점검-정비 모형에서 열화부품의 발견확률을 고려한 시스템의 최적 점검주기

김대경,박병노,송미옥,임재학 한국신뢰성학회 2022 신뢰성응용연구 Vol.22 No.4

Purpose: The determination of the optimal inspection interval of a system is a critical factor that can influence its maintenance. Frequent inspections yield shorter inspection intervals and higher inspection costs compared with infrequent inspections, which lead to an increase in the total maintenance cost due to the frequent occurrence of failures. The objective of this study is to determine the optimal inspection interval, which minimizes the total expected cost until the system is overhauled. Methods: We developed an inspection - maintenance cost model by considering the unit inspection cost, the cost for preventive maintenance, and the cost for corrective maintenance as well as the cost and quantity of a component, the distribution of the lifetime of components, and the probability of finding fault or failure during inspections. Results: We propose a novel method for determining the optimal inspection interval, which minimizes the total expected cost. The proposed method can be applied to systems consisting of one or more types of components. The data, which is derived from the case study that is documented in the previous research [13], are utilized to illustrate that the proposed method is effective for determining the optimal inspection interval and for conducting sensitivity analysis. Finally, we apply the proposed method to determine the optimal inspection interval pertaining to a component of auxiliary power that is built into railway trains. Consequently, we observed that a relationship exists between the reduction in the cost of operating the system and the current inspection interval. Conclusions: The proposed method can be effective for other repairable systems, which undergo inspection, preventive maintenance, and corrective maintenance.

Genetic Algorithm-based Optimum Inspection Interval Determination for Plant Maintenance

(Kwang Kyu Seo) 상명대학교 공학기술연구소 2004 공학기술연구 Vol.2004 No.1

The operation and management of a plant require proper accounting for the constraints coming from reliability requirements as well as from budget and resource considerations. Most of the mathematical methods to decide the inspection time interval for plant maintenance by reliability theory are too complicated to be solved. Moreover, the mathematical and theoretical models are not usually cases in the practical applications. In order to overcome these problems, we propose a new the method for a genetic algorithm based optimal inspection interval determination to minimize the maintenance cost with reliability theory. The most merit of the proposed method is to decide the inspection interval for a plant machine of which failure rate λ(t) conforms to any probability distribution. Therefore, this method is more practical. The efficiency of the proposed method is verified by comparing the results obtained by GA-based method with the inspection model having regular time interval.

위험도평가 기반의 항공기 구조물 RCM 적용 방안 연구

김근원 ( Keun Won Kim ),신기수 ( Ki Su Shin ) 한국항공경영학회 2013 한국항공경영학회지 Vol.11 No.1

신뢰도중심정비는 최소의 비용으로 장비의 요구 신뢰도를 유지하기 위한 최적의 정비 방법을 찾는데 사용되는 기법이다. 항공기 구조물에 대한 건전성을 보장하고 총 수명주기 비용을 최소화하기 위하여 신뢰도중심정비 기반의 정비정책 수립이 중요하다. 신뢰도중심정비 분석에 있어서 항공기 구조물의 건전성을 보장하기 위해서는 확률론적 파괴역학 기반의 위험도평가를 수행하고, 이를 신뢰도중심정비 분석에 반영하는 노력이 필요하다. 특히 항공기 구조물의 경우 운영단계에서의 실제 운용 정비자료를 이용하여 위험도평가를 수행함으로써 신뢰도중심정비 능력을 극대화 시킬 수 있다. 본 연구에서는 신뢰도중심정비와 위험도평가 개념을 알아보고, 신뢰도중심정비 적용을 위한 위험도 평가 활동을 분석하였다. 그리고 항공기 구조물의 신뢰도중심정비 적용을 위한 위험도평가 프로세스를 제시하고, 수치예제로 cockpit upper longeron에 대한 위험도평가를 수행하였다. 연구수행 결과 실제운용 정비자료를 이용하여 위험도평가를 수행함으로써 개선된 정비계획 및 점검주기 산정이 가능함을 확인할 수 있었다. RCM(Reliability Centered Maintenance) is an analytical process to determine the appropriate maintenance strategies. RCM is recommended to ensure the integrity of aircraft structural and reduce total life cycle cost. Processing RCM analytical, it is one of essential factor to regard the risk assessment based on probabilistic fracture mechanics. Especially, the probabilistic risk assessment, which was conducted by utilizing operational maintenance data during sustainment phase, could enhance the ability of RCM. In this paper, the concept of RCM and risk assessment was described. Furthermore, the activity of risk assessment for applying RCM has been analysis. In addition, we suggest the risk assessment process for applying RCM of aircraft structural. As a numerical example, the cockpit upper longeron was selected to evaluate probabilistic risk assessment process. In conclusion, it was revealed that the proposed process could improve for maintenance plan and inspection interval.

예방정비 후 신뢰성 변동 모니터링 기법에 관한 연구

김종운(Kim, Jongwoon),엔드하르타 알폰수스 주란토(Alfonsus Julanto Endharta) 한국도시철도학회 2021 한국도시철도학회논문집 Vol.9 No.3

철도시스템과 같이 수명주기가 길고 지속적인 유지보수가 필요한 시스템은 운영 및 유지보수(O&M: Operation & Maintenance) 단계에서 효과적인 신뢰성 관리가 매우 중요하다. 따라서 유지보수의 품질 확보 및 효과적인 유지보수 정책 수립을 위해 예방정비 후 신뢰성 변동을 모니터링하는 것이 필요하다. 예방정비 후 경과시간을 기준으로 구간고장률이 증가하면, 예방정비의 효과가 크고 그 주기를 줄임으로써 신뢰성을 향상할 수 있음을 의미한다. 그 반대의 경우는 예방정비 품질에 문제가 있어 예방정비가 역효과를 내고 있음을 의미한다. 본 연구에서는 예방정비 후 경과시간을 기준으로 구간고장률을 산출하는 방법을 제안한다. 그리고, 수치 예제를 통해 제안한 방법의 적용 절차 및 결과를 설명한다. For systems with long life cycles and requiring continuous maintenance, such as railway systems, an effective reliability management is critical at the Operational and Maintenance (O&M) stage. Thus, it is necessary to monitor reliability changes after preventive maintenance (PM) performance to ensure the quality of maintenance and to establish effective maintenance policies. An increase in the interval failure rate based on elapsed time after PM shows that the effectiveness of the PM is significant and the reliability can be improved by reducing its PM interval. In the opposite case, there is a problem with the quality of PM, which means that PM performance is counterproductive. In this study, a method for calculating the interval failure rate based on the elapsed time after every PM is proposed. Furthermore, the application procedures and results of the proposed method are illustrated through numerical examples.

항공기 정비계획을 위한 J79 엔진 Transfer Gearbox의 고장데이터 분석

최재만(Jae Man Choi),양승효(Seung Hyo Yang),황영하(Young Ha Hwang),손익상(Ik Sang Son),온용섭(Yong Sub On),김영진(Young Jin Kim) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.6

고장의 특성을 예상하는 것은 미래의 고장을 예견하고 최적의 교체간격을 결정할 수 있도록 해주기 때문에 정비 계획에서 매우 중요하다. 본 연구에서는 신뢰도 해석에서 가장 전통적인 방법 중의 하나인 확률지에 도시하는 기법을 이용하여 J79 엔진 Transfer Gearbox의 고장 분포를 검토하였다. 고장 데이터에 대한 적절한 분포를 찾기 위해서 다양한 확률분포가 이용되었으며, 얻어진 상관계수는 고장데이터가 대수정규분포에 가장 근접함을 나타내었다. 예상되는 비계획 정비행위의 횟수와 다양한 비용 비율에 대해서 최적의 교체간격을 구하였다. Forecasting possible failure characteristics is very important in maintenance planning because it helps in predicting any future failures and determining the optimum replacement interval. This paper examines the time?to-failure distribution of the transfer gearbox of a J79 engine by using a probability plotting technique which is one of the most convenient techniques for reliability analysis. Various probability distributions are evaluated for determining the suitable probability distribution of the failure data of the transfer gearbox, and the resulting correlation coefficient indicates that failure data have a lognormal distribution. The expected number of unscheduled maintenance actions and the optimum replacement interval for various values of cost ratios are determined.

‘좇다’와 ‘쫓다’의 의미 관계

정희창 ( Jeong¸ Hui-chang ) 반교어문학회 2020 泮橋語文硏究 Vol.0 No.55

‘좇다’와 ‘쫓다’는 ‘무엇을 따르다’는 의미를 갖는다는 점에서 공통되지만 ‘좇다’가 추상적인 대상이 나타나는 반면 ‘쫓다’는 구체적인 대상이 나타난다는 차이가 있다. 또한 ‘쫓다’에는 ‘무엇을 따르다’와 상반되는 ‘무엇을 물리치다’는 의미가 나타나는데 ‘물리치다’의 의미일 때는 추상적인 대상도 나타날 수 있다. ‘쫓다’의 ‘따르다’와 ‘물리치다’는 ‘일정한 간격의 유지’라는 의미를 공유한다고 생각된다. 다만 주체와 서술어가 지시하는 대상과의 관계에서 ‘일정한 간격’의 동작 방향이 어디에 놓이느냐에 따라 의미가 갈라진다. 주체의 관점에서 멀어지려는 대상과의 간격을 조정함으로써 일정한 간격을 유지하고자 하는 경우 ‘따르다’의미가 나타나는데 이 의미가 바로 ‘쫓다1’에 해당한다. 이와 달리 가까워지려는 대상과의 간격을 일정하게 유지하고자 하는 경우 ‘물리치다’의 의미가 나타나는데 이 의미가 ‘쫓다2’에 해당한다. ‘좇다’ and ‘쫓다’ are common in that they have the meaning of 'to follow something', but there is a difference that ‘좇다’ shows an abstract object while ‘쫓다’ shows a specific object. In addition, the meaning of ‘to defeat something’ contrary to ‘쫓다’ appears in ‘to chase’. It is thought that ‘따르다’ and ‘물리치다’ share the meaning of ‘keeping at regular intervals’. The two meanings of ‘쫓다’ can be described as being divided according to the direction of the central object, ‘maintaining a certain distance.’ When an object is physically distant from the subject and needs to be maintained at a certain distance, the meaning of ‘따르다’ appears. On the contrary, when an object is closer to the subject and needs to maintain a certain distance, the meaning of ‘물리치다’ appears. In other words, when the meaning of ‘쫓다’ is divided into ‘쫓다1’, ‘쫓다2’, it can be said that the object being the center of the movement is a contextual meaning derived according to the direction of movement.

철도차량의 좌우측절단자료를 이용한 2단계 상태기반 점검주기 연구

박종훈(Jong Hun Park),박병노(Byoung-Noh Park),송미옥(Mi-Ok Song),성시일(Si-Il Sung) 한국신뢰성학회 2022 신뢰성응용연구 Vol.22 No.2

Purpose: This paper introduces two-phase condition-based maintenance by analyzing left-truncated and right-censored field data, with characteristics managed by the existing maintenance schedule. Methods: The failure rate was initially observed as a constant failure rate (CFR) and, after a certain point, as an increasing failure rate (IFR). Therefore, a two-phase condition-based maintenance policy with each stage maintenance cycle was proposed. In addition, a maintenance model was developed to determine the optimal maintenance schedule in terms of economic feasibility. Results: The optimal maintenance schedule was derived by minimizing the total cost, including the inspection cost, failure cost, and improvement factor. Further, changes in the optimal maintenance schedule were examined based on the ratios of the inspection cost, failure cost, and improvement factor. Conclusion: Designing a maintenance policy to evaluate the system conditions and mutual adequacy between the cost and improvement effect in terms of light and medium maintenance is essential.

필드데이터에 의한 철도차량 신호장치 구성품의 최적 교체주기 결정에 관한 연구

박병노,김경화,김재훈 한국안전학회 2023 한국안전학회지 Vol.38 No.2

Rolling stock maintenance, which focuses on preventive maintenance, is typically implemented considering the potential harm that may be inflicted to passengers in the event of failure. The cost of preventive maintenance throughout the life cycle of a rolling stock is 60%–75% of the initial purchase cost. Therefore, ensuring stability and reducing maintenance costs are essential in terms of economy. In particular, private railroad operators must reduce government support budget by effectively utilizing railroad resources and reducing maintenance costs. Accordingly, this study analyzes the reliability characteristics of components using field data. Moreover, it resolves the problem of determining an economical replacement interval considering the timing of scrapping railroad vehicles. The procedure for determining the optimal replacement interval involves five steps. According to the decision model, the optimal replacement interval for the onboard signal device components of the “A” line train is calculated using field data, such as failure data, preventive maintenance cost, and failure maintenance cost. The field data analysis indicates that the mileage meter is 9 years, which is less than the designed durability of 15 years. Furthermore, a life cycle in which the phase signal has few failures is found to be the same as the actual durability of 15 years.

복수의 열화특성을 가진 철도설비에 대한 최적정비주기 산출방법

박면규,장명석,박찬우 한국철도학회 2021 한국철도학회논문집 Vol.24 No.4

Railway equipment reliability (or failure rate) provides the basis for the estimation of the maintenance interval required in the process of maintenance management. In particular, the failure rate trend is needed to determine the optimal maintenance (or replacement) interval in a preventive maintenance policy. In other words, the optimal maintenance interval is determined depending on whether the failure rate is decreasing, constant, or increasing. This study proposes a method to estimate the optimal maintenance interval for railway equipment with multiple degradation characteristics and demonstrates the result by simulated data. The method can be used in cases in which equipment condition is monitored by IOT sensors that detect various degradation phenomena.

Optimal Maintenance Scheduling in a Two Identical Component Parallel Redundant System Subject to Exponential Power Hazards

El-Damcese, M.A.,Helmy, A.N. The Korean Reliability Society 2008 International Journal of Reliability and Applicati Vol.9 No.2

This paper presents equations, which can be used to evaluate the failure frequency and the failure rate of a two identical component parallel redundant system in which each component can operate in its wear out period, and the failure rate of each component is exponential power distribution. The optimum maintenance interval for a two identical component parallel redundant system can be obtained using these equations. The proposed approach is presented and illustrated using several numerical examples. The optimum maintenance interval for each component in a two identical parallel redundant system will depend on factors such as: failure rate, repair and maintenance times of each component in the parallel redundant systems.