be said a succession of coal mine gas explosion that engaged in the relevant departments and personnel mine operation to learn many lessons of grief, which also take the measures, but the explosion accident remains unabated, suggesting that in addition to the previous accident summed up the reasons, and of the underlying predisposing factors.
The author in recent years, many cases of coal mine gas explosion accident and published by the cause of the accident as the incomplete statistics, analysis of coal mine gas explosion accident of subjective and objective factors are in many aspects, but most fundamental factors directly to nothing more than two main aspects: one is inside the mine local gas concentration reached explosion limit; the second is in the first as a result of the basis for the existence of the mine multi class electrical equipment defect or illegal operation induced by electrical spark or explosion caused by. The first due to the elimination of, has been made fruitful discussion, below the author mainly second to for statistics and analysis, and put forward the corresponding suppression electrical incentive for existing views.
Electric inducement types of coal mine gas explosion accident
The material basis for the coal mine explosion, gas is gas mine coal or other carbon material is formed, its main composition is methane, than the air light, flammable, explosive. Gas accumulation to a certain concentration, in inside the mine air combustion supporting, once encountered electrical spark ignition source, there will be an explosion. According to the Chinese Academy of engineering and the Coal Information Institute jointly made the situation of China's coal mine production safety, gaps and Countermeasures "the subject report, at present China mine intrinsic safety facilities serious aging, a lot of equipment extended active duty. Coal mine can not be fully and safely cast, not only the new equipment can not be added, the maintenance of the original equipment is also omitted. The author in recent years, various types of electrical equipment defect cause of coal mine gas explosion case are summarized as follows:
1.1Mine power supply
The power supply reliability of the power supply is poor, and the capacity of the power supply is small, the selection and configuration of the power supply is not reasonable, the operation performance is poor, the power supply is interrupted.
Example1:Shanxi province in March 2004 a coal mine explosion, 28 miners were killed. According to the local production safety supervision and management departments, the afternoon of March 1, 6 minutes and 48, the coal city TVU grid electricity blackout starts just purchased 400KW generator, the generator automatic adjustment of voltage, but the voltage up to 280v, and does not rise to the rated voltage of 380V. A 90kw old generator for another coal mine, due to the capacity of the motor is small, can only drive the main fan, the production of other power supply, poor ventilation, resulting in local gas accumulation. At 11 in the evening, the city electricity power grid calls, underground gas explosion occurred soon.
1.2Electrical equipment defects in mines
(1)Mine power network defects
Generally, the power cable insulation and moisture, damage, the occurrence of a single phase or interphase short-circuit, sparking electrical or cable explosion, causing gas explosion accident.
Example2:November 2000, Hubei Province, a coal mine gas explosion occurred. Investigation group of experts believe that the coal mine for high gas mine, when the cause of the accident: mine roof collapsed, smashed the insulation layer of the cable and wires by electric spark, resulting in gas combustion and explosion. August 28, 2004, Guangdong Province, a coal mine underground cable explosion, triggering a fire.
(2)Defects of power distribution equipment in mine
General mine distribution transformer or power distribution device, do not have the explosion-proof performance, because of bad operation environment, resulting in single relatively insulated or interphase insulation to reduce, destroy, electric spark, ignite the gas.
Example3:The direct cause of the "3.29" gas explosion accident in Hunan in 2004. Experts believe that: electrical spark occurred in the coal mine underground power distribution room at the exit of the roadway at the junction of the transformer. Flooded underground as a result of borehole environment changes, and mineral wells original appliances without replacement for explosion-proof electric appliance, wet the terminal box of the three-phase electrical insulation to reduce, ultimately leading to line insulation failure causes a spark and ignite the gas.
(3)Mine lighting electricity for lighting equipment defects, crack, gas explosion
Example4:In November 2000, occurred in Guangdong, a coal mine gas explosion. The reason is miners illegal cross-border operations, cul de sac in high gas concentration, day lighting explosion spark, causing gas explosion. August 2004 n, a coal mine gas explosion occurred in Jiangxi. To find out the cause of the accident: one eyed wells, there is no ventilation system, causing downhole gas accumulation of explosion concentration, meet lamp explosion electrical fire, causing a heavy responsibility for the gas explosion accident.
(4)Electrical equipment defects of mine power
For coal use does not have the explosion-proof motor, fan, submersible pump leakage caused by gas explosion.
Example5:On March 17, 2004, Yunnan occurred with a major gas explosion accident, find out the mine due to mining, the one eyed, resulting in excessive gas, the leakage does not have the explosion-proof submersible pump and drainage caused by gas explosion. Also mine electrical operation does not comply with the rules for safe operation, such as coal in did not do a good job in the relevant security measures, without stopping, power transmission, or electricity well. Electrician charged installed electrical equipment, or mine workers allowed to open the lamp shade, unsafe use of lighting, can generate electric spark caused by gas explosion accident.