Bucket Wheel Excavator Research Articles

The influence of constructive parameters on response of bucket wheel excavator superstructure in the out-of-resonance region

The influence of constructive parameters on response of bucket wheel excavator superstructure is investigated by using a four degrees-of-freedom discrete dynamic model. Four representative geometric configurations of the superstructure are examined. The maximum displacements and accelerations are observed when the bucket wheel boom is in its lowest position. Further analysis on this configuration is performed to determine the effects of the structural elements stiffness and the bucket wheel weight on the system response. A set of the magnitudes of the parameters that may cause resonance are also determined.

Comments on “Determination and Analysis of the Theoretical Production of a Bucket Wheel Excavator” / Uwagi I Komentarze Do Pracy: ”Określanie I Analiza Teoretycznej Wydajności Pracy Koparki Wielonaczyniowej Kołowej”

Abstract This paper comments on the recently published work dealing with the problem in the determination of the theoretical output of the bucket wheel excavator. It also includes remarks on the inadequacy in the problem approach and highlights the mistakes in the mathematical model. This work emphasizes the demand for a much wider and deeper approach to the problem of determining the output of the bucket wheel excavator.

Disaster of the bucket wheel excavator caused by extreme environmental impact: Consequences, rescue and reconstruction

A slope failure was the cause of a severe accident of bucket wheel excavator (BWE) Takraf SRs 1200. This paper is dedicated to the engineering challenges that accompanied the process of returning the BWE from its after accident state to the state of full exploitation readiness. After the accident, temporary stabilization of the superstructure was carried out as well as cutting off of severely damaged parts of the bucket wheel boom (BWB) with excavating device. Successful completion of the very delicate BWE rescue and balancing operation was followed by the reconstruction of the heavily damaged slewing platform. The integrity of the slewing platform structure was preserved by removing structural parts which were seriously damaged during long-term exploitation and breakdown, and installing the newly designed elements in critical zones. The redesign of the slewing platform structure produced favorable loads and stiffness distribution while eliminating geometrical stress concentrators. Comparative analyses of the stress states pointed out that the redesigned slewing platform structure meets the strength criterion, unlike the original structure. The redesign solution enabled reconstruction in field conditions. This way the time of the reconstruction realization was drastically cut and losses due to the downtime of the machine were reduced several times over. After completing the slewing platform reconstruction, the newly manufactured BWB structural elements as well as the newly manufactured bucket wheel with drive were installed i.e. a partial revitalization of the BWE was done and by that the BWE’s life was essentially prolonged.

The Dynamics of Impacts Tools the Loading Boom Bucket Wheel Excavators

One of the major problems of long-distance belt conveyor technology, and not only in the North Bohemian mines, are impacts of rock blocks on the belts which increases the belts wear and reduces their service life. Therefore, in this paper there are widely discussed the rock impacts dynamics, a new type of device - the impact rods intended for significant reducing the number of punctures in the conveyor belts and thus for prolongation of their service life and modeling of the proposed devices. Application of the impact rods is estimated in the impact stands of the systems of conveyors removing the coal extracted by the bucket wheel excavator KU 300.

Structural integrity assessment for a component of the bucket-wheel excavator

Purpose – The purpose of this paper is to present a methodology for assessing the structural integrity of a tie member from a bucket-wheel excavator, ESRC 470 model, which was in operation for about 20 years. The tie member is made of S355J2N structural steel. Following the period of operation, the occurrence of microcracks which can propagate by fatigue is almost inevitable. It is therefore necessary to analyze the structural integrity and the remaining life of the component analyzed. Design/methodology/approach – In principle, the assessment methodology is based on three steps: first, the evaluation of mechanical properties of the material component; second, a BEM analysis using FRANC 3D software package to estimate the evolution of the stress intensity factor based on crack length and applied stress; third, risk factor estimation and remaining fatigue life predictions based on failure assessment diagram and fatigue damage tolerance concept. Findings – Following the evaluation procedure were made predictions of failure risk factor and remaining fatigue life function of crack length and variable stress range, for a high level of confidence. Originality/value – As results of this analysis was implemented a program for verification and inspection of the tie member for the loading state and development of small cracks during operation.

DETERMINATION AND ANALYSIS OF THE THEORETICAL PRODUCTION OF A BUCKET WHEEL EXCAVATOR

Abstract The theoretical capacity of a bucket wheel excavator is the basis of mining theory. The paper concludes that the use of “1/cosφ” to adjust the speed of a bucket wheel excavator will result in rapid speeds, which may cause nonuniform flow from the distribution of material flow, and decreased capacity utilization. Consequently, this scenario may produce unreasonable structure parameters and performance parameters that are based on theoretical analysis and mathematical derivation. If the rotary speed of an excavator body is too fast, it will require excessive mechanical strength and will generate increased rotary drive power, power consumption and extractive costs. Thus, the rotary speed of an excavator body should be appropriately reduced.

3D laser scanning of mining machines at Nastup Tusimice mine in the Czech Republic

3D laser scanning of bucket wheel excavators is useful in identifying key geometric parameters and in the creation of mathematical models. Thus, a compact and highly accurate 3D point model of a bucket wheel excavator was obtained. The evaluation consisted of vectorising their important features. These data were used to visualise the spatial position of excavators and track their movements in real time. Knowing the position of excavators, particularly the displacement of the bucket wheel relative to the digital terrain model (opencast mine), coupled with the geological model is important for mine management and calculation of volumes of extracted materials in real time. The 3D laser scanning measurements were carried out at Severočeské Doly mines.

Rehabilitation and reliability bucket excavator ER-1250 17/1, 5

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.

Bucket Wheel Excavator Damage by Fatigue Fracture – Case Study

This paper considers some problems of breakdown structure of bucket wheel excavator. Problems are caused by the effect of design, manufacturing, service conditions, welding joint quality and its defects. As is known, the applied load is variable depending on many factors which together with identified high stress concentration on critical points make this case the key to understanding the structure devastation process.Very important how crack initiation is transferred to a lug since final fast fracture has occurred indicating poor origin design of loading transfer in the structure of bucket wheel excavator. So, it is shown effects of applied load and stress distribution on fracture mechanism.

Effects of operating conditions on the Acoustic Emissions (AE) from planetary gearboxes

In the last decade, the use of acoustic emissions has received growing acceptance for its application in machine condition monitoring. This is because it offers good possibilities to diagnose failures at early stages and low rotational speeds. The use of acoustic emissions for condition monitoring of gears, however, is still an active field of research, because several questions remain unanswered. One of these questions is the effect of operating conditions on the AE generated during gear meshing. In this work, the results of experiments carried out on a non-faulty planetary gearbox test bench are presented. A planetary gearbox is considered, because of its usual application on machines subjected to variable operating conditions. The effects of lubricant temperature, load and rotational speed are investigated. The conclusions obtained from the experiments are used for the analysis of the AE measured on the planetary gearbox of a bucket wheel excavator.

Failure investigation of the bucket wheel excavator crawler chain link

The high mobility of open pit machines in heavy duty conditions provides fertile ground for the occurrence of various failures of the traveling mechanisms’ vital parts such as chain links. The goal of the study presented in this paper was to diagnose the cause of the damage of the bucket wheel excavator crawler chain links. In order to identify the reasons behind chain link failures, stress state calculations were performed as well as experimental investigations which, given the nature of the failure, included visual and metallographic examinations, chemical composition analysis and tests of mechanical properties. Based on the results of the numerical–experimental analyses, it was concluded that the chain link breakdowns are caused by ‘manufacturing-in’ defects. The results of the presented analyses also emphasize the importance of a comprehensive quality control of chain links.

Theory and experimental research on six-track steering vehicles

The structural characteristics and steering behaviour of a six-track vehicle are described in this paper. Kinematic analysis for skid steering of a six-track vehicle under steady-state conditions on firm ground is conducted, with the relationship between thrust force and speed instantaneous centre of the track–terrain interface taken into consideration. A mechanical model for steady steering of a six-track vehicle is also presented based on the kinematic analysis. In this model, the steering inaccuracy and efficiency are defined to evaluate steering performance. The steering performance of a six-track vehicle is numerically simulated to analyse the effect of the structural parameters and deflection angles on tracks. A virtual prototype model is established based on the multi-body dynamics software RecurDyn for steering simulation and the findings coincide well with theoretical results. The theory and the virtual prototype simulations presented are verified by a power test of a bucket-wheel excavator. The method for analysing the steering performance of a six-track vehicle proposed in this paper provides a basis for designing a six-track vehicle.

‘Designing-in’ failures and redesign of bucket wheel excavator undercarriage

The traveling mechanism of the C-700S bucket wheel excavator is of the two-crawler type. Rigid connections between the undercarriage and the crawler beams offer a very high factor of safety against tipping but at the same time create unfavorable conditions for ground surface adaptation. Connections between the crawler beams and the undercarriage cylindrical girder were realized by means of connection girders with open cross sections (I sections). In order to eliminate the occurrence of cracks, the original undercarriage structure (variant I) has been redesigned (variant II). The key idea was to strengthen the already mentioned connection girders by building in vertical plates. In this way the cross-sections were closed and their torsional rigidity became considerably greater, which led to the adaptation of the traveling mechanism to the ground surface becoming practically impossible. Because of that alone, and within a very short period after the reconstruction, new cracks occurred on elements of the original structure and even on added structural elements. Based on the FEA results, it was concluded that cracks occurrence for variants I and II of the undercarriage structure is caused by highly pronounced stress concentration. Subtle load and stress analyses in various working regimes, presented in the paper, led to the achievement of a re-redesigned undercarriage structure (variant III) with more uniform stress distribution. Stress level in the critical zone for variant III of the undercarriage structure is considerably lower than stress levels for both variant I (≈2.1 times) and variant II (≈2.5 times). It is very important to note that the weight of the new built-in elements for variant II is six times greater than that for variant III. During ensuing exploitation in extremely heavy duty conditions, no damages for variant III of the considered structure were observed.

METHODOLOGY DEVISING FOR BUCKET-WHEEL EXCAVATOR SURVEYING BY LASER SCANNING METHOD TO DETERMINE ITS MAIN GEOMETRICAL PARAMETERS

The application of laser scanning techniques to bucket-wheel excavator surveying seeks primarily to determine the machines’ key geometric parameters and to establish realistic mathematical descriptions of their movement dynamics in 3D space. The data will be used to visualize excavator movement and to control the coal extraction process in real time. The measurements take place at Doly Nástup Opencast Coal Mine, Tušimice, North-Bohemian Lignite Coal Field, Czech Republic. GNSS technology and inclinometric measurements are used to calculate 3D positions of the bucket-wheel excavators. The data is transferred to the research team workplace and stored in a database. KVAS software is used to visualise the bucket-wheel excavators and their 3D movements in real time.

SENSITIVITY ANALYSIS OF TANGENTIAL DIGGING FORCES OF THE BUCKET WHEEL EXCAVATOR SCHRS 1320 FOR DIFFERENT TERRACES

Researches in the field of economy of control of mining processes of minerals are continually met with a number of unsolved and newly arising problems. New deposits of brown coal are located at greater depths than before and are more difficult to mine. Problems in the field of rock mining stem from the greater diversity of rocks in mining, and it results in more difficult mining conditions. On the other hand, even greater demands are made to decrease the economic demand of mining. Current research is aimed at the most optimal utilization of energy provided on the bucket wheel of excavators, such that the energy demand of the mining process decreases, whilst preserving maximum performance. These requirements place greater demands on the precision of planning of mining and maximum economic efficiency. The presented article illustrates the possibilities of the utilization of Sobol sensitivity analysis during the investigation of the influence of the parameters of mining processes on tangential digging forces. Analyses are carried out for the mining process of bucket wheel excavator SchRs 1320. For purposes of the study, detailed measurements of operational parameters were performed on the excavator during a whole work cycle.

Study of Dependability Evaluation for Multi‐hierarchical Systems Based on Max–Min Composition

This article presents the model for calculating the performance of dependability for complex technical systems. According to ISO‐IEC 300, dependability is an overall indicator for the quality of service and considers simultaneously reliability, maintainability, and maintenance support. For a proper understanding of the quality of service for any technical system, it is important to define dependability performance at the level of single component as well as at the upper levels—levels of subsystems and entire system. As dependability indicators (reliability, maintainability, and maintenance support) have been defined as linguistic variables, the fuzzy max–min composition has been used for the dependability determination and integration of its indicators. A procedure for the synthesis of single components dependability performance to upper levels in complex technical system is proposed. Max–min composition is again used as a tool for fuzzy synthesis because it enables obtaining the comprehensive and synergetic effect in a process of dependability evaluation. A practical engineering example (mechanical systems at bucket wheel excavator) has been used to demonstrate the proposed dependability synthesis model. Copyright © 2012 John Wiley & Sons, Ltd.

Comparison of existing open coal mining methods in some countries over the world and in Europe

Comparison of existing mining methods on open coal mines in some countries over the world and in Europe evidence how different technology is in given areas. In Czech Republic (CR) so as in Germany and other countries of Europe the Bucket Wheel Excavators are used as the predominant technology. In Australia and USA the Draglines or Truck and Shovels are most common. In this paper the attempt is made to compare these technologies from the point of view of geological conditions and try to find out if it would be profitable accept oversea technology in CR and other Europe countries.

External Load Variability of Multibucket Machines for Mechanization

This paper discusses the problems of identifying external loads of multibucket machines for mechanization. External loads are dominantly dynamic with distinguished stochasticity in certain cases. The paper presents the procedures for determining external loads caused by resistance-to-excavation (for bucket wheel excavators) or grabbing soil (for bridge-type coal stacker-reclaimers), as well as a short description of the model upon which is based and defined the response of the stacker-reclaimer to the external changeable load. It points to the significance of the problem of identifying the external load, as well as to the potentially very detrimental and dangerous consequences of eventual shortcomings during solving the mentioned problem.

Analysis of the drive shaft fracture of the bucket wheel excavator

Drive in most bucket wheel excavators (BWEs) is accomplished through its electric motor, cardan shaft and planetary gearbox. In the BWE SchRs630/6x25, the planetary gearbox is cantilevered at the end of the hollow shaft which transmits the torque through the sprocket to the caterpillar track chain. In this BWE, the drive shaft fracture occurs at the point of support on the penetration side. Experimental testing of the chemical composition and mechanical properties of the material of the shaft and metallographic inspections of the fracture surface by means of electronic and light microscopes carried out in the first part of the paper have shown that there are no significant inhomogeneities and errors in the material of the shaft and that they do not cause damage. Further, the analysis of results referring to the mechanical properties and chemical composition of the repaired shaft at the point of welding, and particularly in the transition zone, shows that they considerably deviate from those prescribed for the material used. Significant inhomogeneity of the material, occurrence of cracks as well as the difference in the microstructure appear in this zone, which is the cause of shaft damage. The second part of the paper presents the FEM analysis of effects of the cantilever type of support of the planetary gearbox and stress concentration at the point of support due to inadequate finishing, which caused the occurrence of an initial crack. The user unsuccessfully tried to eliminate this weakness by repair welding of the shaft.

Redesign of the Bucket Wheel Excavators Substructures Based on the Comparative Stress – Strain Analysis

Failures caused by heavy duty conditions, as well as the changes of technological requirements, are basic reasons for the redesign of specific substructures of the bucket wheel excavators (BWE). The efficient redesign should be based on subtle external load identification and sufficient accuracy of stress – strain states determination. This paper gives solutions of reconstruction and comparative stress analyses for original and redesigned representative and vital BWE subsystems - slewing platform, undercarriage and two wheel bogie. The efficiency of these reconstructions is unquestionably confirmed by failureless service of mentioned subsystems.