• Asia-Pacific Journal of Business Venturing and Entrepreneurship
• /
• v.7 no.4
• /
• pp.41-47
• /
• 2012

Railroad rolling stock has long service life and a lot of maintenance cost running on rail by wear and vibration. And it is very important to get optimization of maintenance. This paper want to analyze rolling stock maintenance situation of KORAIL and find out its improvement methods. Especially, the purpose of this paper is to adopt the most effective maintenance period and methods to daily inspection which needs many maintenance manpower in rolling stock. Rolling stock has self-diagnosis function using computer system and the quality of rolling stock has much improved these days but current daily inspection repeat for short period routinely and it is very ineffective. Therefore, the paper adopt improved daily inspection period reflecting the characteristics of rolling stock, and want to secure reliability of rolling stock and minimize maintenance cost.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.38 no.3
• /
• pp.100-107
• /
• 2015

Recently as the manufacturers want competitiveness in dynamically changing environment, they are trying a lot of efforts to be efficient with their production systems, which may be achieved by diminishing unplanned operation stops. The operation stops and maintenance cost are known to be significantly decreased by adopting proper maintenance strategy. Therefore, the manufacturers were more getting interested in scheduling of exact maintenance scheduling to keep smooth operation and prevent unexpected stops. In this paper, we proposedan integrated maintenance approach in injection molding manufacturing line. It consists of predictive and preventive maintenance approach. The predictive maintenance uses the statistical process control technique with the real-time data and the preventive maintenance is based on the checking period of machine components or equipment. For the predictive maintenance approach, firstly, we identified components or equipment that are required maintenance, and then machine parameters that are related with the identified components or equipment. Second, we performed regression analysis to select the machine parameters that affect the quality of the manufactured products and are significant to the quality of the products. By this analysis, we can exclude the insignificant parameters from monitoring parameters and focus on the significant parameters. Third, we developed the statistical prediction models for the selected machine parameters. Current models include regression, exponential smoothing and so on. We used these models to decide abnormal patternand to schedule maintenance. Finally, for other components or equipment which is not covered by predictive approach, we adoptedpreventive maintenance approach. To show feasibility we developed an integrated maintenance support system in LabView Watchdog Agent and SQL Server environment and validated our proposed methodology with experimental data.

• Communications for Statistical Applications and Methods
• /
• v.15 no.1
• /
• pp.77-86
• /
• 2008

This paper develops the optimal periodic preventive maintenance policy following the expiration of non-renewing warranty. We assume that Wu and Clements-Croome's (2005) periodic PM model with random maintenance quality is utilized to maintain the system after the non-renewing warranty is expired. Given the cost structure to the user during the cycle of the product, we drive the expressions for the expected cost rate per unit time. Also, 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.

• Journal of Korean Society for Quality Management
• /
• v.17 no.1
• /
• pp.1-10
• /
• 1989

In general, the characteristics of components which consist of multi-component system can not be the same. This paper proposes a maintenance model of multi-component system considering the characteristics of each component. In this paper, multi-component system is divided into three components-critical unit, major unit and minor unit, respectively. This paper determines the optimal replacement time of the system which minimizes total maintenance cost, optimal replacement period of major unit and initial stock quantity of minor unit within this optimal replacement time. Numerical examples are shown when the failure times of each unit have gamma distribution.

• Proceedings of the KSR Conference
• /
• 2010.06a
• /
• pp.1642-1649
• /
• 2010

At present, KORAIL is in the middle of renovating. All steps exert great effort at cost reduction and a profit improvement. Especially to improve maintenance method and inspection period at the rolling-stock division lots of research is under progress. Daily inspection of rolling stocks is to operate the rolling stock normally. Daily inspection items are driving control device, coupling device, brake system, water system and air conditioning system, electrical system etc. Half of the maintenance manpower are inputted at daily inspection. Strengthens the quality and optimize the proportion of daily inspection are urgent problem. Daily inspection period extension aim is as follows. KTX from 3,500km to 5,000km, passenger car from 1st to 3,500km, new style electric locomotive from 2nd to 5,000km, the diesel locomotive is 2,800km from 1,200km. In this paper, the optimal daily inspection period and methods are considered including expected problem and counter measures.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.19 no.10
• /
• pp.82-88
• /
• 2018

The decoy defensive weapon system is a one-shot system. Reliability is maintained through periodic inspection and high reliability is required to confirm whether or not the functioning is normal after launch. The maintenance cycle of a decoy was set up without target reliability and reliability prediction during the development period. However, the number of operations in the military has been increasing, necessitating the optimization of the maintenance cycle. Reliability is analyzed using the maintenance data of a decoy operated for several decades and the optimal maintenance cycle is suggested. In chapter 2, data collection and classification methods are presented and analysis methodology is briefly introduced. In chapter 3, the data distribution analysis and fitness verification confirmed that applying the Weibull distribution is the most suitable for the maintenance data of the decoy. In chapter 4, we present the analysis result of percentile, survival probability and MTBF and the optimal maintenance cycle was derived from the reliability analysis. Finally, we suggest the application methods for this paper in the future.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.42 no.4
• /
• pp.145-152
• /
• 2019

All machines deteriorate in performance over time. The phenomenon that causes such performance degradation is called deterioration. Due to the deterioration, the process mean of the machine shifts, process variance increases due to the expansion of separate interval, and the failure rate of the machine increases. The maintenance model is a matter of determining the timing of preventive maintenance that minimizes the total cost per wear between the relation to the increasing production cost and the decreasing maintenance cost. The essential requirement of this model is that the preventive maintenance cost is less than the failure maintenance cost. In the process mean shift model, determining the resetting timing due to increasing production costs is the same as the maintenance model. In determining the timing of machine adjustments, there are two differences between the models. First, the process mean shift model excludes failure from the model. This model is limited to the period during the operation of the machine. Second, in the maintenance model, the production cost is set as a general function of the operating time. But in the process mean shift model, the production cost is set as a probability functions associated with the product. In the production system, the maintenance cost of the equipment and the production cost due to the non-confirming items and the quality loss cost are always occurring simultaneously. So it is reasonable that the failure and process mean shift should be dealt with at the same time in determining the maintenance time. This study proposes a model that integrates both of them. In order to reflect the actual production system more accurately, this integrated model includes the items of process variance function and the loss function according to wear level.

• KIEAE Journal
• /
• v.10 no.5
• /
• pp.171-179
• /
• 2010

Korea owns vast amount of apartment houses no less than those of world prominent countries, but did not pay enough efforts to maintain existing apartment houses and develop policies to reuse them due to growth driven policy of housing supply like construction of new houses. Korea constructed tremendous amount of houses in short period through government led forced house supplying policy, and resulted in excess houses such that present house supply rate happened to be reaching 110%. However, recently there are growing demand of change in housing policy due to social environmental changes like low birth rate and aging of society etc and nationals' demand for improvement of residential quality. When such social changes are demanded and 80% of apartment houses in Korea are less than 20 years old, renovations and remodeling of apartment houses are anticipated to emerge as important matter. In particular, the apartment houses in Seoul and the 1st generation new cities like Bundang and Ilsan etc have passed considerable period of time after construction and require safety measure, it is quite impending to loan programs for the maintenance of existing apartment houses. The objective of this study is to compare and analyze the system of loan programs about apartment houses of Japan, and then to propose to accelerate loan programs about maintenance for apartment houses in korea.

• Journal of Korean Society of Industrial and Systems Engineering
• /
• v.44 no.1
• /
• pp.45-50
• /
• 2021

Machines and facilities are physically or chemically degenerated by continuous usage. The representative type of the degeneration is the wearing of tools, which results in the process mean shift. According to the increasing wear level, non-conforming products cost and quality loss cost are increasing simultaneously. Therefore, a preventive maintenance is necessary at some point. The problem of determining the maintenance period (or wear limit) which minimizes the total cost is called the 'process mean shift problem'. The total cost includes three items: maintenance cost (or adjustment cost), non-conforming cost due to the non-conforming products, and quality loss cost due to the difference between the process target value and the product characteristic value among the conforming products. In this study, we set the production volume as a decreasing function rather than a constant. Also we treat the process variance as a function to the increasing wear rather than a constant. To the quality loss function, we adopted the Cpm+, which is the left and right asymmetric process capability index based on the process target value. These can more reflect the production site. In this study, we presented a more extensive maintenance model compared to previous studies, by integrating the items mentioned above. The objective equation of this model is the total cost per unit wear. The determining variables are the wear limit and the initial process setting position that minimize the objective equation.

• The Journal of Korean Physical Therapy
• /
• v.21 no.4
• /
• pp.89-96
• /
• 2009

Purpose: This study examined the effects of manual lymph drainage (MLD) on edema and the quality of life (QOL) of lymphedema patients in the maintenance phase. Method: Forty five lymphedema patients, who had completed intensive decongestive therapy, were enrolled in this study. All subjects were assigned randomly to two groups: Experimental (MLD) group (n=23) and control (self-MLD) group (n=22). MLD by a specialist was applied with a comfortable pressure for 40~60 minutes in the experimental group and self-MLD was carried out by the control group 5 times a week for 2 weeks. The % edema and a SF-36 questionnaire were used to measure the decrease in edema and the QOL. A paired t-test was used to compare the period, and an independent T-test was used to compare experiment and control groups. Result: The % edema was significantly lower in the experimental group after MLD (p<0.05). The physical, vitality, and mental health scores of the experimental group was significantly higher than those of the control group (p<0.05). Conclusion: TMLD by a specialist in the maintenance phase is effective in reducing the % edema and enhancing the QOL of lymphedema patients. Further studies will be needed to determine if there are differences in the effects of many types of treatment methods in the lymphedema treatment.