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The paper deals with the calculation of the operational reliability for the cutting-teeth mounted on bucket wheel excavators used in lignite extraction in the Oltenia Basin. Based on the data recorded for three types of cutting-teeth used in production, a reliability study has been carried out which determines the main reliability indicators of the quality level of these cutting-teeth. The study compares the constructive and functional characteristics of the three types of cutting-teeth, which is the basic criterion for purchasing a certain type of cutting-tooth, as well as for the supply of spare parts.

Operation of vertical transport installations is based on adjustable electrical drive systems which must ensure the technical conditions regarding the variation in time of the speed, the current of the main motors and the accelerations at start and brake phases. Electric drives are part of the fast process of automation equipment. In the case of a vertical transport installation, speed is the characteristic which has to be controlled in command phase, while the dependent factor is the tachograph. The adjustment determines the dependence of the quantity in the process – based on a default law - with respect to the independent quantities and also to the process dependents, thus reducing the influence of the perturbations to the process. There are different ways to define the stability of an automatic system. The balance survey / analysis also approaches the determination of the functions of variation in time of the main actuation motor current and speed (main motor rpm), at the moments of starting the vertical transport installation, and the study of the variation in time of the speed in the case of a load shock. To perform calculations needed for stability assessment and draw all the diagrams a Turbo C 2.0 program was written by the authors.

The bucket wheel excavator (BWE) is a complex continuous digging machine, used to excavate material using a layout of buckets installed on a rotor (bucket wheel), and at the same time, using the conveyor system installed on its boom, transferring this material to the main conveyor. The bucket wheel is the operating equipment, and it rotates in the vertical plane and performs (with the boom) a pivoting movement in the horizontal plane and an ascendant – descendent movement in the vertical plane. The paper presents a new grafo-numeric method of determination of the operation power of the BWE rotor, using computer simulation in SolidWorks. The aim of using virtual models for the analysis of the operation of some components of the BWE is to reduce the specific energy consumption during cutting while maintaining the installed operation power of the rotor, to increase the excavation capacity and to improve the cutting – loading system.

An important feature of the drums of mine shearers, is the material loading capacity onto the armored face conveyor. This characteristic is influenced by both the shape of the vane and the pitch of the helical vane. Thus, the pitch of the helical vane can be either constant or variable. This variable pitch can also have two variants. The first one is with an axial pitch when there is a progressive increase in the pitch of the helical vane towards the conveyor direction, thus resulting in a productivity increase of 15-20% compared to drums with a constant pitch. This constructive variant does not ensure the placement of the cutting picks to achieve a balanced working regime. The second constructive variant is with a radial pitch when the helical vane profile has a variable height along the generating curve. This constructive variant is considered more advantageous, ensuring a more rational placement of the cutting pitch by maintaining a constant axial pitch. In this paper a modeling is proposed for the drum of the CA-1 longwall shearer with variable axial-radial pitch. [ABSTRACT FROM AUTHOR]

The shield of the SMA-2 utilizes a quadrilateral mechanism with a corner cylinder generating a lemniscate. The synthesis of the quadrilateral mechanism, its geometric and kinematic analysis in correlation with the geometry and kinematics of the entire support, raises challenging analytical issues. For this reason, in the present work, we have theoretically and practically analyzed the geometry and kinematics of the mechanism, demonstrating the utility of using computer software for modeling and simulation in addressing these problems. [ABSTRACT FROM AUTHOR]

The maximum internal pressure developed during the ignition of the explosive mixture with air within the encapsulation is directly dependent on the volume released through clearances or other discharge devices, if present. Consequently, the increase in explosion pressure must be correlated with the study of explosion-proof joints to prevent the transmission of the explosion through clearances to the ambient atmosphere. Through a comparison of defects observed during dynamic explosion tests and checks with static overpressure, a safety factor simulating the explosion demands has been identified. By checking the static overpressure at a certain pressure increase factor, the encapsulations are no less stressed than during an explosion. It has been determined that an overpressure increase factor of 1.5 times above the maximum reference explosion pressure value, during hydrostatic testing, ensures the mechanical stress of the encapsulation equivalent to the stresses resulting from overpressure through explosion. This paper presents the mechanical stress simulation of the explosion-proof encapsulation with a cylindrical frame using the SOLIDWORKS application. [ABSTRACT FROM AUTHOR]

Mine winding systems are a complex set of machines, devices, and mechanisms, which work together both to transport useful mineral substances or tailings from the mine to the surface or to other horizons, as well as to transport personnel, materials, and equipment, from surface to underground. The mine winding systems consists of the actual mine hoisting machine, the head-frame, cables (ropes), conveyances, auxiliary equipment, control and safety devices. The braking system can operate as service brake or safety brake. The service brake acts on the rope wheel to achieve the required tachogram, while the safety braking occurs independently of the operator's will, in the following situations: the lack of power supply, the decrease in the pressure of the hydraulic fluid, over winding of the conveyances, exceeding the maximum permitted extraction speed. A functional condition imposed on the brakes of a mine windings system is to ensure the immobilization of the conveyances after a safety braking. This paper proposes a study of the stresses and deformations to which the drive wheel drum of a single-rope friction mine hoist is subjected to, when it must keep the conveyances immobilized following a safety braking. To solve the mentioned problem, a virtual model of the drum of such an installation was created in SOLIDWORKS. [ABSTRACT FROM AUTHOR]

The processes and technologies for supporting the roof of underground mining works have advanced during the years, thus fundamental changes resulted in both the roof control and the exploitation from economic and technical points of view. The support of the underground excavation roof is carried out by two methods, namely using individual supports, usually metal beams and props, or hydraulic powered supports/shields, the latter representing the most up-to-date technology. The paper presents a virtual model of a powered roof support section made in SOLIDWORKS. For its components a mechanical analysis was performed through the static simulation of the pressure of the roof on the support beam. [ABSTRACT FROM AUTHOR]

Over the past twenty years, the increasing significance of virtual spaces created by the internet, GPS and multimedia communication networks has played a major role in the growing interest attributed to the study of space. The promises and the menaces of globalization, the political and economic events which have reshaped the world in the last decades are just a few examples of the re-spacing of the globe. Accordingly, in the humanities and social sciences in general, the questions of space and place have marked a shift to inquiries about location, political space and mobility. The approaches and concepts proposed by the prestigious theorists Henry Lefebvre, Bertrand Westphal and Yi-Fu Tuan serve as a methodological framework for this paper. This study is intended as a reflection on the interconnection between the space of the Jiu Valley and its representation, far from exhausting all the possibilities of research and debate. The reading of space is accomplished through the direct and sensorial perception of space, covering various manners in which a person constructs reality and allowing for an understanding of the Jiu Valley in critically imaginative ways. Interviews conducted in situ provide an authentic interpretation of space, describing how individuals interact with their environment. By offering an alternative perception of reality, we hope to accomplish a value judgement of the Jiu Valley’s unique setting and its animated community. [ABSTRACT FROM AUTHOR]

One of the frequent problems that need to be addressed when mining coal deposits is the presence in the working face of cohesive materials having high mechanical strength in relation to the average rock to be excavated. These are generally called "hard formations" or "hard inclusions" and are in the form of either continuous layers or boulders. This problem is of particular importance in Europe where lignite deposits are exploited in large opencast mines utilizing Bucket Wheel Excavators (BWEs) as the main means of excavation. Often it is difficult or impossible to excavate these hard inclusions with BWEs, because the excavators operating in these countries are not fully adapted to such conditions. In Romania, a typical situation is encountered in Husnicioara open pit. As a first approach in order to study the impact of these inclusions on the working regime of BWEs, the laboratory essays devoted to establish the main metrics of the cuttability of these rock formations. [ABSTRACT FROM AUTHOR]

the paper deals with the results of laboratory experimental researches, performed in the past years, in view to establish the parameters characterizing the behavior at cutting of different mineral substances (coal, salt) and surrounding rocks (marl, clay, sandstone) and the laws governing their interdependence in respect to increase the working effectiveness of rock cutting equipment such as shearer loaders and roadheaders. [ABSTRACT FROM AUTHOR]