By Steve Fiscor, Editor-in-Chief
During July, Bucyrus hosted an event in conjunction with Cliffs Natural Resources for the mining press and stock analysts at its facilities in Houston, Pa. Cliffs recently purchased a new fully automated Bucyrus GH 1600 plow system for the Pinnacle mine, located near Pineville, W.Va. This will be the first state-of-the-art plow system installed in the United States. The Pinnacle mine is the only longwall mine in the country that uses a plow instead of a shearing machine and the existing system needed to be replaced. This was a major achievement for both companies. They celebrated it with an afternoon soiree that included a preview of a portion of Pinnacle’s new equipment assembled and operating on the factory floor.
Bill Tate, executive vice president, Bucyrus Int’l, and president, Bucyrus America, presided over the event. The crowd heard presentations from Tim Sullivan, president and CEO, Bucyrus Int’l; Joe Carraba, CEO, Cliffs; Don Gallagher, North American business unit president, Cliffs; and Keith O’Neil, director product management for the Bucyrus longwall products group.
Bucyrus’ Houston facility manufactures room-and-pillar mining equipment, but it also serves as the U.S. support facility for the company’s longwall equipment, most of which is made in Lunen, Germany. “As U.S. coal operators pursue thinner seams, we believe the technology we are going to unveil today will be embraced more and more,” Sullivan said. “Shearing machines in low-seam applications cut rock along with coal. Environmentally, out of seam dilution is becoming less acceptable, especially in Appalachia. Plows offer a viable alternative.”
Longwall mining is the safest form of underground coal mining and an automated plow system could improve safety performance by removing miners from the face. The entire longwall can be operated by one miner in the headgate or theoretically from any computer with Internet access.
Longwall mining is capital intensive and a system such as this could cost as much as $85 million. Bucyrus claims the plow systems offer some advantages over shearing machines, such as higher availability, less restrictions on the armored face conveyor (AFC) under the shearer and higher rates of advance.
“Bucyrus has more than 30 longwall plow systems installed worldwide, including coal mines in China, the Czech Republic, Russia, Kazakhstan, Germany and Mexico,” Sullivan said. “Yet, this is the first modern plow system in the U.S. When plow systems were first developed, they lacked power and were not automated. In low coal, that’s a tough, cumbersome way to mine. We have advanced quite a bit since the first system was developed during 1941 in Germany. Today the plow system has automatic shield advancement, the depth of cut can be controlled electronically, and the system can be operated from a remote location—this is a modern system that operates flawlessly.”
Cliffs is a diversified iron ore miner that purchased the Pinnacle mine and Oak Grove mine in Alabama from PinnOak Resources three years ago. As Carraba explained, met coal is a finite resource. “Steel is the building block for modern society,” Carraba said. “Whether you are talking about rebuilding American infrastructure or new Chinese car purchases, steel consumption will continue to grow. Met coal demand will grow as a function of steel consumption. That’s why we have the confidence to install a new technical solution into this mine in West Virginia instead of a patch work solution.”
Cliffs is planning to expand met production from 5 million metric tons per year (mtpy) today to 12 million mtpy by 2012. “This system will give us a nice supplemental boost toward achieving that goal and a good look into the future of taking people off of the face,” Carraba said.
Cliffs evaluated the new plow purchase decision for about four months, Gallagher explained. “We knew Pinnacle needed a new longwall when we purchased the PinnOak assets,” Gallagher said. “We compared shearers with plows. The plow system Pinnacle currently operates is about 20 years old and has nowhere near the power, size, strength or engineering of this new system.”
Cliffs assembled a cross-function team of engineers, supply chain personnel and operators. The group participated in a fact-based decision making process assessing a number of variables, such as safety concerns, component costs, maintenance aspects, etc. “We evaluated not only the initial purchase price, but the operating costs of this unit for many years to come,” Gallagher said.
The GH 1600 meets the highest safety standards with new automated features that increase the safety for longwall miners, Gallagher explained. Some of the features he mentioned included the automated control of the plow and shields, which reduces operator exposure; and the overall engineering with more powerful motors, stronger hydraulics and more robust shields, which should reduce maintenance needs at the coal face. “The shields have a much higher yield strength than what we currently use,” Gallagher said. “The shields were manufactured with ergonomics in mind. A new modular design also eases maintenance for the system.”
Gallagher believes the new plow system will operate at a lower cost compared to a shearer in the same setting. “More powerful motors will increase plow speed and production levels,” Gallagher said. “The system can mine lower coal faces efficiently and navigate through difficult geology. It can be broken down and moved from panel to panel easily and efficiently. This new system will effectively extend mine life at Pinnacle.”
O’Neil briefed the group on the technical aspects of the equipment. The GH 1600 has a GH 42 AFC with PF4-1132 line pans. With a 1,000-mm raceway and a twin-strand 34-mm chain powered by two 800-hp motors, the 1,025-ft long AFC is rated for 3,000 tons per hour (tph). The AFC uses MR 45 drive frames with 7-tooth sprockets. “A PMCD system controls both the plow and AFC drives,” O’Neil said. “Using a KP 30 CST drive, the AFC operates at a speed of 422 feet per minute [fpm].”
The GH 1600 plow body is pulled by two P45 UEL drives with overload protection to prevent and minimize chain breakage, O’Neil explained. Using a 42-mm plow chain with 2-speed 600/300 kW (800/400 hp) motors, the plow speeds amount to 395 fpm and 197 fpm respectively.
The system uses a 90-ft long PF5-1542 stageloader with twin-strand 34-mm chain on a 1,400-mm raceway. It’s rated at 3,500 tph at 525 fpm, with two 300-hp motors. “The stageloader has to be rated higher than the plow system to prevent a bottleneck,” O’Neil said. “The system also uses an SB 0815 V-belt crusher powered with a 300-hp motor, which provides higher inertial impact to handle rock.”
The face consists of two types of shields: face shields, which support the roof where coal is being mined, and gate shields that protect the gate ends of the plow system. The gate shields have a collapsed height of 35 inches and an extended height of 77.5 inches. A 300-mm hydraulic cylinder provide a yield strength of 715 tons. “The transport length, which is critical to moving a shield around the mine, is 222 inches and the shield weighs 16.3 tons,” O’Neil said.
The gate shields have a yield strength of 945 tons, a retracted height of 45 inches and an extended height of 120 inches. “The collapsed and extended height ranges are slightly higher to accommodate and protect the equipment in the gate entry,” O’Neil said. The length and weight increase substantially to 322 inches and 26.1 tons.
“These roof supports have been designed and validated through rigorous testing to a level of 60,000 cycles at a 12% overload factor,” O’Neil said. The life expectancy will enhance the overall performance and the ultimate payback, O’Neil concluded. The crowd gathered as Bucyrus fired up the system and marveled as the plow traversed the length of the floor.