Mining Topic: Fire Control and Suppression

Fire Suppression

What is the health and safety problem?

Fire in an underground coal mine is hazardous because of the confined space, possible effects on the ventilation system, and limited and long evacuation routes. Mine fires, in conveyor belt entries, can produce smoke and high levels of toxic gases that are carried throughout the mine by the mine ventilation system. Also, a fire in an underground coal mine with appreciable levels of methane can be especially dangerous, potentially causing a catastrophic explosion.

What is the extent of the problem?

The number of underground coal mine fires averaged 15 to 20 per year in the 1970s, but decreased to about 5 per year in the early 2000s. This decrease can be attributed to a number of factors, including the impact of fire research conducted by NIOSH’s Office of Mine Safety and Health Research (OMSHR). However, this number has increased to an average of 9 per year for the period from 2007 to 2009. It is believed that advances in mining technologies may be responsible for this resurgence..

How is OMSHR addressing the problem?

To reduce the hazards of underground coal mine fires, particularly in conveyor belt entries, OMSHR is evaluating and applying recent technological advances in the areas of fire-resistant belt materials and belt fire suppression systems.

What are the significant findings?

Recent OMSHR studies have determined that the ventilation air velocity has a significant effect on the detection, activation, and suppression capabilities of mine fire detection and suppression systems.

What are the next steps?

OMSHR will investigate how airflow affects fire suppression systems in conveyor belt entries. This information, coupled with the findings from recent OMSHR studies, enables the mining industry to adjust their practices to mitigate any health and safety issues resulting from a change in mining practices. OMSHR will use modern fire computer codes developed for use in large, above-ground structures and supplement them with computation fluid dynamic (CFD) computer codes to evaluate suppression systems under current conveyor belt drive area configurations. The CFD codes and the new MFIRE 3.0 code will be used to model airflow and its interaction with the suppression system and agent. The goal is to develop more effective engineering designs for installation of fire detection and suppression systems.

Noteworthy Publications & Products

• Fire Detection for Conveyor Belt Entries (2012-08)
  This report details the results of a series of large-scale experiments where small coal fires were used to ignite the conveyor belt at specific air velocities, and showed conditions required for early detection of conveyor belt entry fires.
• Flammability of Wider Conveyor Belts Using Large-scale Fire Tests (2012-08)
  This paper describes the results of recent experiments comparing results from using the BELT and the large-scale tests for six different belts.
• Impact of Air Velocity on the Detection of Fires in Conveyor Belt Haulageways (2012-08)
  This paper discusses the impact of ventilation airflow on alarm times of the smoke detectors and video cameras, CO levels, smoke optical densities and smoke obscuration, total smoke mass concentrations, and fire heat release rates.
• Improvements in Conveyor Belt Fire Suppression Systems for U.S. Coal Mines (2012-08)
  NIOSH conducted full-scale fire suppression experiments, and this report discusses the large-scale experimental configuration, installation of the fire suppression system, and conclusions regarding the effect of air velocity and other factors.