from Scripps Howard News Service The West Virginia coal mine racked by a presumed methane gas explosion this week had one of the more advanced systems available for communicating with and tracking miners underground.
Yet those telecommunications were lost after the blast that claimed at least 25 lives Monday, leaving rescuers on the surface with no way to tell if several missing miners survived or where they were. The situation highlights a problem facing safety officials not only in hundreds of underground mines but also rescuers in any mishap that might occur in tunnels of railroad and subway lines, underground utilities and parking garages -- radio signals don't travel well through dense materials. The typical radio, GPS and cell-phone signals of the above-ground world won't penetrate more than a few yards down. Although a major federal mine-safety bill approved in 2006 called for survivable or redundant communications gear to be in all mines by June 2009, the federal Mine Safety and Health Administration (MSHA) backed off the requirement at the end of 2008 after concluding the technology just wasn't good enough to hold the industry to the standard. Only in the past several months has the government started to certify equipment, and manufacturers continue to work on new gear that will work in the hostile underground environment. "Being able to communicate throughout a mine, and not only in limited areas of a mine, is essential for a system that would be needed for two-way communication from the surface with miners trapped underground after a mine explosion or collapse,'' said Jeffrey Kohler, associate director for mining at the National Institute for Occupational Safety and Health (NIOSH), which is coordinating a government-industry partnership to develop new emergency communications technologies. Communicating inside a coal mine is particularly challenging because equipment must be low-powered (1,000 to 2,000 times less energy than an average cell phone) to minimize the risk of triggering an explosion from methane and coal dust, yet must also reach through miles of twisting and turning tunnels full of equipment and natural formations that interfere with transmission. Some of the more promising approaches use low-frequency radio waves that can travel through several hundred feet of rock, or medium-frequency radio nets that can use metal already in a mine to conduct signals through tunnels. Massey Energy's Upper Big Branch Mine was one of dozens that had responded to West Virginia mining rules by starting to install a radio and miner tracking system linked by strings of underground repeaters designed to keep working even if an accident disabled some circuits. State rules require tracking gear to tell what section of a mine workers are in, but not a specific location; federal regulations call for more precise tracking. MSHA officials said the telecommunications system in the Big Branch mine had not been able to trace or make contact with the four miners still missing in a deep section of the mine beyond the blast site. "We know how many people are in that area, but we don't know their exact location,'' MSHA coal administrator Kevin Stricklin said during a briefing. And rescuers could only bang on pipes sunk from the surface to try and contact any survivors. Fixing that may take a new generation of transmitters. While several manufacturers are working on low-frequency transmissions, one of the more advanced is "through-the-earth radio" technology being developed by Vital Alert Communications Inc. of Toronto and its U.S. subsidiary, Vital Alert Technologies of Cleveland. Scientists at Los Alamos National Laboratory in New Mexico developed the technology. It uses very-low-frequency electromagnetic waves to carry digitally compressed voice or data to underground areas. Last month, prototype equipment successfully sent signals through 350 feet of rock, earth and concrete at a mine in Sunbury, Ontario. "It's totally wireless, no cable, no conductors, and you can connect it to any type of communications equipment you want," said Heather Simmons, chief executive of both Vital Alert companies. Vital Alert has also done field demonstrations for U.S. law-enforcement agencies and New York City subway officials. "The signals are slow -- about 1 kilobyte per second-- but they get through or around interference, including areas with flame and smoke,'' Simmons said, adding that the equipment should be on the market by November. Company technicians haven't experimented with distances of more than 350 feet, but think the outside range of their signals is 600 feet -- not deep enough to reach the miners more than 1,000 feet down in West Virginia, but sufficient for many mines and most other underground installations. Kutta Technologies of Phoenix has been working with systems it originally designed for military use as emergency alternatives for mine communication. One, a small wireless transmission system intended for use in Afghanistan's caves, achieved a voice range through the earth of more than 800 feet in one government-sponsored test inside a mine. The other approach tested through NIOSH is a portable radio system that would broadcast medium-frequency transmissions in a mine using metal objects like rails, electrical wires and water lines to carry a signal that could also be picked up through existing high-frequency systems already inside most mines. Tests showed this system could carry signals more than a mile through a mine and could be used to cover an entire mine. (Contact Lee Bowman at BowmanL(at)shns.com) _______________________________________________ NMCAVER mailing list nmca...@caver.net http://caver.net/mailman/listinfo/nmcaver_caver.net
