Sunday, January 16, 2011

Safety System Dysfunctional Before Mine Blast

Legally required water systems at Massey Energy's Upper Big Branch coal mine in West Virginia were not functioning properly before the April 5 explosion that killed 29 mineworkers, according to multiple sources familiar with the disaster investigation.

Some mine safety experts believe that these safety systems might have helped prevent the explosion if they had been working as designed.

From All Things Considered


Fireball could have been prevented: Saturday on NPR


How The Blast Might Have Happened

Nine months after the Upper Big Branch coal mine explosion, investigators are homing in on possible causes. The following illustrations present some basic information about the area where the explosion is believed to have originated, along with possible causes. The illustrations (courtesy of NPR) are not to scale (click on image to enlarge).

Each of these dysfunctional systems funnel water to the longwall mining machine that investigators believe was the source of the deadly explosion. When they're functioning, the systems spray water (right) on the longwall's cutting tool, known as a shearer, and along the coal seam as the shearer cuts into it.

The sprayers help keep coal dust down so it won't clog the lungs of miners or float in the air. When coal dust is floating, it is highly explosive. The sprayers also help cool and extinguish sparks when the shearer cuts into hard rock. The shearer (below left - click on image to enlarge) also contains a water-based fire suppression system.

But on April 5, none of these safety systems were working properly, according to four people familiar with explosion evidence.

The malfunctioning systems include:
  • The fire suppression system on the shearer. Sources say it didn't work. Massey Energy admits that one of two valves on the system was missing, and a hose was "manually plugged."
  • A water-spraying arm or boom at the shearer was disconnected, according to sources. Massey says it was broken off.
  • Sprayers on the shearer itself were missing or clogged. Some looked like they had had nails driven into them. Tests conducted on the shearer sprayer system before Christmas indicate little or no water sprayed the shearer as it cut into six inches of sandstone in the coal seam, and likely kicked off sparks and churned up coal dust.
With no effective water spray, any seepage of explosive methane gas could easily ignite and form what miners describe as small fireballs. Add floating coal dust and those fireballs are apt to trigger massive explosions.

"What typically happens with these ignitions is that water sprays on the miners can put these ignitions out," says Ellen Smith, (right) owner and editor of Mine Safety and Health News. "All the backup systems worked when something went wrong.

Smith has collected and reviewed federal reports of methane ignitions in underground coal mines.

"We know that there have been about 600 ignitions since 2000," Smith reports. "And they have not resulted in mines blowing up."

Consequences Of Weak Ventilation System

Smith points out that a mine's ventilation system also works to control coal dust and methane underground. The system manages airflow so that methane gas dissipates or is swept away. Good ventilation also helps control coal dust. Inadequate ventilation has been a persistent problem at Upper Big Branch.
"The water and everything, that would have helped," says Stanley "Goose" Stewart, a veteran coal miner at Upper Big Branch who once operated the longwall shearer. "But ventilation is the biggest factor in my mind."
A week before the blast, miner Gary Quarles told Stewart that the ventilation at the shearer was so weak and the coal dust so thick, he could barely see. Quarles died in the April 5 explosion. Stewart survived a smaller blast underground in 1997.

"When I saw the glow coming in from behind the wall down on the [tailgate], I took off as hard as I could toward the [headgate]," Stewart recalls. "I thought I was a dead man. I was engulfed in fear."

Finding What Ignited The Fireball

Two miners likely experienced something similar on April 5 at Upper Big Branch, according to NPR's sources and Massey Energy. The two men were working at the longwall shearer when methane gas seeped toward it. There's disagreement about the source of the methane. Massey has insisted that a nearby crack in the mine floor produced a sudden, unpredictable infusion of gas that could not be controlled. It's located just beyond the longwall at the tailgate of the machine.

Some of NPR's sources point to two additional cracks back toward the headgate of the longwall but close to the shearer. One is a newly discovered crack found between two of the floor-to-ceiling shields that protect the machine and the miners from falling rock as they work. These sources describe a scenario in which methane from that crack migrated to the tailgate, bypassed the shearer and its methane detectors, then turned back into the spinning and sparking shearer.

Other sources say it's impossible to determine the precise source of methane. They note that Upper Big Branch is such a gassy mine that methane seeps from the coal face and the mined-out area known as the gob.

Even if methane suddenly rushed out of a crack, that's a predictable event, says Smith of Mine Safety and Health News.
"These huge inundations from gas seams have occurred in this mine and in other mines," Smith notes, referring to federal records that also track these incidents. "And when the ventilation systems were working, you did not have an explosion."
On April 5, the two miners at the longwall shearer most likely witnessed the formation of a small fireball, sources say, as methane reached the shearer and its sparks. If the ventilation was poor, they would have known that floating coal dust would soon explode. So they ran.

Investigators know they ran because they either shut down the longwall machine themselves or phoned the machine's operator at the tailgate. In any case, power and water were cut, and 60 seconds later, the mine erupted. The two men were found about a third of the way up the longwall face along with two other miners. They were gone in an instant, as were 25 others as much as two miles away underground.

Evaluating The Water Sprayers

The new revelations show that the mine had "conditions that created a circumstance that allowed an explosion to happen, which never should have happened," says Mark Moreland, an attorney whose law firm is officially designated as a miners' representative in the disaster investigation. Moreland's firm also represents the families of two Upper Big Branch victims in wrongful-death suits filed against Massey Energy.
"This operation was not operated according to law and was, in fact, if all these circumstances are true, operating in an illegal fashion," Moreland contends.
To continue reading article click here.

Source:
NPR,
"Safety System Dysfunctional Before Mine Blast", by Howard Berkes, accessed January 16, 2011

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