Coal mine construction borehole fire accident and prevention

I. Overall situation of coal mine construction drilling accidents in recent years in Henan Province

According to incomplete statistics, 16 coal mine construction drilling accidents have occurred in Henan Province since 1987. Judging from the construction drilling use of accidents, 11 gas drainage holes were drilled, one for water exploration, coal exploration, fault stratum, roof grouting and one coal sample drilling hole; from the accident distribution area, Jiaozuo mining area From 5, there were 4 Dengfeng mining areas, 1 Xinmi mining area, 4 Pingdingshan mining areas, and 1 Anyang and Yongcheng mining areas. From the mine gas type of accident, 14 occurred in the prominent mine and 2 occurred in the mine. Low gas mine; from the way of the powder discharge in the accident coal mine construction, 15 of the air drainage methods are adopted, and one of the self-discharge type (dry discharge type) of the thread drill pipe is adopted; See, 1987, 1991, 1993, 1997, 1999, 2000, 2003, 2004, 2005, 1 each, 3 in 2009, 4 in 2010; from the accident caused by personnel death There were 4 fatal accidents in 16 accidents, resulting in 12 deaths. From the nature of the mines where fatal accidents occurred, one occurred in the main mines of the provincial backbone coal enterprises, and three occurred in the township coal mines or provincial backbone coal enterprises resources. Integrate the mine; from the year of the death, one person in 2004

In summary, no matter what kind of application is used for coal mine drilling, as long as the drilling tool contacts the coal seam during the drilling process, there may be a fire accident, which will occur in the prominent mine, and also in high gas or low gas. Mines; they will occur in the main mines of the provincial backbone coal enterprises, and will also be integrated in the mines of township coal mines or provincial backbone coal enterprises. At the same time, the coal mine drilling process using the wind-discharge method is more prone to fire accidents than other coal mine construction drilling processes. In addition, from 1987 to the present, the occurrence of fire accidents in coal mine construction has shown that it has evolved from one year to one year, and then to several years, and the death accidents occur in nearly two. year. Therefore, the situation of drilling safety work in coal mine construction in our province has shown an increasingly severe trend. It is very necessary and urgent to do a good job in preventing and controlling fire accidents in coal mine construction.

Second, preliminary analysis of the causes of fire accidents in coal mine construction

At present, there are three basic types of powder discharge methods for coal mine drilling: water discharge, water discharge and self-discharge (including dry discharge and two types of wet drainage in the borehole). Among them: the coal drilling method of the wind-discharge type coal mine is prone to fire accidents; the drilling process of coal mine construction type of dry-discharge type may cause drilling fire accident; the water discharge type and the self-discharge mode of wet-discharge type coal mine Drilling and fire accidents are generally not encountered in the construction drilling process. Therefore, this paper makes a preliminary analysis of the direct cause of the fire accident in the dry-discharge type coal mine construction in the air-discharge mode and the self-discharge mode.

There are several direct reasons for the construction of a wind-discharge type drilling accident:

First, the drill bit or the drill pipe continues to drill after it is detached. The drill bit and the drill pipe, the drill pipe and the drill pipe frictionally generate high temperature, and at the same time, the oxygen condition is provided due to the supply of air into the borehole, causing pulverized coal or gas combustion.

Secondly, after the occurrence of stuck drilling and top drilling, the drilling continues, the friction between the drill bit and the coal seam increases to produce high temperature, and at the same time, the oxygen condition is provided due to the supply of air into the borehole, causing combustion of coal powder or gas.

The third is the mixing of new and old drill pipes or different types of drill pipes. The gap between the drill pipes is not matched or even the slide buckles, causing the drill pipes to rub against each other to generate high temperature. At the same time, due to the supply of air into the boreholes, oxygen conditions cause pulverized coal or Gas burning.

Fourth, the wind pressure of the borehole is reduced, causing the powder to be uncleaned or the amount of powder in the borehole is too large. At the same time, due to the supply of air into the borehole, the oxygen condition is met, and then the high temperature is caused, causing the combustion of the coal powder or gas.

The direct cause of the drilling accident in the dry-discharge type coal mine construction in the self-discharge mode is that the high temperature is caused by the forced drilling after the drill or the top drill, the friction between the drill bit or the drill pipe, and the like, resulting in the borehole. After the high-temperature pulverized coal, gas or a mixture of the two is discharged from the drilled hole, it is exposed to oxygen, or the combustible material such as gas or coal powder at the place where the coal mine is drilled is ignited, thereby causing a fire accident.

In addition, due to the following reasons, some coal mine construction drilling accidents have been expanded, resulting in large economic losses and even casualties.

(1) In some coal mine construction drilling operations, the dust is too large, and the sensors such as carbon monoxide and gas are missing or the suspension position is wrong, which causes the on-site operators to not detect the early warning signs and delay the accident disposal time. For example, in 2009, a coal mine in Dengfeng mining area was too close to the coal wall due to the carbon monoxide digital portable instrument suspended at the construction drilling site. It was impossible to truly detect the concentration of carbon monoxide in the return airflow at the working site, which caused the field workers to fail to find the construction drilling hole in time. After the accident has been expanded, the mine rescue team will be involved in the disposal, and the fire will be extinguished, resulting in greater economic losses.

(2) Many coal mine construction drilling site operators have insufficient experience in emergency disposal and their ability is not high. After the accident, no precautionary measures and reports were taken in time to make the accident develop. For example, in a construction drilling accident in a coal mine in the Jiaozuo mining area in 1987, the on-site operators felt dizzy and nausea and did not take any measures to evacuate them. Because they continued to supply air into the borehole, they had oxygen conditions and other reasons. The inside of the borehole caught fire until the mine rescue team rushed to the underground to take water supply measures into the borehole before extinguishing the fire.

(3) Some coal mines do not place or use fire-fighting equipment at the construction drilling site, or use or place flammable materials at the coal mine construction drilling site. For example, after a fire accident occurred in a coal mine in a coal mine in Xinmi Mining Area in 2009, the site personnel did not use fire extinguishers or water injection to extinguish the fire. Instead, they used coal to bury the fire, which affected the fire fighting process and used combustible plastic around the drill hole. The network was prepared for the protection. As a result, the plastic preparation network was ignited by about 0.5 square meters, which had an adverse impact on the rescue and relief work.

(4) Some coal mine construction drilling workers have low safety quality and poor self-rescue ability. They do not use emergency equipment such as self-rescuer and self-rescue after the accident. For example, after a coal mine construction drilling accident occurred in a coal mine in Anyang mining area in 2010, one of the three people at the accident site was rescued by using the self-rescue equipment and self-rescuing device. The other two people only rushed to retreat, neither using pressure. The wind self-rescue device does not use a self-rescuer, and as a result, it is poisoned and died on the way back.

(5) Some coal mine ventilation systems are unreasonable, the roadway section is small, the air volume distribution is uneven, and the overall disaster resistance is poor. For example, in 2010, the roadway where the drilling operation site of a coal mine in the Jiaozuo mining area was located was breeze. After the construction hole fire accident occurred, the wind flow in the vicinity of the construction site was partially reversed, causing two miners to die when the reverse wind flow retreated to the area.

(6) Some coal mining enterprises or mine dispatching room personnel are unfamiliar with the emergency handling procedures, and the level of emergency command is not high. After the accident, the personnel in the accident-stricken area cannot be informed of the reasonable evacuation route or the use of first-aid equipment or facilities.

Third, the prevention and treatment of coal mine construction drilling accidents

In order to strengthen the safety production of coal mine construction and prevent such accidents from happening again, the following suggestions for prevention and control of coal mine construction drilling accidents are proposed:

First, coal mining enterprises must provide special training for construction drilling operators to understand the operating principles of drilling rigs and drilling tools, familiar with operational procedures and special safety technical measures, and pass the assessment and record in the training files. At the same time, the construction drilling rigs and drilling tools should be regularly inspected, repaired and technical files should be established to keep the rigs and drilling tools intact. It is necessary to make the drill pipes with different old and old levels or different types of drill pipes not to be mixed; Drill pipes that are damaged or cracked may not be used.

Second, before the construction of the coal mining enterprise, the water should be discharged in the water and self-discharged according to the actual situation (meaning that it does not rely on hydraulic or wind power, but relies on the rotary force of the drill pipe to discharge powder, which can be divided into adding appropriate amount of water into the borehole. In the two types of wet pulverized powder of wet coal powder and dry row powder without water, the method of drilling and discharging powder is preferred. When selecting the air-discharge method, the “wind and water” tee must be installed on the drilling rig and the drilling tool, and the water supply pipe with a diameter of not less than 50 mm, which has the function of spraying water into the borehole, must be ensured to switch to the drilling at any time. Supply air or water supply, and the supply air and water supply pressure shall not be less than 0.5 MPa.

Third, a carbon monoxide sensor or portable alarm device must be installed within 2 meters of the return hole of the construction drilling. If the safety monitoring system or portable alarm device connected to the carbon monoxide sensor alarms, or the field operator smells coal tar, hydrogen sulfide, etc., or finds that the borehole is burning, it must stop drilling immediately, cut off the power supply, and process it. . In the case of using the air-discharge method, when the drilling does not occur, immediately open the water supply valve and close the air supply valve; when the drilling occurs, use the fire extinguisher while opening the water supply valve and closing the air supply valve. Fire, such as loess. By observing the return water temperature and the concentration of carbon monoxide, it is confirmed that the drilling and combustion can be stopped before the water supply is stopped and the drill pipe is withdrawn, and then the non-combustible material such as loess is used to seal the hole, and the length of the sealing hole is not less than 2 meters.

Fourth, the gas inspector must be arranged to check the gas situation at the construction drilling site. Low-gas mines should be inspected no less than 2 times per shift; high-gas mines should be inspected no less than 3 times per shift; there is a danger of gas effluent and large gas outflows, abnormally changing areas and prominent mines are frequently inspected by fixed gas inspectors. It is also necessary to set a methane sensor or a suspended methane portable alarm device within 0.8-1 meter of the return hole side of the construction hole. When the gas concentration in the wind tunnel of the construction drilling site and its roadway exceeds 1%, stop drilling immediately and find out the cause. For treatment; when the gas concentration exceeds 1.5% or the local gas exceeds the relevant regulations (with a borehole center, a radius of 0.4 m, within 0.6 m from the coal wall, the gas concentration shall not exceed 2%), stop drilling and stop immediately. Supply air to the borehole (when using the wind discharge mode), cut off the power supply, retreat along the disaster avoidance route, and report to the mine dispatching room.

Fifth, during the construction drilling process, when the on-site operation personnel found that the drill bit fell off, the drill pipe slip buckle, the fracture or the breakage, etc., the drilling was immediately stopped and processed; the card drill, the top drill, the powder discharge was unfavorable or the drilling speed was found. When slowing down, etc., immediately stop drilling and stop supplying air to the borehole (when using the air-discharge method), find out the cause, and handle it. At the same time, the on-site operators should always check the temperature of the drill pipe and the orifice and the gas condition. When the temperature rises, the drilling will stop immediately and be processed. When the gas injection hole is found, immediately stop drilling and exit part of the drill pipe to release the gas. After confirming the pressure relief of the gas, the drilling can be resumed.

Sixth, the mine ventilation system must be reasonable to ensure sufficient air volume at the construction drilling site, and the layout, section size and wind speed of the roadway in the construction drilling operation area are in compliance with the provisions of the “Safety Regulations for Coal Mines”, and the ventilation facilities such as the relevant dampers and closed walls are firm and reliable. And in the construction of the drilling, it is strictly prohibited in the return air system that may be affected by it.

Seventh, coal mining enterprises and their mines shall formulate and improve special emergency plans and on-site disposal plans for construction drilling and fire accidents, strengthen emergency rescue drills and emergency disposal skills training, improve the emergency response capability of managers and field operators, and establish and implement mines ( Auxiliary) Ambulance team downhole work system, timely handling and rescue of accidents.

Eighth, the construction site operator must carry the self-rescuer with him, and the mine must be installed within 20 meters of the construction drilling site to meet the needs of the maximum number of personnel to meet the pressure self-rescue device, and at the same time with at least 2 sets of qualified sites Fire extinguishers, sandboxes and loess not less than 0.2 cubic meters. Fire extinguishers, sandboxes and loess should be placed within 5 meters of the windward side of the rig.

Nine is that coal mining enterprises should improve the system, highlight key points, prevent and improve measures, implement responsibilities, and continuously strengthen the safety management of coal mine construction drilling. In particular, the provincial backbone coal enterprises should strengthen resource integration, merger and reorganization, mine prevention and construction, drilling and fire accidents. All work to prevent accidents.

Ten is to strengthen scientific and technological research, in-depth study on the basis of quantitative analysis of coal hardness, viscosity, composition, ignition point, structure and other parameters, determine the best way to drill drilling powder; in the wind-drilling method drilling rig, drilling tools The project has a complete set of "wind and water" automatic switching and "carbon monoxide, wind" locking devices, etc., and gradually perfects and promotes the use of "Mineral Drilling and Anti-Fire Safety Protection Device" developed by Henan Mahua Coking Coal Company. (With the automatic switching of “wind and water” after carbon monoxide over-limit, the over-limit alarm of gas, the automatic power-off of the rig after feng shui under pressure), further improve the technical level of construction drilling safety technology and ensure the safe production of coal mine.

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