Report: APP CMHS Project 1

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3.6.2. Explosion Control

Current Technologies

Explosions in underground coal mines are caused by accumulations of flammable gas and/or combustible dust mixed with air in the presence of an ignition source. The main preventative measures practised in U.S. underground coal mines include:

  • Monitoring and minimisation of methane concentrations through methane drainage and ventilation.

  • Addition of sufficient rock dusts to inert the coal dust. As a precautionary measure against the dust explosion hazard rock dusting has been widely used in U.S. coal mines.

  • Reduction of coal dust. Water sprays are widely used to control coal dust at coal faces, chain haulage, lump breakers, conveyor belts and conveyor transfer points. Coal dust control with water sprays have focused on spray optimisation and design. Dust scrubbers have been shown to provide a significant reduction in airborne dust and are currently installed on longwall crushers, continuous miners and auxiliary fans.

  • Elimination of ignition sources such as electricity, welding or heat from cutting machines and spontaneous combustion of coal.

Explosion effects are mitigated by using barriers (water or limestone dust) to suppress propagating explosions and seals. In 2008 the Mine Safety and Health Administration (MSHA) promulgated the Final Rule on “Sealing of Abandoned Areas”. In this Final Rule, seals must either (1) withstand 50 psi if the sealed area is monitored and maintained inert, or (2) withstand 120 psi if the sealed area is not monitored, or (3) withstand greater than 120 psi if the area is not monitored and certain conditions exist that might lead to higher explosion pressure.

Application Sites

The relevant requirement and procedures in explosion prevention and control in U.S. underground coal mines are included in 1977 Federal Mine Health Safety Act and subsequent amendments. MSHA is the agency responsible today for health and safety regulations governing the mining industry. Detailed information can be found in MSHA’s web site

Technology Gaps/Needs

The increased utilisation of high production, mechanised mining methods in deeper and gassier coal seams place additional demands on those responsible for mine safety, particularly in the area of explosion preventions. Compliance and enforcement along with the development and implementation of affordable, practical, and useful technologies can eliminate deadly mine explosions in the future.

A number of areas requiring further improvements in exposition prevention and control include:

  • Development of effective, automatic and on-line gas composition monitoring methods inside both active and sealed goafs. This will provide necessary information for analysing possible explosive atmosphere in the goafs and allow preventive measures such as inertisation to be taken if required.

  • Methane drainage from goafs. It can be an efficient method to prevent methane from coal seams located above and below from migrating into the active workings

  • The general application of a hand-held dust explosibility meter (CDEM) for evaluating the explosibility of coal and rock dust mixtures in situ

  • Development of computer hydrocode and advanced reactive flow models for reconstructing gas and dust explosions. These will provide the ability to completely reconstruct complicated explosion dynamics. These will allow government and independent investigators to unravel complicated blast patterns and chemical reactions of participating gas and coal dust. These models may even facilitate the development of new techniques for explosion mitigation.

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