Observed and unobserved heterogeneity in failure data analysis

In reality, failure data are often collected under diffract operational conditions (covariates), leading to heterogeneity among the data. Heterogeneity can be classified as observed and unobserved heterogeneity. Un-observed heterogeneity is the effect of unknown, unrecorded, or missing covariates. In most reliability studies, the effect of unobserved covariates is neglected. This may lead to inaccurate reliability modeling, and consequently, wrong operation and maintenance decisions. There is a lack of a systematic approach to model the unobserved covariate in reliability analysis. This paper aims to present a framework for reliability analysis in the presence of unobserved and observed covariates. Here, the unobserved covariates will be analyzed using frailty models. A case study will illustrate the application of the framework

SIMULACIJA DOSTUPNOSTI I ANALIZA RADA OKLOPNOGA TRANSPORTERA U ŠIROKOČELNOME RUDARENJU

Since coal mining production systems are very complex, repairing equipment is expensive. If a system failure occurs, it will cause disturbances such as inoperable equipment, reduced operating time, increased production costs, and reduced equipment performance. Therefore, it is necessary to consider the availability of the coal mining industry more than ever. For this purpose, the Armored Face Conveyor (AFC) machine failure data was gathered over a period of 29 months from the Tabas Coal Mine. Descriptive statistics, trends, and serial correlation tests of the data were calculated. Then, the system’s mean and point availability were simulated. Based on the results, the mean availability (all events) and point availability (all events) at 360000 h are 96% and 95%, respectively. The mean time to first failure (MTTFF) of the AFC machine was about 23.61 h. The ReliaSoft Failure Criticality Index, ReliaSoft Downing Event Criticality Index, and ReliaSoft Downtime Criticality Index electrical equipping have the largest effect, whereas the main drive subsystem is the least important. Analysis showed that availability has a direct correlation to activity management and improvements in the quality, efficiency, and the product extraction.Sustavi proizvodnje ugljena u rudnicima vrlo su složeni, stoga je i popravak opreme skup. Kvar sustava uzrokovat će smetnje kao što je nedostupna oprema, smanjeno vrijeme rada, povećani troškovi proizvodnje i smanjene performanse opreme. Stoga je nužno da se dostupnost industrije ugljena razmatra više nego ikad. U tu svrhu 29 mjeseci prikupljani su podatci o kvaru stroja tipa oklopljenoga širokočelnoga transportera iz rudnika ugljena Tabas. Izračunane su opisna statistika, trendovi i test serijske korelacije podataka. Zatim su simulirane srednje vrijednosti i dostupnost bodova u sustavu. Na temelju rezultata prosječna dostupnost (svi događaji) i dostupnost točke (svi događaji) na 360 000 h iznose 96 % odnosno 95 %. Prosječno je vrijeme do prvoga kvara (MTTFF) transportnog stroja oko 23,61 h. U trima metričkim vrijednostima, ReliaSoft indeksu kritičnosti kvara, ReliaSoft indeksu kritičnosti pada sustava i ReliaSoft indeksu kritičnosti zastoja, električno opremanje ima najveći učinak, dok je glavni pogonski podsustav najmanje važan. Utvrđeno je da analiza dostupnosti kontrolira upravljanje operacijama i poboljšanja u kvaliteti, učinkovitosti i izvedbi linije

PREGLED ODRŽIVOGA RAZVOJA I ODRŽIVOSTI OKOLIŠA U RUDARSKOJ DJELATNOSTI

A comprehensive systemic approach is needed to make effective decisions for global sustainability. The system’s points of view introduced sustainable development (S.D.) and sustainability in prior years. Sustainable development is expressed as a desire followed by humanity to live in a better condition considering all the limits that nature could have. Social, environmental, and economic responsibilities are the wide-ranging developmental characteristics that form sustainability. In this paper, with the help of search engines like Scopus and Web of Science, several documents related to environmental sustainability in the mining industry were studied. The principal investigated problems were tailings dam failure, forestland use in mining operations, social and environmental issues in crushed stone mining industries, landfill mining challenges, climatic problems, economic problems, and fatalities in artisanal and small-scale mines. Also, a table was designed to categorise these problems and determine the solution and primary goal. This study investigates the severity of mining operation conditions and environmental issues in this industry. The common environmental problems in the mining industry include soil degradation, deforestation, land subsidence, acid mine drainage, waste production, natural landscape destruction, coal production, carbon footprint, dust pollution, greenhouse gas emissions and climatic problems. To have a more sustainable mining industry, all the mining stages, from the exploration to the post-closure stages, must minimise resource and energy consumption and waste products.Za donošenje učinkovitih odluka u sklopu globalne održivosti potreban je sveobuhvatan sustavan pristup, što posebno dolazi do izražaja prethodnih godina. Održivi razvoj izražava se kao želja čovječanstva za životom u boljim uvjetima uzimajući u obzir moguća ograničenja prirode. Društvene, ekološke i ekonomske odgovornosti ubrajaju se među brojne karakteristike razvoja koje čine održivost. U ovome radu, uz pomoć tražilica poput Scopusa i Web of Science, proučavano je nekoliko dokumenata vezanih uz održivost okoliša u rudarskoj industriji. Glavni fokusi studija vezani su uz probleme kao što su klizanje jalovišta, korištenje šumskoga zemljišta u rudarskim radovima, socijalna i ekološka pitanja u eksploataciji i proizvodnji tehničko-građevnoga kamena, izazovi eksploatacije na odlagalištima, klimatski problemi, ekonomski problemi i smrtni slučajevi u privatnim i malim rudnicima. Također, osmišljena je tablica koja kategorizira te probleme i njihova rješenja te primarni cilj. Ova studija istražuje važnost radnih uvjeta u rudarstvu i probleme okoliša u rudarskoj industriji. Uobičajeni ekološki problemi u toj industriji uključuju degradaciju tla, krčenje šuma, slijeganje zemljišta, odvodnju kiselih otpadnih voda iz rudnika, proizvodnju otpada, degradaciju prirodnoga krajolika, proizvodnju ugljena, ugljični otisak, onečišćenje prašinom, emisije stakleničkih plinova i klimatske probleme. Kako bismo imali održiviju rudarsku industriju, sve faze rudarstva, od istraživanja do faza nakon zatvaranja, moraju minimizirati potrošnju resursa i energije te otpadne proizvode

Building ecological literacy in mining communities: A sustainable development perspective

Ecological Literacy (EL) is understanding and applying ecological principles to environmental issues. It involves recognizing the interdependence of living organisms and ecosystems and the impacts of human actions on the environment. EL individuals possess knowledge of biodiversity, ecological processes, and sustainability, enabling them to make informed, environmentally responsible decisions. This knowledge is essential for addressing ecological challenges and promoting sustainable development in all industries and communities. EL is a new concept in the mining industry introduced in this paper. Mining has a direct impact on ecology. This paper provides an overview of EL and its application in the mining industry, examining the potential benefits of EL for achieving sustainable and responsible mining. Results show that prioritizing EL Training (ELT) in the mining communities for countries with many mines has a higher priority than other industries. Also, in mining communities, ELT to workers, engineers engaged in mining, and government managers have a higher priority than other sectors in mining, respectively

Integration of renewable energy and sustainable development with strategic planning in the mining industry

With an increase in the world population, the global demand for minerals is rising, increasing energy consumption. Due to the distance of mines from urban areas, the energy required for mining is highly dependent on fossil fuels. Using renewable energies is an effective solution to reducing this problem. This study examines the challenges and opportunities of integrating renewable energy into mining operations and the impact of this integration on the attainment of Sustainable Development Goals (SDG). The present study also investigates the strategic management of renewable energy use in the mining sector via the Strengths, Weaknesses, Opportunities, and Threats (SWOT) method. The results indicate that despite the high potentialities of renewable energy in mining, much more investigation is required for the technical use of this technology in the mining industry. Using renewable energy can create new jobs, reduce environmental pollution, increase knowledge in the mining area, create a circular economy in the mining industry, and reduce mining operating costs. All mentioned factors can have a positive effect on sustainable development indicators. On the other hand, mine owners' lack of information about the positive effects of renewable energy, high investment, lack of skilled labor, and high maintenance costs can create challenges for using renewable energy in mines. The SWOT strategic management analysis results demonstrate that the strengths and possible opportunities of using this technology in mining outweigh the weaknesses and possible threats. Hence, the aggressive strategy, defined as the maximum use of strengths to benefit from created opportunities optimally, is suggested

Spare-part management in a heterogeneous environment.

Spare-part management has a significant effect on the productivity of mining equipment. The required number of spare parts can be estimated using failure and repair data collected under the name of reliability data. In the mining industry, failure and repair times are decided by the operational environment, rock properties, and the technical and functional behavior of the system. These conditions are heterogeneous and may change significantly from time to time. Such heterogeneity can change equipment's reliability performance and, consequently, the required number of spare parts. Hence, it is necessary for effective spare-part planning to check the heterogeneity among the reliability data. After that, if needed, such heterogeneity should be modeled using an adequate statistical model. Heterogeneity can be categorized into observed and unobserved caused by risk factors. Most spare-part estimation studies ignore the effect of heterogeneity, which can lead to unrealistic estimations. In this study, we introduce the application of a frailty model for modeling the effect of observed and unobserved risk factors on the required number of spare parts for mining equipment. Studies indicate that ignoring the effect of unobservable risk factors can cause a significant bias in estimation

Tire demand planning based on reliability and operating environment

Tires represent a critical spare part in mines. There is a shortage of medium and large tires. In addition, with increased mining activities and the creation of new mines, the demand for tires has increased significantly. Thus, it is particularly important for mining engineers to identify tire characteristics and correctly manage the spare part inventory. Spare parts management is critical from an operational perspective, especially in asset intensive industries, such as mining, as well as in organizations owning and operating costly assets. A knowledge of the tires’ behavior (historical data) must be considered together with the operating environment conditions (covariates). This study uses multiple regression analysis based on Cox’s regression model to incorporate machine operating environment information into systems reliability analysis to estimate spare parts. It considers a proportional hazard model and a stratified Cox regression model for time independent and dependent covariates. Based on the results, the study develops a mathematical model for spare parts estimation at the component level for non-repairable parts (tires). It validates the outcomes using a case study of loader tires in Sungun mine in Iran. There is a significant difference in the results of spare parts forecasting and inventory management when considering and not considering covariates

Prediction of remaining useful life (RUL) of Komatsu excavator under reliability analysis in the Weibull-frailty model

It is an essential task to estimate the remaining useful life (RUL) of machinery in the mining sector aimed at ensuring the production and the customer’s satisfaction. In this study, a conceptual framework was used to determine the RUL under the reliability analysis in a frailty model. The proposed framework was implemented on a Komatsu PC-1250 excavator from the Sungun copper mine. Also, the Weibull-frailty model was selected to describe the failure behavior and compare it with the classical-exponential model. The frailty model was also used to evaluate the impact of unobserved environmental conditions on the RUL values. Both applied models were fitted to the obtained data from 80 operational hours of the Komatsu PC-1250 excavator. Plotting the results from the reliability analysis of two models demonstrated that the mine system with the frailty model performs better than the classical model before reaching the reliability of 80%. Besides, the frailty model shows a coherent with the operational time of the excavator, while the classical model demonstrates a sinusoid variation. The obtained results may be used for the development of maintenance, preventive repairs planning, and the spare parts replacement intervals