Depletion of coal resources amenable to shearer longwall extraction in the USA is being accompanied by a resurgence of interest in plow technology to recover thin seam reserves.

At present, the only American company using DBT-supplied plow technology is US Steel Mining Company’s No.50 mine in West Virginia, the lowest-seam longwall on the North American continent, operating at a mining height of 48 inches and below. The mine holds the world record for thin seam production of 22,710 clean tonnes per day.

Harry Martin, DBT’s vice president, account management and global marketing, said in recent months at least six US coal mine operators had requested presentations on plow technology, with half of these already progressing to the feasibility stage. By the end of 2002, at least one additional plow could be operating in the US, he said.

Other advanced plow projects in North America include the MICARE and MIMOSA mines in Mexico. MICARE has 70% of its coal seams under 1.6m in thickness. Martin said the Mexicans were in the process of learning and adapting German methods for plow longwall mining. These included the use of head and tail gate entry and the development of bigger roadways with steel arches.

Undoubtedly the most exciting plow project DBT recently concluded was the installation of China’s first automated plow at the Tiefa mine in Liaoning province. Within three weeks of operations beginning in January, the mine had produced 4000t of run-of-mine coal, which is believed to be a production record for a Chinese thin seam longwall.

While DBT faced some unique challenges in taking its plow technology into China, the early success of the three-year project will serve as an operating model for DBT in future installations. Language and cultural barriers were among the challenges confronting DBT. You ignored these at your peril, Martin said.

Among the methods DBT used in the installation and handover of the equipment was commissioning of a Chinese mining professor to interpret and translate training manuals, thus avoiding verbatim translations of technical terms that are meaningless to end-users.

The most significant success was achieved through hands-on training delivered by German service engineers and coal miners who operated plows at DSK mines in Germany.

“I know for sure if we sold this type of technology, which is not widely known outside of Germany, we’d take the same approach and use hands-on operators as part of the training package,” Martin said.

Unlike its competitors, DBT has elected to enter China as a manufacturing company that retains control of its products and procedures. The more common route (and one DBT has examined in detail in the past) is for a mining machinery manufacturer to form a joint venture with a Chinese company or engage in technology transfer. “We decided to go it alone against the advice of many,” Martin said. “The former China National Coal have their own longwall manufacturing divisions in China. Our logic is whether it’s technology transfer or a joint venture, it takes such a long time to transfer the know-how — anywhere up to eight years and by then the technology is already out of date.”

The Tiefa order was for DBT to supply the plow, plow running track, shield controls and advancing mechanism. The rest of the system was supplied by Chinese manufacturers.

Amazingly, compatibility between the two sets of equipment was not a major issue despite language and cultural differences as all the parties involved worked well together with a determination to make the project a complete success. This type of alliance between a major international equipment supplier and Chinese manufacturers is fairly rare and is said to have significantly reduced costs for the mine.

Also, as Martin remarked: “We have found a way to tap the Chinese domestic market with DBT technology by marrying the two technologies.”

To support its Chinese activities, DBT has built a manufacturing plant in China at Langfang, which will serve as a base for DBT to provide its full range of aftermarket services. The facility recently began manufacturing pans, using Chinese sourced steel that met DBT’s rigorous manufacturing standards.

Martin said under the leadership of manufacturing director Dirk Vorsteher, DBT’s manufacturing division had been totally revamped, which meant a pan made anywhere in the world, whether in Germany, USA, Poland, or China, would conform to exactly the same manufacturing and material quality standards.

“From our Langfang manufacturing facility we would consider making more plow components and even shearer components are not beyond imagination,” Martin said.

DBT senior chief engineer global product strategy, Uli Paschedag, who gained his PhD in plow technology research, has been involved with the US presentations to potential plow clients and believes further orders for plows could be placed this year. “The major step forward (in plow technology) has been without doubt the implementation of incremental plowing, avoiding jamming of the plow and the so-called shadow-plowing where the plow runs through the face without cutting coal because the AFC had not been pushed over. This was common in the old days where the push action was done by constant low pressure push,” he said.

Other changes are increased horsepower of up to 2 x 400kW (2 x 540hp) for the plow alone, with 38 mm plow chains and increased plow speed of up to 3m per second. The first underground trial of the so-called “Sensor-plow” in Germany is currently underway and looks very promising, according to Paschedag. The plow body is fitted with a sensor for the cutting horizon that sends a signal to the gobside activating steering cylinders to keep the plow in the seam at all times.

With vast resources of thick seam coal, Australian producers are, ironically, on the opposite end of the technology spectrum. One of the current methods being closely scrutinised is top coal caving, developed and perfected by the Chinese.

Originally published in the March 2001 edition of Australia's Longwalls.