Skip navigation

Rock duster mechanizes coal-mine safety procedure

Low-profile Diesel Duster
Fig. 5. Low-profile Diesel Duster delivers and distributes powdered limestone.
Simplified schematic
Fig. 6. Simplified schematic diagram of Diesel Duster hydraulic circuit.

Coal dust — an unavoidable byproduct of coal mining — adds a combustion or explosion risk in any underground mine. Federal and state safety regulations mandate that any coal dust be diluted with powdered limestone, also known as rock dust, to minimize the danger. Delivering and distributing large volumes of rock dust to underground mines presents an interesting logistics challenge. At many sites the task is currently approached with very basic tools. Battery-powered tractors pull tenders and shuttles filled with bags of rock dust into the mine. Once at the distribution site, work crews open the bags by hand and empty them into trailers which are then pulled around the area by another tractor. This procedure is laborintensive and inefficient.

RCI Equipment, Morganfield, Ky., automates the procedure with the self-propelled Diesel Duster, Figure 5, that hauls three tons of bulk rock dust. The machine may simply transport rock dust, or can broadcast dust while moving, or blow dust through a 400-ft long, 21/2-in. hose for remote spray application. A 57-hp, mining- certified Isuzu diesel engine provides propulsion and application power.

Because all on-board drives are hydraulic, the engine can be tucked conveniently under the starboard side of the cargo hopper. Hydrostatic, 60-gpm pump A, Figure 6, is connected directly to the engine and protected by crossover relief valve B. Pressurized oil from the pump is fed to proportioning diversion valve C. With this valve fully in transport position, all power goes to the drive wheels; with the valve all the way in application position, the machine puts all power to the blower and auger in the bottom of the V-shaped cargo hull. The operator also may position the valve somewhere in between to allow the vehicle to travel and apply rock dust simultaneously. Top speed of the Diesel Duster is 10 mph.

Key components in the wheel-drive loop are gerotor flow divider D, gerotor motor E, and hub drum motors F with integral brakes. The multi-section flow divider assures uniform delivery of power to all driven wheels. The front wheels are mounted on an independent suspension/differential with half shafts and steering linkage. Gerotor motor E drives this axle, which also carries the primary braking system. The two rear wheels are mounted on hub drum gerotor motors F with brakes. These rear drum brakes — used for parking — are actuated mechanically by a cable linked to a latching lever at the operator’s position.

For dust application, gear motor G drives an auger at the base of the hopper. The auger moves rock dust into a barrel at the end of the hopper where blowing air is introduced. Axial-piston hydrostatic motor H powers the air blower. Adjustable flow-control valve I in the line to the auger drive allows the operator to vary the rate of rock dust feed, while gerotor flow divider J in the application circuit splits power between the auger and the blower.

The Diesel Duster gives mine operators new flexibility in transporting and applying rock dust. The machine has the power and chassis to carry a sizable stock of dust to the work site. The hydraulic drive arrangements offer the ability to apply material as the machine is driven. Even the maintenance shop gets a break because components are easy to reach and service. RCI brings a rugged tool to an important underground mine safety job.

Ben Morgan, president of RCI Equipment, provided details on his Diesel Duster design. White Hydraulics, Inc., Hopkinsville, Ky., builds the gerotor propulsion motors and flow dividers installed on this equipment.