and coal was being stored on the spade. Shuttle car away time refers to the total time in minutes that was utilised by a loaded shuttle car to travel from the continuous miner to the feeder breaker, tip the loaded coal and travel back to the continuous miner to be loaded again. Cutter operation time refers to the total time in minutes that the cutterhead was running. Relocation time refers to the total time in minutes that was utilised in order to relocate a continuous miner to a different heading after the maximum allowable unsupported length of the previously cut heading was reached. Utilisation of the modified cutting cycle has improved the general consistency of the production machines in achieving the target values of the key performance indicators. This is confirmed by means of continuous production reporting that monitors and documents the key performance indicators on a shift basis. The following table shows an example of a typical summary of key performance indicators and the actual numbers achieved. It is illustrative of the success with which the bi-directional cutting cycle is being run at a South African coal mine. From these figures it is clear that the number of shuttle car loads is significant and above target. The shuttle car change time is also significantly impacted. Cutting cycle comparison In order to justify the selection and utilisation of the bi-directional cutting cycle a comparison is to be made between the one-directional and bi-directional cutting cycle. Different Key performance indicators are utilised by different companies to quantify the performance of machines operating in production sections. The most appropriate figure to be utilised in the justification of the bi-directional cutting cycle is the tons per hour figure. The increase in the production rate due to the improved cutting cycle serves as the differentiating figure. Through analysis of several production reports from South African coal mines, the following comparative figures were obtained for the two cutting cycles. From the above-mentioned averages obtained from production reports it is clear that the bi-directional cutting cycle maintains a larger average production rate. This increase in the production rate serves as the justification of the utilisation of the improved cutting cycle and illustrates the value of the consideration of manageable and adjustable elements of the production process in conventional underground coal mine sections. References Coal mining