Published in the August 2009 Coal USA Magazine

As the only longwall mine in the 10th-largest coal-producing state in the US, the Buchanan mine is considered to be of average depth for the area, but is quite deep by eastern coalfield standards. With overburden ranging between 1300 feet and 2400ft, its seam and cutting heights are quite healthy – as is typical with all of Consol Energy’s mines – at 60-156 inches on average.

Initial development and production at Buchanan by continuous miner began in 1983, with the first longwall panel cut in 1987. The mine has seen success with three active sections in the Pocahontas 3 seam which, by press time, will become four with the addition of another CM unit and associated fleet.

Longwall mining is currently in a period of transition at Buchanan, with the average 1000ft-wide panels being reduced to about 700ft by 11,500ft for the remainder of the mine design using this method.

Central Appalachia operations vice president Jack Richardson said while the change in cut would affect tonnage going forward, it was being made due to the geology in the area, to further enhance safety and to match current production needs with market demand.

After the current panel, Buchanan’s Joy 7LS1A shearers, featuring a 58in drum diameter and 42in width with 4160 volts of installed power, will be placed in the new, smaller panels as the longwall continues to make progress in the mine’s 3 East area. While the former 1000ft face used 173 Joy two-leg shields with 1025-ton yields, the new faces will require about 122 shields with the balance going back into the producer’s equipment rotation fleet.

Finishing out the mine’s longwall set-up is a Joy face conveyor, with a 42mm by 146mm Thiele face chain powered by three 800hp motors running at 345ft per minute, as well as a beam stage loader by Longwall Associates and a Joy 300hp crusher.

Buchanan assistant superintendent Danny Atwell noted that, with 48in longwall belts zipping along at a 3000t per hour capacity, the infrastructure ran smoothly and sufficiently for the mine’s needs.

Longwall availability is consistently high. Including belt performance, the mine’s mean availability is approximately 92-95% while longwall availability is almost always 98% or above.

Through years of practice, longwall moves are basically a science now for Buchanan crews, according to central Appalachia general manager of mining Danny Quesenberry. Everyone participates in moves, but because the mine has pan line, drives, chains, belt and the balance of the longwall system in its equipment rotation program, the only components actually being moved from panel to panel are shields.

Once the infrastructure has been put in place, moves take just 4-4.5 days on the mine’s 1000ft faces. Now that the face length has been reduced, management anticipates just three days from stop to start to complete a move.

Despite its depth, Richardson noted there were no significant issues with roof geology at Buchanan either currently or historically. The roof rock is predominantly shale, although there are areas where sandstone is encountered.

“The roof control supports we use are typical for this area,” Richardson said, adding that when adverse conditions were encountered from time to time, the mine used longer bolts or additional cable bolts to shore up the area.

Typically, the mine uses a variation of 4ft, 6ft and 8ft fully grouted resin Jennmar bolts throughout, with typical 4ft by 4ft spacing. For cable bolting, that range typically sits between 8ft and 20ft.

Another potential problem Appalachian mines sometimes encounter is methane; however, Buchanan has in place a very robust ventilation system as well as an impressive degasification program. Methane captured from these efforts is sent to CNX Gas, a Consol company, for processing and resale.

“Through our degas program, we drill horizontally in each big block. We also drill vertical ventilation holes in our longwall gob areas,” Richardson said.

“Once we bleed the methane off, we typically keep three holes online for water infusion once the longwall starts up.”

The success of the degas program, he added, is evident when one considers the amount of downtime due to methane issues.

“Our degas program has greatly improved things on the face and on the miner sections, where methane isn’t typically a problem now.”

Included in the ventilation circuit are five main fans that circulate a total 2.5 million cubic feet of air per minute. Exhaust ventilation is used on the miner sections, splitting the air in the face.

The longwall is ventilated to its own separate bleeder system and vent shaft.

Development at the mine, designed on a four-entry system, is done with the CM fleet, which includes two Bucyrus 25M series miner units as well as six Joy 14-15CMs. Two miners are put to work on each working section.

After making amendments to the mine design to increase the size of pillars, Atwell calculated current dimensions to be 150ft by 50ft on yields and 450ft by 170ft on stable pillars. A range of 18ft to 22ft was allowed for the operation’s belt/track entry.

Between the experienced workforce at the always well-staffed Buchanan, the high level of availability and sufficient belt capacities from the active working areas to the surface, both the longwall and sections achieve notable daily progress. The average longwall retreat on a daily basis averages 54ft and 75ft on 1000ft and 700ft faces respectively, and the CMs achieve approximately 80ft on each of the three shifts.

There are no maintenance shifts per se at Buchanan, maintenance foreman Jeff Ball explained. The mine runs 24/7, 361 days a year, and his team carries out preventative maintenance while the production crews perform their tasks. It also keeps a close eye on monitoring with vibration and temperature analysis, and oil sampling.

At press time, Buchanan was installing a new Pillar Innovations belt monitoring system, scheduled to be fully operational by the end of the year. The primary impetus for the expenditure, Ball said, was the decision to increase availability through remote monitoring and troubleshooting.

The mine is also testing and evaluating proximity detection systems, which so far has garnered mixed results as operators work to get to a proper comfort level with the equipment. However, Ball thinks this technology will work and further enhance safety. A system has been placed on one CM unit already, with plans to install it on the entire group of units at Buchanan and throughout Consol’s central Appalachia operations.

As for communication underground, Buchanan has a leaky feeder communication system and has placed a strong focus on safety through technology in its decision to install an American Mine Research tracking system. The first phase of components will be installed this fall and plans are for the system to be up and running before the close of the year.

As expected in such a productive operation, and one which never rests, hot seat changeouts are vital to keeping article continues, click here.