This study has considered an overview of the equipment availability for one longwall mine and one shortwall mine, each modeled as a system of mining components linked in series, so that a delay of any single component causes an equal delay in the entire system. Through computerized statistical reduction of delay and shift data from selected shift reports for the two mines, each for a period of 11 months, and using this series model, bottleneck components and major trends in delays have been identified. These bottleneck components are the shearer, face conveyor, and external conveyors in longwall mines; and the miner, supports, shuttle cars, and external haulage in shortwall mines. Except for conditions shared by components--such as the electrical power system and cables, geologic conditions, personnel, etc.--components were generally found to experience delays independently. Monthly cycles of delays were found for several components, suggesting potential maintenance frequencies. The various trends in delays are at best drawn from insufficient data, and at worst unexplainable using the available data. Hence, specific recommendations for the design, use, or maintenance of any specific piece of equipment cannot be made with certainty. Limitations posed by the available data have necessarily prompted numerous specific recommendations tomore » improve future data collection. More profitable recommendations can then be made about the equipment and its operation. The data recommendations seek to improve the depth, detail, and duration of delay information, as well as the breadth of factors relevant to coal production. In addition, specialized studies of the components found to be critical in this study are suggested.« less