Effective overload protection is essential for fast, high-power plowing. The HBT planetary UEL overload protection system has an integrated multi-disc clutch with the pressure set to allow the clutch to slip well below the torque required to reach the breaking strength of the chain. If “clutch slip” is sensed, the gearbox torque is immediately decreased, combined with a simultaneous shutdown of the plow motors to prevent damage to the chain.

Benefits

• Eliminates shock loads from all drive components
• Minimizes chain failures and maximizes component life
• Allows for a quick system restart

HBT has developed an innovative shock absorber to provide added protection for the plow and chain. The elastic coupling inserted into the plow pulling sledge contains elastomers with properties that reduce the peak forces applied to the chain. This results in smoother plow operation, minimizing loads on the plow chain, the plow connectors, and the drives, thereby extending their effective service life. The shock absorber is only available for the gliding (GH plow).

Benefits

• Reduces wear and tear on plow, drives and chain
• Smooth plow operation extends overall service life

The key requirements for high-performance plowing are remote control, adjustable cutting depth and the ability to maintain a straight face line. These requirements are all achieved by the HBT incremental cutting system and the fully automated plow longwall system.

Incremental plowing keeps the depth of cut constant regardless of coal hardness or presence of rock bands. The plow makes a double cut — or a cut with double web — at each drive end, always keeping the face straight.

Variable Frequency Drives (VFD) allow speed to be varied between 0 and 120% of nominal while maintaining constant torque throughout a wide range of speeds. Power consumption on the motors is constantly monitored to allow load-sharing between the individual drives.

Effective plow horizon control is necessary to cope with undulations in the coal seam. Providing the plow with the ability to follow the seam minimizes cutting of adjacent rock strata and the associated preparation costs, reduces cutting tool (bit) consumption and reduces power consumption while maximizing seam recovery. HBT has developed an outrigger steering system for vertical horizon control that employs the use of hydraulic cylinders located between the gob side of the AFC and the relay bar of the shield. Extension of the cylinder promotes a downward (digging) cutting direction of the plow. Retracting the cylinder promotes an upward (climbing) direction of the plow. The steering cylinders can be controlled either manually or automatically via the HBT PMC-R 2.0 electro-hydraulic control system. A block anchorage system consisting of cylinders installed between face conveyor and shields (at the face ends) controls conveyor creep and helps maintain the proper tension in the plow chain.