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The durability of bearing units of large machines depends mainly on the condition of their welded joints. With this in mind, we developed numerical models of the analyzed bearing units, for which we performed FEM simulations of the stresses in welded joints in several basic load cases. In each of the respective variants the technical condition of the bearing nodes was different and it corresponded to the severity of the degradation processes. Different positions of the superstructure in relation to the undercarriage were also taken into account. The simulations used the hot-spot method dedicated to FEM analyses of complex welded structures. We discovered that the loads have a significant influence on the values and distribution of von Mises principal stresses and their axial components. Based on the carried out analyses, we identified the most unfavorable load cases that generate the highest stresses in the welded joints of the assessed nodes. We also demonstrated that the applied method effectively assesses the stresses of welded joints subjected to variable working loads. [ABSTRACT FROM AUTHOR]

This work introduces a methodology for the automatic unmineable inclusions detection and Bucket Wheel Excavator (BWE) collision prevention, using electromagnetic (EM) inspection and a fuzzy inference system. EM data are collected continuously ahead from the bucket wheel of a BWE and subjected to processing. Two distinct methodologies for data processing were developed and integrated into the MATLAB programming environment. The first approach, named "Simple Mode", utilizes statistical process control to generate real-time alerts in the event of a potential collision involving the excavator's bucket and hard rock inclusions. The advanced processing flow ("Advanced Mode") requires accurate instrument positioning and data from successive EM scans. It incorporates techniques of local resistivity maxima detection (Position Prominence Index) as well as Neural Network-based Pattern Recognition (NNPR). A decision support process based on a Fuzzy Inference System (FIS) has been developed to assist BWE operators in avoiding collision when digging hard rock inclusions. The proposed methodology was extensively tested using synthetic EM data. Limited real data, acquired with a CMD2 (GF Instruments) EM instrument equipped with GPS, were used to control its efficiency. Increased accuracy in the automatic detection of unmineable inclusions was observed using the Advanced Mode. On the other hand, the Simple Mode processing technique offers the advantage of being independent of instrument positioning as well as it provides real-time inspection of the excavated mine slope. This work introduces a methodology for hard rock inclusion detection and can contribute to the optimization of mine operations by improving resource efficiency, safety, cost savings, and environmental sustainability. [ABSTRACT FROM AUTHOR]

In the present paper we propose a new artificial neural network model for the estimation of coal cutting resistance and excavator performance as a nonlinear relationship between the examined input (excavator movement angle in the left and right direction, slice height and thickness, coal unit weight, compressive and shear strength) and output factors (excavator effective capacity, maximum current/power/force/energy consumption, linear and areal cutting resistance). We analyze the dataset collected from three open-pit coal mines in Serbia: Field D, Tamnava Eastern Field and Tamnava Western Field (all part of the Kolubara coal basin). The model is developed using a multilayer feedforward neural network, with a Levenberg-Marquardt learning algorithm. Results of the preformed analysis indicate satisfying statistical accuracyof the developed model (R>0.9). Additionally, we analyze the individual effects of input factors on the properties of coal cutting resistance and performance of the excavator, by invokling the multiple linear regression. As a result, we single out the statististically significant and physically possible interactions between the individual controlling factors. [ABSTRACT FROM AUTHOR]

Crawler travel gear is a type of heavy vehicle propulsion that is commonly found in tanks, excavators, and specialized off-road vehicles. They have an advantage over wheels when it comes to robust vehicle weight distribution over soft terrain, and some disadvantages as well. They can damage paved roads and have complex design so, considering the enormous weight they must carry, their reliability must be determined and verified. The main parts of the assembly are the drive wheels, which move the crawler, and the supporting structure that holds four-wheel bogies and two-wheel bogies. In this paper, we present a methodology for FEM analysis of parts of an eight-wheel bogie according to DIN 22261-2 standard. [ABSTRACT FROM AUTHOR]

• 0.75 m/s velocity and 200 MPa pressure are found to be fail-safe for pin-roller assembly. • The roller's principal stress transitions from compressive to tensile, at higher velocities. • The hertz stress for the pin-roller-track contacts matches well with the FE model findings. • The bottom roller and pin of the bucket wheel excavator fails due to static overloading. • The failure mode of pin and roller are ductile and mixed-mode, respectively. Mining excavators play a crucial role in the mining industry, and their reliable operation depends on the integrity and efficiency of various components, including rollers and pins. This study presents a comprehensive analysis of mining (Bucket wheel) excavator rollers and pins, aiming to understand their structural characteristics (load capacity and structural integrity), performance, deformation, and failure behaviour as well as potential areas of improvement. The study investigates the performance aspects of excavator rollers and pins in terms of their ability to withstand compressive pressure forces employing Finite Element Modelling (FEM). Numerical studies, in conjunction with experimental validations, are found to be capable of determining stress distribution as well as failure criteria of bottom roller and pin. A thorough quasi-static analysis has been conducted, considering the real-world operating conditions of the excavator. The simulation findings are found to be helpful towards extending maintenance windows, decreasing failures, and improving the roller and pin system efficiency. FE simulations reveal that increased velocity significantly raises von Mises stress and contact pressure, with the highest values at 1.0 m/s, and causes the roller's principal stress to shift from compressive to tensile. Optimal operational parameters are found to be excavator roller translational velocity of 0.75 m/s and an applied pressure load of 200 MPa. Whereas metallographic, chemical analysis, and mechanical characterisation of the failed roller and pin samples establishes the metallurgical reasons of failure of roller-pin assembly, apart from confirming accuracy of the simulation findings. Also, the strain softening from dynamic and static overloading is identified as the main cause of failure mechanism. Fracture surface analysis shows ductile failure in pins and mixed-mode fracture in rollers. [ABSTRACT FROM AUTHOR]

Identification of the basic parameters of static stability (BPSS) of the slewing superstructure is the key step in solving the problem of its static stability, as well as static stability of the entire bucket wheel excavator (BWE). Specificity of the slewing superstructure examined in this paper lies in the kinematic breakdown system (KBS) which prevents the loss of static stability on the counterweight side. Development of a unique method for the formation and two-step validation of the calculation models for this particular design concept was the main objective of the presented research. A two-step validation of the analytical models is conducted based on the experimental results. As the outcome, the final calculation model formed in such manner represents an accurate basis both for the proof of static stability and for the monitoring of the BPSS during exploitation. By comparing the results of the control weighing and the referent values of the final calculation model it was concluded that the existing double-walled bucket wheel represents a 'weak point' of the considered BWE. [ABSTRACT FROM AUTHOR]

During open pit coal exploitation inevitably comes to land degradation. The negative changes, processes and consequences impose need for parallel working on sanitation and in general arranging destroyed natural areas. The one of sanitation criterion is implementation of reclamation which has a goal to restore completely or as much as it is possible, the destroyed area to its previous purpose. The priority has consistent conducting of technical reclamation of spoil in accordance with planned landscaping.

Crawler travel gear is a type of heavy vehicle propulsion that is commonly found in tanks, excavators, and specialized off-road vehicles. They have an advantage over wheels when it comes to robust vehicle weight distribution over soft terrain, and some disadvantages as well. They can damage paved roads and have complex design so, considering the enormous weight they must carry, their reliability must be determined and verified. The main parts of the assembly are the drive wheels, which move the crawler, and the supporting structure that holds four-wheel bogies and two-wheel bogies. In this paper, we present a methodology for FEM analysis of parts of an eight-wheel bogie according to DIN 22261-2 standard.

In the paper the authors present the procedure of measuring vibration and obtained data accruing in a bucket wheel excavator's operator cabin. Details of the selection and location of the measuring points are firstly given. In the following part, the example of for the bucket wheel excavator SchRs 1200, will be presented. This machine is in use at one of Poland's open cast mins. The operating conditions are briefly characterized in the descriptions of the measurement series. The measuring equipment is also presented. The recorded data are presented in two ways. The first of the presents time waveforms for each measuring channel. The second one presents Fast Fourier Transform (FFT) spectrums after filtering the measured signals. The obtained data is used to develop a vibrations control algorithm.

The primary objective of the case study is to improve monitoring, controlling, planning and managing the extraction processes in surface lignite mining. Under the North Bohemian Lignite Basin (also Most Basin) conditions and the Sokolov Basin, wheeled excavators are deployed as the main technology for extracting coal and overlying rock. Their real-time spatial position can be tracked based on data from GNSS technology, inclinometers, and incremental rotary encoders. The measured data is sent to a remote server and stored in the database. It also serves to calculate volumes of extracted masses. Volume calculation, space position visualisation, and wheel boom movements are performed in KVASoftware. It is a program designed for modelling and designing quarries. Knowing the position of the wheel against the digital terrain (quarry), the model is essential for the implementation of many risk-elimination applications, namely with respect to the geological conditions, occupational safety, observance of the profile grade line, the area of extraction, qualitative parameters of the raw material, etc. The mathematical model of backfilling extracted materials is also an integral part of the above-mentioned system. [ABSTRACT FROM AUTHOR]

This paper deals with the issue of the service life of the boom of a bucket wheel excavator (BWE) in a lignite open-pit, solved through a fatigue analysis with the aid of the SolidWorks application. To this purpose, the boom of the excavator, which is a spatial structure of a truss type, has been modelled in compliance with the geometrical and material conditions of the real system. For the beginning the linear dynamic time response was determined for a load produced by the excavation forces, with a global damping of 2%. The results of the analysis allowed for the determination of the deformations which occur and their frequency. Then the model underwent a static strain analysis with the established deformations to determine the stress generated by the excavation process, whose results cause the events which produce the fatigue. The frequency of the oscillations (vibrations) corroborated with the estimated or actual number of hours of service within a year determines the number of events that cause fatigue. Proceeding from these, the analysis of the fatigue status corresponding to a period of excavation of 10 to 30 years has been determined. Making the fatigue calculations with the aid of the SolidWorks application, it is possible to evaluate the degree of damage according to the period of exploitation, which determines the remaining service life of the BWE boom. [ABSTRACT FROM AUTHOR]

The article presents the results of the numerical experiments designed to determine the effect of obstacles in the form of the drainage wells/piezometer on the basic efficiency parameters of the excavator's work. Simulation research on built model included defining the basic parameters of the excavator working in the front block on stabile front (as a comparison) and on the non-stable front for two variants of drainage infrastructure exposing. [ABSTRACT FROM AUTHOR]

Statistical regularity of random mechanical failures of the bucket wheel excavator will be considered based on dispatcher’s reports about excavator-conveyors-spreader (ECS-III) on the Tamnava - West Field Open Cast Mine in Lazarevac (Serbia) system failures in the period from 2003 to 2011. This kind of failures happens suddenly due to undetectable defects, unexplainable causes, and unavoidable failures. Reliability functions R(t), failure rate λ(t) and failure density f(t) of the bucket wheel excavator will be empirically determined. It was concluded that the random failures could be well approximated by the Exponential distribution. Below, serial reliability configuration of the BWE subsystem was analysed and the failure frequency as well as the values of the failure rate by subsystems were determined. Finally, proactive maintenance approach, which represents the latest innovation in the field of maintenance, will be presented. This approach to maintenance utilizes various technologies in order to achieve extension of operational life and elimination of reactive maintenance.

Breakdown of stackers and excavators in opencast mines is possible because of operating, manufacturing and structural causes, and it produces high financial losses. These can be prevented by using various measures, including analyses and strength tests, with computerized modeling and simulation using FEA or other techniques being implemented in the recent years. In this paper a fatigue study is conducted on the boom of a BWE. Based on a computer model of the boom previously developed in SOLIDWORKS by our author team, first the modal analysis is conducted for three positions of the boom by studying the frequency response during the excavation process. This is followed by the time response determination corresponding to the maximum displacement frequency, in order to assess the stress during the excavation process, which causes the material fatigue in the boom structure. It was found that the maximum displacements appear when the BWE boom operates in a horizontal position. The aim was to estimate the period of time to failure in order to prevent unwanted accidents, and to develop a method that is applicable to any surface mining or industrial machine with similar structure.

Starting from the general principles of material cutting, with applicability to coal and overburden excavation using bucket wheel excavators (BWEs), this paper proposes another method for calculating the drive power of the bucket wheel excavator by computer modeling. This approach required two steps. In the first step, the volume of the excavated material for one slewing movement of the boom and for a particular excavation geometry was determined, and the slewing time in the open pit coal mine was measured. In the second one, the values of the specific energy (SE) consumption for cutting were determined by laboratory tests on samples of material taken from the open pit mine. The proposed method allows for the estimation of the load of the bucket wheel drive motor by taking into account only the specific energy necessary for the cutting of the material, the excavated volume during one slewing, and the time required to excavate this volume, and not the wear coefficients of the teeth or bucket edge. This method is important for establishing the correlation between the height of the excavated slice and the slewing speed of the boom in order to optimize the drive power of the bucket wheel and thus improve energy efficiency, increase the performance of excavators, and reduce operating costs.

This study addresses the use of combined stripping systems to investigate the technical feasibility of extracting thick coal seams underlying deep overburden strata. The possibility of using multiple draglines in tandem with bucket wheel excavator systems is explored. Pit geometry design alternatives incorporating a triple dragline excavation fleet with bucket wheel excavator-cross pit spreader subsystems (BWE+XPS) are examined. A production simulation algorithm, which emphasizes synchronizing excavator units in the triple dragline system, is developed. The combined methodology is evaluated in Sector-D of the Afşin-Elbistan lignite basin, one of the most important resources for electricity production in Turkey. The results reveal that a combined stripping fleet may successfully perform overburden stripping at the predetermined rate and uncover coal seams.

This paper describes a software solution for calculation and analyzed the impact resistance to excavation on technical capacity of a bucket wheel excavator was analyzed at the open pit Gacko. The analysis was carried out for many characteristic cases with the values of resistance to excavation of 750, 1000, 1250 and 1500 N/cm, and in accordance with the set values in the working environment of the open pit Gacko - Central Field.

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Copyright of Archives of Mining Sciences is the property of Polish Academy of Sciences and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Maintenance & Reliability / Eksploatacja i Niezawodność is the property of Polish Scientific & Technical Society Consumables, Polish Maintenance Society and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Buckets are a vital substructure of all digging machines, and are intended for the realisation of the fundamental machine function - soil excavation. This paper presents the results of the experimental-numerical investigation of the cause of the bucket wheel excavator SRs 470 buckets failure. The chemical composition and mechanical properties, the impact toughness, hardness, tendency to cracks and the microstructure were determined using appropriate tests. Experimental examinations of working and residual stresses were performed using strain gauges. The superposition of the experimentally determined working and residual stresses and the calculation of the total principal stresses were conducted using the originally developed procedure presented in this paper. The bucket working stress state was calculated by applying the linear finite element method. Conclusions based on the investigation results show that the main reasons for the buckets failure were the ‘design-in defects’ - oversights made during the procedures of geometrical shaping and material selection. Furthermore, high values of residual stresses, as well as the cold cracking observed on the welded joint of the knife and the bucket body, suggest that the ‘manufacturing-in defects’ also played a significant role in the failure. The superposition of influences of the ‘design-in defects’ and the ‘manufacturing-in defects’ has conditioned the appearance and propagation of long-term fatigue cracks, leading to the total destruction of the buckets. The fact that buckets' failure appeared due to oversights made during geometrical shaping, material selection and manufacturing further points to the importance of the critical approach implementation during the design phase of the earthmoving machines working devices. [ABSTRACT FROM AUTHOR]

This paper presents the modeling and simulation of the sterile rocks excavation process using bucket rotor excavators. The modeling and simulation of the excavation process is carried out in Matlab-Simulink, based on an original mathematical model of the momentary capacity. [ABSTRACT FROM AUTHOR]

Great technical production systems are primarily developed in areas of intensive exploitation mineral resources. These systems monitor a large capital investment. In recent years , the maintenance of large technical systems , an important role is the revitalization (modernization ) of the equipment . The problem that arises when using large technical systems , in this case, bucket wheel excavator , stems from the need for bringing constructive and technical parameters of the excavator , the physical and mechanical characteristics of the material to be excavated , and the technological parameters of digging . The research presented in this paper is to determine whether to increase the reliability of the revitalization of the bucket wheel excavator ER -1250 17/1 , 5.

VŠB – Technical University of Ostrava, institute of geodesy and mine surveying has been cooperating with Severočeske doly j.s.c. (SD) in important research project since 2007. The main goal is improve control system for opencast mining. Two bucket wheel excavators (K800/103 and KU300/27) were equipped with measurement hardware at the Libouš Lignite Mine (North Bohemia brown coal basin). The position of the bucket wheel centre is computed by means of GNSS data, inclinometer and incremental measurements. Data is transferred to a base. All the values measured are saved in this database. The surface layout of the mine as well as positions of underground geological layers are updated on a regular basis in the digital model of the mine. The main aim of the research is verifying the system in connection to digital model for short time prognosis of qualitative parameters of coal (Ad, Sd, Qr, Wr and MS), continuous automatic computation of mined materials (m3, tons) and continuous checking of creation of the movement surface/plane of the excavator and mining goals. Mine surveyors have a lead role in the working team. The paper describes possibilities of using the GNSS for mine surveying and for production planning.

The results of vibration measurements at characteristic points on the belt conveyor drive of bucket wheel excavatorSRs400 manufactured by Takraf are presented in the paper. The operating processes (transport of material on the belt conveyor) belong to the category of impacts, such as fitting, acceleration, sudden loading, and the like, which are extremely pronounced in mining machinery. For monitoring purposes, measurement was undertaken in all three directions, upon overhaul and after 11,850 hours of operation. Movement, speed and acceleration of oscillations were plotted using measured data and the effect of the rear connection of the electromotor mount support on its proper performance was determined. [ABSTRACT FROM AUTHOR]

The paper presents the results obtained in the analysis of maintainability of the EsRC-1400 bucket wheel excavator travel system. The main maintainability indicators are determined that quantify maintenance actions and define the adopted maintenance strategy. The defining elements result from the interpretation of maintainability indicators on which the excavator quality level determination is based. [ABSTRACT FROM AUTHOR]

The paper presents the results obtained in determining the reliability of EsRc-1400 bucket wheel excavator travel system. The main reliability indicators are determined that quantify the operating ability of the travel system and, implicitly, of the excavator. A special attention is given to the interpretation of the reliability indicators that are at the basis of establishing the quality level of the excavator. [ABSTRACT FROM AUTHOR]

In the paper authors present their attempt in the validation process of the numerical model on the basis of experimental results. The Modal Assurance Criterion between the numerical and experimental model was selected as the indicating factor. Moreover, changes in frequencies and the degrees of freedom influencing the most the correlation level were reconsidered. The numerical and experimental models, in most cases, did not cover the influence of the operational load on the dynamic characteristic of the construction. In the new, operational approach, the change in the numerical model composition must be reconsidered, while the old one is no longer valid. Modal analysis performed out of the operational load, give good results but does not represent actual state of the construction in operation. In that case, we have two separate systems with different dynamic characteristics. Identification of the modal model with use of the Operational Modal Analysis gives the information about the object in operation which is a real point of the interest.

Presented paper deals with an evaluation of measuring of vibrations on a bucket wheel excavator (BWE) SchRs 1320 during mining. Vibrations were measured on the BWE’s upper steel structure by using 28 accelerometers. Measured signals were associated with operating data from the BWE’s central control computer. By connecting these two signal groups a complete set of valuable data was obtained. This data set was analyzed by time-frequency transforms. This paper shows results for three selected time periods. Results proved frequency changes in vibrations of upper steel structure of the BWE during moving in mining process.