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Mining Project: Improving Coal Dust Explosion Hazard Assessment Strategies

Principal Investigator
  • Marcia L. Harris, NIOSH OMSHR, 412-386-5780
Start Date10/1/2010

To eliminate coal dust explosions in underground coal mines.

Topic Area

Research Summary

This project has seven research aims, as follows:

  1. Determine the distance an explosion can propagate through an inert zone and the factors that influence this propagation distance.
  2. Re-examine combustible dust assessment procedures used by MSHA and the mining industry for their efficacy in view of modern mining practices.
  3. Examine the impact of variations in rock dust properties and application practices and how these variations may influence inerting effectiveness.
  4. Examine the efficacy of the Coal Dust Explosibility Meter (CDEM) as a compliance tool.
  5. Ascertain the effectiveness of rock dust that is wetted, then dried, in suppressing coal dust explosions and recommend solutions to the caking issue.
  6. Identify potential deficiencies in the current coal dust and rock dust definitions per 30 CFR 75.2.
  7. Develop guidance for practices that effectively distribute rock dust using existing ventilation and rock dusting equipment.

Underground coal dust explosions are highly destructive and often result in a significant loss of life. A primary defense against such dust explosions is application of rock dust to inert accumulations of explosible coal dust. Although past work by the Office of Mine Safety and Health Research justified and subsequently resulted in an increase in the incombustible content requirements in all underground airways, problems continue to exist in the uniformity of rock dust sampling procedures, the adequacy of rock dust performance, and continuity of rock dust application.

This research effort will develop empirically based recommendations for changes to the current combustible dust sampling protocols in US underground coal mines. These protocols include assessments of sample spacing, roof and rib mesh influence, floor dust sampling depth, and use of the CDEM as a compliance tool. This research will also address deficiencies in the current rock dust definition, including an insufficient number of rock dust particles in the most reactive size range, a tendency for the rock dust to form a cake when exposed to water, and an allowance for elevated levels of combustible matter in the rock dust.

Based on the research results, this work will specify a tighter size distribution including a minimum surface area value, the use of additives to maintain dispersibility of the rock dust when wetted and then dried, and a minimum content of combustible matter to maintain inerting effectiveness. Finally, this work will develop guidance to effectively distribute rock dust so that the particle size distributions of the rock dust and explosible coal dust more closely match, increasing inerting effectiveness in the event of an underground coal dust explosion.