Air-quality measurements in a deep underground mine are a critical issue. The cost of ventilation, as well as the geometry of the considered mine, make this process very difficult, and local air quality may be a danger to miners. Thus, portable, personal devices are required to inform miners about gas hazards. There are available tools for that purpose; however, they do not allow the storage of data collected during a shift. Moreover, they do not allow the basic analysis of the acquired data cost-effectively. This paper aims to present a system using low-cost gas sensors and microcontrollers, and takes advantage of commonly used smartphones as a computing and visualization resource. Finally, we demonstrate monitoring system results from a test in an underground mine located in Poland.
Comparative strength analysis of two popular options of the radial centrifugal fan impeller design used in horizontal conveyor dryer for fine-grained raw materials is presented. Three types of materials for impeller manufacturing—ASTM A36 steel, Hardox 450 steel and aluminium alloy 6061-T6 are considered. The finite element method (FEM) has been used to investigate stresses and deformations of the impeller within the operational speed range. Analysis shows that the better design is the impeller made of Hardox 450 steel with a central disk. Although the maximum stress is slightly higher in the blades slot for central disk fitting for this design option, it has greatly reduced stresses in contact edges with two other disks (by 22–38%) and blades bending deformation (by 51%). For this design, the maximum operational rotation speed is 1135 min−1 according to the yield strength with a 15% safety factor, while for basic design, it is 1225 min−1. The rational choice of material depends on maximum value of the yield stress to density ratio as well as taking into account the operating conditions and required fan performance. Recommendations for manufacturing the centrifugal fan impeller related to chosen material are given.
Mine operation in presence of aerological hazards is a challenging issue for mine ventilation services. Increasing depth of exploitation and growing level of mechanization, due to the demand for intensification of extraction, makes it even more difficult regarding thermal hazard. As air temperature is a decisive factor shaping underground thermal working conditions it is extremely important to predict its value. This task determines the possibility of carrying out works in regions with the highest thermal hazard, where, due to the applicable regulations, it is necessary to use air conditioning to ensure appropriate working conditions for people. To determine the required cooling capacity for mining regions, it is crucial to identify the individual heat sources, as well as to define the amount of heat they generate. For this purpose, heat balances need to be set, taking into account the mentioned issues. The main goal of this paper is a presentation of methods available in the literature for determining the thermal balances of mining areas. The article also presents and characterizes the most important heat sources in underground mines. In addition, methods of determining heat fluxes from individual sources were indicated, as well as potential difficulties in the applicability of the above-mentioned methods for mining areas heat balances determination, in which, due to the current depth of exploitation, the thermal hazard is the most important natural hazard that determines the possibility of mining works.
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