Experiments that simulate bearing failures and the presence of cavitation are performed on a pump loop. During the experiments several types of data are acquired such as vibrations, system pressure, flow rate and motor current. A multivariate analysis is then applied to these data. Abnormalities are detected by evaluating the residual between the measured value and the estimated value that is determined from the model in a normal state. Because the influence of bearing failures is limited to a very loc...
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Evaluation of a Multi-Sensors Condition Monitoring Method

１．背景　米国機械学会は、先駆的に原子力発電設備の維持規格制定に取組み、1971年に供用期間中検査を規定したASME Code Section XIを制定している。その後、ASME Code Section XIの1974年版では、検査で発見された欠陥の成長評価と機器の健全性に基づく欠陥評価基準が新たに導入された。この基準は、供用期間中に発見された欠陥については、製造時の許容基準を超えた場合についても健全性を損なわない範囲で許容し、欠陥が存在したまま継続運転可能とするものであり、1960年代に進展した破壊......

The conventional design of structural components such as piping or vessels is made based on the deterministic method. In the design method, the margin of the design integrity is expressed as empirical safety factor. On t he other hand, the stochastic safety factor is calculated from data such as the standard deviation of the mate rial strength in the LRFD (Load and Resistance Factor Design) method. This method allows a rational design bas ed on the up-to-date knowledge. In this study the optimization met...
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Development of Maintenance and Design Optimization Method forPiping System Based on Stochastic Theory

This paper discusses maintenance optimization by the automatic planning tool for regular plant outage work in nuclear power plant using the logic programmin g language “Prolog”. As a result of consideration, the following results were obtained. (1) The automatic planning tool for regular plant outage in nuclear power plant was developed. (2) Using this tool, the work plan for BWR primary recirculation system and residual heat removal systemwas automatically made on the condition of flattening man loading o...
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A Study on Maintenance Optimization by the Automatic Planning Tool for Regular Plant OutageWork in Nuclear Power Plant Using the Logic Programming Language “Prolog”

This study aimed to establish the method for evaluating the amount of bearing flaking in balls. We performed 5 accelerated aging tests of ball bearing s that expedite the occurance of flaking in balls and analyzed the vibraion signal. Some characteristic features for initial stage of flaking in balls are revealed such as sudden decrease of vibarion level or pulse vibration once per several revolutions of a ball. Those knowledge can be used for diag nosing the severity of bearings that indicate the existanc...
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A Study on Evaluating the Amount of Bearing Flaking in Balls

A new electromagnetic method for the nondestructive evaluation of electric pumps with sliding bearings is proposed. A permanent magnet gen erates a static magnetic field and a coil of several hundred turns wrapped around it is used to pick up eddy currents induced inside rotat ing impellers. This electromagnetic nondestructive evaluation method is applied to the canned pump. By monitoring the movement of the impe ller in a canned pump, the rotation speed, the variance of the impeller position as well as th...
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Study of Evaluation Method for the Amount of Wear-Out of Plain bearingswith Electromagnetic Sensor

This study evaluates the size of outer race defects of ball bearings during accelerated life testing by analyzing the signal of an electromagnetic sensor. The electromagnetic sensor consists of a pickup coil wrapped around a permanent magnet. When a conductor passes in the static magnetic field, the generated eddy currents are detected as a change of the magnetic field. The autocorrelation method is applied for sizing defects in the early phase of the damage growth and the RMS method is applied for la...
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Nondestructive Electromagnetic Monitoring and Diagnosis of Damage Growth in Ball Bearings

This study evaluates the outer race defect size of ball bearings in the accelerated life test by analyzing the signal of electromagnetic sensor. The electromagnetic sensor consists of a permanent magnet and a pickup coil. When a conductor passes in the static magnetic field, the generated eddy current is detected as the change of the magnetic field. The autocorrelatio n method is applied for sizing defects in the early phase of the damage progress and the RMS method is developed for bigger defects. With th...
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Electromagnetic Nondestructive Detection for Monitoring the Damage Progress of Ball Bearings

Abstract Maintenance is an activity to keep the functions of systems, structures and components against aging phenomena. Maintenance has so far been carried out based on experience of the experts mainly engaged in the plant. However in order to make a suitable maintenance program, it is necessary to predict the future based on past knowledge and past research data. Then, it is necessary to regard m aintenance as sciences and to systematize maintenance, that is, maintenology needs to be constructed. As the ...
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The Future Activity for Construction of Maintenology

Abstract: This study proposes an electromagnetic method for the evaluation of the condition of a turbine in a nuclear power plant. Experimental results of a small turbine driven by an electric motor are shown in th is paper. A high temperature superconductivity electromagnet is applied outside the case of the turbine to provide excitation magnetic field. On the other hand, pickup coils are placed near the impeller inside the case of the turbine. The experimental results show that it is not only possible to...
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Electromagnetic evaluation of the impeller of a turbine using a hightemperature superconductivity electromagnet