• 제목/요약/키워드: pipes

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지역난방 열배관의 외부작용력 및 되메움재의 안정성 확보에 관한 연구 (The Stability Assessment of Backfill Materials and External Loads in Pre-Insulated District Heating Pipes)

  • 김진만;최봉혁;고현일
    • 대한설비공학회:학술대회논문집
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    • 대한설비공학회 2009년도 하계학술발표대회 논문집
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    • pp.656-661
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    • 2009
  • In this study, theoretical analysis and evaluation tests were performed to assess the pipe stability against compaction equipments and vehicle loads when conventional construction criteria for pre-insulation heating pipes are applied and the alternative material, crushed sand, are used for backfills. The research outcomes shows that (1) the conventional code criteria for pre-insulated heating pipes is well established to support compaction equipments and vehicle loads, (2) the crushed sands as an alternative is usable as backfill materials for pre-insulated heating pipes based on the suitability evaluations of various types of pipes, and (3) the crushed sand agree well with the design consideration of pre-insulated heating pipes construction in the points of economical efficiency and construction criteria.

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확관 응축부를 갖는 진공관형 태양열 집열기용 히트파이프 성능 비교 연구 (A Comparative Study of Heat Pipes with Enlarged Condenser Section for Evacuated Solar Collectors)

  • 부준홍;정원복;곽희열
    • 한국태양에너지학회 논문집
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    • 제22권4호
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    • pp.18-25
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    • 2002
  • For application to medium temperature solar collerctors $(80\sim120^{\circ}C)$, a heat pipe should be designed properly to efficiently transfer heat to a hotter condenser than common applications. Among many wick structure candidates for heat pipes of this type, a slab wick was selected based on promising performance data reported previously. The thermal performance of slab wick heat pipes, screen wick heat pipes and thermosyphons with enlarged condenser section were experimentally investigated for comparison purpose. The heat pipes were 8.0 mm O.D. (evaporator section) and 25.4 mm O.D. (condenser section) made of copper. The experimental data of the heat pipes were analysed in terms of thermal resistance against thermal load and coolant temperature.

Thermal post-buckling analysis of porous functionally graded pipes with initial geometric imperfection

  • Xu, Jia-Qin;She, Gui-Lin
    • Geomechanics and Engineering
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    • 제31권3호
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    • pp.329-337
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    • 2022
  • In this paper, the thermal post-buckling characteristics of functionally graded (FG) pipes with initial geometric imperfection are studied. Considering the influence of initial geometric defects, temperature and geometric nonlinearity, Euler-Lagrange principle is used to derive the nonlinear governing equations of the FG pipes. Considering three different boundary conditions, the two-step perturbation method is used to solve the nonlinear governing equations, and the expressions of thermal post-buckling responses are also obtained. Finally, the correctness of this paper is verified by numerical analyses, and the effects of initial geometric defects, functional graded index, elastic foundation, porosity, thickness of pipe and boundary conditions on thermal post-buckling response are analyzed. It is found that, bifurcation buckling exists for the pipes without initial geometric imperfection. In contrast, there is no bifurcation buckling phenomenon for the pipes with initial geometric imperfection. Meanwhile, the elastic stiffness can significantly improve thermal post-buckling load and thermal post-buckling strength. The larger the porosity, the greater the thermal buckling load and the thermal buckling strength.

국내원전에 매설된 콜타르 코팅 배관의 음극방식과 FEM법을 이용한 방식성능 시뮬레이션 (Protection Performance Simulation of Coal Tar-Coated Pipes Buried in a Domestic Nuclear Power Plant Using Cathodic Protection and FEM Method)

  • 장현영;김기태;임부택;김경수;김재원;박흥배;김영식
    • Corrosion Science and Technology
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    • 제16권3호
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    • pp.115-127
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    • 2017
  • Coal tar-coated pipes buried in a domestic nuclear power plant have operated under the cathodic protection. This work conducted the simulation of the coating performance of these pipes using a FEM method. The pipes, being ductile cast iron have been suffered under considerably high cathodic protection condition beyond the appropriate condition. However, cathodic potential measured at the site revealed non-protected status. Converting from 3D CAD data of the power plant to appropriate type for a FEM simulation was conducted and cathodic potential under the applied voltage and current was calculated using primary and secondary current distribution and physical conditions. FEM simulation for coal tar-coated pipe without defects revealed over-protection condition if the pipes were well-coated. However, the simulation for coal tar-coated pipes with many defects predict that the coated pipes may be severely degraded. Therefore, for high risk pipes, direct examination and repair or renewal of pipes are strongly recommended.

PE 이중벽관의 맞대기 융착 용접 강도 향상에 관한 연구 (Studies on the Improvement of Butt Welding Characteristic of Polyethylene Pipes)

  • 안주선;이경원;김재성;이보영
    • Journal of Welding and Joining
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    • 제29권1호
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    • pp.85-89
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    • 2011
  • Waste water is disposed to sewage disposal plant by underground PE double wall pipes. Various processes have been introduced to join PE pipes, but most of these methods have many disadvantages such as costs, lack of reliability and difficulties in joining, etc. Recently butt welding has been paid much attention to joint PE pipes as this process has many advantages such as cost, safety and reliability. In this study, newly developed heat plate, a patent-pending heat plate with a groove, was used to butt-weld PE double wall pipes with different misalignment gaps to simulate real underground conditions, and the butt welding temperature of PE pipe was determined by thermal analysis (Thermal Gravimetric Analysis, Differential Scanning Calorimetry and Dynamic Mechanical Analysis). The resulting joining characteristics of double wall pipes were compared with those from a conventional heat plate, in terms of stiffness, flattening and leakage tests. The results from the stiffness and flattening test showed that there were no big differences between the butt-welded joints made from these two plates. From the leakage test, although PE pipes welded with a conventional heat plate did leak below the required test conditions (10 min. at 0.75kgf/cm2), the pipes welded with a patent-pending grooved heat plate did not show any leakage even at a pressure 1.5 times higher than the required conditions. It was noted that by utilizing a grooved heat plate more complete fusion at the pipe joints could be obtained, which in turn induced a high quality joints.

플라스틱 관종의 물리적 상태예측모형 개발 (A Study of Physical Condition Predicting Model Development of Plastic Pipes in Water Mains)

  • 기남연;배철호;이두진;정관수
    • 상하수도학회지
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    • 제26권6호
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    • pp.871-881
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    • 2012
  • This study suggested a model that can predict a degradation condition over time of two plastic pipes, PE and PVC, which are currently used in the country. This study was analyzed physical characteristics change of plastic pipes by comparison with initial physical characteristics (on the case of new pipes). Since this is dependent on accidents that already occurred, there are limitations that it only decides a priority on improvement based on relative corrosion status rather than precautionary aspects. The comparison results between physical degradation by the deducted performance rating and a conventional numerical scoring method showed that correlation coefficient was 0.67 for PE pipes and 0.86 for PVC pipes, indicating a high correlation. According to this result, it has been decided that the performance rating suggested herein can be applied naturally to the criterion of an improvement decision, which was based on Scoring System. From results of the research, it is expected that a reliable result can be provided to an improvement decision process related to degradation of plastic pipes by comprehensively comparing and evaluating a condition of pipe materials(direct factors) and an environmental impact(indirect factors).

상수도용 도복장강관의 용접 및 외부하중에 의한 응력 특성에 관한 연구(I) - 후열처리에 의한 용접부의 잔류응력 특성 - (A Study on the Stress Distribution of Steel Water Pipes(I) - Characteristics of Residual Stress Distribution by PWHT -)

  • 윤석환;이승기;나석주;고명환
    • Journal of Welding and Joining
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    • 제19권3호
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    • pp.285-291
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    • 2001
  • Large steel water pipes are joined prevalently by the bell end method, and are welded both at inside and outside of lapped parts. In practice, welded joints of water pipes are very critical, because in most cases failure of pipes causing leakage occurs at the welded joint. Therefore some methods have been developed to ensure the soundness of welded joints of water pipes, like leakage tests and nondestructive tests (NDTs). But one of the major characteristics that affects the soundness of welded Joints is the stress distribution caused by welding and external forces. Some studies have been carried out on the residual stress of steel water popes, but complex stress distributions by welding and external forces are rarely studied. In this study, temperature and stress distributions in steel water pipes produced by welding are predicted by a three-dimensional finite element method(FEM). Also, stress values are measured from real steel water pipes by the hole-drilling methods, and compared with predicted ones. The influence of some typical post weld treatments on residual stress distribution was also investigated by residual stress measurements.

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내부 및 외부 원주방향 표면균열이 존재하는 배관의 두께효과를 고려한 소성한계하중 계산식 제시 (New Plastic Limit Load Equations of Pipes with Inner and Outer Circumferential Surface Cracks Considering Thickness Effect)

  • 김연수;허남수
    • 한국압력기기공학회 논문집
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    • 제15권2호
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    • pp.71-80
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    • 2019
  • In this study, limit load equations of thick-walled pipes with inner and outer circumferential surface cracks were derived based on force and moment equilibrium conditions. Since the limit load equations based on the mean radius at uncracked ligament, previously proposed by Kanninen et al., are based on the premise that the pipe wall thickness is relatively thin, the existing limit load solutions are only applicable to thin-walled pipes. In order to analyze the effect of the pipe thickness and surface crack depth on the limit load results, the predictions using the present limit load equations are compared with those using the existing solutions for thin-walled pipes. Being derived considering the thickness effect, the limit load solutions from this paper are believed to be more accurate for thick-walled pipes than the limit load equations presented for thin-walled pipes, and thus to be valuable equations for integrity assessment of thick-walled pipes.

Experimental behavior assessment of short, randomly-oriented glass-fiber composite pipes

  • Salar Rasti;Hossein Showkati;Borhan Madroumi Aghbashi;Soheil Nejati Ozani;Tadeh Zirakian
    • Steel and Composite Structures
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    • 제47권6호
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    • pp.679-691
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    • 2023
  • The application of short, fiber-reinforced polymer composite pipes has been increasing rapidly. A comprehensive review of the prior research reveals that the majority of the previously-reported studies have been conducted on the filament-wound composite pipes, and fewer studies have been reported on the mechanical behavior of short, randomly-oriented fiber composite pipes. On this basis, the main objective of this research endeavor is to investigate the mechanical behavior and failure modes of short, randomly-oriented glass-fiber composite pipes under three-point bending tests. To this end, an experimental study is performed in order to explore the load-bearing capacity, failure mechanism, and deformation performance of such pipes. Fourteen properly-instrumented composite pipe specimens with different diameters, thicknesses, lengths, and nominal pressures have been tested and also simulated using the finite element approach for verification purposes. This study demonstrates the effectiveness of the diameter-to-thickness ratio, length-to-diameter ratio, and nominal pressure on the mechanical behavior and deformation performance of short, randomly-oriented glass-fiber composite pipes.

구조해석을 통한 도시가스 매설배관의 지진 영향 분석 (Seismic Impact Analysis of Buried Citygas Pipes through Structural Analysis)

  • 조윤호;최마리아;양주안;전상일;전지훈
    • 한국가스학회지
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    • 제27권4호
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    • pp.19-26
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    • 2023
  • 지진은 지하 구조물에 영향을 미치는 가장 중요한 재해 중 하나이다. 도시가스 지하 매설 배관은 지진 발생 시 구조물의 안전성 문제가 발생할 수 있다. 우리나라는 디지털 관측을 시작한 이래로 지진 발생 횟수가 꾸준히 증가하고 있다. 도시가스배관의 내진 설계 기준은 2008년에 KGS GC204 가스배관 내진설계 기준이 제정되었지만 이는 배관 설치 시 기준으로 지진 발생 시 배관의 영향을 추정하기는 어렵다. 본 연구에서는 국내에서 매설배관으로 주로 사용하고 있는 PE(폴리에틸렌관)배관과 PLP(폴리에틸렌 피복강관) 배관을 대상으로 지진 발생 시 환경 및 배관의 변수에 따른 구조해석을 수행하였다. 본 연구는 CAE(Computer Aided Engineering)를 통해 배관을 모델링하고 지반에 변위를 발생시켜 가장 취약한 매설배관의 변수를 찾고자하였다. 이 연구를 통해 토양은 탄성계수가 클 수록, 매설심도는 깊을 수록, 관경은 작을 수록, 압력은 높을 수록, PE 보다 PLP 배관이 더 지진에 영향을 많이 받는 것을 확인할 수 있었다. 이 결과를 토대로 매설 도시가스배관의 취약지점을 유추하여 지진발생 시 매설배관의 특별점검에 활용하고자한다.[1]