• Title/Summary/Keyword: Process fault

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Literature Review of Machine Condition Monitoring with Oil Sensors -Types of Sensors and Their Functions (윤활유 분석 센서를 통한 기계상태진단의 문헌적 고찰 (윤활유 센서의 종류와 기능))

  • Hong, Sung-Ho
    • Tribology and Lubricants
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    • v.36 no.6
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    • pp.297-306
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    • 2020
  • This paper reviews studies on the types and functions of oil sensors used for machine condition monitoring. Machine condition monitoring is essential for maintaining the reliability of machines and can help avoid catastrophic failures while ensuring the safety and longevity of operation. Machine condition monitoring involves several components, such as compliance monitoring, structural monitoring, thermography, non-destructive testing, and noise and vibration monitoring. Real-time monitoring with oil analysis is also utilized in various industries, such as manufacturing, aerospace, and power plants. The three main methods of oil analysis are off-line, in-line, and on-line techniques. The on-line method is the most popular among these three because it reduces human error during oil sampling, prevents incipient machine failure, reduces the total maintenance cost, and does not need complicated setup or skilled analysts. This method has two advantages over the other two monitoring methods. First, fault conditions can be noticed at the early stages via detection of wear particles using wear particle sensors; therefore, it provides early warning in the failure process. Second, it is convenient and effective for diagnosing data regardless of the measurement time. Real-time condition monitoring with oil analysis uses various oil sensors to diagnose the machine and oil statuses; further, integrated oil sensors can be used to measure several properties simultaneously.

Controller Backup and Replication for Reliable Multi-domain SDN

  • Mao, Junli;Chen, Lishui;Li, Jiacong;Ge, Yi
    • KSII Transactions on Internet and Information Systems (TIIS)
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    • v.14 no.12
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    • pp.4725-4747
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    • 2020
  • Software defined networking (SDN) is considered to be one of the most promising paradigms in the future. To solve the scalability and performance problem that a single and centralized controller suffers from, the distributed multi-controller architecture is adopted, thus forms multi-domain SDN. In a multi-domain SDN network, it is of great importance to ensure a reliable control plane. In this paper, we focus on the reliability problem of multi-domain SDN against controller failure from perspectives of backup controller deployment and controller replication. We firstly propose a placement algorithm for backup controllers, which considers both the reliability and the cost factors. Then a controller replication mechanism based on shared data storage is proposed to solve the inconsistency between the active and standby controllers. We also propose a shared data storage layout method that considers both reliability and performance. Besides, a fault recovery and repair process is designed based on the controller backup and shared data storage mechanism. Simulations show that our approach can recover and repair controller failure. Evaluation results also show that the proposed backup controller placement approach is more effective than other methods.

A System Architecture for Facility Fault Diagnosis and Repair Action in Smart Factory (스마트 팩토리에서 설비 장애 진단 및 조치 시스템 구조)

  • Cho, Jaehyung;Lee, Jaeoh
    • KNOM Review
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    • v.23 no.1
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    • pp.18-25
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    • 2020
  • Recently, a research on a smart factory was developed from a concept of factory automation(FA) to the formation of collecting and analyzing data. This trend is accelerated as the development of communication technology(5G) and IoT devices are developed in various ways according to the field situation. In addition, digital transformation has been actively conducted in the strengthening corporate competitiveness, and various optimization studies are being conducted through process re-adjustment by combining data received from various IoT equipment and automated facilities. Therefore, in this paper, we propose a system architecture and its related components in diagnosing and repairing facility failure using a prediction system which is one of the related researches.

A study on the bonding properties of YBCO coated conductors with stabilizer tape (안정화 선재의 YBCO 초전도 접합 특성)

  • Kim Tae-Hyung;Oh Sang-Soo;Ha Dong-Woo;Kim Ho-Sup;Ko Rock-Kil;Shin Hyung-Seop;Park Kyung-Chae
    • Progress in Superconductivity and Cryogenics
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    • v.8 no.3
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    • pp.23-26
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    • 2006
  • For mechanical and electrical stability and environment protection. Cu and stainless steel stabilizers are laminated to a Ag layer to produce a composite neutral-axis(N-A) architecture in which the YBCO layer is centered between the oxide buffered metallic substrate and stabilizer strip lamination. This architecture allows the wire to meet operational requirements including stresses at cryogenic temperature. winding tensions as well as mechanical bending requirements including thermal and electrical stability under fault current conditions. We have experimentally studied mechanical properties of the laminated stainless steel and Cu stabilizers on YBCO coated conductors. We have laminated YBCO coated conductors by continuous dipping soldering process. We have investigated lamination interface between solder and stabilizer of the YBCO coated conductor. We evaluated bonding properties. tensile / shear bonding strength. and peeling strength laminated YBCO coated conductors.

A study on the properties of SmBCO coated conductors with stabilizer tape (SmBCO 고온 초전도 선재의 안정화재 특성)

  • Kim, Tae-Hyung;Oh, Sang-Soo;Kim, Ho-Sup;Ko, Rock-Kil;Song, Kyu-Jeong;Ha, Hong-Soo;Lee, Nam-Jin;Park, Kyung-Chae;Ha, Dong-Woo
    • Progress in Superconductivity and Cryogenics
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    • v.9 no.3
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    • pp.9-12
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    • 2007
  • In this study. we searched for the mechanical and electrical properties of laminated coated conductors with stabilizer tape. Stabilizer tape plays a role for mechanical and electrical stability and environmental protection. Cu material stabilizer was laminated to Ag capping layer on SmBCO conductor layer. This architecture allows the wire to meet operational requirements including the stressless at cryogenic temperature and winding tension as well as mechanical bending requirements including thermal and electrical stability under fault current conditions. First, we have experimentally studied mechanical bonding properties of the laminated Cu stabilizers on SmBCO coated conductors. We have laminated SmBCO coated conductors by continuous dipping soldering process, Second, we have investigated electrical properties of the SmBCO coated conductors with stabilizer lamination. We evaluated bonding properties, peeling strength and critical current for laminated SmBCO coated conductors with Cu stabilizers.

Management of Knowledge Abstraction Hierarchy (지식 추상화 계층의 구축과 관리)

  • 허순영;문개현
    • Journal of the Korean Operations Research and Management Science Society
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    • v.23 no.2
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    • pp.131-156
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    • 1998
  • Cooperative query answering is a research effort to develop a fault-tolerant and intelligent database system using the semantic knowledge base constructed from the underlying database. Such knowledge base has two aspects of usage. One is supporting the cooperative query answering Process for providing both an exact answer and neighborhood information relevant to a query. The other is supporting ongoing maintenance of the knowledge base for accommodating the changes in the knowledge content and database usage purpose. Existing studies have mostly focused on the cooperative query answering process but paid little attention on the dynamic knowledge base maintenance. This paper proposes a multi-level knowledge representation framework called Knowledge Abstraction Hierarchy (KAH) that can not only support cooperative query answering but also permit dynamic knowledge maintenance. The KAH consists of two types of knowledge abstraction hierarchies. The value abstraction hierarchy is constructed by abstract values that are hierarchically derived from specific data values in the underlying database on the basis of generalization and specialization relationships. The domain abstraction hierarchy is built on the various domains of the data values and incorporates the classification relationship between super-domains and sub-domains. On the basis of the KAH, a knowledge abstraction database is constructed on the relational data model and accommodates diverse knowledge maintenance needs and flexibly facilitates cooperative query answering. In terms of the knowledge maintenance, database operations are discussed for the cases where either the internal contents for a given KAH change or the structures of the KAH itself change. In terms of cooperative query answering, database operations are discussed for both the generalization and specialization Processes, and the conceptual query handling. A prototype system has been implemented at KAIST that demonstrates the usefulness of KAH in ordinary database application systems.

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A comparative study on learning effects based on the reliability model depending on Makeham distribution (Makeham분포에 의존한 신뢰성모형에 근거한 학습효과 특성에 관한 비교 연구)

  • Kim, Hee-Cheul;Cheul, Shin-Hyun
    • The Journal of Korea Institute of Information, Electronics, and Communication Technology
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    • v.9 no.5
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    • pp.496-502
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    • 2016
  • In this study, we investigated the comparative NHPP software model based on learning techniques that operators in the process of software testing and development of software products that can be applied to software test tool. The life distribution was applied Makeham distribution based on finite fault NHPP. Software error detection techniques known in advance, but influencing factors for considering the errors found automatically and learning factors, by prior experience, to find precisely the error factor setting up the testing manager are presented comparing the problem. As a result, the learning factor is larger than automatic error that is usually well-organized model could be established. This paper, a trust characterization of applying using time among failures and parameter approximation using maximum likelihood estimation, after the effectiveness of the data through trend examination model selection were well-organized using the mean square error and $R^2$. From this paper, the software operators must be considered life distribution by the basic knowledge of the software to confirm failure modes which may be helped.

A Return Bender Automatic Brazing Welding System for Heat Exchangers (열교환기용 리턴 밴더 자동 브레이징 용접 시스템)

  • Lee, Yong-Joong;Kang, Jin-Kap;Lee, Hyung-Woo
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.5 no.2
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    • pp.49-55
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    • 2006
  • In the consideration of the problem occurred by certain return bender brazing welding works that depend only on handworks, the automatization of the whole production line is impossible due to the high dependency of skillful workers. In addition, it is difficult to establish a standardization due to the various heat exchanger model and irregular amount of orders, and the fault reduction is also impossible due to the severe difference in brazing conditions. It is necessary to develop a method, which quantitively analyzes the problem existed in this manual brazing welding of return benders and technically solves that problem, and to lead the improvement of the productivity and cost reduction in order to increase the business competitive power. Then, this will contribute the technical development of automatic welding for Korea's heat exchanger businesses. Thus, this study develops an automatic technology, which automatically controls the flame strength using digital control methods, for various models and produces a sample model. It is possible to increase the productivity and produce uniformed and qualified products by solving the problem existed in manual processes using the developed automatic return bender brazing system. In addition, the brazing condition can be automatically controlled according to the model and line speed, and such an economical operation can reduce the production cost. The developed system is expected to future applications not only heat exchangers in the field of refrigeration and air conditioning, but also other various industrial fields that apply heat exchangers, such as car and boiler industries.

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A Method for Pedestrian Accident Reconstruction Using Optimization (최적화방법을 이용한 보행자 충돌사고 재현기법 개발)

  • 유장석;홍을표;장명순;박경진;손봉수
    • Journal of Korean Society of Transportation
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    • v.20 no.3
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    • pp.105-113
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    • 2002
  • As the number of pedestrian accident increases, the reconstruction of an accident becomes important to find the source of the fault. Generally, accidents are reconstructed by the intuition of experts or primitive physics. A reconstruction method is proposed using sophisticated optimization technology. At first, a dynamic simulation model is established for the accident environment. Occupant analysis for automobile crashworthiness is employed. The situation before an accident is identified by optimization. The impact velocity and the position of the pedestrian are utilized as design variables. The design variables are found by minimizing the difference between the simulation and the real accident. The optimization process is performed by linking an occupant analysis program MADYMO to an optimization program VisualDOC. Since the involved analysis is dynamics and highly nonlinear, response surface method is selected for the optimization process. Problems are solved for various situations.

A Study on the Improvement of Reliability of Safety Instrumented Function of Hydrodesulfurization Reactor Heater (수소화 탈황 반응기 히터의 안전계장기능 신뢰도 향상에 관한 연구)

  • Kwak, Heung Sik;Park, Dal Jae
    • Journal of the Korean Society of Safety
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    • v.32 no.4
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    • pp.7-15
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    • 2017
  • International standards such as IEC-61508 and IEC-61511 require Safety Integrity Levels (SILs) for Safety Instrumented Functions (SIFs) in process industries. SIL verification is one of the methods for process safety description. Results of the SIL verification in some cases indicated that several Safety Instrumented Functions (SIFs) do not satisfy the required SIL. This results in some problems in terms of cost and risks to the industries. This study has been performed to improve the reliability of a safety instrumented function (SIF) installed in hydrodesulfurization reactor heater using Partial Stroke Testing (PST). Emergency shutdown system was chosen as an SIF in this study. SIL verification has been performed for cases chosen through the layer of protection analysis method. The probability of failure on demands (PFDs) for SIFs in fault tree analysis was $4.82{\times}10^{-3}$. As a result, the SIFs were unsuitable for the needed RRF, although they were capable of satisfying their target SIL 2. So, different PST intervals from 1 to 4 years were applied to the SIFs. It was found that the PFD of SIFs was $2.13{\times}10^{-3}$ and the RRF was 469 at the PST interval of one year, and this satisfies the RRF requirements in this case. It was also found that shorter interval of PST caused higher reliability of the SIF.