Engineering practices for a safe, inert atmosphere in sealed areas of coal mines
, 2015, Vol. 67, No. 9, pp. 53-60
Zipf, Jr., R.K.
The 2008 Mine Safety and Health Administration Final Rule on Sealing of Abandoned Areas of Coal Mines focuses on seal design to resist explosion pressure. By designing sealed areas to become inert and remain permanently inert, it may be possible to use more economical 345-kPa (50-psi) seals under the new rule, if the required monitoring is met. Most sealed areas pass through the explosive range for methane in air within a few weeks after seal construction and then remain inert permanently, but data about the proportion of sealed-area atmospheres that are permanently inert and safe are lacking.
Certain practices that were in use prior to the new regulation may have contributed to the formation of explosive atmospheres within sealed areas. Sealing low-methane-inflow mines at shallow depth may have created explosive atmospheres in sealed areas that persisted for months or more. Complex seal lines involving many seals could have led to some parts of the seal line ingassing to form an explosive mixture and other parts of the line outgassing to increase the methane gas load on the ventilation system.