This paper presents the results of a study conducted to determine the dynamic power of a hydraulic leg. The hydraulic leg is the basic element that maintains the position of a powered roof support. ...It is located in the structure between the canopy and the floor base. The analysis assumes that its power must be greater than the energy of the impact of the rock mass. The energy of the rock mass is generated by tremors caused mainly by mining exploitation. The mining and geological structure of the rocks surrounding the longwall complex also have an influence on this energy generation. For this purpose, stationary tests of the powered roof support were carried out. The analysis refers to the space under the piston of the leg, which is filled with fluid at a given pressure. The bench test involved spreading the leg in the test station under a specified pressure. It was assumed that the acquisition of dynamic power would be at the point of pressure and increase in the space under the piston of the leg under forced loading. Based on the experimental studies carried out, an assessment was made with the assumptions of the methodology adopted. The results of the theoretical analysis showed consistency with the experimental results.
This paper presents the results of lab-simulated tests on longwall powered supports under dynamic loading conditions. The tests were carried out on a test site, where the tested prop was subjected to ...a dynamic load using a controlled mass falling under gravity onto the support. The loading on the support was therefore determined based on the weight used and the distance of freefall before impact. The operating characteristics of the valve were determined, specifying temporary changes in the pressure and the prop’s dynamic yield rate and total deformation. The research aimed to determine the operational parameters of the valve to be used in new and improved components for powered roof supports. One of the most essential elements of the powered roof support hydraulic system is the safety valve. The results confirm the validity of the concept and the possibility of applying the tested valve to the developed control system of the prop of the powered roof support. The forged safety valve has been designed to significantly improve the safety and efficiency of the powered roof support, especially in conditions of safety hazards.
The mining and geological conditions in which coal mining is carried out are highly variable, which results in dynamic rock manifestations. These include rock mass dynamic failure (seismicity), ...causing dynamic impacts and also quasi-static rock movements that do not result in seismicity but increases pressure in the powered roof support. The paper analyses the resulting damage to the stabilisation actuator of the cap piece. The analysis was carried out based on the research results conducted in real conditions (a mining longwall). This research study aims to obtain information about the pressure created in hydraulic actuators. Exceeding the design pressure limits caused damage to the bolt holes of the cap piece actuator. The pressure in the sub-piston space of the hydraulic prop was also analysed. The previous research conducted on mechanically powered roof supports focused mainly on bench tests. The results of the analysis carried out under real testing conditions currently comprise the starting point for the development of a new method to reduce adverse effects. Under the mining and geological conditions where the research was carried out, a high load on the roof’s side was under the load applied directly on the powered roof support. The load of the test’s results identified problems related to the safety valve in the sub-piston space of the actuators as it did not reach its opening time during the build up of the load.
A powered roof support is an element of a longwall complex. It is connected with a scraper conveyor by a sliding system. The conveyor carries a shearer mining the coal. The second function of the ...powered roof support is to protect the excavation against uncontrolled impact of the rock mass. This paper focuses on the analysis of the effectiveness of the powered roof support. The main objective is to determine the factors influencing failure-free operation in the exploitation process. Moreover, the author discusses performance requirements for the powered roof support.
A powered roof support is one of the most important machines of a longwall system. Its basic task is to ensure the safety and continuity of the mining process. The conditions of coal mining process ...are constantly changing and have significantly deteriorated in recent years, which in turn has also resulted in a significant increase in the requirements for mining support. As a result, it is necessary to develop an appropriate methodology that will facilitate the design and testing process of a power roof support as well as will help to select a roof support adjusted to given conditions. The article presents such a methodology. It is based on forecasted load impacting on a roof support, tests covering selected systems and elements of the section as well as legal conditions regarding the admission of the roof support to operation. This idea was developed in the form of a procedure that, by combining the three areas, should support the decision-making process in the case of different underground conditions. In terms of the expected load impacting on the support, the research team identified the most dangerous phenomena occurring in the rock mass that can generate these loads. Stand tests included impact load and permanent clamping of an excavation. The element that significantly impacts the safety of the support operation is a hydraulic leg, and therefore it was tested together with the safety system and the control system. Model tests were also carried out for the system with a safety valve. The developed concept takes into account legal conditions, which should include test results and different support operating conditions in a more flexible way. The main purpose of the work was to develop a comprehensive methodology for testing and assessing the possibility of using a powered roof support for given mining and geological conditions based on an analysis of safety and control systems. The presented approach is undoubtedly new and original, and can be widely used. It enables better adaptation of the support to given conditions. It also fits the research and activities designed to minimize the presence of miners or service workers in hazardous underground exploitation zones and to improve efficiency and boost sustainable development of the mining industry.
A powered roof support is a basic protection mean for longwall excavations in which highly efficient mining is carried out. The support operates properly when its individual sections are spragged ...correctly in a working and their operating parameters meet specific requirements. The geometry of the section, and in particular, the correct position of the floor base and the canopy, have a significant impact on the parameters and effectiveness of its work. Disturbances in this area, in many cases, are the cause of damage and improper operation of the support. Therefore, a new method of testing the position of the section in a longwall was developed based on an analysis of its geometry. The basis of this method are inclinometers (angle sensors) mounted on the main structural elements of the section. Recorded values of the angles of inclination of these elements and the developed analytical models are used to determine the positioning of the section in a longwall. The main purpose of the research was to develop a method that would allow, in the simplest possible way, the analysis of section geometry in real conditions. A simplified analytical model was used to determine the actual geometry of the section. It was used then as a basis of an analysis of possible states of the position of the section in the mining wall, including the surrounding rock mass. The results were applied during tests of the section carried out in a testing station and in real (underground) conditions. The developed measuring system helped to determine selected geometrical parameters of the section during these tests. The purpose of the research was to verify the developed model and demonstrate that the geometry of the section has a significant impact on its uneven loading. The obtained results, especially from underground tests, confirmed that during operation the support sections are twisted, which may cause overloading of their construction and disturbance of the operation process. The developed method of testing the geometry of the section is a new approach to analyzing the work of the powered roof support operating in variable mining and geological conditions. The developed method of testing the position of the section based on the angle of inclination of its individual elements is undoubtedly a new approach to this research area. The results obtained should be successfully used in practice to optimize the support section and when selecting support for specific working conditions.
Dear colleagues—readers and authors of Energies journal, we present the Special Issue “Mining Technologies Innovative Development II”, which continues the previous issue, developing the ideas of ...sustainable mining of fossil energy sources, concentrating around the innovative modernization of the mineral resource sector in the context of achieving sustainable development goals ...
Today science faces the task of ensuring the innovative development of the mineral extractive sector of the economy in resource-rich countries, in the context of unfolding two opposite trends ...
Various types of natural hazards are inextricably linked to the process of underground hard coal mining. Ventilation hazards—methane and spontaneous combustion of coal—are the most dangerous; they ...pose a major threat to the safety of the workers and decrease the effectiveness of the whole coal production process. One of the methods designed to limit the consequences of such hazards is based on the selection of a ventilation system that will be suitable for the given mining area. The article presents a case study of an active longwall area, where—due to increasing ventilation hazard (methane and spontaneous combusting of coal)—the whole system was rebuilt. The U-type ventilation system was used in the initial stage of the extraction process, however, it often generated methane in amounts that exceeded the allowable values. Consequently, such conditions forced the change of the ventilation system from a U–type to Y–type system. The new system was installed during the ongoing mining process, unlike the usual practice. The article presents the results of tests on mine gas concentrations and descriptive statistics for both types of ventilation system. The results clearly demonstrate that the U-type longwall ventilation system, in the case of high methane release hazard, prevents safe and effective operation. At the same time, the use of this system limits the carbon oxidation reactions in the goaf, leading to spontaneous heating and combustion, which is confirmed by the low concentrations of gases—by-products of these reactions. In turn, the use of the Y-type longwall ventilation system ensures safe and effective operation in areas with high methane release hazard, but at the same time deteriorates the safety associated with the spontaneous combusting of coal. The presented case—both from a scientific and practical perspective—is quite interesting and greatly broadens the knowledge in the scope of an efficient ventilation system for underground workings.
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