Objective is to determine the relation between pressure difference of a filter and parameters of a filtering layer to lengthen the protection period. The study involved elements of system analysis and mathematical modeling. Basic statements of the theory of nonstationary filtration and aerohydrodynamics were applied to develop a dust-loaded filter model. Dependence of pressure difference in a filter upon certain changes in packaging density of dust-loaded fibers has been determined; the dependence makes it possible to define minimum fiber packaging density to provide maximum dust capacity. To provide maximum dust capacity and high protective efficiency, the number of filtering layers in multilayered filters depends upon dust concentration within the air of the working zone, specified protection level of a respirator, air loss, and maximum dust volume which may be accumulated in the finishing filtering layer in terms of fiber packaging density being determined according to the minimum pressure difference in a filter at final time of respirator operation. A model of changes in pressure difference in filtering respirators in the process of aerosol particles depositing on filters has been improved; contrary to other available models, that one takes into consideration changes in fiber packaging density while dusting, filtration coefficient, and the amount of aerosol particles.
In this paper, a solution to the problem of the change in the pressure drop in a respirator filter during cyclic air motion is suggested since the current theory of filtering is based on steady-flow processes. The theoretical dependence of the pressure drop in the respirator filter on air flow rate is determined, which is represented by the harmonic law, which characterizes the human respiration process during physical work. For the calculation, a filter model was used, which is represented by a system of parallel isolated cylinders with a length equal to the total length of the filter fibres surrounded by porous shells formed by a viscous air flow field, with a size determined by the equal velocities of the radial component of air flow and undisturbed flows. The flow-around process in the proposed model of air flow through the respirator filter is described by the Brinkman equation, which served to establish the total air flow resistance in the proposed system under conditions of velocity proportionality. It consists of two parts: the first characterizes the frictional resistance of the air flow against the surface of the cylinder, which imitates the filter fibre; the second—the inertial part—characterizes the frequency of pulsations of respiratory movements during physical performance. The divergence of the analytical results and experimental studies is no more than 20%, which allows the use of the established dependence to estimate the change in pressure drop in a respirator filter made of filter material “Elephlen” when the user carries out different physical activities. This allows the period of effective protective action of respirators with different cycles of respiration during physical activities to be specified, which is a very serious problem that is not currently regulated in health and safety regulations, and it also allows the prediction of the protective action of filters and respiratory protection in general.
Protective efficiency of filtering dust respirators depends on the properties of filter materials from which filters are made and the structure of a half mask frame, which influences how tightly the respirator fits the face. The conducted studies on the “Lepestok 40” dust respirator revealed a large air leakage through the gaps occurring along the obturation strip. Therefore, the purpose of the study is to develop a dust respirator to provide high level of protection and usability by improving the half mask frame design. A scheme for designing a dust respirator: analysis of operating conditions for the dust respirator; facial anthropometric measurements of potential users; designing a 3D model of half mask frame; laboratory testing of the protective properties of the product. A distinctive feature of this approach is considering the facial anthropometric dimensions of employees of a particular enterprise, standard sizes formation of 3D facial models, which is the basis for designing a half mask frame for dust respirator. A new half mask frame design for dust respirator with a variable geometry of fitting to the face surface has been developed, due to special attachment points that allow changing its size according to the anthropometric dimensions of user’s face.
In the article, aerodynamic resistance of the stope face is studied in case of selective mining the coal seam. To carry out the research, the methodology of the computational experiment for evaluating the longwall face aerodynamic resistance influence on the efficiency of airing the stope face has been substantiated. The model of the stope face section, equipped with mining and backfilling mechanized complex based on the serial 1KD90 roof support has been developed in the 3D modeling software SolidWorks. The diagrams of the air stream velocity distribution, when it flows in the cross section of the longwall face working space with different positions of stoping equipment and the values of rock-cutting thickness of the seam bottom (rock ledge) have been obtained in the environment of computational module FlowSimulation. The pressure drop along the length of the aerodynamic model of the stope face section has been assessed. The dependences of the average velocity of the air stream flow on the value of rock-cutting thickness have been obtained. The obtained results can be used to improve and modernize the elements of mining and backfilling mechanized complex of machinery and equipment, as well as the technology for selective mining of thin and very thin coal seams in the Western Donbas.
Purpose. Determination of the anthropometric distribution of the average Ukrainian worker to increase the reliability of the calculation of the protection factor of respirators due to the improvement of the procedure for laboratory assessment of the penetration factor. Methods. A comparison has been made of the method of selecting respirators based on the methods of mathematical statistics and statistical analysis to establish relationship between the anthropometric dimensions of the users' faces and the Sheffield mannequin of the head, in accordance with the ISO 16900-1:2020 standard "Respiratory protective devices - Methods of test and test equipment - Part 1: Determination of inward leakage" and the Technical Regulations. Results. The procedure for determining the penetration factor of respirators from the selection of the appropriate type of the Sheffield mannequin and the evaluation of the suction coefficient has been improved with regard to the selection of the number of testers who would ensure the compliance of the design parameters of the respirators with the anthropometric parameters of the face of possible users. The determined anthropometric distribution of the average Ukrainian worker for adjusting the parameters (cell size and number of testers in the cells) of the known parametric table for the selection of testers, in relation to conducting a laboratory study to determine the suction coefficient of half-mask respirators by the obturation band or valve system (if available). Scientific novelty. Improving the reliability of studies on the determination of the protection factor of personal respiratory protective devices (RPD) (filtering respirators) is an urgent task. However, in the domestic standards for determining the quality of RPD, there are no data on the anthropometric dimensions of the faces of Ukrainian workers, the Sheffield mannequin of the head, and the requirements for the faces of volunteer testers. The consequence of this is the discrepancy between the technical characteristics of the respirators declared by the developer and the actual ones obtained during their operation in production conditions. Practical significance. On the basis of the obtained data regarding 400 typical users of RPD, workers of Avdiivka Coke and Chemical Plant (ACCP) aged 20 to 55 years, their distribution by length and width of faces has been revealed. According to the results of the research, in which twenty-five volunteers, selected according to ten parameters, took part, the anthropometric dimensions of the face of the average worker of the ACCP and the corresponding Sheffield mannequin of the head have been determined.
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