Bezpieczeństwo Pracy i Ochrona Środowiska w Górnictwie Number 08/2016

This paper presents the findings and comments from a portion of tests done on explosion-proof equipment which focus on investigating the effects of higher current harmonics on power feeders of that Ex-proof equipment. Attention is drawn to the negative effect of higher current harmonics that results in increased surface temperatures of mining equipment power feeder cables. This phenomenon accelerates the wear of power cable insulation systems, and it has also initiated further investigation into the effects of higher current harmonics on the ageing of electrical cable and feeder insulating materials in explosion hazard areas. The paper also presents the related magnetic field distribution, current density and power loss density with the measurement results for current harmonics content and conductor power losses. The magnetic field distribution, resistance and conductor power loss were calculated, and specific harmonic numbers with highest amplitude harmonics were identified. The paper also refers to the accelerated development of modern technological solutions for power supply equipment, e.g. inverters, thyristor starters and advanced lighting equipment. The increasing availability of these solutions, advantages linked to the comfort of use and cost effectiveness considerations make these products increasingly popular in underground mines.

The most popular methane hazard countermeasure used in the underground mines of JSW S.A. is in-process methane extraction the performance of which is simultaneous with the mining of coal beds within the rock formation. The highest efficiency of in-process methane extraction is by removal of the gas via a parallel air heading or an overlying drainage heading. The high efficiency of these countermeasures comes at a great financial cost. Given the positive experiences with alternative countermeasures reported from other countries (Australia, China, and the USA), JSW S.A. has decided to elect a more cost-efficient methane extraction solution: downhole directional drilling. To test it in the operating conditions of Polish mines, an Australian VLI 1000 Series directional drilling rig was purchased, a system designed for directional drilling in underground headings. The modular design of this rig system has been specifically designed to the JSW S.A. requirements; the small footprint of the customised drilling rig facilitates transport in the headings at KWK Pniówek. The rig features downhole motors with a number of drill bits for working the rock formations with the compressive strength Rc values up to 120 MPa. The DDMS (Directional Drilling Management System) of the directional drilling rig enables real-time operating data output for comparative verification of compliance with the borehole design tolerances. The DDMS helps the drilling rig operator control the directional borehole trajectory and correct any deviations on the go. The VLI 1000 Series modular drilling rig can make long directional boreholes which, when combined with branches, create a complex system for geosurveying purposes with pre-process and in-process methane extraction (the latter applies when the mining process disrupts the rock formation balance). During the hands-on training in the drilling rig operation, the KWK Pniówek personnel has fully mastered the long directional drilling, system performance capabilities, borehole design principles, and the DDMS operation. Although the actual performance has fallen short of the scheduled progress in the operation of the directional drilling rig for methane extraction, the experience that will be acquired in time will help develop a methane extraction system with better performance at lower costs.

In 2013, a tunnel boring machine (TBM) was used in the Grosvernor Coal Mine (Australia) to make two dip tunnels in a rock formation with methane and varying physical and mechanical characteristics. The TBM applied on site was a hybrid design, combing single shield tunnelling with rock formation pressure equalization. The TBM has been designed not only to secure efficient tunnelling with the installation of prefabricated concrete casing segments, but also to assure safe operation in methane explosion hazard areas. The first conveyor dip tunnel began in soft subsurface rocks and continued through hard rock down to the target coal bed. The tunnelling was accomplished in 20 weeks at an average production of ca. 40 m/week and an average drilling speed of 1.32 m/h. Next, the TBM was withdrawn from the finished conveyor dip tunnel and moved to begin drilling a dip gate road. This time, the processing performance was better. The 988.40 m long heading was breached in just 13.5 weeks. The average production of 70.6 m/week was achieved at an average drilling speed of 1.83 m/h.
The undisputed TBM advantages in this case were the work progress rate and the improvement of health and safety conditions, which prevented the miners from exposure to operation under unsupported ceilings, dust, and smoke at all tunnelling stages. The concrete casing deployed with the TBM has made both dip tunnels the highest quality development headings of all coal mines in the world, both in terms of aesthetics and service life. The segmented casing is stable and very durable, especially at points with very weak and brittle rocks. Another advantage of the casing is its very low maintenance demand. The Grosvernor project has proven that TBMs are well suited for breaking main development headings and gate roads and provide numerous advantages that are superior to the traditional boring technologies.

This paper presents the educational process in the field of occupational health and safety, as implemented in the postgraduate curriculum at AGH University of Science and Technology in Krakow. It also discusses training methods developed for new and graduating students alike. This paper furthermore presents the teaching content of safety-related modules, which are offered by a variety of courses at AGH, and characterizes a new specialization in Health and Safety Management, launched as part of the postgraduate course in Engineering Management. Lastly, this paper discusses the content and teaching methods of the postgraduate course in Industrial Safety which has been taught at the Faculty of Mining and Geoengineering which completion grants students with professional qualifications in the field of industrial safety. The abovementioned issues and the experience of the Faculty of Mining and Geoengineering in teaching occupational health and safety provide valuable insights that could prove helpful in launching a new course in safety engineering.