• Title/Summary/Keyword: periodic inspection

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Analysis on Safety Management of Elevator (승강기 안전관리제도의 문제점 분석에 관한 연구)

  • Choi, Gi-Heung
    • Journal of the Korean Society of Safety
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    • v.22 no.6
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    • pp.7-12
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    • 2007
  • This study focuses on the statistical analysis on safety management of elevators. Specifically, frequency and severity of accidents in relation to conditional pass in periodic inspection, maintenance, market surveillance are analysed based on the statistical data and social loss due to poor management is estimated. The results of statistical analysis performed in this study will provide logical basis and future direction for improving the safety management system.

Rapid Defect Inspection of Display Device with Optical Spatial Filtering

  • Yoon, Dong-Seon;Kim, Seung-Woo
    • International Journal of Precision Engineering and Manufacturing
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    • v.1 no.1
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    • pp.56-61
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    • 2000
  • We present a fast inspection method of machine vision for in-line quality assurance of liquid crystal displays(LCD) and plasma display panels(PDP). The method incorporates an optical spatial filter in the Fourier plane of the imaging optics to block the normal periodic pattern, extracting only defects real time without relying on intensive software image process. Special emphasis is on designing a collimated white light source to provide high degree of spatial coherence for effective real time Fourier transform. At the same time, a low level of temporal coherence is attained to improve defect detection capabilities by avoiding undesirable coherent noises. Experimental results show that the proposed inspection method offers a detection accuracy of 15% tolerance, which is sufficient for industrial applications.

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Reliability analysis for fatigue damage of railway welded bogies using Bayesian update based inspection

  • Zuo, Fang-Jun;Li, Yan-Feng;Huang, Hong-Zhong
    • Smart Structures and Systems
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    • v.22 no.2
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    • pp.193-200
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    • 2018
  • From the viewpoint of engineering applications, the prediction of the failure of bogies plays an important role in preventing the occurrence of fatigue. Fatigue is a complex phenomenon affected by many uncertainties (such as load, environment, geometrical and material properties, and so on). The key to predict fatigue damage accurately is how to quantify these uncertainties. A Bayesian model is used to account for the uncertainty of various sources when predicting fatigue damage of structural components. In spite of improvements in the design of fatigue-sensitive structures, periodic non-destructive inspections are required for components. With the help of modern nondestructive inspection techniques, the fatigue flaws can be detected for bogie structures, and fatigue reliability can be updated by using Bayesian theorem with inspection data. A practical fatigue analysis of welded bogies is utilized to testify the effectiveness of the proposed methods.

Periodic Inspection of a Random Shock Model

  • Lee, Eui Yong;Lee, Jiyeon;Sohn, Joong Kweon
    • Journal of Korean Society for Quality Management
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    • v.24 no.3
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    • pp.31-36
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    • 1996
  • A Markovian stochastic model for a system subject to random shocks is considered. Each shock arriving according to a Poisson process decreases the state of the system by a random amount. A repairman arrives at the system periodically for inspection and repairs the system only if the state is below a threshold. Costs are assigned to each inspection of the repairman, to each repair, and to the system being in bad states below the threshold. The expected long run average cost is obtained and compared with that of the random inspection introduced by Lee and Lee(1994).

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Development of Stochastic Decision Model for Estimation of Optimal In-depth Inspection Period of Harbor Structures (항만 구조물의 최적 정밀점검 시기 추정을 위한 추계학적 결정모형의 개발)

  • Lee, Cheol-Eung
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.28 no.2
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    • pp.63-72
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    • 2016
  • An expected-discounted cost model based on RRP(Renewal Reward Process), referred to as a stochastic decision model, has been developed to estimate the optimal period of in-depth inspection which is one of critical issues in the life-cycle maintenance management of harbor structures such as rubble-mound breakwaters. A mathematical model, which is a function of the probability distribution of the service-life, has been formulated by simultaneously adopting PIM(Periodic Inspection and Maintenance) and CBIM(Condition-Based Inspection and Maintenance) policies so as to resolve limitations of other models, also all the costs in the model associated with monitoring and repair have been discounted with time. From both an analytical solution derived in this paper under the condition in which a failure rate function is a constant and the sensitivity analyses for the variety of different distribution functions and conditions, it has been confirmed that the present solution is more versatile than the existing solution suggested in a very simplified setting. Additionally, even in that case which the probability distribution of the service-life is estimated through the stochastic process, the present model is of course also well suited to interpret the nonlinearity of deterioration process. In particular, a MCS(Monte-Carlo Simulation)-based sample path method has been used to evaluate the parameters of a damage intensity function in stochastic process. Finally, the present stochastic decision model can satisfactorily be applied to armor units of rubble mound breakwaters. The optimal periods of in-depth inspection of rubble-mound breakwaters can be determined by minimizing the expected total cost rate with respect to the behavioral feature of damage process, the level of serviceability limit, and the consequence of that structure.

Feasibility Study for Low Pressure Turbine Inspection of Nuclear Power Plant Using Shear Wave Phased Array Ultrasonic Transducer (횡파 위상배열 초음파탐촉자를 이용한 원자력발전소 저압 터빈 검사 적용 타당성 연구)

  • Yoon, Byung Sik;Kim, Yong Sik;Kim, Jin Hoi
    • Transactions of the Korean Society of Pressure Vessels and Piping
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    • v.9 no.1
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    • pp.8-14
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    • 2013
  • Steam turbine blades and discs of nuclear power plants are one of the most highly stressed areas of turbine rotor, and periodic inspection of the blade roots is essential for monitoring integrity and preventing turbine failure. Ultrasonic technique is applied for volumetric inspection of blade root. However, the complexity of blade root geometry imposes challenges to inspection of blades and discs. Recently, phased array ultrasonic inspection technology is being applied to numerous power generation inspection applications including turbine rotor. The phased array ultrasonic technique requires customized inspection wedges which are generally necessary to generate effectively higher incident angle. But the usage of this wedge can cause access limitation for the lower stage blades of turbine because of the wedge front length. Therefore, the shear wave phased array probe which can generate high inspection angle without wedge is essentially necessary. In this study, feasibility study is conducted for the shear wave phased array ultrasonic probe application to blade and disc inspection. As results, the experimental results show that the shear wave phased array probe can detect the flaw and measure its size with reliable accuracy. Therefore if this shear wave phased array probe is applied to field inspection of blade and disc, more reliable inspection is expected for turbine having access limitation.

A Study on the Seal Life Improvement of the Hydraulic Servo Actuator for Steam Control of Power Plants (발전소 스팀제어용 유압서보 액추에이터의 씰 수명 향상에 관한 연구)

  • Lee, Yong Bum;Lee, Jong Jik
    • Journal of Drive and Control
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    • v.15 no.2
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    • pp.32-37
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    • 2018
  • The power plants use turbine output control devices to supply or shut off steam to high pressure and low-pressure steam turbines connected to generators. This turbine output control device is driven by a hydraulic servo actuator. The gas flows into the hydraulic servo actuator during periodic inspection or normal operation, and the resulting adiabatic compression of the gas raises the internal temperature of the actuator to $500^{\circ}C$. This temperature increase causes the seals to burn and show wear and tear, resulting in failure. In this study, an air vent valve was installed to allow gas inside the hydraulic servo actuator to flow large quantities of air at the beginning of the operation and after the periodic inspection. Gas was passed through for only minute flow during normal operation of the power plant. By applying the air vent valve, it improves the reliability of the hydraulic servo actuator by discharge the gas appropriately to improve the life of the seal.

The Impact of Nonconforming Items on (s, S) Inventory Model with Customer Order Reservation and Cancellation

  • Takemoto, Yasuhiko;Arizono, Ikuo
    • Industrial Engineering and Management Systems
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    • v.8 no.2
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    • pp.72-79
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    • 2009
  • The ultimate goal of inventory management is to decide the timing and the quantity of ordering in response to uncertain demands. Recently, some researchers have focused upon an impact of distortions in the information, e.g., customer order cancellation, on an economical inventory policy. The customer order cancellation is considered a kind of distortions in demands, because a demand that is eventually cancelled is equivalent to a phony demand. Also, there are some additional distortions in the inventory information. For instance, the procurement of suppliers may include some nonconforming items as a result of imperfect production and inspection by the suppliers, and/or damage in transit. The nonconforming item should be considered a kind of distortions in the inventory information, because the nonconforming item is equivalent to a phony stock. In this article, we consider an inventory model under the situation that customers can cancel their orders and the procurement of suppliers may include some nonconforming items. Then, we introduce the customer order reservation into the inventory model for the purpose of avoiding the costly backlogs, because the customer order reservation gives retailers a period to fulfill customer's requests. We formulate a periodic review (s, S) inventory model and investigate the economical operation under the situation mentioned above. Further, through the sensitivity analysis, we show the impact of these distortions and the effect of the customer order reservation on the inventory policy.

A Study on Management Body Consciousness for Managing Facility Safety Inspection and Diagnosis (시설물 안전 점검 및 진단 실시에 대한 관리주체 의식에 관한 연구)

  • Kim, Hak-Eung;Jung, Soo-Il
    • Journal of the Korea Safety Management & Science
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    • v.10 no.3
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    • pp.19-27
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    • 2008
  • Since 1995, the facility of class 1 and 2, classified by law had been subject to system of post maintenance management where periodic safety inspection and diagnosis to identify any problems and to take appropriate measures as a matter of urgency. Although the standards and systems had been revised many times for continuous improvement due to surrounding environmental factors, the technical factors and other factors for improvements, continuous researches and efforts are needed to ensure even higher effectiveness. Furthermore, the consciousness of the management body that executes and implements such improvements for facility management is most important. Therefore in this study, through such analysis, more realistic management consciousness review was performed. Also the direction for improvements is proposed, to carry out more effective facility safety management systems implementation.

A Study on the inspection item classified by reinforcement method for the construction slope maintenance (건설공사 비탈면 유지관리를 위한 보강공법별 점검항목에 관한 연구)

  • Kim, Yong-Soo;Chang, Buhm-Soo;Shin, Kwan-Young
    • Proceedings of the Korean Geotechical Society Conference
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    • 2005.03a
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    • pp.759-764
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    • 2005
  • With the tunnel to case of the construction slope it executes the periodic maintenance due to an objectivity standard. But, the standard connected with construction slope is not integrated with the important public paper organic enemy and it is duplicated and the standards which conflict are being scattered. Also, it is referred to some specifications simply and the feature which is diffuse appears. Therefore, there is a necessity which it investigates the problem point of the maintenance civil official and it improves rationally and it takes a triangular position a confusedly be standard system. In this research which it sees accomplished the fundamental research against the inspection item classified by reinforcement method for the construction slope maintenance.

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