• 한국소음진동공학회논문집
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• 제26권3호
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• pp.298-307
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• 2016

In the building process of FPSOs(floating production, storage and offloading units) is the increasing demand of high performance piping joints that can be installed on its turret system and maintain smooth and long-term flow of ultra-high pressure crude oil, being subjected to external excitations such as wind and wave on the sea. Following such a trend, in this paper, a new-type piping joint of four effective degrees of freedom has been designed, and its dynamic characteristics predicted through mathematical modeling and computer simulations. Moreover, via an example it was shown how the yaw motion in particular can be independently controlled for future durability test despite strong kinetic couplings.

• 한국소음진동공학회논문집
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• 제26권4호
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• pp.398-405
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• 2016

A shape of loop-pipe in a compressor affects the vibration of compressor. In this paper, optimal design of shape of loop-pipe to decrease the stress was carried out. Body and shell were assumed to be rigid, while loop-pipe is considered to be flexible. The finite element model was derived and programmed. Genetic algorithm was used for optimization. Locations of 18 point in loop-pipe were considered as shape variables, while the shapes of loop-pipe were interpolated as polynomials or ellipses. Maximum stress of loop-pipe was used as a fitness function for optimization. The spatial constraints and acceleration response of shell were also considered in optimization. The maximum stress and acceleration could be reduced by 79 % and 49 % respectively.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.327-332
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• 2004

Leak noise is a good source to identify the exact location of a leak point of underground water pipelines. Water leak generates broadband noise from a leak location and can be propagated to both directions of water pipes. This sound propagation due to leak in water pipelines is not a non-dispersive wave any more because of the surrounding pipes and soil. However, the necessity of long-range detection of this leak location makes to identify low-frequency acoustic waves rather than high frequency ones. Acoustic wave propagation coupled with surrounding boundaries including cast iron pipes is theoretically analyzed and the wave velocity was confirmed with experiment. The leak locations were identified both by the acoustic emission (AE) method and the cross-correlation method. In a short-range distance, both the AE method and cross-correlation method are effective to detect leak position. However, the detection for a long-range distance required a lower frequency range accelerometers only because higher frequency waves were attenuated very quickly with the increase of propagation paths. Two algorithms for the cross-correlation function were suggested, and a long-range detection has been achieved at real underground water pipelines longer than loom.

• 한국지진공학회논문집
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• 제26권1호
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• pp.39-48
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• 2022

Many piping systems installed in the power plant are directly related to the safety and operation of the plant. Various dampers have been applied to the piping system to reduce the damage caused by earthquakes. In order to reduce the vibration of the piping system, this study developed a steel coil damper (SCD) with a straightforward structure but excellent damping performance. SCD reduces the vibration of the objective structure by hysteretic damping. The new SCD damper can be applied to high-temperature environments since it consists of steel members. The paper introduces a design method for the elastoplastic coil spring, which is the critical element of SCD. The practical applicability of the design procedure was validated by comparing the nonlinear force-displacement curves calculated by design equations with the results obtained from nonlinear finite element analysis and repeated loading test. It was found that the designed SCD's have a damping ratio higher than 25%. In addition, this study performed a set of seismic tests using a shaking table with an existing piping system to verify the vibration control capacity on the piping system by SCD. Test results prove that the SCD can effectively control the displacement vibration of the piping system up to 80%.

• 한국진공학회지
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• 제15권4호
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• pp.421-426
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• 2006

화학증착 시스템의 파이프내 발생하는 오염입자의 진단을 위하여 초음파 및 진동진단법을 각각 비교, 연구하였다. 초음파 진단의 경우 파이프 외벽에 초음파 센서를 부착하여 펄스를 가한 후 에코 분석을 통해 파이프내벽의 오염입자를 관찰하였고 진동 진단의 경우 파이프외벽에 부착된 진통발생기를 통해 파이프에 인위적인 진동을 발생시켜 여기에서 발생되는 주파수 차이를 분석, 파이프내의 오염입자 여부를 관찰하였다. 초음파 진단의 경우, 오염입자가 파이프 내벽에 부착되어 있을 때는 효과가 좋았으나 오염입자가 시간이 지남에 따라 건조되어 파이프 내벽에서 떨어져 나와 파이프 내벽과 오염입자사이에 틈새가 생길 경우 초음파 펄스는 이 공간을 통과하지 못하고 파이프 내벽에서 다시 반사되어 오염입자를 진단하지 못하는 경우가 발생하였다. 따라서 초음파 진단법으로는 진공장비의 오염입자 관찰에 재현성을 보여주지 못하는 것으로 확인되었다. 반면 진동진단법의 경우 위와 같이 일정시간이 지난 동일한 샘플의 경우에서도 오염입자에 의한 차이가 관찰되었다, 즉 파이프내 오염입자가 존재시 새 파이프에 비해 진동음이 저주파대로 떨어짐이 확인되어 추후 화학증착 시스템의 파이프내 오염입자 모니터링 연구에 가장 효과적인 방법으로 기대된다.

• 한국산학기술학회논문지
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• 제20권1호
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• pp.426-433
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• 2019

지진의 2차사고 중 화재 및 가스 폭발에 의한 사고는 아파트형 주거 형태와 대형 복합화 된 건물이 많은 도시 일수록 인명피해의 우려가 커지게 되고, 이를 방지하기 위하여 화재 방호 계통 스프링클러 시스템의 경우 내진 설계가 필수적으로 수행되어야 한다. 하지만 현재 일반적으로 사용하고 있는 화재 방호 계통 스프링클러 시스템 배관은 대부분 스테인리스 계열의 금속 파이프를 사용하고 있고 일부 특수 위치에서 합성수지 계열의 파이프를 사용하고 있어 진동 및 지진 등에 취약한 소재가 적용되고 있다. 이에 본 연구에서는 폴리에틸렌(Polyethylene, 이하 : PE)과 알루미늄(Aluminum, 이하 : Al)의 다층구조 복합관이 보유한 변위 흡수 유연성이 진동 환경과 지진 발생에 대한 내진 성능을 상승 시키는 특성으로 판단하였고, PE-Al-PE 복합관을 기존 스테인리스 관, PE관과 비교하여 내진 성능을 실험 하였다. 내진 특성은 스프링클러 파이프가 전달하는 진동의 양과 범위를 측정하면 진동에 대한 흡수 정도를 알 수 있고 이는 지진에 대하여 대상체가 자체적으로 진동을 감쇠하는 내진 특성 판단의 방법으로 횡 형 진동 측정법으로 발생한 진동의 최초 응답 변위에 대한 대수 감쇠율을 비교하여 파이프의 내진 특성을 확인하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2008년도 정기 학술대회
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• pp.561-566
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• 2008

Recently, because of development of the high speed train technology, the vibration loads by train is significantly increased ever than before. This buried gas pipelines are exposed to both repeated impact loads, and, moreover, they have been influencing by vibration loads than pipeline which is not located under vehicle loads. The vibration characteristic of pipeline is examined by dynamic analysis, and variable is only train speed. Since an effect of magnitude of vibration loads is more critical than cover depth, as increasing the train speed, the vibration speed of buried pipelines is also increased. The slope of vibration velocity is changed by attenuation of wave, at train speed, 300 km/h. From the analysis results, the vibration velocity of pipelines is satisfied with the vibration velocity criteria which are established by Korea Gas Corporation. The results present operation condition of pipelines under rail loads has fully sound integrity based on KOGAS specification.

• 대한전자공학회논문지
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• 제9권4호
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• pp.7-16
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• 1972

고체화된 연산증폭기를 중심으로 구성한 광전측광장치를 구성하였다. 광원에 대응하여 광전자증배관에서 얻는 미소전류의 증폭과 별의 등급측정을 위한 대수변환은 동일연산증폭기의 변형으로 얻고 있다. 측정기능의 한계는 주로 증폭기입력단의 bias전류에 좌우되므로 이것은 광산증폭기의 선택상 주요기준이 될 것이다. 이러한 연산증폭기는 종래 전위계진공관 혹은 진동용량형전위계 등으로 가능하였던 각종 미소전류·전압의 증폭에 높은 신뢰성과 경제적인 증폭방식으로 적용된다.

• 한국안전학회지
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• 제14권4호
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• pp.71-77
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• 1999

Exposed gas pipeline in underground, especially subway construction site, has been continuously vibrated by vehicle above ground. Because this vibration can cause unexpected damages to pipeline, we had measured and analyzed the vibration. This paper presents results of the vibration analysis of exposed gas pipeline and the results are as follows. The major vertical vibration frequency of pipeline was about 13 Hz and the other frequency components disappeared when the vibration transmitted to I-beam and wire rope. Existence of wooden casement had not affect vibration of exposed gas pipeline. The results of modal analysis by experimental and analytical methods have good agreement and it is also shown that exposed pipeline has possibility of resonance at second mode.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1026-1030
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• 2007

A linear compressor used in a refrigerator has higher energy efficiency than a reciprocating compressor. But its vibration level is still severe than others. The vibration level of linear compressor at the frequency of 60Hz is dominant since it is the exciting frequency of a motor. Experimental approach to reduce the vibration needs much effort and long period. In this paper, simulation tool to predict the vibration of the shell of the linear compressor was developed. The piston, body and shell are assumed to be rigid, while the loop pipe is flexible. The results by the developed tool showed good agreements with those by experiments.