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LeTourneau First Mining Dozer

Diesel Progress North American Edition

March 1,2005

Longview, Texas-based LeTourneau Inc. has introduced the first mining dozer to its product line. The new D-950 dozer is one of two models introduced under the new Pit Bull series, which includes the 54,000 lb. payload L-950 wheel loader.

When developing the Pit Bull series, LeTourneau took some cues from the larger loaders in its popular 50 series range, using similar componentry and assembly to design the machines. Like the other 50 series machines, the D-950 and L-950 have a modular component configuration which, LeTourneau said, allows for faster maintenance and easier parts replacement. With the addition of the L-950, the 50 series covers a payload range of 54,000 to the 160,000 lb.

Both machines in the Pit Bull series are offered with 1050 hp Cummins or MTU Detroit Diesel engines. The Cummins power option is a 30.5 L, 12-cylinder, turbocharged/aftercooled QST 30 engine, while the MTU Detroit Diesel engine is a 31.86 L, 16-cylinder turbocharged 16V 200 diesel. The engines are paired with an L&M or AKG split-flow, side-by-side thermostatically controlled radiators and LeTourneau's self-cleaning Klenz air filtration system. The Klenz system is designed to provide a steady stream of air to the engine and hydraulic systems, and performs regular self-purging to remove trapped dirt, which is designed to increase the life of the filter as well as its efficiency.

Ground power for the machines is provided through a LeTourneau 6-R ac generator, which drives four LeTourneau B40 switch-reluctance (SR) wheel motors. LeTourneau said the ac drive system provides a simpler system than the dc drive systems more typically used in diesel-electric equipment, the company said, as no power conversion is required.

The company also said the SR drive provides a longer system life and generally requires less maintenance. LeTourneau produces the SR drive system under its Drive Systems Group which also manufactures the ac generator and power conversion system. The drive system is matched with Bosch Rexroth planetary gears which are mounted within the rim of the tires.

The 235,000 lb. D-950 dozer and 220,000 lb. L-950 loader both use a dynamic electrical braking to slow their 15 mph maximum travel speed. By using regenerative braking, LeTourneau said, a significant element of the machine's maintenance is reduced by eliminating much of the wear on the machines' secondary brake pads and discs.

Bosch Rexroth hydraulics drive the dozer's and loader's steering, front articulation and boom and bucket functions. The hydraulic assembly consists of four variable output axial piston pumps which are shaft driven through a self-lubricating gearbox. The pumps supply the L-950 loader's 160,000 lb. breakout force and the D-950 dozer's 163,000 lb. rim pull. Bucket capacity on the loader is 10 cu.yd., while standard blade capacity on the dozer is 35 cu.yd. The dozer is also available with a 60 cu.yd. coal blade.

To monitor the system operation of the Pit Bull machines, LeTourneau installed its module-based computer system, designated the LeTourneau Integrated Network Control System (LINCS). The PC-based LINCS digitally regulates and monitors all of the hydraulic, engine and drive functions and performance. A master LINCS control unit, placed inside the operator cab, communicates with linked modules located throughout the machine, displaying real-time system diagnostics, bucket position, net weight, cycle time, cumulative truck load and total tonnage on a dash-mounted display. Remote monitoring and downloadable data can be retrieved from the system using an RF modern. The series also features digital controls, twin joysticks, eight-way adjustable air-ride seat, thermo pane glass and filtered and pressurized cab ventilation.

LeTourneau processes the majority of the steal that goes into its mining equipment at its Longview, Texas, steel mill, operated by its Steal Group. The company began production of the Pit Bull series in 2004 for application in coal, iron, ore, copper and precious metal mining operations worldwide.