February 7, 2006 By Blake Harris
Following the Sago coal mine explosion in Tallmansville, West Virginia, where 12 trapped miners died in the worst mine disaster in that state since 1968, U.S. experts have started to assess how new wireless technologies might mitigate such incidents in the future.
The U.S. Department of Labor's Mine Safety and Health Administration (MSHA) announced this month that it is evaluating and testing a personal emergency device (PED) and a locator system for underground mines. CONSOL Energy and Peabody Coal Company have agreed to work with MSHA to test the systems.
The PED was developed in Australia by Mine Site Technologies. The system uses either a surface- or an underground-powered loop which radiates a radio frequency signal enabling one-way communication to underground. The system dims and flashes a miner's cap lamp for about 10 seconds, then sends a text message to the wearer. Individual, group or broadcast messages can be sent.
MSHA is currently surveying underground mines around the U.S. that use the PED to determine its effectiveness and discuss operational issues that have arisen in different mine environments. Of particular concern are the issues created by the underground antenna loop and the need to withdraw power in the event of a fire or explosion.
Mine Site Technologies was previously issued MSHA approval for their Model PED1 Paging Receiver/Cap Lamp, meaning that this system may be marketed in the U.S. for use in underground gassy atmospheres. According to Department of Labor spokesman, Dirk Fillpot, further testing of the device by the department is intended to ascertain the effectiveness and safety in emergency situations, including the potential for damage to the receivers by fire, explosion or roof falls which could compromise the ability to track and/or send messages on the data line.
The MSHA is also evaluating a locator system (Tracker IV) from the same company. This system enables identification of a miner's location in an underground mine. The miner wears a transmitter that sends out a unique pulsed signal to receiver beacons strategically spaced underground. MSHA will be looking at possible concerns. While the Tracker IV units have received MSHA approval, the beacons have not, in part because the beacons might be subject to damage from fire or explosions. This could compromise the ability to track or send messages. The company suggests that this might be handled by placing the beacons in explosion proof boxes.
One other concern for the tracking units is that tracking of personnel is limited to identifying their location in the "zone" between two beacons where any given transmitter is located. Therefore, if the beacons are spaced (as commonly done in other mines) at 3000' intervals, a signal is received when the transmitter passes beacon A, but then not again until it passes beacon B. If the system is disrupted in an emergency and personnel need to be located, this limitation would create a potential search window of over