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Coal Mine Prevention Gas Explosion Measures
Gas explosions in mines can be prevented through a combination of technical measures, primarily focusing on three key areas: preventing gas accumulation, avoiding ignition sources, and limiting the spread of explosions. The most effective strategies are the first two—gas control and fire prevention.
**1. Preventing Gas Accumulation**
- **Enhancing Ventilation**: Proper ventilation is essential to avoid gas buildup. Mines must ensure adequate airflow, use mechanical ventilation systems, and implement district-level ventilation by separating return airways. Coal mining and excavation faces should have independent ventilation, and goafs must be sealed promptly. Additionally, diffuse ventilation is strictly prohibited for gas-prone headings, and local ventilators must be sized appropriately to handle gas emissions. If ventilation stops due to maintenance or power outages, personnel must evacuate and power supplies cut off.
- **Addressing Localized Gas Buildup**: Gas tends to accumulate in specific areas such as the upper corner of coal faces, roof voids, low-velocity roadways, and blind alleys. Increasing airflow or wind speed can help dilute these pockets. In cases of significant buildup, gas extraction may be necessary to manage risks effectively.
- **Gas Drainage**: When regular ventilation is insufficient, gas drainage systems are used to reduce emissions, especially in high-gas mines.
- **Regular Inspections**: Continuous monitoring of gas levels is crucial. Areas prone to accumulation require strict management, and any exceedance of limits must be addressed immediately.
**2. Preventing Gas Ignition**
- **Eliminating Open Flames and Sparks**: Smoking and carrying ignition tools underground is strictly forbidden. Electric welding, gas welding, and torch work are only permitted with proper safety protocols approved by higher authorities.
- **Controlling Electrical Hazards**: Only explosion-proof or spark-safe equipment is allowed in gas mines. Cables must not have improper joints (like "sheep tails" or "chicken paws"). Friction sparks from metal pillars under pressure must also be managed. Electrical systems must maintain good insulation and prevent dangerous sparks.
- **Power and Ventilation Management**: During power outages or ventilation shutdowns, gas inspectors must check levels before restoring power. The "one shot, three inspections" system ensures that gas levels are checked before blasting, and proper sealing of blastholes is required.
- **Gas Concentration Limits**: Specific thresholds are set for safe operations. For example, drilling must stop if gas reaches 1%, and work must halt at 1.5%. Blasting is prohibited if gas levels near the site reach 1%, and all operations must cease if gas exceeds 1% in return airways. If gas levels in main return air exceed 0.75%, immediate action is required.
**3. Preventing the Spread of Gas Explosions**
- **Simplified Ventilation Systems**: A straightforward ventilation layout with zoned airflow is critical. Each level and working face should have independent intake and return airways, and unused tunnels must be sealed. Main air shafts and return airways must be protected with two wind walls to prevent short circuits during an explosion.
- **Anti-Wind Devices**: Main local ventilators must be equipped with anti-wind devices, including dual-direction dampers, to ensure stable airflow.
- **Explosion Protection Measures**: Water sheds, rock dust barriers, and explosion-proof doors are installed to minimize the impact of potential explosions.
- **Maintaining Ventilation During Explosions**: If an explosion occurs, the local ventilator should continue operating to help restore normal airflow. Workers in the affected area should stay calm, use self-rescuers, cover their mouths with wet towels, and move toward the nearest refuge chamber.
These comprehensive strategies help ensure a safer working environment in gas-prone mines and significantly reduce the risk of catastrophic events.