• 산업경영시스템학회지
• /
• 제41권2호
• /
• pp.24-31
• /
• 2018

As a system complexity increases and technology innovation progresses rapidly, leasing the equipment is considered as an important issue in many engineering areas. In practice, many engineering fields lease the equipment because it is an economical way to lease the equipment rather than to own the equipment. In addition, as the maintenance actions for the equipment are costly and need a specialist, the lessor is responsible for the maintenance actions in most leased contract. Hence, the lessor should establish the optimal maintenance strategy to minimize the maintenance cost. This paper proposes two periodic preventive maintenance policies for the leased equipment. The preventive maintenance action of policy 1 is performed with a periodic interval, in which their intervals are the same until the end of lease period. The other policy is to determine the periodic preventive maintenance interval minimizing total maintenance cost during the lease period. In addition, this paper presents two decision-making models to determine the preventive maintenance strategy for leased equipment based on the lessor's preference between the maintenance cost and the reliability at the end of lease period. The structural properties of the proposed decision-making model are investigated and algorithms to search the optimal maintenance policy that are satisfied by the lessor are provided. A numerical example is provided to illustrate the proposed model. The results show that a maintenance policy minimizing the maintenance cost is selected as a reasonable decision as the lease term becomes shorter. Moreover, the frequent preventive maintenance actions are performed when the minimal repair cost is higher than the preventive maintenance cost, resulting in higher maintenance cost.

• 대한기계학회논문집A
• /
• 제34권9호
• /
• pp.1325-1330
• /
• 2010

터빈설비 각 중요부품의 고장은 발전정지라는 큰 파급효과를 유발하며, 예기치 못한 고장으로 설비의 이용률이 감소하게 되면 막대한 경제적 손실이 발생한다. 현재 발전설비는 제작사에서 제시한 정비주기를 기준으로 보수적인 예방정비를 실시하고 있으나, 급변하는 경영환경에서 경쟁력을 유지하기 위해서는 신뢰도를 유지하면서 정비비용을 절감하는 신뢰도 기반 정비방법을 도입 해야 할 필요가 있다. 신뢰성 있는 정비주기를 선정하기 위해서는 설비의 고장이력에 대한 면밀한 분석을 통하여 고장확률을 예측해야 한다. 본 논문은 발전설비 중 터빈 각 부품들의 고장이력을 데이터베이스로 만들고, Weibull 함수를 이용하여 최적의 정비시점을 예측하며, 정비주기를 결정하는 방법에 대하여 연구하였다.

• 한국신뢰성학회지:신뢰성응용연구
• /
• 제15권1호
• /
• pp.6-11
• /
• 2015

Maintenance plays an important role in keeping product availability, reliability and quality at an appropriate level. In this paper, two-types of maintenance policies are studied following the expiration of two-dimensional (2D) free replacement warranty. Both the fixed-maintenance-period policy and the variable-maintenance-period policy are based on a specified region of the warranty defined in terms of age and usage where all failures are minimally repaired. An accelerating failure time (AFT) model is used to allow for the effect of usage rate on product degradation. The maintenance model that arises following the expiration of 2D warranty is discussed. The expected cost rates per unit time from the user's point of view are formulated and the optimal maintenance policies are determined to minimize the expected cost rate to the user. Finally numerical examples are given to illustrate the optimal maintenance polices.

• 교육시설 논문지
• /
• 제19권5호
• /
• pp.21-28
• /
• 2012

Current maintenance costs of the educational facilities have been determined by the years of services according to their foundation year. However, these maintenance costs have not considered maintenance and repairing. Therefore, this study suggests a new method to recalculate the years of services of schools by using the data of maintenance and repairing which is stored in the CAD drawing of the educational facilities. Also, since the data of maintenance and repairing has to be kept only for 5 years, the data is limited for the BTL project which has a maintenance period of 20 years. Thus, this study developed a new model to expand 5 years' data to the period of 20 years. This proposed model is expected to contribute in the maintenance and repairing of the BTL project.

• International Journal of Reliability and Applications
• /
• 제18권1호
• /
• pp.1-8
• /
• 2017

In this paper, we study an extended warranty model under minimal repair-replacement warranty (MRRW) which is suggested by Park, Jung and Park (2013). Under MRRW policy, the manufacturer is responsible for providing the minimal repair-replacement services upon the system failures during the warranty period. And if the failure occurs during the extended warranty period, only the minimal repair is conducted. Following the expiration of extended warranty, the user is solely responsible for maintaining the system for a fixed length of time period and replaces the system at the end of such a maintenance period. During the maintenance period, only the minimally repair is given for each system failure. The main purpose of this article is to suggest the extended warranty and replacement model with MRRW. Given the cost structures incurred during the life cycle of the system, we formulate the expected cost and the expected length of life cycle to obtain the expected cost rate.

• 전기학회논문지
• /
• 제62권8호
• /
• pp.1177-1183
• /
• 2013

In this paper, the analysis of inspection period bases on reliability is suggested in the field of traction power system. Even though there are several maintenance models, the most commonly used maintenance assessment has been focused on time based maintenance in real traction power systems. The maintenance intervals are selected on the basis of long-time experience. It ensures high availability and exact planning of staff. Reliability centered maintenance, which evaluates criticality and severity of each failure mode, achieves the operation, maintenance, and cost-effective improvement that will manage the risks of equipment. This paper deals with electrification in railway inspection frequency and applied reliability based inspection frequency instead of constant intervals. The distribution function of failure rate in traction power system belongs to Weibull function. Also, the fault data and the number of installed equipments for electrifications are collected. The failure history is investigated and classified in detail. Though these complicated procedures, it contribute to extend equipment lifetime and to reduce maintenance costs.

• Journal of Advanced Marine Engineering and Technology
• /
• 제23권6호
• /
• pp.785-793
• /
• 1999

There are two kinds of method in ship maintenance. One is the corrective maintenance and the other is the preventive maintenance. For these maintenances recently the stochastic techniques are widely used to keep the maximum availibility and the optimal maintenance period minimizing a given cost function. Thus this paper suggest a method to decide the optimal policy of ship's maintenances by using dynamic programming and the effectiveness of the method is verified through several examples in which failure rates and maintenance data of ship's machineries and parts are given.

• 한국신뢰성학회:학술대회논문집
• /
• 한국신뢰성학회 2005년도 학술발표대회 논문집
• /
• pp.115-120
• /
• 2005

This paper introduces models for preventive maintenance policies and considers periodic preventive maintenance policy with minimal repair when the failure of system occurs. It is assumed that minimal repairs do not change the failure rate of the system. The failure rate under prevention maintenance received an effect by a previously prevention maintenance and the slope of failure rate increases the model where it considered. Also the start point of failure rate under prevention maintenance considers the degradation of system and that it increases quotient, it assumed. Per unit time it bought an expectation cost from under this prevention maintenance policy. We obtain the optimal period time and the number for the periodic preventive maintenance by using Nakagawa's Algorithm, which minimizes the expected cost rate per unit time. Finally, it suppose that the failure time of a system has a Weibull distribution as an example and we obtain an expected cost rate per unit time the optimal period time and the number when cost of replacement and cost of minimal repair change.

• 에너지공학
• /
• 제20권2호
• /
• pp.154-162
• /
• 2011

예방정비기준은 기기의 높은 신뢰성을 유지하기 위해 정비방법을 문서화한 것으로 기기별 최적화된 예방정비 항목과 주기를 명시하고 기기의 성능저하 메커니즘을 설명하는 지침서이다. 기존의 기기 또는 설비에 대한 정비전략은 상태감시 정비보다는 일정한 주기가 되면 정비를 수행하는 주기정비가 주된 전략이었다. 본 논문은 원전 정지형 여자기에 대하여 기존의 주기정비 형태가 아닌 상태기반 정비 기법을 강화하고 정비 프로그램을 표준화하여 최적화된 정비전략을 구축하기 위한 예방정비 기준을 개발한 내용으로 기기 신뢰성, 발전소 이용률을 향상시킬 수 있는 기반이 될 것으로 판단된다.

• 전기학회논문지
• /
• 제62권11호
• /
• pp.1511-1519
• /
• 2013

This paper proposes the allocation method for capacitor-reactor banks in a distribution system with dispersed generators to reduce the installation costs, the maintenance costs and minimize the loss of electrical energy. The expected lifetime and maintenance period of devices with moving parts depends on the total number of operations, which affects the replacement and maintenance period for aging equipment under a limited budget. In this paper, the expected device lifetimes and the maintenance period are included in the formulation, and the optimal operation status of the devices is determined using a genetic algorithm. The optimal numbers and locations for capacitor-reactor banks are determined based on the optimal operation status. Simulation results in a 69-bus distribution system with the dispersed generator show that the proposed technique performs better than conventional methods.