• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.3383-3388
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• 2007

To compare the sensor performance of AE leak diagnosis system which can measure valve leak conditions, AE activities such as RMS voltage level, AE signal trend, leak rate degree according to AE database, FFT spectrum were measured on valve of the simulated test system for power plant. AE activities were recorded and analyzed from various operating conditions including different temperature, pressure difference, valve size and fluid using both piezoelectric acoustic emission sensor and Pb-Free acoustic emission sensor. The results of this study are utilized to select the type of sensors, the frequency band for filtering and thereby to improve the signal-to-noise ratio for diagnosis or monitoring of valves in operation. As the final result of application study above, portable type leak diagnosis system by AE was developed. The outcome of the study can be definitely applied as a means of the diagnosis or monitoring system for energy saving and prevention of accident for power plant valve.

• 한국진공학회지
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• 제16권4호
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• pp.235-243
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• 2007

지금 국내에서는 토카막 핵융합실험장치, 대전류 중성입자빔 실험장치 및 우주 모의실험실 같은 거대시설의 건설과 운용이 활발하다. 이런 시설의 핵심설비인 대형 진공용기는 중소형 용기에 비해 누설 가능성은 높은 반면 기체누설을 검사하는 것은 까다롭다. 중소형 용기에서 널리 사용되는 헬륨누설검사 방법을 어떻게 효율적으로 이런 대형 용기에 적용할 수 있는가 알아보기 위해, 다양한 가상적인 누설검사 시스템들을 구성하고 압력분포 및 헬륨 분압을 계산하여 주어진 장치조건에서 적절한 검사 시스템을 찾는 방법에 대해 논한다.

• 한국유체기계학회 논문집
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• 제19권4호
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• pp.39-42
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• 2016

A PFA lined ball valve, which is machined with fluorinated resin PFA to its inner part for improving corrosion resistance, non-stickness, heat-resistance, has been widely used to the chemical/pharmaceutical industries, the semiconductor/LCD manufacturing processes, etc. with the high purity chemicals as working fluid. EPA stated that 60% of all fugitive emissions come from the valve stem packing in a typical petroleum or chemical processing plant. They monitor regulated components for leaks and maintain seal performance at acceptable levels. Korean industrial standards only deals with the bubble test for in-line leakage of valves, which has the detectable leak rate of $10^{-4}$ [$mbar{\cdot}L{\cdot}s^{-1}$], therefore, it is not sufficient to check fugitive emissions. In this study, we conducted Helium leak detection from a PFA lined ball valve and evaluated fugitive emissions according to ISO 15848-1, which has the detectable leak rate of $10^{-9}$ [$mbar{\cdot}L{\cdot}s^{-1}$], for manufacturing the high-reliable PFA lined ball valves against fugitive emissions.

• 한국산학기술학회논문지
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• 제21권4호
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• pp.546-551
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• 2020

함정에는 격벽으로 구분되어 나누어지는 공간인 격실이 종류와 목적에 따라 수개 혹은 수십 개가 존재한다. 이러한 격실들은 화재 및 화재로 인한 연기의 전이방지, 침수 시 침수의 확산 방지 등 특정 격실에서 발생하는 특이 상황들이 타 격실로의 전이를 방지하여 생존성 향상에 목적을 두고 설계된다. 생존성 향상 목적 달성을 위하여 각 격실들은 기밀 또는 수밀을 유지하도록 건조하며, 각 격실의 기밀 또는 수밀 정도를 확인하기 위하여 함정 건조 단계에서 평가를 수행한다. 건조하고 있는 군함에 관한 평가는 해군 지침에 의거하여 함 건조업체 주관으로 해군 및 국방기술품질원이 입회하여 평가를 실시한다. 생존성과 직결되는 만큼 격실 기밀 평가의 중요성은 매우 높아 명확한 기준에 따라 수행되고 있으나, 1개 이상의 복수개 격실 기밀 평가 시 1개 압력센서로 압력을 측정하여 격실 압력을 실시간으로 확인하는 것과 각 격실별 미세한 압력 변동 사항 확인이 제한되는 것을 식별하였다. 따라서 본 연구에서는 현재 수상함정 중 군함에서 실시하고 있는 그룹 격실 기밀평가 방안에 대한 개선 방안 및 신뢰성 검증 방안에 대해 서술하였다.

• Corrosion Science and Technology
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• 제3권1호
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• pp.30-33
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• 2004

It has been reported that some events of a rupture of seam generator tube have occurred in nuclear power plants around the world. Main causes of the leakage are from various types of corrosion in the steam generator(SG) tubings. Primary water stress corrosion cracking(PWSCC) of steam generator tubings have occurred in many tubes in Korean plant, and they were repaired using sleeves or plugs, In order to develop proper repair criteria, it is necessary to ascertain the leak behavior of the tubings. A high pressure leak and burst testing system was manufactured. Various types of Electro Discharged Machined (EDM) notches were developed on the SG tubes. Leak rate and burst pressure were measured on the tubes at room temperature. Burst pressure of the part through wall defected tubes depends on the defect depth, Water flow rates after the burst were independent of the t1aw types; tubes having 20 to 60 mm long EDM notches showed similar flow rates regardless of the defect depth. A fast pressurization rate gave the tube a lower burst pressure than the case of a slow pressurization.

• 한국초전도ㆍ저온공학회논문지
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• 제7권3호
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• pp.39-42
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• 2005

In this paper, the thermal characteristics of multilayer insulation (MLI) were experimentally investigated by using boil-off calorimetry method for seeking optimum standards of thermal insulation conditions. It is necessary to design the thermal insulating efficiency for applying to cryogenic instruments such as HTS power cable system. It is well known that the thermal characteristics and heat transfer of MLI are greatly affected by various MLI structures such as the number of layers and layer density, etc. However, it is difficult to know the thermal characteristics of MLI correctly. The heat leak by MLI between room temperature and liquid nitrogen temperature was measured at various conditions using a cylindrical cryostat. The cryostat consists of two guard vessels located at both end sides and a test vessel between them. The guard vessels are also filled with liquid nitrogen to prevent radiation heat leak through the both end side of the cylindrical test vessel to measure the heat leak only through MLI.

• 한국압력기기공학회 논문집
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• 제4권2호
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• pp.29-33
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• 2008

As the measures of nuclear power plant utilities and manufacturers to reduce the defects of tube expansion region during manufacturing steam generators, many types of NDEs(Non-Destructive Examinations) are conducted to inspect the expansion region. The expansion region of tube is subject to degrade because of stress concentration induced by tube expansion, sludge pile and high temperature. So the inspections for tube expansion region have been reinforced. Liquid penetrant test, helium leak test, Bobbin profile test and hydraulic test are performed to confirm the integrity of tube expanded by hydraulic expansion method. Liquid penetrant test and helium leak test are used to inspect seal weld region on tubesheet end part. Bobbin Profile test is used to inspect fully the expanded region of steam generator tube. Hydraulic test finally verifies the integrity of seal weld region on tubesheet end part.

• 한국마이크로전자및패키징학회:학술대회논문집
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• 한국마이크로전자및패키징학회 2001년도 추계 기술심포지움
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• pp.129-133
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• 2001

In this paper, hermetic sealing was studied fur wafer level packaging of the MEMS devices. With the flip-chip bonding method, this B-stage epoxy sealing will be profit to MEMS device sealing and further more RF-MEMS device sealing. B-stage epoxy can be cured 2-step and hermetic sealing can be obtained. After defining $500{\mu}{\textrm}{m}$-width seal-lines on the glass cap substrate by screen printing, it was pre-baked at $90^{\circ}C$ for about 30 minutes. It was then aligned and bonded with device substrate followed by post-baked at $175^{\circ}C$ for about 30 minutes. By using this 2-step baking characteristic, the width and the height of the seal-line were maintained during the sealing process. The height of the seal-line was controlled within $\pm0.6${\mu}{\textrm}{m}$ and the strength was measured to about 20MPa by pull test. The leak rate of the epoxy was about $10^7$ cc/sec from the leak test.

• 한국기계가공학회지
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• 제16권1호
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• pp.9-16
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• 2017

This study describes the development of a 1-inch cryogenic glove valve for an LNG pumping system and localization development achieved through the performance test. The cryogenic valve used in the LNG pumping system plays an important role in maintaining a flow rate by LNG transportation. This trial manufactured goods, which was achieved through reverse engineering and developing the assembly process. The result of the leak test satisfied the internal pressure condition using the 78-bar normal temperature test and maintained the anti-leakage condition. Also, the result of the cryogenic leak test (BS 6364: low temperature test procedure) maintained anti-leakage at -196 and 52 bar, which satisfied the test standards.

• 상하수도학회지
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• 제30권3호
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• pp.313-319
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• 2016

In this study, the performance experiment was conducted to compare the permeate flux of hollow fiber Vacuum Membrane Distillation module according to leak problem between module housing and membrane bundle. For the permeate flux performance experiment of the two Vacuum Membrane Distillation modules, the Lab-scale experimental equipment was built in the capacity of $1m^3/day$. The performance test of the two Vacuum Membrane Distillation modules were analyzed according to the feed water conditions. As a result, it was analyzed that the leak VMD module decreased about 14% of permeate flux than normal VMD module.