Abstract
The longwall system of mining coal, providing advantages in the areas of productivity as well as health and safety, is described, and technological developments leading to a full automation of the system are discussed. In the longwall system large blocks of coal (up to 600 feet wide and up to 5000 feet long) are developed, with each block mined out by taking successive slices across the short dimension of the block and loading the broken coal onto a conveyor. A self-advancing system supports the roof over the length of the face throughout cutting and loading, with the supports advanced with the face, and the roof allowed to collapse behind them. A double-ranging drum longwall shearer provides the system with an efficient yaw, roll, and variable-thickness vertical control. Currently two machine operators function as error detectors and controllers. It is shown that electronic sensors can lead to a fully automated vertical control system, and automatic roll control is achievable with available instruments and machine tilt actuators.
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