High Productivity A Question of Shearer Loader Cutting SequencesK. Nienhaus, A. K. Bayer & H. Haut, Aachen University of Technology, GERAbstractRecently, the focus in underground longwall coal mining has been on increasing the installed motor power of shearer loaders and armoured face conveyors (AFC), more sophisticated support control systems and longer face length, in order to reduce costs and achieve higher productivity. These efforts have resulted in higher output and previously unseen face advance rates. The trend towards “bigger and better” equipment and layout schemes, however, is rapidly nearing the limitations of technical and economical feasibility. To realise further productivity increases, organisational changes of longwall mining procedures looks like the only reasonable answer. The benefits of opti-mised shearer loader cutting sequences, leading to better performance, are discussed in this paper.1 IntroductionsTraditionally, in underground longwall mining operations, shearer loaders produce coal using either one of the following cutting sequences: uni-directional or bi-directional cycles. Besides these pre-dominant methods, alternative mining cycles have also been developed and successfully applied in underground hard coal mines all over the world. The half-web cutting cycle as e.g. utilized in RAG Coal Internationals Twentymile Mine in Colorado, USA, and the “Opti-Cycle” of Matlas South African shortwall operation must be mentioned in this context. Other mines have also tested similar but modified cutting cycles resulting in improved output, e.g. improvements in terms of productiv-ity increases of up to 40 % are thought possible.Whereas the mentioned mines are applying the alternative cutting methods according to their spe-cific conditions, e.g. seam height or equipment used, this paper looks systematically at the differ-ent methods from a generalised point of view. A detailed description of the mining cycle for each cutting technique, including the illustration of productive and non-productive cycle times, will be followed by a brief presentation of the performed production capacity calculation and a summary of the technical restrictions of each system. Standardised equipment classes for different seam heights are defined, after the most suitable and most productive mining equipment for each class are se-lected. Besides the technical parameters of the shearer loader and the AFC, the length of the long-wall face and the specific cutting energy of the coal are the main variables for each height class in the model. As a result of the capacity calculations, the different shearer cutting methods can be graphically compared in a standardised way showing the productivity of each method. Due to the general char-acter of the model, potential optimisations (resulting from changes in the cutting cycle and the benefits in terms of higher productivity of the mining operation) can be derived. 2 State-of-the-art of shearer loader cutting sequencesThe question “Why are different cutting sequences applied in longwall mining?” has to be an-swered, before discussing the significant characteristics in terms of operational procedures. The major constraints and reasons for or against a special cutting method are the seam height and hard-ness of the coal, the geotechnical parameters of the coal seam and the geological setting of the mine influencing the caving properties as well as the subsidence and especially the length of the longwall face. For each mining environment the application of either sequence results in different production rates and consequently advance rates of the face. The coal flow onto the AFC is another point that varies like the loads on the shearer loader, especially the ranging arms and the stresses and the wear on the picks. A thorough analysis is necessary to choose the best-suited mining cycle; therefore, general solutions do not guarantee optimal efficiency and productivity. A categorization of shearer loader cutting sequences is realised by four major parameters . Firstly, one can separate between mining methods, which mine coal in two directions meaning from the head to the tailgate and on the return run as well or in one direction only. Secondly, the way the mining sequence deals with the situation at the face ends, to advance face line after extract-ing the equivalent of a cutting web, is a characteristic parameter for each separate method. The nec-essary travel distance while sumping varies between the sequences, as does the time needed to per-form this task, too. Another aspect defining the sequences is the proportion of the web cutting coal per run. Whereas traditionally the full web was used, the introduction of modern AFC and roof sup-port automation control systems allows for efficient operations using half web methods. The forth parameter identifying state of the art shearer loader cutting sequences is the opening created per run. Other than th