• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.11
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• pp.1029-1035
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• 2011

Pressure pulsation of exciting sources that generally occurs on the piping system connected to the discharge of BFP(boiler feed water pump) in power plants causes wave reflection, wave interference, resonance, standing wave and so on. But if the operating speed of the pump is changed, the state of the noise and vibration can be done because characteristics of the exciting source are changed. This paper is to investigate the cause of the noise and vibration occurring on the piping system when the operating speed of BFP is down in accordance with lowering of the power generation. It is approached to two points of view ; Firstly, it is examined whether the pulsation source impacts on the shell mode vibration that vibrates radially across the cross-section of the pipe. But it doesn't affect the shell mode as much as the resonance occurs. Secondly, to find the relation between the pulsation source and the acoustic mode of the piping system, analysis for the piping system by indirect BEM(boundary element method) is carried out. Therefore it is investigated that the mechanism of the noise and vibration relates with acoustic mode of the piping system.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.11 no.4
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• pp.511-517
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• 1999

Determining the simultaneous flow rate in any particular section of piping is the important step in order to determine the size of water supply piping. Now we are using the diversity curve of common water closet in order to determine the simultaneous flow rate of water supply piping, but there is a difference between a determined flow rate of general water closet and that of water closet for water saving. This study aims to find out the fixture unit of a flush valve type water closet for water saving in office building, and to determine the correlation between the fixture units and peak flow rates on the basis of the probability theory. A flush valve type water closet for water saving that have a 7.5 second duration of flush operation with an average design flow rate 72 $\ell$/fin was considered. Simulation results indicate that the number 5 is shown to be reasonable to the fixture unit of water closet for water saving. And the design can be undersized considerably with the revised diversity curves using modified fixture unit.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1-5
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• 2007

A majority of piping vibration problems are induced by internal fluid pulsation; turbulent flow, vortex shedding at internal discontinuities, and pressure pulsation at equipment nozzles. The pulsation at the pressure sources resonates acoustically with the piping and the amplified pressure pulsation can generate shell mode vibration in the piping. Reheater attemperator piping supplies water from feedwater pump to reheater attemperator to control the boiler temperature. In normal operating condition, the high frequency shell mode vibration occurred in the piping with the high level of sound(105 ${\sim}$ 117 dB). The vibration sources are pressure pulsation in the pump nozzle and the frequencies are related to the blade passing frequencies. The objects of this paper are to analyze the cause of the high frequency vibration and to establish corrective actions.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.27 no.4
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• pp.228-232
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• 2015

The water supply galvanized steel pipes of apartment buildings in Bucheon city constructed with building permission before 1994 have many problems such as leaks, the water containing rust, and low water pressure due to corrosion. Therefore, this study aims to find a way to renew the water supply pipes under investigation through a survey. As a result, when replacing the galvanized steel pipe with the corrosion-resistant pipe, the water supply system should also be changed from the gravity tank system to the booster pump system and the hygienic water storage tank. It is necessary to redraft the long-term repair plan including the replacement of the water supply system. Also, it is necessary to save the allowance reserve according to the modified long-term repair plan.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.05b
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• pp.186-192
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• 1996

가압기의 유체 조건이 증기에서 이상유체로 변화하는 완전급수상실사고 경우에 대한 안전감압계통의 가압기 노즐 및 밸브 전단에서의 유량, 밸브 후단에서의 압력 변화 등 RELAP5/MOD1과 RELAP5/MOD3로 계산된 열수력 조건이 유사한 추세를 나타내었다. 또한 RELAP5/MOD1-CALPLOTFIII와 RELAP5/MOD3-CALPLOTFIII 전산체제로 계산된 안전감압계통의 각 배관부위에서의 동하중도 유사한 추세를 나타내었다. 즉, RELAP5/MOD1-CALPLOTFIII와 RELAP5/MOD3-CALPLOTFIII 전산체제를 이용한 안전감압계통의 열수력 과도현상 해석 결과가 유사하여 RELAP5/MOD1 대신에 RELAP5/MOD3가 안전감압계통의 열수력 과도현상 분석에 대체사용될 수 있을 것으로 판단된다. 그러나 본 연구는 안전감압계통에 국한하여 수행되었으며, RELAP5/MOD1과 RELAP5/MOD3를 이용한 가압기안전밸브 방출배관에 대한 기존의 연구 결과에 의하면 RELAP5/MOD3가 만족스러운 곁과를 제공하지 못하는 바, 다른 계통에 RELAP5/MOD1 대신 RELAP5/MOD3를 대체적용하기 위해서는 개별적으로 각 계통에 대한 비교 평가가 선행되어야 할 것으로 판단된다.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.20 no.1
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• pp.15-28
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• 1991

불단수(不斷水) 공법(工法)은 기존(旣存)의 상수도(上水道) 배관(配管)으로 부터 지관(支管)을 분기(分岐)할때, 급수(給水)의 중단(中斷)없이 공사(工事)를 시행(施行)하는 방법이다. 이 방법(方法)은 이미 미국이나 유럽의 모든 국가(國家)에서 공통적으로 적용하고 있는 공법(工法)이며, 특히 일본(日本)은 우리나라와 상황(狀況)이 매우 유사하므로, 일본(日本)의 사례(事例)를 중심으로 불단수(不斷水) 공법(工法)의 개요(槪要)와 장단점(長斷點), 공법(工法)을 적용하기 위하여 필요한 장비(裝備)와 공구(工具) 및 관련 제품(製品)에 대하여 요약(要約) 기술(記述)하였다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1065-1069
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• 2003

In this paper, Firstly, it is shown that the high vibration and noise source of piping and pump system is the acostic resonance. Secondly, in order to decrese the high vibration and noise of piping and pump system, the acostic mode of piping have been changed and its effectiveness is investigated as applied it at piping system practically.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.7
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• pp.717-722
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• 2011

The aim of this study is to identify the locations at which local wall thinning occurs and to determine the turbulence coefficients related to local wall thinning. Experiments and numerical analyses of the tee sections of different down-scaled piping components were performed and the results were compared. Numerical analyses of full-scale models of actual plants were performed in order to simulate the flow behaviors inside the piping components. In order to determine the relationship between the turbulence coefficients and the rate of local wall thinning, numerical analyses of the tee components in the main feedwater systems were performed. The turbulence coefficients obtained from the numerical analyses were compared with the local wear rate obtained from the measurement data. From the comparison of the results, the vertical flow velocity component (Vr) flowing to the wall after separating in the wall due to the geometrical configuration and colliding with the wall directly at an angle of some degree was analogous to the configuration of local wall thinning.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.5
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• pp.385-393
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• 2013

In this paper, the mechanism identification and the avoidance measures on the phenomena of transient acoustic vibration amplified at the water-supply piping system to regulate the steam temperature of the boiler reheater in 500MW class supercritical power plant are presented. The pressure pulsation waves induced by the impeller passing of two feed-water pumps with five blades are coincident with the local acoustic modes of boiler reheater water-supply piping system. There are the phenomena amplified at the peaks of 5X, 10X, 15X and 20X in spectrums of piping vibration, sound pressure, and the feed-water's pressure pulsation waves. The shut-off device is installed in the piping system for the interception of pressure pulsation waves transmitted from two feed-water pumps and the modified design change of the piping layout is applied for the acoustic resonance avoidance. The acoustic natural frequencies are separated from the harmonics of pressure pulsation waves induced by the pump impellers passing through the design change of the span length. The acoustic vibration is gone by resonance avoidance measures. As a result, more than 20 dBA reduction is achieved from 100 dBA to 80 dBA.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1290-1295
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• 2006

The 120 meters high pressure feedwater heater drain piping in nuclear power plant had been suffered by excessive vibration from the beginning of power generation. As time goes by, the piping vibration was beyond the allowable limit and an appropriate countermeasure was required to prevent the fatigue failure of the pipeline from the abnormal vibration. In this study, the vibrational characteristics of high pressure feedwater heater drain piping and the countermeasure for abnormal vibration were investigated. Among the several vibration reduction methods, the piping layout changed by making the smooth pipeline was applied to the high Pressure feedwater heater drain piping in nuclear Power plant. Applying the countermeasure, the vibration level was found to reduce over 54 percents and was satisfied under the allowable velocity at the full-power operation condition.