GH800 - Plow System

Horizon Control

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. Caterpillar has developed an outrigger steering system for vertical horizon control that employs the use of hydraulic cylinders located between the gobside 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 Cat PMC™-R 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.

Load-sharing

Variable Frequency Drive (VFD) motors 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.

Overload Protection

Effective overload protection is essential for fast, high-power plowing. The Cat 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.

Shock Absorber

Caterpillar 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).

Incremental Plowing

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 Cat incremental cutting system and the fully-automated plow longwall system. With conventional plows, variations in coal hardness lead to variations in cutting depth that often result in overloading of the conveyor and downstream equipment or jamming of the plow. Incremental plowing prevents these problems by keeping 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, keeping the face straight at all times. Under favorable roof conditions - where the shield tip-to-face distance is not an issue - the shields are positioned in a saw tooth form: Only every 4th or 5th shield performs the “lower - advance - set” sequence during each plow pass. This minimizes the hydraulic pump capacity required for the shields and assures that plowing does not need to be halted for the purpose of advancing shields. If the roof is friable, shields can be programmed to advance more frequently, minimizing the average shield tip-to-face distance and maximizing the effective support. Also, in order to guarantee effective support of the roof, the PMC™-R electrohydraulic control system monitors pressure in the shield legs and prevents two adjacent shields from being lowered simultaneously.

For Thin to Medium Seams

The gliding plow system GH800 is the standard plow of choice today and can be used in seams from approximately 0.9 m (35 in) up to 2.0 m (79 in), regardless of the inclination of the seam or the hardness of the coal. The gliding plow guide is welded to the face side of the AFC conveyor.

Modular Design

All parts of the plow body, especially the wear parts, can be replaced underground - a major benefit. Due to its modular design, the height of the plow body can be adjusted by simply inserting or removing bit blocks with a height of 265 mm (10 in) each.

State-of-the-Art Conveyor Technology for Underground Mining

The innovative PF plow line pans from Caterpillar define the new state of the art for underground face conveyor technology. They are based on the tried-and-tested PF3 and PF4 generations that meet all requirements regarding quality, wear resistance and conveying capacity.

Separation of Wear Parts and Structural Parts

The smart and totally new concept of segregating the different functional areas separates the wear elements from the structural elements. Extremely hard and wear-resistant materials are used for parts subject to wear, while the structural parts are made of tough, high-strength steels. The pan design allows problem-free replacement of worn-out top troughs, which delivers a lower cost of ownership during its lifetime.

Optimized Contact Surfaces

The use of the proven PF profile in the top race means maximum contact surface between the flightbar and the profile. This minimizes the surface pressure of the flightbars in snakes and undulating seams. Special shaping of the bottom race - which almost doubles the contact surface - reduces the wear of the flightbar shoulder while substantially reducing friction. Also, the curve-shaped transition at the pan ends greatly reduces the noise level during operation of the chain conveyor.

Electronic Roof Support Control System

The modern, reliable and easy-to-operate electrohydraulic PMC™-R shield control systems are designed, manufactured and programmed by Caterpillar. Their primary function is automation of the cutting process using incremental plowing.

Caterpillar® Global Customer Service

At Caterpillar, our relationship does not end with the sale of new equipment - it is just the beginning of a long-term partnership. We offer full life-cycle customer service with every purchase.