• 한국압력기기공학회 논문집
• /
• 제16권1호
• /
• pp.22-29
• /
• 2020

In nuclear power plants, there is a risk of thermal fatigue in equipment and piping affecting system soundness because the temperature change of the system accompanies in every operation and shutdown. Therefore, in order to prevent the excess of the fatigue limit during the lifetime of plants, the fatigue limit of each piping material is determined in the designing stage. However, there are many cases where equipment or piping is locally subjected to thermal fatigue that is not considered in the design, resulting in damage to the equipment and piping, and failure during operation. Currently, local thermal fatigue generation mechanisms that are not taken into account in the design stage are gradually being identified. In this paper, the effects of the fluid temperature fluctuations on the piping soundness due to the mixing of hot and cold water, one of the local thermal fatigue generating mechanisms, were evaluated.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2006년도 춘계학술대회논문집
• /
• pp.1285-1289
• /
• 2006

In a large diameter piping system, high frequency energy can produce excessive noise, high vibration, and failures of thermo-well, instrumentation, and attached small-bore piping. High frequency energy is generated by flow induced vibration like vortex shedding in orifices and valves. Once this energy is generated, amplification may occur from acoustical and/or structural resonances, resulting in high amplitude vibration and noise. At low frequencies, pipe vibration occurs laterally along the pipe's length, but at higher frequencies, the pipe shell wall vibrates radially across its cross-section. The simple beam analogy which is based on the beam mode vibration can not be applied to evaluate shell mode vibration. ASME OM3 recommends that the stress be measured directly by strain gauge and be evaluated according to the fatigue curves of the piping material. This Paper discusses the excitation and amplification mechanism relevant to high frequency energy generation in piping system, the monitoring method of the shell mode vibration in ASME OM3, the evaluation method generally used in the industry. Finally this paper presents the stress evaluation of the cavitating venturi down stream piping, where high frequency shell mode vibrations were observed during the operation.

• 한국해양공학회:학술대회논문집
• /
• 한국해양공학회 2001년도 춘계학술대회 논문집
• /
• pp.350-356
• /
• 2001

SG-50 steel is an important material and used for manufacturing a pressure vessel which the gas piping. In this investigation, the elastic plastic fracture toughness of this material is evaluated by the an unloading compliance method according to the ASTM E813-97 and E1152-97 method on the smooth and side groove 1CT specimens. The effect of smooth and side groove is studied on the elastic plastic fracture toughness. The side grooved specimen is very useful in estimation of the J$_{IC}$. Because it is much easier than the smooth specimen to the onset of the ductile tearing by the R curve method. Besides, it improves the accuracy of toughness values, decreases the scattering of them and tunneling and shear lip by the side groove.e.

• 한국화재소방학회논문지
• /
• 제29권4호
• /
• pp.61-66
• /
• 2015

건축물 내에 노출배관의 자재에 대한 별도의 규정을 두지 않음에 따라 내부식성, 내약품성 측면에서 우수하다고 알려진 Poly Vinyl Chloride (PVC)관을 많이 사용하고 있다. 그러나 화재시 유독가스의 발생과 화재의 확산 방지에 취약하다는 우려의 시각이 있다. 노출배관은 불연재를 사용하여야 화재시 유독가스의 확산을 방지하면서 인명이나 재산상의 피해를 최소화할 수 있다. 초대형 건축물이 많이 건설되고 있는 시기에 화재시 피해의 심각성이 매우 우려된다. 건축물의 화재안전기준을 강화하고, 높아진 안전의식을 수용하여야 선진국으로의 진입에 한걸음 더 나아갈 수 있다. 노출배관에 사용되는 자재를 조사하고, 선진국의 기준에 대해 분석하여 효율성을 연구함으로서 국민안전을 증대시킬 수 있다. 국내 각 지역별 건축물의 노출배관에 대해 현장의 실태를 조사하여 대안을 모색하고자 한다. 건축물 안전과 거주자의 안전 확보 및 국내 외 노출배관의 불연재 사용에 대한 실태를 바탕으로 관련법규를 개선함으로 국민안전에 대하여 그 효율성을 제고한다.

• 한국화재소방학회논문지
• /
• 제27권6호
• /
• pp.44-49
• /
• 2013

고강도/연성소재이면서 화학적으로 안정된 폴리에틸렌 소재가 배관으로 양산되면서 수도용 및 산업용으로 그 사용이 확산되고 있다. 최근에는 국내 플랜트에서도 기존 주철배관의 부식 누설 해소방안으로 고밀도 폴리에틸렌 배관이 사용되고 있는데, 각각의 플랜트 설계조건 및 운전조건을 적절히 고려하지 않을 경우 고밀도 폴리에틸렌 배관은 물리적인 손상이 유발될 수 있다. 폴리에틸렌 소재의 대구경 배관을 플랜트에 적용함에 있어 관련기준 및 설치 경험사례를 고찰한 결과, 수충격이 발생되는 환경에서 균열손상 가능성이 있어 폴리에틸렌 배관을 대구경 배관으로 사용시주의가 필요하다고 판단된다.

• 한국기계가공학회지
• /
• 제5권4호
• /
• pp.33-40
• /
• 2006

The quality of the supply water which is supplied to consumer is not the thing of water after filtrating but the thing of water from faucet through pipe. As a result, heavy metals and microorganism, that is the major materials, which cause the distrust of the supply water is generated by supply process. Especially, the heavy metal is generated by the corrosion of waterworks. Besides, rupture by corrosion of pipe becomes the factor of supply water's pollution in waterworks and the factor of pollution of the soil and environment in drain pipe. Therefore, this research examined the weight reduction electric potential measure to measure the corrosion degree of piping materials after testing the corrosion of piping materials(Copper Pipe, Galvanized Steel Pipe, Stainless Steel Pipe) which is generally used at the moment in various corrosion environments(subterranean water, supply water, 3.5% NaCl, 3.5% $HNO_3$). And let me show basic design data about problem occurrence such as leakage water, rust water, inside and outside corrosion from this.

• 한국압력기기공학회 논문집
• /
• 제11권1호
• /
• pp.25-32
• /
• 2015

Many crack flaws have been detected at tubing seal weld zone in Steam Generator with Alloy600 material tubes. it is very difficult to discriminate the signal from parent material and that from weld zone because weld zone gives complicated ECT signal due to manufacturing processes. ECT signal analysis in the seal weld zone is very important since the tubes with crack in this area shall be out of service by plugging. The purpose of this paper is to distinguish between Parent material and Weld Zone ECT signal in the seal weld zone through the demonstration test of Steam Generator seal weld mock-up.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집A
• /
• pp.609-615
• /
• 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.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집A
• /
• pp.616-621
• /
• 2001

Flow-accelerated corrosion(FAC) is a phenomenon that results in metal loss from piping, vessels, and equipment made of carbon steel. FAC occurs only under certain conditions of flow, chemistry, geometry, and material. Unfortunately, those conditions are in much of the high-energy piping in nuclear and fossil-fueled power plants. Also, for domestic NPP secondary pipings whose operating time become longer, more evidences of FAC have been reported. The authors are studying on FAC management using CHECWORKS, computer code developed by EPRI. This paper is on the prediction results of metal loss by FAC in the one of CANDU type NPP secondary piping systems.

• 한국압력기기공학회 논문집
• /
• 제16권1호
• /
• pp.42-48
• /
• 2020

The effect of improving the tensile and J-R fracture toughness properties of SA508 Gr.1a on the LBB margin for the main steam pipe is investigated. The material properties and microstructure images of the existing main steam piping material SA106 Gr.C used in domestic nuclear power plants and the newly selected material SA508 Gr.1a were compared. For each material, LBB margins were calculated and compared through finite element analysis and crack instability evaluation. The LBB margin of the improved SA508 Gr.1a is found to be greatly improved compared to that of the existing SA106 Gr.C and SA508 Gr.1a. This is because of the increased material's strength and J-R fracture toughness compared to the previous materials. In order to analyze the effect of physical property change on the LBB margin, the sensitivity of each LBB margin according to the variation of tensile strength and J-R fracture toughness was analyzed. The effect of the change in tensile strength was found to be greater than that of the change in fracture toughness. Therefore, an increase in strength significantly influenced the improvement of the LBB margin of the improved SA508 Gr.1a.