The shearer on the longwall chews through the face of the coal seam as coal falls onto a conveyor.
The longwall operation at Twentymile Coal Co. removes an average of 22,000 tons of coal from the mine each day.
Sections of coal to be mined by the longwall are called panels.
Imagine the longwall operation like a lawn mower the width of a football field that in one swoop is removing coal from one end zone and traveling up three miles’ worth of yard lines to the other end zone. More than 10,000 horsepower are attached to the machine.
The longwall and panels at Twentymile are 1,000 feet wide with a shearer that passes along the width of the panel. With each pass, the shearer cuts 40 inches of coal from the face of the seam. It also cuts the height of the seam, which is nine to 10 feet tall.
Pat Sollars, general manager of Peabody Energy’s Colorado operations, said the shearer can move along the face at a top speed of 144 feet per minute. As the longwall moves forward through the panel, coal is captured on a conveyor.
Longwall panels are three miles long, and a 50-foot section is removed each day.
The longwall is composed of 2-meter shields weighing 38 tons each. The purpose of the shields is to support the weight of the roof, and Sollars said each shield is capable of supporting 1,300 tons. As the longwall and shields move forward, the roof safely collapses behind the shields.
If coal sales are up at Twentymile, Sollars said the longwall will run for 18 hours each day.
He said the longwall is taken apart and moved to a new panel about every six months. In 2012, the longwall was moved three times.
When the longwall is not running, the mine is not making money so they try to move fast. The record time at Twentymile for breaking down the longwall and setting it back up is 10 3/4 days.
“We have people from all over the world that come to see the longwall moved,” Sollars said.
2011 US coal production by county