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Model Approaches to Life Cycle Assessment of Auxiliary Machines Based on an Example of a Coal Mine in Serbia
Abstract
The paper presents two model approaches to life cycle assessment of auxiliary mining machines: one of them is based on reliability theory and the other on the principle of cost-effectiveness. During exploitation of machines, the level of their reliability decreases while operating costs increase. These indicators of opposing trends detect the operating capacity of machines and provide the basis for making a decision on the validity of further operation, maintenance, or replacement of machines. By considering an example of a dozer, as the most frequently used machine for the performance of auxiliary works in the surface coal mines of Electric Power Industry of Serbia, a comparative analysis was made for applying both model approaches including assessment and conclusion.
... The methods for monitoring the life cycle of mining machines are different and depend on the type of machine and its classification into the category of machines for the mining area. Krunic et al. (2018) presented two model approaches to life cycle assessment of mining machines: one of them is based on reliability theory and the other on the principle of cost-effectiveness. During the exploitation of Sustainability 2020, 12, 10454 4 of 13 machines, the level of their reliability decreases while operating costs increase. ...
... During the exploitation of Sustainability 2020, 12, 10454 4 of 13 machines, the level of their reliability decreases while operating costs increase. These indicators of opposing trends detect the operating capacity of machines and provide the basis for making a decision on the validity of further operation, maintenance, or replacement of machines [21]. In praxis are using various methods of diagnostics. ...
... Sustainability 2020, 12, x FOR PEER REVIEW 4 of 13 the category of machines for the mining area. Krunic et al. (2018) presented two model approaches to life cycle assessment of mining machines: one of them is based on reliability theory and the other on the principle of cost-effectiveness. During the exploitation of machines, the level of their reliability decreases while operating costs increase. ...
This article summarizes the arguments within the scientific discussion on the issue of using mining machines and their life cycle. The main goal of the article is to investigate the impact of a combination of mobile and stationary mining machines and their optimal distribution in the mining process to increase the efficiency of mining and processing of raw materials. The following methods of research were focused on the use of technical indicators for the valuation efficiency of the mining process: a simulation method was used for the distribution of mining machines, comparison analysis was used for the real and past state of mining machines, and a decision tree was used as managerial instrument for optimal alternatives of mining machines. The research empirically confirms and theoretically proves that optimal distribution of mining machines and machine parks is very important for mining companies. The benefit of this research for the mining company was the new location of the machines and the combination of stationary production lines and mobile equipment. The optimal layout of the machines reduced the number of conveyor belts and improved the transfer of limestone processing to mobile devices, saving time, which was reflected in transport costs. The results can be useful for other mining companies seeking to create an optimal machine park.
... The dependability of technical systems is conceptually stipulated by ISO-IEC standards [49,50]. ...
... Logistical support performances according to the ISO-IEC Standard are defined as: "The ability of maintenance system, i.e., the organization that performs maintenance, to provide under given conditions the required maintenance of the technical system in accordance with the maintenance policy" [48,49], the Standards of the IEC 300 series deal with the concept of logistic support for maintenance [50]. ...
This study presents a unique model for assessing the dependability of continuous parts of combined systems in open-pit mining through the application of fuzzy logic. Continuous sub-systems as part of the combined system of coal exploitation in surface mines have the basic function of ensuring safe operation, high capacity with high reliability, and low costs. These subsystems are usually part of the thermal power plant’s coal supply system and ensure stable fuel supply. The model integrates various independent partial indicators of dependability into an expert system specifically designed for evaluating these systems. It deconstructs the complex parameter of system dependability into distinct partial indicators: reliability, maintainability, and logistical support. These indicators are then integrated using fuzzy composition (max-min composition). Historical data from 2018 to 2023 are utilized alongside the fuzzy model to provide a retrospective analysis of system dependability, serving to validate the model’s effectiveness. What sets this model apart from conventional approaches is its consideration of practical dependability indicators, thereby obviating the need for extensive long-term monitoring and data collection to portray the system’s status accurately over time. This model serves as a valuable tool for assisting decision-makers in open-pit mining operations, facilitating planning, exploitation control, and the selection of maintenance strategies to ensure consistent production and cost reduction. Designed for quick assessment, the model relies on expert judgments and assessments to determine system dependability efficiently.
... Operational safety: ʺA collective term used to describe the availability performance and factors that determine these performances: reliability performances, maintainability performances, and logistics support performancesʺ [35] The dependability of technical systems is conceptually stipulated by ISO-IEC standards [36,37]. ...
... Logistical support performances according to the ISO-IEC Standard are defined as: ʺThe ability of maintenance system, i.e. the organization that performs maintenance, to provide under given conditions the required maintenance of the technical system in accordance with the maintenance policy [35,36] the Standards of the IEC 300 series deal with the concept of logistic support for maintenance [37]. In terms of the number of linguistic variables, it can be inferred that seven is the maximum count of variables that a person can rationally recognize simultaneously while retaining the same meaning [39]. ...
This study presents a unique model for assessing the dependability of continuous parts of combined systems in open-pit mining through the application of fuzzy logic. Continuous sub-systems as part of the combined system of coal exploitation in surface mines have the basic function of ensuring safe operation, high capacity with high reliability and low costs. These subsystems are usually part of the thermal power plant's coal supply system and ensure stable fuel supply. The model integrates various independent partial indicators of dependability into an expert system specifically designed for evaluating these systems. It deconstructs the complex parameter of system dependability into distinct partial indicators: reliability, maintainability, and logistical support. These indicators are then integrated using fuzzy composition (max-min composition). Historical data from 2018 to 2023 is utilized alongside the fuzzy model to provide a retrospective analysis of system dependability, serving to validate the model's effectiveness. What sets this model apart from conventional approaches is its consideration of practical dependability indicators, thereby obviating the need for extensive long-term monitoring and data collection to portray the system's status accurately over time. This model serves as a valuable tool for assisting decision-makers in open-pit mining operations, facilitating planning, exploitation control, and the selection of maintenance strategies to ensure consistent production and cost reduction. Designed for quick assessment, the model relies on expert judgments and assessments to determine system dependability efficiently.
... It is important for the owner of the equipment to identify the reference points between the lifetime stages of the engineering system or the machine. The property of these stages is the level of cost, which can be minimal, acceptable, or unacceptable [3]. The major task here is to determine the maximal profit and to establish an acceptable level of cost for the owner, i.e., to identify the specific period of the machine's lifetime [4]. ...
This paper presents the model for the identification of reference points on the lifetime curve of engineering systems. This curve commonly represents the increase and decline of failure in relation to time. A direct correlation between failure rate and costs is assumed in this paper, therefore, statistical and empirical analysis of costs provided reference points. This approach is used for positioning stages of the engineering system’s lifetime with a minimal number of failures and costs, regardless of whether these are acceptable or not. The following three stages are usually identified: the beginning, the stationary part and the end of life. The boundaries between them are recognized on the basis of minimum total lifetime costs and on economic lifetime costs. Model is tested on the dozers, machines frequently used in the mining industry for the earthmoving operations, and which are characterized by high operating and maintenance costs.
... (2) The computational cost of analysis method and numerical evaluation is high, which can not realize the real-time and rapid evaluation of ventilation system reliability. (3) The factors affecting the reliability of the ventilation system are complex and diverse, and the changes in the system state are uncertain, which are difficult to describe with existing models. (4) Ventilation system reliability analysis is mostly focused on the current ventilation system reliability judgment, which can only be used offline. ...
Mine ventilation systems play a key role in creating and sustaining a healthy and safe working environment within the mine, and as such, should always be maintained at optimal performance levels. This paper establishes a model based on Markov chain that can quickly evaluate the reliability of the ventilation system. Firstly, the operation status of the ventilation system is divided into normal, risk and failure. Then, according to the failure rate and repair rate of the system, the operation state of the system under the specified total operation time T and time interval Δt is simulated based on Monte Carlo method, the Markov chain state transfer probability matrix of the system can be obtained. Combined with the current operation state of the system, the reliability indexes such as the system operation state transfer probability and the steady state probability in the future can be quickly analyzed to realize the rapid evaluation of the operation reliability of the ventilation system. Finally, the model is used to evaluate the reliability of XQ mine ventilation system, which shows the effectiveness of the model. This research provides theoretical reference and technical support for mine safety production.
In reliability engineering, the Weibull distribution is one of the most widely used distributions for modeling lifetime data. Often when analyzing experimental data, it is important to determine whether the underlying distribution is Weibull. To this end, the Weibull plot is often recommended for visually assessing whether the underlying distribution is Weibull or not. Unfortunately, this visual assessment is subjective. In this paper, using the sample correlation coefficient from the Weibull plot, we propose a method for objectively assessing the goodness of fit of the Weibull distribution by using a formal hypothesis test. In order to construct a critical region for the proposed hypothesis test for Weibullness, one needs the distribution of the sample correlation coefficient from the Weibull plot. However, it is impossible or extremely difficult to obtain the explicit distribution of the sample correlation coefficient. Extensive Monte Carlo simulations are carried out to obtain the empirical distribution of the sample correlation coefficient and the critical values. These critical values can then be used to construct a critical region for the proposed hypothesis test for Weibullness. Illustrative examples with real data sets are also provided.
In this paper the average malfunction costs (lost production) of the overburden excavation system on the Tamnava - East field open-pit mine caused by the failure of belt conveyor rubber belts which work on the bucket wheel excavator, belt wagon and spreader are determined, i.e. the unit cost of system malfunction per hour of belt conveyor work during belt lifetime. The basis for the calculation of malfunction costs is presented by the proposed methodology for the analysis of rubber belt working time to failure based on the fact that working time until sudden failure (tear, breakthrough) can be described by exponential distribution while working time until gradual failure can be described by normal distribution. The proposed methodology as well as the expression for malfunction cost determination can be used, with appropriate adoptions, in the analysis of the functioning of other open-pit mines for better planning of malfunctions, requirements for spare rubber belts as well reductions in working costs, i.e. they can indicate better (optimal) maintenance strategy.
A theoretical concept and an illustrated practical example of the limited interval dynamic model, aimed for application in
optimizing the exploitation life of the mining machinery with shorter life cycle such as bulldozers, scrapers, haul trucks,
excavators with one working element and smaller capacity, etc., is presented in this paper.
The paper is focused on the problem of determining the optimal exploitation life of the long-lasting mining machinery, such
as bucket-wheel excavators, excavators with one working element of large capacity, spreaders, self-propelled transporters,
conveyor belts and similar machinery. A concept of approach is presented, and an application of the dynamic model with the
undefined interval is given by using the example of the bucket-wheel excavator. The paper concludes with observations and
assessments regarding the subject matter.
Key wordsBucket-wheel excavators-machinery exploitation life-optimization-operations research-replacement theory-dynamic programming
Traditional reliability-based design optimization (RBDO) minimizes a cost-type objective function subject to reliability constraints. The reliability constraints are based on physical models, such as finite element simulation, which are used to specify the state of a component or a system. Hence the reliability is the so-called physical reliability. The reliability constraints are usually static without accounting for product lifecycle issues. In this work, several reliability-based design optimization models incorporating several maintenance policies are proposed. The product lifecycle cost is minimized while the constraints of product lifecycle reliability or availability are satisfied. The First Order Reliability Method (FORM) is employed to calculate the time dependent reliability. An engineering example is used to illustrate the proposed models.
To reduce the maintenance cost and improve the effectiveness of the maintenance activities in series-parallel systems, a preventive maintenance (PM) decision model for series-parallel systems subject to reliability was developed. This model considered the effect of failure maintenance on PM cycle and the restriction of system reliability in maintenance decision making, thus can help decision-maker to arrange appropriate and effective maintenance activities. Finally, an example was given to validate the proposed model.
This research highlights the criteria and methodologies of a simulation tool that predicts the reliability and remaining lifetime of circuit boards. A new approach to determine component position in circuit boards is presented, where the criteria of determining the position of the failed components on the board layout and their effect on the entire board are demonstrated. Given an existing design and specified operating conditions, a user is able to evaluate circuit boards and determine which components, sets of components, or the complete board are most likely to fail and when. This in turn will allow one to anticipate and identify failures before they occur, thus reducing downtime and saving money.
Using classical design methods for tillage machines does not completely guarantee a safety and satisfactory performance, due in part to the randomness of tillage forces. This randomness is derived from the variability in soil engineering properties and the variations in tool design parameters and operational conditions. In this paper, a reliability-based design approach was developed, for the first time, by integrating the randomness of tillage forces into the design analysis of tillage machines, aiming at achieving reliable machines. The proposed approach was based on the uncertainty analysis of basic random variables and the failure probability of tillage machines. The failure probability was estimated according to two performance criteria related to the structural design requirement and the quality of tillage operation. Two reliability methods, namely the Monte Carlo simulation technique and the first-order reliability methods were used for this purpose. This approach was implemented for the design of a chisel plough shank.The results showed that there were many values of the shank dimensions that guaranteed the required reliability level. However, in order to achieve the best design solution from an economic point of view, minimizing the volume of the shank structure was integrated into the reliability-based design approach. This led to the reduction of the initial volume of the shank structure by 6.86%. It was concluded that integrating the economical constraint into the reliability-based design approach can lead to optimal designs of tillage tools that ensures the required reliability level at low cost.
Methods for Optimization of the Exploitation Length of Mining Machines, Electric Power Industry of Serbia
- S Vujic
- R Stanojević
- T Tanaskovic
- B Zajic
- R Zivojinovic
- S Maksimovic
Dynamic Programming, The Institute of Economy
- R Stanojevic