• Journal of Applied Reliability
• /
• v.7 no.1
• /
• pp.13-22
• /
• 2007

A preventive maintenance model, caller FNBM (${\alpha},{\delta},{\gamma}$) model, is proposed to decide an optimal repair number under achieved availability requirements (r) along with taking two types of failures (repairable or irrepairable) into account. In this model, the current system is replaced by a new one in case when it doesn't meet the achieved availability requirement, even though it is repairable failure; Othewise it is replaced in time of the first irrepairable failure. Assumed that the j-th failure is repairable with probability ${\alpha}_j$ minimal repairs are allowed for repairable failure between replacements. Expected cost rate for preventive maintenance model is developed using NHPP (Non - Homogeneous Poisson Process) in order to de term in the optimal number $n^*$, also numerical examples are shown in order to explain the proposed model. Since the proposed FNBM (${\alpha},{\delta},{\gamma}$) model includes Park FNBM model (1979) and Nakagawa FNBM (p) model (1983) m this proposed model is thought to be better than previous model, especially for weapon system which requires availability as primary parameter.

• Journal of the Korean Data and Information Science Society
• /
• v.25 no.4
• /
• pp.791-798
• /
• 2014

Wu and Clements-Croome (2005) suggest the preventive maintenance (PM) model with random maintenance quality. They assume that each PM resets the failure rate to zero and the rate of increases of the failure rate gets higher after each additional PM. However a system may not be restored to as good as new immediately after the completion of PM. Thus, this paper modifies the Wu and Clements-Croome's PM model and then the optimal PM policy is suggested. To determine the optimal PM policy, we utilize the expected cost rate per unit time for our model. That is, we obtain the optimal number and the optimal period by minimizing the expected cost rate per unit time. The numerical examples are presented for illustrative purpose.

• Industrial Engineering and Management Systems
• /
• v.8 no.4
• /
• pp.221-227
• /
• 2009

There are customer services jointly provided by two facilities so that each customer will complete the course made up of both facilities' sub-services. The two facilities are assumed invested respectively by an infrastructure owner and one subordinate facility owner, whose partnership is built on their capital investments. This paper presents a mathematical model of Stackelberg competition between the two facility owners to derive their optimal Nash equilibrium. In this study, each facility owner's profit is consisted of fixed revenue fractions of sold services, operating costs (including depreciation cost) and maintenance costs of her facility. The maintenance costs of one facility are incurred both by failures and deterioration due to usage. Moreover, for both facilities, failures are rectified immediately by minimal repairs and preventive maintenance is carried out at a fixed time epoch. Additional assumptions are also employed to develop the model such as customer arrivals are manipulated to follow a Poisson process, and each facility's lifetime is independently Weibull-distributed. The Stackelberg game proceeds as follows. At the first stage of decision making process, the infrastructure owner (acting as a leader) decides the allocation of revenue shares based on her self-interest. After observing the allocation of revenue shares, the subordinate facility owner determines her own optimal price of services. This paper investigates actions and reactions of the two partners in the system. Then analytical conditions are proposed to achieve a unique optimal Nash equilibrium. Finally, some suggestions for further research are discussed.

• Journal of Navigation and Port Research
• /
• v.33 no.6
• /
• pp.429-436
• /
• 2009

Container cranes are main equipments to load and unload containers to container ships at container terminals. If a crane breakdowns, it can reduce the productivity of container terminals. This paper deals with Preventive Maintenance (PM) schedules for the container cranes. The cranes consist of many parts and we analyze the structure of a container crane using the tree models. Next, we apply a Genetic Algorithm (GA) for determining optimal PM schedule and evaluate the performance of the proposed method through simulation system Finally, we explain how to adjust the PM schedule found in industry based on work schedules.

• Journal of Korean Society for Quality Management
• /
• v.28 no.3
• /
• pp.11-17
• /
• 2000

This paper presents a model for determining the optimal number of general repairs and supplementary input cost limit rate in addition to minimal repair cost rate to implement preventive maintenance. The basic concept parallels the periodic replacement model with minimal repair at failure introduced by Barlow and Hunter(1960) and Park(1979), only difference being the replacement signalled by the number of previous general repairs performed on the system. A general repair brings the state of the system to a certain better state than before repaired. Numerical examples are provided.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.56 no.2
• /
• pp.254-259
• /
• 2007

PM(Preventive Maintenance) can avail the generating unit to reduce cost and gain more profit in a competitive supply-side power market. So, it is necessary to perform reliability analysis on the power systems in which reliability is essential. Thus, to schedule optimal PM planning based on reliability that is defined RCM(Reliability-Centered Maintenance), FMECA(Failure Mode Effects and Criticality Analysis) assessment is very important. Therefore, in this paper, the procedure of FMECA assessment for optimal RCM is proposed by probabilistic approach using real historical failure data of combustion-turbine generators in Korean power systems. The stochastic FMECA is performed based on the effects of probable failure modes of combustion-turbine generating unit.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.2
• /
• pp.1-7
• /
• 2016

Although the second driving device of KTX, which consists of the wheel and the axle reduction gears unit, is a mechanically integrated structure, its preventive maintenance (PM) requires two separate intervals due to the different technical requirements. In particular, these subsystems perform attaching and detaching work simultaneously according to the maintenance directive. Therefore, to reduce the unnecessary amount of PM and high logistic availability of the train, it is important to optimize PM with regard to reliability-centered maintenance toward a cost-effective solution. In this study, fault tree analysis and reliability of the subsystems, considering the criticality of the components, were performed using the data derived from field data in maintenance. The cost optimization of the PM was derived from a genetic algorithm considering the target reliability and improvement factor. The cost optimization was derived from a maximum of the fitness function of the individual in generation. The optimal TBO of them using the genetic algorithm was 2.85x106 km, which is reduced to approximately 21% compared to the conventional method.

• Communications for Statistical Applications and Methods
• /
• v.12 no.1
• /
• pp.1-9
• /
• 2005

Burn-in is an engineering method which is used to eliminate early failures of products or systems after they have been produced. Recently, various models for determining optimal burn-in times have been developed, where some preventive maintenance policies were considered together with burn-in problem. In this paper, a survey of recent research in burn-in is undertaken.

• Journal of Korean Institute of Industrial Engineers
• /
• v.39 no.6
• /
• pp.599-608
• /
• 2013

This study is intended to propose optimal maintenance organization to process industry, especially paper industry by analyzing maintenance organization of paper industry and finding out how the maintenance organization and the allocation of maintenance resources influence maintenance performance indices here in this paper. In this study, we analyzed the maintenance organization in detail and studied correlation between maintenance organization and equipment failure rate for the major top six domestic paper-mills in market share. According to the study, the maintenance organization has been changed in accordance with its business environment, but its performance was different by both the allocation way of maintenance resources and the structure of maintenance organization. For paper industry, whose availability is the most important key index that determines the success or failure of a business, it turns out to be the most effective strategy that operates the combination maintenance combined central maintenance with area maintenance and allocates the maintenance resources mainly for preventive maintenance. In particular, it turned out to be that there is the strong positive correlation between the rate of shift workers and the equipment failure rate. The results of this study is not limited to paper industry, but expandable to other industry. So it is expected that the direction of the maintenance organization would be given to the company which is struggling to improve its availability.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.8
• /
• pp.1457-1465
• /
• 2016

A RCM approach to maintenance of the catenary system of electric railway is proposed. The proposed RCM approach provides a maintenance-oriented FMECA procedure to derive critical failure modes by analyzing failure effects and a RCM decision logic tree to suggest optimal maintenance works for the derived failure modes. By applying the proposed RCM procedures to the catenary system of high speed railway, it is suggested that strand breaks of dropper and voltage equalizing wire, and trolly wire wear-out are the critical failure modes for whom maintenance works based on condition monitoring should be applied instead of conventional time-based preventive maintenance. It is also proposed by reliability analysis that replacement time of dropper can be reduced from 18 years to 10 years. These results show that the proposed RCM approach can optimize the maintenance procedures of catenary system.