A ray of light

Nov 1, 2007 12:00 PM, By Mary Rose Roberts

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“Before you go under the mountain into the coal mine, you look up at the sky and wonder if that's the last time you'll ever breathe fresh air,” said Bob Hammonds, who worked in southeastern Kentucky's coal mines in the 1990s. “Every night when I went under the mountain that was my last thought. The next morning when I came up, looked out and saw the sun, I thought, ‘Whew, I made it.’”

Coal-mining is a dangerous job. Miners work thousands of feet underground beneath millions of pounds of rock. They are surrounded by high-voltage electrical lines, darkness, dust and highly explosive methane gas that seeps from the coal. Death isn't certain, but it's always a possibility, Hammonds said.

In fact, the Bureau of Labor Statistics' 2006 Census of Fatal Occupational Injuries reported fatality rates for coal-mining jumped 84% in 2006 to 49.5 fatalities per 100,000 workers, up from 27.8 in 2005 — much of which resulted from the Jan. 2, 2006, Sago Mine disaster in West Virginia that trapped 13 miners for nearly two days, killing all but one.

The Mine Safety and Health Administration (MSHA) responded to the Sago tragedy by sponsoring the Miner Act of 2006, which mandated coal-mine communication technology benchmarks. The act called for coal-mine operators to implement post-accident communications that provide a redundant means of communication with the surface for people underground. It also called for post-accident tracking systems that identify the location of all mine personnel who are underground.

Coal-mine operators now will be required to present a wireless communication plan to the agency no later than June 15, 2009, that defines the degree of functionality provided by the wireless two-way communications and tracking systems to be used to enhance miners' safety.

Congress seems to believe that new technologies may be the solution for mine communications, as evidenced by the $23 million it allocated to the National Institute of Occupational Safety and Health for the development of subterranean communication technology. Agency officials reported that 40 new communication and tracking systems supported by the funding are currently under review.

However, vendors face an uphill battle to pass MSHA inspections and meet manufacturing deadlines, said Dave D. Lauriski, formerly the U.S. Assistant Secretary of Labor for Mine Safety and Health and the head of MSHA under President George W. Bush from 2001 to 2004.

Potentially viable technologies must pass muster with the MSHA's Approval and Certification Center, which certifies products for use in underground coal mines. Among other standards, the technology must be intrinsically safe, meaning no explosion hazard under normal operations when used in gassy or dusty environments — especially in coal mines were large amounts of methane gas can accumulate. Following approval, a license is issued authorizing a manufacturer to produce and distribute products for use in coal mines.

Meanwhile, miners and their families question why communications systems aren't where they need to be — especially after the Aug. 7 disaster at the Crandall Canyon Mine in Huntington, Utah, where six trapped miners and three rescuers were left for dead 1800 feet underground.

“[Families] are taking the agency and mine operator to task over the adoption rate,” Lauriski said. “The simple matter is that the demand is greater than what can be produced right now, and it's going to take some time for the production and manufacturing levels to increase to supply communication devices for all mines.”

Currently, most mine operators deploy two-way radios and so-called leaky feeder systems for subterranean communications, Lauriski said. To allow radios to function underground, a standard surface antenna system is replaced with a cable network designed to “leak” a signal, letting radio signals both seep from and into the cable. The systems are used for both data and voice communications, he said.

Leaky feeder systems usually are hung at the top of the mine opening and intertwined with electrical conduit, said Joe Watts, Kenwood USA's senior product manager. In 2006, Kenwood's portable radios became the first to be approved by MSHA for use in underground mines. The company offers two models: the UHF/VHF TK-290 and TK-390. The ruggedized radios meet MIL STD 810 for dust and drops, as well as MSHA's intrinsically safe requirement.

MSHA also requires that the amount of stored energy in a two-way radio doesn't exceed a certain amount — making it an even more difficult challenge to provide reliable radio communications in coal mines, Watts said.

“I don't know of a perfect solution,” he said. “But a combination of voice communications with personnel accountability or location tracking might be the best solution, so if a disaster does happen at least you know the last location of those personnel.”