Mining Contract: Design and Construction Considerations for a Protected Compressed Air Line to a Refuge Alternative

Contract Status & Impact

This contract is complete. To receive a copy of the final report, send a request to mining@cdc.gov.

One of the most important issues related to refuge alternatives (RAs) in underground coal mines is the ability to provide breathable air to the refuge area after a catastrophe. According to 30 CFR Part 7, a refuge alternative is defined as a protected, secure space with an isolated atmosphere and integrated components which create a life-sustaining environment for persons trapped in an underground mine when escape is impossible. There are several methods to provide the breathable air to trapped miners, including boreholes with fresh air blowing fans; buried or otherwise protected air lines supplied by surface positive pressure (compressed air lines) blowers and routed to locations that will isolate miners from contaminated environments; compressed air cylinders, oxygen cylinders, or chemical oxygen generators located at a designated area. The advantage of air supply through fans or compressors installed at the surface is the unlimited supply of air to the refuge. Compressed air lines are required when breathable air is supplied using fans or compressors installed on the surface.

To guarantee the success of air delivery and maintain a safe atmosphere for mine workers trapped in an emergency, the integrity of the compressed air line must be kept at all times. To this end, OMSHR is interested in exploring this need in a practical way through laboratory tests and design and construction considerations for compressed air lines to a refuge alternative. These considerations include the compressed air source itself, identification of the factors affecting compressed air line integrity, air line materials, bending strength requirements, anchoring systems, corrosion effects, drainage, and protection of the compressed air lines against explosions and live loads.

Considering that the last federal research on compressed air lines to refuge alternatives was conducted 30 years ago, and that the proposed rule from 2008 on Refuge Alternatives for Underground Coal Mines is considered to be a general guideline, there is the need to re-examine specific design and construction principles of compressed air lines. Under this contract, the University of Kentucky will conduct an extensive landscape assessment of commercially available compressors to determine appropriate requirements for compressor size, location, redundancy, required power, and location. This information will also allow for maximum airline lengths to be calculated and borehole distances to be designated. This research will also explore the definition of expected ranges for explosions and live loads, the types of tests and load ranges for compressed air lines, evaluation of the anchoring system, and recommendations for implementation of compressed air lines in mining environments.