• Title, Summary, Keyword: Imperfect Maintenance

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Optimal Preventive Maintenance Policy with Cost-dependent Improvement Factor (비용 종속적인 개선지수를 고려한 최적 예방보전 정책)

  • Hong, Seok-Soo;Park, Jong-Hun;Lie, Chang-Hoon
    • Journal of Korean Institute of Industrial Engineers
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    • v.36 no.2
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    • pp.108-116
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    • 2010
  • The maintenance of a deteriorating system is often imperfect. Previous studies have shown that the imperfect preventive maintenance (PM) can reduce the wear out and aging effects of deteriorating systems to a certain level between the conditions of as good as new and as bad as old. In this paper, we employ the concept of the improvement factor in investigating two optimal PM policies; failure limit policy and periodic PM policy. We redefine the improvement factor model as a function of the cost of PM, using this concept, we derive the conditions of optimal PM policies and formulate expressions to compute the expected cost rate. Based on this information, the determination of the maintenance policies which minimize the cost rate is examined. Numerical examples for the Weibull distribution case are also given.

Developing a Non-Periodic Preventive Maintenance Model Guaranteeing the Minimum Reliability (최소 신뢰도를 보장하는 비 주기적 예방보전 모형 개발)

  • Lee, Juhyun;Ahn, Suneung
    • Journal of Applied Reliability
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    • v.18 no.2
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    • pp.104-113
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    • 2018
  • Purpose: This paper proposes the non-periodic preventive maintenance policy based on the level of cumulative hazard intensity. We aim to construct a cost-effectiveness on the proposed model with relaxing the constraint on reliability. Methods: We use the level of cumulative hazard intensity as a condition variable, instead of reliability. Such a level of cumulative hazard intensity can derive the reliability which decreases as the frequency of preventive maintenance action increases. We also model the imperfect preventive maintenance action using the proportional age setback model. Conclusion: We provide a numerical example to illustrate the proposed model. We also analyze how the parameters of our model affect the optimal preventive maintenance policy. The results show that as long as high reliability is guaranteed, the inefficient preventive maintenance action is performed reducing the system operation time. Moreover, the optimal value of the proposed model is sensitive to changes in preventive maintenance cost and replacement cost.

Parameter estimation using GA with failure data under preventive maintenance (예방 정비가 실시된 고장 자료에서의 유전 알고리즘을 이용한 모수 추정)

  • 윤영원;정일한;김종운;신주환
    • Journal of Applied Reliability
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    • v.1 no.1
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    • pp.47-54
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    • 2001
  • This paper considers the parameter estimation problem of the failure intensity function and maintenance effect in a repairable system. We propose estimation procedures for repairable systems on which preventive maintenance is performed. The failure process is modeled by a proportional age reduction model [Brown, Mahoney and Sivazlian(1983)] which is useful to model the imperfect effect of preventive maintenance. When failure and maintenance (preventive) times are given, the maximum likelihood method is used to estimate the maintenance effect and the parameters of intensity function, simultaneously We obtain the maximum likelihood estimators using a genetic algorithm. A numerical example is also presented.

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Cost Optimization of Ineffective Periodic Preventive Maintenance

  • Jung, Gi-Mun;Park, Dong-Ho;Yum, Joon-Keun
    • Communications for Statistical Applications and Methods
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    • v.6 no.1
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    • pp.99-106
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    • 1999
  • This paper considers an imperfect repair model for which the repairable system is maintained preventively at periodic times and is replaced by a new system when a predetermined number of preventive maintenance has been applied. our main objective of this is to determine the optimal number of preventive maintenances before the system is replaced and the optimal length of interval between two consecutive preventive maintenances under a new repair model which is referred to as an ineffective preventive maintenance. Such a model assumes a periodic preventive maintenance in which the system is effectively maintained with a certain probability. Otherwise the system is not improved at all after each maintenance and thus the failure rate remains the same as before. The criteria to determine the optimal number of preventive maintenances and length of period is the expected cost rate per unit time for an infinite time span. We give the explicit expressions for the expected cost rate per unit time. Some numerical examples are presented for illustrative purposes.

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On determining a non-periodic preventive maintenance schedule using the failure rate threshold for a repairable system

  • Lee, Juhyun;Park, Jihyun;Ahn, Suneung
    • Smart Structures and Systems
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    • v.22 no.2
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    • pp.151-159
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    • 2018
  • Maintenance activities are regarded as a key part of the repairable deteriorating system because they maintain the equipment in good condition. In practice, many maintenance policies are used in engineering fields to reduce unexpected failures and slow down the deterioration of the system. However, in traditional maintenance policies, maintenance activities have often been assumed to be performed at the same time interval, which may result in higher operational costs and more system failures. Thus, this study presents two non-periodic preventive maintenance (PM) policies for repairable deteriorating systems, employing the failure rate of the system as a conditional variable. In the proposed PM models, the failure rate of the system was restored via the failure rate reduction factors after imperfect PM activities. Operational costs were also considered, which increased along with the operating time of the system and the frequency of PM activities to reflect the deterioration process of the system. A numerical example was provided to illustrate the proposed PM policy. The results showed that PM activities performed at a low failure rate threshold slowed down the degradation of the system and thus extended the system lifetime. Moreover, when the operational cost was considered in the proposed maintenance scheme, the system replacement was more cost-effective than frequent PM activities in the severely degraded system.

Developing the Optimal Decision-Making Process through Preventive Maintenance Policy Based on the Reliability Threshold for Leased Equipment (대여장비의 신뢰도 기반 예방보전 정책을 통한 최적 의사결정 과정 개발)

  • Bae, Kiho;Lee, Juhyun;Park, Seonghwan;Ahn, Suneung
    • Journal of Applied Reliability
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    • v.17 no.3
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    • pp.246-255
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    • 2017
  • Purpose: This study proposes the optimal PM (preventive maintenance) policy of leased equipment for lessee's decision-making using two types of reliability condition. Methods: We consider reliability threshold based PM model. Equipment reliability is estimated and used as condition variable. The effect of repair for maintenance is imperfect and represented by age reduction factor. Results: We provide two PM policies. Policy 1 is focused on minimized total cost. This policy guarantees reliability threshold until last maintenance action. Policy 2 focus on maintaining reliability threshold during leased period. The proposed approach provides optimal reliability threshold under number of PM. Through result, we finally construct decision-making process for lessee using reliability threshold and end of reliability. Conclusion: This study provides two PM policy for lessee's decision-making. Through numerical example, we get a result of optimal reliability threshold, number of PM, optimum alternative under lessee's reliability condition.

A Value-Based Real Time Pricing Under Imperfect Information on Consumer Behavior

  • Kim, Bal-Ho H.
    • Journal of Electrical Engineering and Technology
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    • v.4 no.1
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    • pp.49-54
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    • 2009
  • One of the major challenges confronting a multiservice electric utility is the establishment of the right prices for its services. The key objectives of particular pricing schemes are reasonableness of company earnings, economic efficiency, the responsiveness of supply and of the allocation of sources to the desires of consumers, and maintenance of some degree of competition. This paper proposes a value-based pricing mechanism amenable to the current deregulation situation in electricity market allowing service differentiation. The proposed pricing mechanism can be implemented in a nodal auction model, and can also be applied to direct load control.

A Value-based Real Time Pricing Under Imperfect Information on Consumer Behavior

  • Kim, Balho H.;Park, Jong-Bae
    • Journal of Energy Engineering
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    • v.8 no.4
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    • pp.505-511
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    • 1999
  • One of the major challenges confronting a multiservice electric utility is the establishment of the right prices, for its services. The key objectives of particular pricing schemes are reasonableness of company earnings. Economic efficiency, the responsiveness of supply and of the allocation of sources to the desires of consumers, and maintenance of some degree of competition. This paper proposes a value-based pricing mechanism amenable to the current deregulation situation in electricity market allowing service differentiation. The proposed pricing mechanism can be implemented ina nodal auction model, and can also be applied to direct load control.

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