The question of reliability of closing seals in the coal mines in the USA

Abstract

The paper deals with the problem of closing seals in coal mines. After several accidents in Sago, Darby and other mines in the USA the explosion destructed the seals completely. This raised a question of what resistance is necessary for their construction. I would like to express my opinion that the request of federal safety regulation to achieve the resistance of seal of 20 pounds per square inch, which corresponds to the European 0,138 MPa (MegaPascal) is dangerous. If the temperature in the area before explosion is for example 15°C, then after the explosion it can reach up to 2 650°C. After recalculation the absolute temperature of mixture before and after the explosion can be 288 K to 2 923 K. Gases then increase during explosion in volume more than 10 times. According to Mariott law, the original pressure of 0.1 MPa must increase 10 times as much, up to 1 MPa. The seals should be designed, as the prevailing opinions claim, to this pressure value.