The RHH 42 system has been completely redesigned for high productivity in thin seams down to 0.6m.

The cast plow body is rugged and uses the proven DBT 2003 bit system featuring a new bit contour for improved cutting performance. The plow chain is a newly developed type 42 x 137mm with a breaking force of 2370kN, allowing an installed power of up to 2 x 400kW for cutting alone.

Maintenance is simplified by good access to the plow chain – which is located in guides at the gob side – and to wear elements that all can be changed out underground quickly.

The plow body’s height is adjustable up to 300mm in its normal configuration. Extension blocks allow plowing up to a height of about 1.6m.

The cutting depth is electronically adjustable through DBT’s latest electrohydraulic control system PMC-R. This degree of control further minimises mining of adjacent rock.

The plow system is purely mechanical, where drives located at either end of the longwall pull the plow back and forth at speeds of up to 3.6m per second (720 feet per minute) at a cutting depth of up to 250mm (nearly 10 inches) depending on coal hardness. This allows plow systems to mine up to 3000 tonnes (3300 tons) of coal per hour, even in low seams.

Seam thickness, coal hardness and desired output are the major factors affecting the cutting force required of the plow. DBT uses a cuttability method developed by DMT – an independent German mining and geology consultant – to evaluate coal hardness and to calculate drive power and other parameters of plow operation at the coal face.

Data gathered from over 100 underground tests in different countries allows DBT to determine the cutting resistance of a specific coal seam. The control system can then optimise depth of cut, drive power, plow speed and AFC speed for the required output.

DBT makes two types of plow: the Reisshaken, or base-plate plow, suitable for extremely thin seams as low as 0.6m; and the Gleithobel, or GH plow, suitable for seams ranging from 0.9m to more than 2m.