Rock dusting considerations in underground coal mines

Rock dusting to prevent coal dust explosions has been in widespread use in U.S. underground coal mines since the early 1900s. Underground coal mining technology has changed significantly over this same time period, becoming highly mechanized and produces finer coal dust particles which are more explosive. Despite the advances in mining technology, mine-wide dust sampling practices have remained essentially unchanged. There are many factors associated with the practice of rock dust sampling that, if not properly considered, can adversely impact the effectiveness of the rock dust and the potential explosibility of the coal dust. Dust on elevated surfaces is dispersed and entrained by the developing explosion much more readily than dust on the floor. The increased use of meshing to control roof and rib spall provides elevated surfaces for coal dust to collect which significantly increases the potential for dust explosion propagation if not adequately inerted. In addition to holding more coal dust, the meshing makes the collection of representative dust samples by using current band sampling equipment inadequate. This paper discusses these and other related factors that could result in a potential undetected dust explosion hazard, when using current dust sampling procedures, in an area that otherwise appears to be adequately protected with rock dust. Recommendations are made for further investigation into how these and other factors affect explosion propagation and the need for sampling procedure changes.