First, the method of controlling the discharge of gas
In order to make the exhaust gas flow mixed with the full wind pressure airflow, the gas concentration is not exceeded, the control discharge method must be adopted, and the â€œone wind blowâ€ is strictly forbidden. The control methods adopted at the site mainly include:
1. Increase the resistance and limit the wind method. The essence of the increase-resistance limit wind method is to increase the working wind resistance of the local ventilator to limit the air volume of the local ventilator and achieve the purpose of controlling the discharge of gas. There are two main methods:
1 is blocked by wooden board at the air inlet of the local ventilator.
2 is tied with a rope on the wind side of the fan.
2, the wind is limited to wind. The essence of the wind-restricted wind method is to let the wind flow split, and only part of the wind flow enters the single-head roadway through the air duct to discharge the gas, and the other wind flow dilutes the discharged gas together with the full-wind pressure air flow. There are two main types:
1 is to set up a "three-way" on the wind outlet side of the fan, and control the air volume entering the single-head roadway by adjusting the opening degree of the two valves.
2 is to disconnect the air duct at the air outlet of the fan, adjust the position of the counterpart to control the air volume sent to the single lane.
3. Segment-by-segment discharge method. The section-by-segment discharge method means that the air duct is disconnected in the single-head roadway, and the gas accumulated in the single-head roadway is discharged from the outside to the inside.
The above three types of methods for controlling the discharge of gas have their own advantages and disadvantages. The disadvantage of the increase in the resistance and wind restriction method is that the fan is started and operated under the condition of high wind resistance, which is easy to be in an unstable state, and the air volume control is difficult to grasp. The disadvantage of the wind-restricted wind method is that the air volume is not easily controlled according to the gas concentration at the full-wind pressure mixing. In actual operation, the air volume is too small to affect the discharge speed, and the air volume is too large, which increases the amount of gas discharged, so that the full wind The gas concentration in the pressure mixing zone is exceeded. If the air supply to the single lane is automatically controlled by the probe provided at the full wind pressure mixing, this method is also ideal. The disadvantage of the segment-by-segment discharge method is that the gas-discharging personnel are in the turbid wind, and there are hidden dangers when the operation is improper. If the discharge personnel have certain work experience and can strictly control the discharge amount, the safety problem can be solved. The advantage of this method is that the air volume sucked by the fan is all used to discharge and dilute the gas, so the gas concentration accumulated in the wind stop area is high. When the total wind pressure is not too large, it is better to use segment-by-segment emissions.
Second, the control of gas concentration
Article 146 of the Regulations stipulates that if the gas concentration exceeds 1% or the carbon dioxide concentration exceeds 1.5% in the wind-stop zone, safety measures for removing gas or carbon dioxide must be established to control the airflow so that the exhausted airflow is in the same full-pressure airflow. The gas and carbon dioxide concentrations in the mixing zone must not exceed 1.5%, and the return air system must also be powered off. Only after gas inspection, it is confirmed that the gas concentration in the roadway of the restored ventilation is not more than 1% and the concentration of carbon dioxide is not more than 1.5%, and the power supply of all electrical equipment in the roadway for supplying air to the local ventilator can be manually restored. Article 42 of the â€œExecution Noteâ€ stipulates that the gas concentration discharged from the headway must be no more than 1% in the full-wind pressure mixed flow, and the carbon dioxide concentration should not exceed 1.5%. For the regulation of gas concentration in the full-pressure mixed zone, the "Procedures" and "Executive Instructions" are different, and the standards for on-site implementation are also different. It should be noted that the lower the gas concentration in the exhaust airflow, the safer, but the corresponding discharge time is longer. For some tunneling working faces with large gas emission, during normal production, the gas concentration in the return air flow is close to 1%. In the process, there is a large amount of gas germination in the single lane. If the gas concentration of the full wind pressure mixing zone is not more than 1%, the required discharge time is too long, which has a greater impact on the production in other parts of the well. Some mines Basically, it is impossible to implement, so there is some resistance, simply do not follow the regulations, and quickly discharge, the concentration will have no numerical control, and improper handling may lead to an accident. The author believes that the gas concentration of the full wind pressure mixing zone is strictly controlled below 1.5%, which is more realistic. The method is to set up a gas probe in the mixing place to perform alarm power failure.
3. The scope of power outages and withdrawals when discharging gas
When discharging gas, in order to prevent the occurrence of gas explosion, the first is to strictly control the concentration of methane in the exhaust gas flow; the second is to resolutely put an end to the discharge of gas from all sources of fire on the line, so it is necessary to determine the scope of power outage; In the event of an accident, in order to minimize casualties and prevent personnel from entering the danger zone, it is necessary to clearly identify the scope of withdrawal.
Coal Safety Document No. 153 is more comprehensive in terms of power outages when gas is discharged. That is to say, â€œall diverticulum, roadways and gas-exhausted gas outlets that are affected by gas emissions must be withdrawn from the operation. Designate the location of the alert personnel and prohibit other personnel from entering. The electrical equipment that discharges gas flowing through the roadway must be designated to cut off the power at the same time in both the substation and the distribution point of the mining area, and set up warning signs and special personnel to watch. According to this regulation, when the methane concentration reaches a certain level, the methane power-off meter will automatically cut off the underground power supply. At this time, the operation must be stopped and the corresponding electrical equipment must be powered off. However, there are some differences in the understanding of this regulation on the spot. First, the understanding of the concept of â€œcutting off the safety exitâ€ is a cut-off safety exit in a long distance. The mining work surface on the return air side of the exhaust gas roadway is designated as the mining work face cut off by the safety exit, and the mining work face on the air inlet side does not belong to this column. For each mining area where partition ventilation is implemented, the mining area is bounded. In a mining area, as long as there is a discharge gas project, all the mining face in the mining area must be withdrawn and stopped, and the safety factor is greater.
Gas emissions are themselves a safety measure to eliminate hidden dangers, but poor implementation can also cause problems. In order to do this work, the key points are as follows:
First, strictly control the emission concentration, and use the methane concentration sensor to ensure that the concentration of methane in the wind flow of the mixed gas flow and the full wind pressure does not exceed 1.5%, and that no circulating wind occurs;
Secondly, the discharge line should be correctly selected. If necessary, the ventilation system should be properly adjusted so that the exhaust gas flow enters the total return air system along the shortest route as much as possible, avoiding the safety exit of other diverticulum and mining face, and ensuring the system's Stability and reliability;
Thirdly, for the scope of power outages, it is necessary to increase the safety factor appropriately. For areas that may or may not be affected, it must be classified as blackout and withdrawal. This aspect is to prevent explosions. In the event of an accident, personnel injuries can be minimized;
Fourth, we must strengthen on-site supervision and management, and all departments must work closely to prevent mistakes.
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