• 해양환경안전학회지
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• 제21권2호
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• pp.130-139
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• 2015

본 연구에서 순천만 일대 새우 양식장 부근에서 이뤄지는 태양광 발전에 따른 소음영향평가방법을 진단하였다. 순천만 폐양식장에 태양광 발전시설이 설치되는 경우, 임계거리 17미터 이내에 위치한 새우양식장 $S_2$와 $S_3$(15미터 이격)은 소음에 대한 저감대책을 수립하지 않은 상태로 작업할 경우에는 악영향이 나타날 수 있다. 소음 스트레스를 감소시키기 위해 방음 판넬을 설치할 시, 본 연구에서 고려한 공사장비 최저효율(Case A), 일반효율(Case B), 최고효율(Case C)에 대한 수중소음 환경목표기준을 만족하는 것으로 나타났다. 건설 장비에서 발생되는 대기 소음이 수중으로 전파될 경우, 보다 합리적인 계산을 통해 수중 소음도 예측과 함께 주변 양식장에 미치는 누적 영향에 대한 심도 있는 평가 및 대책 수립이 필요하다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 추계학술대회 논문집
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• pp.380-384
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• 2010

A disturbance flow at piping bands and discontinuous regions such as a valve, a header has a intense broadband internal pressure field and a sound field which are propagated through the piping system The fields becomes the source of a vibration of this piping system. Intense broadband disturbance flow at a discontinuous region such as elbows, valves or headers generates an acoustical pulsation. The pulsation becomes the source of structural vibration at the piping system. If it coincides with the natural frequency of the pipe system, excessive vibration results. High-level vibration due to the pressure pulsation affects the reliability of the plant piping system. This paper discusses the high vibration and the branch vent pipe's failure of condensate-water supply piping system due to the effect of acoustical pulsations by flow turbulence from the flow control valves of globe type in a power site.

• Safety and Health at Work
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• 제15권2호
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• pp.181-186
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• 2024

Background: This study aimed to analyze the trend of occupational noise-induced hearing loss (ONIHL) in Brazilian workers at a metallurgical plant with a hearing conservation program (HCP), which has been addressed in a previous study. Methods: All 152 workers in this time series (20032018) participated in the HCP and used personal protective equipment. All annual audiometry records in the company's software were collected from the electronic database. The trend of ONIHL was analyzed with the joinpoint regression model. The hearing thresholds of ONIHL cases at the end of the series were compared with those found in a national reference study. Results: The binaural mean hearing thresholds at 3, 4, and 6 kHz at the end of the series were higher for ages ≥50 years, exposures ≥85 dB (A), time since admission >20 years, and maintenance workers. Significance was found only in the group divided by age. There was an increasing time trend of ONIHL, though with a low percentage variation for the period (AAPC = 3.5%; p = 0.01). Hearing thresholds in this study differed from the reference one. Conclusion: Despite the unmet expectation of a stationary trend in the study period, the time pace of ONIHL evolution did not follow what was expected for a population exposed to noise. These findings signal to the scientific community and public authorities that good ONIHL control is possible when HCP is well implemented.

• 동력기계공학회지
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• 제12권5호
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• pp.65-70
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• 2008

The purpose of this study is to verify availability of the acoustic emission in-situ monitoring method to the internal leak and operating conditions of the turbine major valves relating to safety for turbine operating and prevention of turbine trouble at nuclear power plants. In this study, acoustic emission tests are performed when the pressurized electro-hydraulic control oil flowed through turbine electro-hydraulic controller oil check valve and turbine power/trip fluid solenoid valve in the condition of actual turbine operating. The acoustic emission method was applied to the valves at the site, and the background noise was measured far the abnormal plant condition. To judge for the leak existence ell the object valves, voltage analysis and frequency analysis of acoustic signal emitted from infernal leak in the valve operating condition are performed. It was conformed that acoustic emission method could monitor for valve internal leak to high sensitivity.

• 소음진동
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• 제9권6호
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• pp.1200-1209
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• 1999

This paper reports a peculiar example of flow-induced vibration in a very large plant and the whole procedure of reducing the vibration. During the operation of flue gas desurfurization unit of the thermal power plant, serious vibration was dtected at all around the plant. The worst vibration was recorded on the heat exchanger surface, which weighed 180 tones, as 17.8 m/$s^2$ in vibration amplitude at 34 Hz. To identify the vibration, frequency analysis on the response vibration as well as on the expected excitation forces and the system resonance was executed. This investigation revealed that the cause of the vibration was vortex shedding from the circular pipes in the heat exchanger. Vortices from the pipes excited acoustic resonance in the heat exchanger room, which, in turn, made the structure vibrate. Through inserting the baffles between the pipes, which had an effect of cutting the acoustic wave at resonance frequency, the vibration was eliminated dramatically.

• 동력기계공학회지
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• 제11권1호
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• pp.39-44
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• 2007

The purpose of this study is to verify availability of the acoustic emission in-situ monitoring method to the internal leak and operating conditions of the major valves at nuclear power plants. In this study, acoustic emission tests are performed when the pressurized temperature water and steam flowed through glove valve(main steam dump valve) and check valve(main steam outlet pump check valve) on the normal size of 12 and 18". The valve internal leak monitoring system for practical field was designed. The acoustic emission method was applied to the valves at the site, and the background noise was measured for the abnormal plant condition. To improve the reliability, a judgment of leak on the system was used various factors which are AE parameters, trend analysis, frequency analysis, voltage analysis and amplitude analysis of acoustic signal emitted from the valve operating condition internal leak.

• 대한전기학회논문지
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• 제37권5호
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• pp.311-318
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• 1988

An adaptive control problem for a plant with unmodelled dynamics is studied. The upper bounds of the output due to the unmodelled dynamics and measurement noise is assumed to be known. This problem was studied by Middleton et al. They used a modified form of the least square method in estimating the plant paramaters. In this paper, the bounds of the parameters are estimated by linear programming and the parameters are estimated by the projetion type algorithm incorporating the bounds of the parameters. The stability of the proposed adaptive control system can be proved in nearly the same way as the proof of Middleton. The performance of the proposed method is found to be much better than the method of Midlleton's with respect to the parameter convergence and plant output in computer simulations.

• 플랜트 저널
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• 제17권4호
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• pp.53-60
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• 2021

본 연구에서는 국내 진동감시시스템 제작업체인 (주)나다와 발전소 회전기기 진동데이터 취득 및 분석에 효과적인 휴대용 진동분석기를 개발하고자 하였다. 개발된 휴대용 진동분석기의 하드웨어는 측정기기의 교정을 위한 측정 불확도를 통해 얻은 측정값을 시스템에서 보정함으로써 측정오차를 최소화하였고, 고속 데이터 처리로 높은 분해능을 가진 신호처리 장치로 구성되었다. 소프트웨어 구조는 다양한 진동 플롯을 구현하여 상세한 분석프로그램을 실행하며, 회전기기 운전 중 외란으로 발생하는 노이즈 측정 및 제거에 효과적인 알고리즘을 적용하였다. 개발품은 사용자의 이동 편의성 증대 및 고속 데이터 처리로 분해능을 높임으로써 성능향상은 물론, 국산화 개발에 따른 구입비용 절감에도 크게 기여하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 춘계학술대회논문집
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• pp.41-45
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• 2007

Palo Verde Unit 1 nuclear power station which is located in Arizona, USA had been operating at reduced power levels around 25% since December 25, 2005 due to vibration in one of its shutdown cooling lines. During an outage from March 18, 2006 to July 7, 2006 the necessary work and modifications to remedy the situation were performed. It cost approximately $46million to buy electricity to replace that lost as a result of this event. Therefore in this study, the vibration of shutdown cooling lines in the same nuclear power plant in Korea as Palo Verde Unit 1 should be measured by the operating condition of power plant. And it was evaluated using the expression for allowable velocity in ASME OM-S/G-2003. From the result of this study it is evaluated whether it is safe or not. If not the countermeasure should be considered in this study.

• 한국소음진동공학회논문집
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• 제17권7호
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• pp.572-578
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• 2007

Two stroke low speed diesel engines are widely used for marine propulsion or as power plant prime mover. These engines have many merits which includes higher thermal efficiency, mobility and durability. Yet various annoying vibrations occur sometimes in ships or at the plant itself. Of these vibrations, torsional vibration is very important and dictates a careful investigation during the engme's initial design stage for safe operation. With the rule and limit on torsional vibration in place, shaft strength fatigue due to torsional vibration however demands further analysis which possibly can be incorporated in the classification societies' rule and limit. In addition, the shaft's torsional vibration stresses can be calculated equivalently from accumulated fatigue cycles number due to transient torsional vibration in time domain. In this paper, authors suggest a new estimation method combined with Palmgren-Miner equation. A 6S70MC-C ($25,320ps{\times}91rpm$) engine for ship propulsion was selected as a case study. Angular velocity was measured, instead of shaft's strain, for simplified measurement and it was converted to torsional vibration stress for accumulated fatigue cycle numbers in shafting life time. Likewise, the accumulated fatigue calculation was compared with shaft fatigue strength limit. This new method can be further realized and confirmed in ship with two stroke low speed diesel engine.