• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.128-132
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• 1997

This paper deals with the optimization of pipe-support allocation using the genetic algorithm, and shows the feasibility of the optimization method to actual design problems and also the convergence characteristics of optimization calculation with respect to the various seismic waves. The piping system was modeled as mass-spring system with 5 degrees of freedom and the support was as spring-damper. The support allocation problem was formulated to minimize the response of the piping system to seismic excitation.

• Corrosion Science and Technology
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• v.14 no.1
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• pp.1-11
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• 2015

Local wall thinning and integrity degradation caused by several mechanisms, such as flow accelerated corrosion (FAC), cavitation, flashing and/or liquid drop impingements, are a main concern in carbon steel piping systems of nuclear power plant in terms of safety and operability. Thinned pipe management program (TPMP) had been developed and optimized to reduce the possibility of unplanned shutdown and/or power reduction due to pipe failure caused by wall thinning in the secondary side piping system. This program also consists of several technical elements such as prediction of wear rate for each component, prioritization of components for inspection, thickness measurement, calculation of actual wear and wear rate for each component. Decision making is associated with replacement or continuous service for thinned pipe components. Establishment of long-term strategy based on diagnosis of plant condition regarding overall wall thinning is also essential part of the program. Prediction models of wall thinning caused by FAC had been established for 24 operating nuclear plants. Long term strategies to manage the thinned pipe component were prepared and applied to each unit, which was reflecting plant specific design, operation, and inspection history, so that the structural integrity of piping system can be maintained. An alternative integrity assessment criterion and a computer program for thinned piping items were developed for the first time in the world, which was directly applicable to the secondary piping system of nuclear power plant. The thinned pipe management program is applied to all domestic nuclear power plants as a standard procedure form so that it contributes to preventing an accident caused by FAC.

• Journal of the Earthquake Engineering Society of Korea
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• v.19 no.1
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• pp.29-36
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• 2015

Base isolation is considered as a seismic protective system in the design of next generation Nuclear Power Plants (NPPs). If seismic isolation devices are installed in nuclear power plants then the safety under a seismic load of the power plant may be improved. However, with respect to some equipment, seismic risk may increase because displacement may become greater than before the installation of a seismic isolation device. Therefore, it is estimated to be necessary to select equipment in which the seismic risk increases due to an increase in the displacement by the installation of a seismic isolation device, and to perform research on the seismic performance of each piece of equipment. In this study, modified NRC-BNL benchmark models were used for seismic analysis. The numerical models include representations of isolation devices. In order to validate the numerical piping system model and to define the failure mode, a quasi-static loading test was conducted on the piping components before the analysis procedures. The fragility analysis was performed by using the results of the inelastic seismic response analysis. Inelastic seismic response analysis was carried out by using the shell finite element model of a piping system considering internal pressure. The implicit method was used for the direct integration time history analysis. In addition, the collapse load point was used for the failure mode for the fragility analysis.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.187-192
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• 2006

The effect where the multiple sound arrest ing goes mad to the human being does the zone. From like that cotton, this dissertation the both sides flag executed the research regarding a sound arresting reduction in the object in one example. It compared the piping structure which generally is space-time and a specific piping structure and it tested and research and the modeling regarding a sound arresting reduction the simulation which leads and it executed result and comparison of existing it analyzed. The duplication where the reduction effect is bigger the result general VG2 piping structure than escape it did with the fact that it appears the large effect the piping structure which it connects. Also, the straight pipe effect of multiple sound arresting could not go mad with the fact that.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.9
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• pp.2251-2256
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• 1994

An experimental study was conducted on water hammer phenomena generated by quick valve operations in piping systems of buildings. Transient water hammer pressure waves were measured for three different types of valves, i. e. a ball valve, a solenoid valve, and on one-touch valve. The effects of flow rate and valve closing time on the maximum water hammer pressure were investigated. Based on the experimental results, general design recommendations were provided to prevent water hammer phenomena in piping systems of high-rise apartment buildings.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.05a
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• pp.393-398
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• 2001

Pulsations, vibration and stress are the basic dynamic phenomena in power plant piping systems which directly affect system reliability. These phenomena are both acoustical and mechanical in nature and are closely interrelated. It was noticed that thermodynamic parameters were changed after replacing with new type tube bundles of reheat exchanger. It was reported later that the drain piping connecting the new bundle header with the associated drain tank is regularly pulsating at about every 3 second with 13.4㎐ and 7.5mm, p-p in amplitude. This amplitude is about 6 times higher than reference level of sound piping. The results of finite element analysis of the pipeline showed that its dominant natural frequency is 13.4㎐. The soundness is predicted whether the bending dynamic stress evaluated excesses the maximum allowable high cycle fatigue stress or not by the measured amplitude of vibration.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.609-615
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• 2001

This study proposes analysis and evaluation method of time series ultrasonic signal using attractor analysis for fusion joint part of polyethylene piping. Quantitatively characteristics of fusion joint part is analysed features extracted from time series. Trajectory changes in the attractor indicated a substantial difference in fractal characteristics. These differences in characteristics of fusion joint part enables the evaluation of unique characteristics of fusion joint part. In quantitative fractal feature extraction, feature values of 4.291 in the case of debonding and 3.694 in the case of bonding were proposed on the basis of fractal dimensions. In quantitative quadrant feature extraction, 1,306 point in the case of bonding(one quadrant) and 1,209 point(one quadrant) in the case of debonding were proposed on the basis of fractal dimensions. Proposed attractor feature extraction can be used for integrity evaluation of polyethylene piping material which is in case of bonding or debonding.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.11 no.2
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• pp.25-30
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• 2015

In the present study, complex leakage probabilities of nuclear pipes due to fatigue and stress corrosion cracking are evaluated by using the PINTIN(Piping INTegrity INner flaws) that is developed based on the existing PRAISE(Piping Reliability Analysis Including Seismic Events) program. With regard to the aging and crack instability, small leak and big leak probabilities are calculated for several pipes in a reactor coolant system of domestic nuclear plant. Moreover, sensitivity analysis is also performed to find out the effect of parameters for the leakage of pipes, which shows the coolant temperature is the most influencing parameter.

• Ocean Systems Engineering
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• v.9 no.1
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• pp.79-95
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• 2019

The material analysis of an offshore structure is generally conducted in the contract design phase for the price quotation of a new offshore project. This analysis is conducted manually by an engineer, which is time-consuming and can lead to inaccurate results, because the data size from previous projects is too large, and there are so many materials to consider. In this study, the piping materials in an offshore structure are analyzed for contract design using a big data framework. The big data technologies used include HDFS (Hadoop Distributed File System) for data saving, Hive and HBase for the database to handle the saved data, Spark and Kylin for data processing, and Zeppelin for user interface and visualization. The analyzed results show that the proposed big data framework can reduce the efforts put toward contract design in the estimation of the piping material cost.

• Fire Science and Engineering
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• v.30 no.3
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• pp.55-61
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• 2016

In this study, to determine whether it is possible to apply Polyethylene (PE) compound pipe, which was developed to solve the problem caused by the corrosion of the fire protection piping currently in usein water based fire extinguishing systems, we performed an actual mockup fire test. Since no test standard was available related to the developed compound pipe, we compared and analyzed domestic and international technical materials and test standards and selected suitable fire test standards to evaluate the performance of the PE compound pipe. we applied two fire test standards to the PE compound pipe, viz. those for CPVC and metallic pipes, and conducted a total of 6 experiments to evaluate its performance. According to the results of the first and second fire tests based on the test standard for the CPVC pipe, neither the fitting nor the piping was damaged or deformed and no leakage was observed in the pressure test, which was performed for 5 minutes. For the fire test based on the metallic pipe test standard, a total of 4 experiments were conducted. The first two experiments were conducted to simulate the wet piping system. In the results of this fire test, neither leakage nor rupture was observed from the PE compound pipe and no damage was caused, such as the secession of the PE material. However, in the next two experiments, which simulated the dry system, the PE compound pipe suffered damage and rupture, including deformation before the fire fighting water was discharged. Therefore, we found that the piping performance of the PE compound pipe did not undergo any deterioration, including fusion, deformation, or damage, in the wet piping system simulated fire test.