CHARLESTON, W.Va. -- At first, "passive barriers" to prevent the spread of underground coal-mine explosions sound a bit like the old practical joke where you balance a bucket of water on a partly opened door, and the first person who walks through gets drenched.But by simply hanging containers of water or limestone dust in key places throughout underground coal mines, other coal-producing countries have been able to keep smaller methane ignitions from turning into major mining disasters.The technique got a few sentences in a May report on coal-dust explosion prevention from the National Institute for Occupational Safety and Health."Passive barriers have been deployed in most leading coal-producing nations to provide supplemental protection against coal dust explosions," the NIOSH report said. "Barriers are designed to quench an explosion immediately on arrival at the location."And Labor Secretary Hilda Solis told President Obama in an April preliminary report on the Upper Big Branch Mine Disaster that such devices "can suppress propagating explosions to mitigate their effects."But the U.S. Mine Safety and Health Administration doesn't require coal mine operators to use explosion barriers. The devices aren't mentioned these days in congressional hearings, pending legislation, or the national media coverage of mine disasters.Even long-time mine safety advocates have to think back in history to remember them being considered in the United States.Davitt McAteer, who ran the U.S. Mine Safety and Health Administration during the Clinton years, said last week he recalls making a push on the subject in the early 1970s. The idea apparently went nowhere, but McAteer says it should be resurrected, especially in light of the deaths of 29 miners in what experts believe was a methane and coal-dust explosion at Massey Energy's Upper Big Branch Mine on April 5."It's proven technology," McAteer said. "We should be doing this."
A variety of old Bureau of Mines and NIOSH research reports discuss the use of explosion "barriers" in other countries, and outline ways that the devices could be deployed in the United States.For example, one 1974 Bureau of Mines study outlines the use of plastic tubs or troughs hung through underground mine tunnels."During a dust explosion, the dynamic pressures induced ahead of the propagating flame tilts or ruptures the water containers, releasing and dispersing the water, which acts to suppress the approaching flame," the report said.Water containers could also be made of wood or metal, the report said, and could be of varying size and capacity, depending on their locations in the mine.
Michael Sapko, a now-retired NIOSH researcher, provided a broad overview of explosion barriers as part of a presentation on coal-dust controls in September 1989 at an international mine safety conference in Washington, D.C.In his written presentation, Sapko produced a chart that showed barrier requirements in many other mining countries, including Australia, Germany, Poland and the Soviet Union.
His report also listed examples where barriers had proven successful:| At the Fenton Colliery in the U.K. in 1963, barriers controlled the spread of a methane explosion at the working face of the mine."There was clear evidence that the flames had actually reached the barrier," the report said. "A [coal] transfer point was located just [beyond] the barrier where there were ample deposits of coal dust, and there was little doubt that without the operation of the barrier the explosion would have increased in intensity and traveled much further."| Also in 1963, at the Mainsforth Colliery in Durham, U.K., a rock-dust barrier on the mine intake airway "was completely discharged and without doubt arrested the spread of flame."| In March 1984 at a mine in Belgium, water barriers helped contain the damage from an explosion that killed seven men."The investigation indicated that the first five sets of distributed barriers operated ... and arrested the explosion," the report said. "This was suggested as the reason why men who were located 290 meters from the face were not injured."
| On July 16, 1986 at the Moura Mine in Australia, water barriers helped stop an explosion that had already killed 13 miners, preventing even more deaths.Sapko notes that barriers are more difficult to use in smaller mines with "low coal" seams, and in some mines using "room-and-pillar" mining configurations. But, he said, they can be more effective in more mechanized mines, especially those using longwall machines. Research on the devices continues to help them improve, he said."The overall direction in research on mine explosion prevent seems to be headed in the right direction," he wrote. "But it is disappointing that quantum improvements in the practice of rock dusting do not appear imminent."Reach Ken Ward Jr. at firstname.lastname@example.org or 304-348-1702.