• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.9
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• pp.1331-1338
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• 2010

Recently, the need for improving the economical efficiency of pumped-storage power plants has increased because of the decrease in the availability of electricity caused by an increase in the consumption of electricity at night. Therefore, a preventative maintenance cycle, especially an overhaul cycle, is required. Unconditional extension cannot be implemented because it may cause unanticipated failures due to insufficient maintenance. Therefore, in this study, a methodology for optimizing the preventative maintenance cycle by taking into account both reliability and economical efficiency is presented; this methodology has been developed by reviewing previous studies on reliability and considering the characteristics of pumped-storage power plants. Finally, an extended overhaul cycle is derived by applying this methodology to a domestic pumped-storage power plant.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.4
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• pp.96-104
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• 2017

A one-shot system (device) refers to a system that is stored for a long period of time and is then disposed of after a single mission because it is accompanied by a chemical reaction or physical destruction when it operates, such as shells, munitions in a defense weapon system and automobile airbags. Because these systems are primarily related with safety and life, it is required to maintain a high level of storage reliability. Storage reliability is the probability that the system will operate at a particular point in time after storage. Since the stored one-shot system can be confirmed only through inspection, periodic inspection and maintenance should be performed to maintain a high level of storage reliability. Since the one-shot system is characterized by a large loss in the event of a failure, it is necessary to determine an appropriate inspection period to maintain the storage reliability above the reliability goal. In this study, we propose an optimal inspection policy that minimizes the total cost while exceeding the reliability goal that the storage reliability is set in advance for the one-shot system in which periodic inspections are performed. We assume that the failure time is the Weibull distribution. And the cost model is presented considering the existing storage reliability model by Martinez and Kim et al. The cost components to be included in the cost model are the cost of inspection $c_1$, the cost of loss per unit time between failure and detection $c_2$, the cost of minimum repair of the detected breakdown of units $c_3$, and the overhaul cost $c_4$ of $R_s{\leq}R_g$. And in this paper, we will determine the optimal inspection policy to find the inspection period and number of tests that minimize the expected cost per unit time from the finite lifetime to the overhaul. Compare them through numerical examples.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.3
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• pp.91-100
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• 2017

The solution was developed for the maintenance decision support of combined cycle power plant gas turbine. The developed solution was applied to MHI501G gas turbine and is, in present, on the process of field test at GUNSAN combined cycle power plant, South Korea. The developed solution provides the calculated result of optimal overhaul maintenance period through following modules: Real Time Performance Monitoring, Model-Based Diagnostics, Performance Trend Analysis, Optimal Overhaul Maintenance Interval, Compressor Washing Period Management, and Blade Path Temperature Analysis. Model-Based Diagnostics module analyzed the differences between the data of gas turbine performance model and the online measurement. Compressor washing management module suggests the optimal point of balancing between the compressor performance and the maintenance cost.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.482-486
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• 2008

It has been built or remodeled in every year train maintenance centers including subways. However, there is no standard to measure exact capacity. In today, most of criteria is referenced on Japanese. In general, we can standardize the process for 'Train Overhaul Maintenance' because its processes are similar or same patterns. The processes can be the base standard of train maintenance after being classified in detail and validating it. This study is adapt BPR methodology to present standardizes processes and the processes are mapping to layout drawing to constraint from the real world, and then evaluate the capacity using simulation. To guarantee objectivity of input data, we use research data by the National Railroad Administration and Association of Japanese Railway Engineering. Using these data to simulation, we compare to the 'Allowances' and evaluate its adequacy.

• Journal of the Korean Society of Safety
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• v.36 no.5
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• pp.71-78
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• 2021

There are regularly planned overhaul periods in thermal power plants, which involve the maintenance of the boiler of the power plants. However, thermal power plants workers are always exposed to risk during overhaul periods owing to the narrow space and significant dust inside the boiler. Therefore, it is essential to develop a safety monitoring system that is suitable for operating in this type of environment. In this study, we developed not only a worker three-dimensional (3D)-location monitoring system that can monitor and record the entry/exit of workers, their 3D-location, and fall accidents but also a method to secure the working environment and operation efficiency. This system comprises of a worker tag, which was equipped with an inertial measurement unit, a barometric pressure sensor, and a Bluetooth low energy (BLE), and the tags were given to each worker. In addition, the location of workers inside the boiler was measured using a pedestrian dead reckoning (PDR) method and BLE beacons. The location data of the workers tag were transmitted to the integrated database (DB) server through a gateway, and to the administrator monitoring system. The performance of the system was demonstrated inside an actual thermal power plant boiler, and the accuracy and reliability of the system were verified through a number of repeated tests. These results provide insights on designing a new system for monitoring enclosed spaces.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.4
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• pp.477-487
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• 2019

Objectives: Firefighters are known to be exposed to a variety of toxic substances, but little information is available on the exposure profile of firefighting activities. The aims of this study were to conduct exposure monitoring of toxic chemicals at fire scenes, to compare the concentrations of respective chemicals among firefighting tasks, and to assess the main factors influencing the concentrations of chemicals. Methods: Researchers performed sampling at firefighting scenes during four weeks in 2013. At the scene, we collected samples based on firefighters' own activities and examined the situation and scale of the accident. Collected samples were classified into three categories, including fire extinguishing and overhaul, and were analyzed in the laboratory according to respective analysis methods. Results: A total of fourteen fire activity events were surveyed: five fire extinguishing, six overhaul, and three fire investigations. Although no substance exceeded the ACGIH TLV, PAHs were detected in every sample. Naphthalene ranged from 0.24 to 279.13 mg/㎥ (median 49.6 mg/㎥) and benzo(a)pyrene was detected in one overhaul case at 10.85 ㎍/㎥. Benzene (0.01-12.2 ppm) was detected in every task and exceeded the ACGIH TLV. No significant difference in concentrations between tasks was shown. Conclusions: These results indicate that all firefighting tasks generated various hazardous combustion products, including possible carcinogens.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1251-1253
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• 2002

Most of the substations, which had been constructed so far, only took into account the current distortion as an evaluation factor for harmonics. There is, however, growing tendency for the currently constructed substations to construct transmission lines in an underground way. Therefore, the overhaul investigation on the psophometric current is all the more necessary. In this study, the harmonic current, the current distortion and the psophometric current, which flow into the substation in accordance with a feeding system and the number of trains in operation are investigated and compared based on the six-port analysis method of feeding system, which has been proposed.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.47-55
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• 2015

This paper proposes the installation of a new modular multilevel converter based high-voltage direct current (MMC-HVDC) system to connect between mainland and Jeju island power systems in Korea in 2020. The purpose is to combine with two old line-commutated converters (LCC)-based HVDC system to achieve a stability of the Jeju island power system. The operation of the overall system will be analyzed in three cases: (i) wind speed is variable, (ii) either one of the LCC-HVDC systems is shutdown because of a fault or overhaul, (iii) a short circuit fault occurs at the mainland side. The effectiveness of the proposed control method is confirmed by the simulation results based on a PSCAD/EMTDC simulation program.

• Journal of Arbitration Studies
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• v.16 no.1
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• pp.121-151
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• 2006

As globalisation extends its effect and particularly following China's accession to the World Trade Organization(WTO) in 2001, ever greater numbers of international transactions will feature a Chinese party. China has certainly made efforts in recent years to rectify law problem. While conducting business in China, foreign companies occasionally find themselves embroiled in disputes with Chinese individuals and companies. As foreign businesses invest in the extraordinary market opportunities in China, international arbitration has also become the preferred method for handling disputes with Chinese partners or with other foreign corporation over operations in China. The new Arbitration Rules of the International Economic and Trade Arbitration Commission(CIETAC) came into force on 1 May 2005. The new rules represent a major overhaul of CIETAC arbitration procedures and are sure to enhance CIETAC's position as a leading player in the resolution of China-foreign business disputes. The changes are significant for all companies doing business in China. So, this article investigated some amendments on the basis of 2000 Rules.

• Journal of Korean Society for Quality Management
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• v.32 no.3
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• pp.166-181
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• 2004

The aircraft production quality management system in Korea has been implemented to support the developmental phase of Korean aircraft industries, from overhaul of the aircraft and engines to development of military trainer aircraft. After the deletion of the Mil-Q-9858A standard in 1996, Korean aerospace companies established ISO 9001 and AS 9100 as their basic aerospace quality management system specifications. These quality standards were adopted in the same period of time by other leading international aircraft manufacturing companies. This paper presents a future direction on the improvement of quality management systems for Korean aircraft production company by considering (1) Korean governments strategy for the development of Korean aircraft Production industries, (2) short and long term business plan of Korean aerospace industries, and (3) benchmarking leading international company's quality management systems.