A. Nouri Qarahasanlou; M. Ataei; R. Shakoor Shahabi
Abstract
Whether directly in the form of expenses or indirectly, the objective of maintenance in the mining industry is self-evident in time losses and loss of production. In this paper, the reliability-based maintenance is examined with a different insight than before. The system goes back to the Good As New ...
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Whether directly in the form of expenses or indirectly, the objective of maintenance in the mining industry is self-evident in time losses and loss of production. In this paper, the reliability-based maintenance is examined with a different insight than before. The system goes back to the Good As New (GAN) state or too Bad As Old (BAO) maintenance state; why so, the maintenance of the system shifts to the midrange state. On the other hand, the implementation of repairs is strongly influenced by the environmental factors that are known as the “risk factors”. Therefore, an analysis requires a model that integrates two basic elements: (1) incompleteness of the maintenance effect and (2) risk factors. Thus, an extensive proportional hazard ratio model (EPHM) is used as a combination of the Proportional Hazard Model (PHM) and the Hybrid Imperfect Preventive Maintenance model (HIPM) in order to analyze these elements. In this regards, four different preventive maintenance strategies are proposed. All four strategies are time-based including constant interval or periodic (the first and second strategies) and cyclic interval (the third and fourth strategies). The proposed method is applied for a Komatsu HD785-5 dump-truck in the Songun copper mine as a case study. The PM intervals with a mean value of risk factors for the four activities to reach the 80% reliability for the first and second strategies are about 5 and 48 hours. These intervals for the third strategy are calculated as 48.36, 11.58, 10.25, and 9.035, and for the fourth strategy are 5.06, 4.078, 3.459, and 1.92.
Amid Morshedlou; Hesam Dehghani; Seyed Hadi Hoseinie
Abstract
Utilizing the gathered failure data and failure interval data from Tabas coal mine in two years, this paper discusses the reliability of powered supports. The data sets were investigated using statistical procedures and in two levels: the existence of trend and serial correlation. The results show that ...
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Utilizing the gathered failure data and failure interval data from Tabas coal mine in two years, this paper discusses the reliability of powered supports. The data sets were investigated using statistical procedures and in two levels: the existence of trend and serial correlation. The results show that the powered supports follow the Gamma reliability function. The reliability of the machine decreases to almost zero after 520 operation hours and after 80 hours the probability of failure of powered supports increases to 60 percent. The failure rate of powered support shows an improving behavior and therefore a decreasing failure rate. In the beginning of the process, the failure rate is 0.021 failures per hour. This reaches the rate of 0.012 after a sudden decrease, thence forward on a gently decreasing rate and after 100 hours gets to the rate of 0.01. Regarding the maintenance policy and to protect the machine’s operation continuity, preventive maintenance strategy can be chosen. The reliability of the discussed machine can be maintained on a descent level by inspecting and controlling the parts in short term intervals. With regard to reliability plots of powered supports operation, preventive reliability-based maintenance time intervals for 80% reliability levels for powered supports is 15 hours.
