• 산업경영시스템학회지
• /
• 제20권44호
• /
• pp.263-271
• /
• 1997

This paper presents a preventive maintenance model for determining the preventive replacement period of a system in which a failure rate is affected by the cumulative damage of fault and inspection. Especially, the failure rate function is considered to be a function of the cumulative damage of the fault and inspection time. Types of replacement considered are preventive replacement and failure replacement. Failure rate and expected cost function between replacement are derived. An optimal policy is obtained that minimizes the average cost per unit time for preventive replacement, failure replacement, inspection and repair.

• 품질경영학회지
• /
• 제49권3호
• /
• pp.299-312
• /
• 2021

Purpose: We provide a condition-based maintenance policy where a surrogate variable is used for monitoring system performance. We constructed a risk function by taking into account the risk and losses accompanied with erroneous decisions. Methods: Assuming a unique degradation process for the performance variable and its specific relationship with the surrogate variable, the maintenance policy is determined. A risk function is developed on the basis of producer's and consumer's risks accompanied with each decision. With a strategic safety factor considered, the optimal threshold value for the surrogate variable is determined based on the risk function. Results: The condition-based maintenance is analyzed from the point of risk. With an assumed safety consideration, the optimal threshold value of the surrogate variable is provided for taking a maintenance action. The optimal solution cannot be obtained in a closed form. An illustrative numerical example and solution is provided with a source code of R program. Conclusion: The study can be applied to situation where a sensor signal is issued if the system performance begins to degrade gradually and reaches eventually its functional failure. The study can be extended to the case where two or more performance variables are connected to a same surrogate variable. Also estimation of the distribution parameters and risk coefficients should be further studied.

• 품질경영학회지
• /
• 제29권3호
• /
• pp.39-48
• /
• 2001

Preventive maintenance(PM) is an action taken on a repairable system while it is still operating, which needs to be carried out in order to keep the system at the desired level of successful operation. In this paper, we consider a Bayesian approach to determine an optimal periodic preventive maintenance policy. When the failure time is Weibull distribution with uncertain parameters, a Bayesian approach is established. Some numerical examples are presented for illustrative purpose.

• 대한산업공학회지
• /
• 제8권2호
• /
• pp.33-36
• /
• 1982

This paper considers preventive maintenance policies for a system with two types of units which is subject to deterioration. Two generalized models are investigated ; a preventive maintenance policy based on the cumulative operating time and a policy based on the number of minimal repairs performed. Optimal preventive maintenance policies which minimize the expected average cost per unit time including the earning loss due to the deterioration are discussed and some numerical examples are given.

• 한국신뢰성학회:학술대회논문집
• /
• 한국신뢰성학회 2000년도 추계학술대회
• /
• pp.329-333
• /
• 2000

Delay time analysis is a pragmatic mathematical concept readily embraced by engineers which has been developed as a means to model maintenance decision problem. This paper considers an inspection period using delay time analysis for fishing vessel equipment. We assume that delay time distribution is Weibull and inspections are perfect. In this paper, we determine the optimal inspection period which minimize the expected downtime per unit time.

• Journal of the Korean Data and Information Science Society
• /
• 제13권1호
• /
• pp.55-65
• /
• 2002

In this paper we present a Bayesian approach for determining an optimal maintenance policy following the expiration of warranty for a repairable system. We consider two types of warranty policies : non-renewing free replacement warranty (NFRW) and non-renewing pro-rata warranty (NPRW). The mathematical formula of the expected cost rate per unit time is obtained for NFRW and NPRW, respectively. When the failure time is Weibull distribution with uncertain parameters, a Bayesian approach is established to formally express and update the uncertain parameters for determining an optimal maintenance policy. We illustrate the use of our approach with simulated data.

• 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.

• Journal of the Korean Data and Information Science Society
• /
• 제27권6호
• /
• pp.1557-1564
• /
• 2016

최근에 기본보증이 종료된 이후에 주어지는 시스템의 추가보증에 대한 사용자의 관심이 증가되고 있다. 따라서 본 논문에서는 사용자 측면에서 비재생보증 하에서의 이단계 보전정책을 제안하였다. 이단계 보전정책의 첫 번째 단계에서는 추가보증을 구입할 것인지의 여부를 결정하고, 두 번째 단계에서는 보증이 종료된 이후의 최적의 교체 주기를 결정한다. 이때, 추가보증 동안에 발생된 시스템의 고장에 대해서는 판매자에 의해서 무료로 최소수리가 이루어진다. 최적의 이단계 보전정책을 결정하기 위해서 사용자 측면에서 기대비용을 사용하였으며, 끝으로 시스템의 고장시간이 와이블 분포를 따를 때 수치적 예를 통하여 제안된 이단계 보전정책을 설명하였다.

• 품질경영학회지
• /
• 제29권2호
• /
• pp.46-53
• /
• 2001

In this paper, a preventive maintenance(PM) policy for a repairable system is considered. The failure rate model proposed by Park et at.(2000) is generalized by assuming that after each PM not only the PM slows down the degradation process of the system but also reduces down the system failure rate by a certain fixed amount. Long-run expected cost rate of the PM policy is derived and the properties of joint solution of the optimal PM period and optimal number of PM which minimizes the expected cost rate are obtained. Numerical examples for the case of a Weibull-type failure rate are given.

• 벤처창업연구
• /
• 제9권2호
• /
• pp.81-86
• /
• 2014

본 논문에서는 그룹교체 정책과 예비품 재고정책을 동시에 고려하여 최적화하는 방안을 제시한다. 일반적으로 보전정책들은 예비품의 재고가 늘 가용하다고 가정하고 있으나 예비품의 재고 확보 여부에 의해 보전활동은 영향을 받을 수밖에 없다. 동일한 여러 유닛들이 동시에 운용될 때 이용되는 그룹교체정책을 바탕으로 이를 지원하기 위한 최적 재고수준을 결정한다. 일정한 개수의 유닛이 고장 나는 시점에서 그룹교체를 수행한다. 예비품의 재고는 일정 횟수의 그룹교체를 할 만큼 주문하여 유지한다. 보전비용과 재고비용 등 운용비용을 최소화할 수 있는 최적의 그룹교체 주기와 재고수준을 구한다.