• Proceedings of the KSR Conference
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• 2011.10a
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• pp.311-319
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• 2011

Track accompanies the process that track alignment by traffic loads is changed. A change of track alignment affects the running safety and riding comfort of train. This is called a track irregularity. The most important task in maintaining the track is to manage these track irregularity within quality parameters. Today, track maintenance of urban transit is enforcing immediate maintenance about section exceeding a safety standard by applying track recording data got through Integrated Measurement. This method is advantage of being easy of the maintenance assesment in case of the running safety, but is disadvantage of being difficult in case of the riding comfort of train. In this study, we propose track irregularity deviation of each track system depending on the time series and present about utilization plans of the Track Irregularity Progress Rate.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.5
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• pp.477-488
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• 2024

The Korean government amended the Facilities Safety Act in 2018 to establish a performance-based maintenance system. This system is designed to comprehensively evaluate the safety, durability, and usage performance of facilities required to maintain their function in use, and to establish corresponding maintenance plans. However, the current maintenance system of utility tunnels is managed by a safety-oriented evaluation method, which has limitations in conducting performance evaluations that consider durability and usage performance. Therefore, in this study, safety, durability, and usage performance items for utility tunnels were selected using the Delphi method, and the weight of each item was calculated using the entropy weighting method. The results of this study are expected to be used in future performance evaluations of utility tunnels to support rational decision making when establishing maintenance plans.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.4
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• pp.24-34
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• 2014

In order to manage essential parts that are required for the repairable parts services performed at the military maintenance depots, the United States Air Force developed the Repairability Forecasting Model (RFM). In the RFM, if the requirements of the parts are assumed to follow the normal probability distribution after applying means from the past data to the replacement rate and lead times, the chance of the AWP (Awaiting Parts) occurring is 50%. In this study, to counter the uncertainties of requirements and lead times from the RFM, the safety level concept is considered. To obtain the safety level for requirements, the binomial probability distribution is applied, while the safety level for lead time is obtained by applying the normal probability distribution. After adding this concept, the improved RFM is renamed as the ARFM (Advanced RFM), and by conducting the numerical stimulation, the effectiveness of the ARFM, minimizing the occurrence of the AWP, is shown by increasing the efficiency of the maintenance process and the operating rate of the weapon system.

• Safety and Health at Work
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• v.15 no.1
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• pp.87-95
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• 2024

Background: This study focuses on assessing occupational risk for the health hazards encountered during maintenance works (MW) in semiconductor fabrication (FAB) facilities. Objectives: The objectives of this study include: 1) identifying the primary health hazards during MW in semiconductor FAB facilities; 2) reviewing the methods used in evaluating the likelihood and severity of health hazards through occupational health risk assessment (OHRA); and 3) suggesting variables for the categorization of likelihood of exposures to health hazards and the severity of health effects associated with MW in FAB facilities. Methods: A literature review was undertaken on OHRA methodology and health hazards resulting from MW in FAB facilities. Based on this review, approaches for categorizing the exposure to health hazards and the severity of health effects related to MW were recommended. Results: Maintenance workers in FAB facilities face exposure to hazards such as debris, machinery entanglement, and airborne particles laden with various chemical components. The level of engineering and administrative control measures is suggested to assess the likelihood of simultaneous chemical and dust exposure. Qualitative key factors for mixed exposure estimation during MW include the presence of safe operational protocols, the use of air-jet machines, the presence and effectiveness of local exhaust ventilation system, chamber post-purge and cooling, and proper respirator use. Using the risk (R) and hazard (H) codes of the Globally Harmonized System alongside carcinogenic, mutagenic, or reprotoxic classifications aid in categorizing health effect severity for OHRA. Conclusion: Further research is needed to apply our proposed variables in OHRA for MW in FAB facilities and subsequently validate the findings.

• Magazine of the Korea Institute for Structural Maintenance and Inspection
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• v.19 no.2
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• pp.44-52
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• 2015

• Journal of Energy Engineering
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• v.23 no.2
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• pp.191-198
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• 2014

Korea Hydro & Nuclear Power Co. (KHNP) has developed and implemented the maintenance effectiveness monitoring (MR) programs for the operating nuclear power plants. MR programs are developed by reflecting design characteristics of the operating nuclear power plants to monitor the plant performance for improving the safety and reliability. Recently, KHNP has developed the MR program for APR1400 safety related systems to establish the advanced maintenance system and will verify the suitability of the MR program through evaluating initial performance. Consequently, it is expected that the safety of the new plant will be improved by developing and implementing the MR program.

• Journal of the Korean Society for Railway
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• v.7 no.3
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• pp.271-277
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• 2004

This paper is concerned with the reliability centered maintenance (RCM) of the Automated Guideway Transit (AGT) vehicle system. Korea Railroad Research Institute (KRRI) has developed the AGT vehicle system from 1999 to 2004. The provisions for a specific maintenance system including RAMS (reliability, availability, maintainability & safety) of AGT vehicle system is necessary for maintaining good operation conditions. RCM is a process used to determine what must be done to ensure that any system continues to do whatever its users want it to do in its present operating conditions. Therefore, we introduce RCM in details and describe how RCM should be applied to AGT vehicle system on Gyeong-San test line. Analyses to approach RCM to AGT vehicle system are demonstrated in the seven steps that contain each main task and detailed operating conditions.

• Journal of the Korean Society for Railway
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• v.15 no.2
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• pp.172-178
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• 2012

Superimposition of vertical and transition curves is not allowed for all types of tracks in Korean regulation of railway construction. However, this criterion has been established on the basis of difficulty of maintenance of the ballasted track. Comparing with the ballasted track, the concrete slab track has the advantage of maintenance and structural, which allows the superimposition of vertical and transition curves when it satisfies the criteria of running safety and riding comfort. In this study, running safety, ride comforts and track acting forces were analyzed and compared by numerical analysis using VAMPIRE program when the vertical and transition curves are superimposed for the ballasted track as well as the concrete slab track. From the analysis results, it was found that running safety, riding comforts and track acting forces in case of superimposition of vertical and transition curves for the both tracks meet all of the criteria. Therefore, although superimposition of vertical and transition curves for the ballasted track is not allowed because of a lot of maintenance works, it can be applied to the concrete slab track considering the advantage of maintenance and structural safety.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.1
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• pp.1-7
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• 2015

The aircraft maintenance demands a lot of aviation mechanics in urgent according to the high season and low season in seasonal demand adjusted, unplanned maintenance work such as AD (airworthiness directives) and troubleshooting of aircraft system fault. The advent of Super-Large Aircraft such as A380 with aircraft materials, power plant and avionics systems which were not in previous models must be expected to increase the complexity of the aircraft maintenance system. This study is intended to propose the development plan for formation of positive flexibility culture in aircraft maintenance organization through the review of previous research on flexibility culture of organization and through empirical research for bureaucratic and poor factors by the evaluation of flexibility culture level of domestic aircraft maintenance organization.

• Nuclear Engineering and Technology
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• v.40 no.1
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• pp.49-68
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• 2008

The purpose of this paper is to extensively review the condition monitoring (CM) techniques using empirical models in an effort to reduce or eliminate unexpected downtimes in general industry, and to illustrate the feasibility of applying them to the nuclear industry. CM provides on-time warnings of system states to enable the optimal scheduling of maintenance and, ultimately, plant uptime is maximized. Currently, most maintenance processes tend to be either reactive, or part of scheduled, or preventive maintenance. Such maintenance is being increasingly reported as a poor practice for two reasons: first, the component does not necessarily require maintenance, thus the maintenance cost is wasted, and secondly, failure catalysts are introduced into properly working components, which is worse. This paper first summarizes the technical aspects of CM including state estimation and state monitoring. The mathematical background of CM is mature enough even for commercial use in the nuclear industry. Considering the current computational capabilities of CM, its application is not limited by technical difficulties, but by a lack of desire on the part of industry to implement it. For practical applications in the nuclear industry, it may be more important to clarify and quantify the negative impact of unexpected outcomes or failures in CM than it is to investigate its advantages. In other words, while issues regarding accuracy have been targeted to date, the concerns regarding robustness should now be concentrated on. Standardizing the anticipated failures and the possibly harsh operating conditions, and then evaluating the impact of the proposed CM under those conditions may be necessary. In order to make the CM techniques practical for the nuclear industry in the future, it is recommended that a prototype CM system be applied to a secondary system in which most of the components are non-safety grade. Recently, many activities to enhance the safety and efficiency of the secondary system have been encouraged. With the application of CM to nuclear power plants, it is expected to increase profit while addressing safety and economic issues.