Two Cat® plow systems modified for specific operations are helping a German mining company successfully overcome the challenge of mining in low and thin coal seams.
In 2013, German mining company RAG Anthrazit Ibbenbüren GmbH approached the Caterpillar Longwall team in Lünen, Germany for an equipment solution to help them mine an anthracite seam that averages only 0.85 meters (33.5 inches) in thickness and that doesn’t exceed 1.0 meters (39 inches) in height. Caterpillar and Ibbenbüren, along with German Cat Dealer Zeppelin, worked together to design and construct a system capable of mining such a seam.
The Cat GH800 plow, with an installed power of 2 x 400 kW, has been a plow of choice for seam heights from 0.9 to 2.0 meters (35 to 78 inches), regardless of seam inclination or coal hardness. The lower the coal seam, the more difficult the extraction process; however, several key modifications to the Armored Face Conveyor (AFC), plow body, and Cat roof supports led to success.
AFC modifications included PF4 plow line pans with a replaceable top trough and a new plow guide made of a one-piece casting to provide extra strength and durability while being much lower in height than the previous welded version. External dogbone connectors between the line pans and a very strong and flexible relay bar between the AFC and the roof supports (shields) further adapt the conveyor for very low seam operation. To increase coal throughput, the engineering team widened the conveyor cross-section with extended side plates.
The plow body was adapted to cutting heights from a maximum 1.55 meters (61 inches) to as low as 0.75 meters (30 inches). An optimized design at both ends of the plow body helps load more coal onto the face conveyor and reduces the amount of cutting power consumed by this process.
The Cat low seam roof supports were also specially designed for this application. Shortened canopies avoid collision with the plow even in their lowest position, and the shield canopies are 8 centimeters (3 inches) thinner to create a more ergonomic working environment for the face crew.
The modified system went underground for operation at Ibbenbüren mine in late 2013. In addition to impressive daily production, the new system has reduced operating and maintenance costs by about 50 percent compared to a nearby coal face. An advance rate of as much as 10 meters (33 feet) per day reveals the enormous production capability of the system. A key to good longwall performance is the highly effective controllability of the plow system, even in very soft floor conditions
RAG plans to operate the GH800B plow system in five consecutive longwall panels of the Ibbenbüren mine.
Convinced of the advanced productivity and effectiveness of the system, RAG placed an order in 2015 for a second Cat GH800B Plow body, this time to mine a seam averaging only 1.04 meters (41 inches) thick. It began production in July on a 220-meter (722-foot) face.
The new system includes a shock absorber, which is an elastomer coupling in the plow pulling sledge to reduce peak loads on the plow system—chain, plow connectors and drives. The effect is smoother plow operation and extended service life of components. RAG has since retrofitted its older plow systems with shock absorbers.
As with the first G800B system, Cat automation of the complete plow longwall as well as remote control of all functions and adjustments enables high production, enhances safety and minimizes operating cost. At Ibbenbüren mine, all underground production operations are controlled from a central control station on the surface.
In 2015 Ibbenbüren expects to produce 1.63 million tonnes (1.8 million tons) of high quality anthracite from its longwall systems working 1 300 meters (4,265 feet) below the surface.
Both systems are supported by Zeppelin and equipped with Cat automation technology, enabling high production, enhancing safety, and minimizing operating costs.
