Mining Contract: Medium Frequency Radio System Modifications for Refuge Chamber Situational Awareness

Contract Status & Impact

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

This contract research tested how medium frequency radio systems could be used to improve refuge chamber situational awareness in an underground coal mine. The contractor conducted a demonstration of the technology at the Safety Research Coal Mine (SRCM) in Pittsburgh, PA. The tests focused on whether the door to a refuge chamber underground had been opened (which would indicate readiness for entry) and under those circumstances whether voice communication to the mine operations center could be provided by some means other than primary communication systems.

Based on a product approved as permissible by the Mine Safety and Health Administration (MSHA), a modified version of the DRUM TTR-100 Tracking Tag Receiver was used for this demonstration. The DRUM 100P was redesigned to make the device able to be worn on a miner’s belt as opposed to being carried. The TTR-100, which already passes tracking data, was also modified to add a special receiver and an indicator light. Once the chamber door had been opened, the modified device would turn on the light and send a signal to the surface over medium frequency. Voice communication would be provided using the already permissible DRUM 100R. The final deliverable was not permissible since it was modified, but the research concept was to demonstrate a product that could potentially be made permissible.

Redesigning existing medium frequency communications and tracking products allowed the contractor to evaluate the performance of these technology adaptations for use in an underground coal mine. Some of the areas tested did not have a defined infrastructure but they had many conductors in them to serve as a path out of the mine. Prior testing has shown that medium frequency signals can travel several miles underground provided there are conductors present.

Testing consisted of using the modified TTR-100 and a wireless switch. This switch did not have a battery but generated a signal capable of being read by the modified TTR-100 located near a rescue chamber. Once the signal had been received by the TTR-100, it was transmitted using medium frequency through some nearby conductors then out of the mine. The signal was then picked up by the mine operations center along with any tracking information. Voice communication was accomplished using the DRUM 100.

The contractor determined that the switch and modified TTR-100 would serve well to signal when miners enter a refuge chamber based on whether the door had been opened. Data related to actions by the miners would be sent to the surface in the event that anyone entered the refuge chamber. Some consideration for antenna placement and the proximity to conductors, so that they could effectively carry the medium frequency signal out of the mine, was made during installation.