• Title/Summary/Keyword: Riser design

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Arrangement Plan of Buoyancy Modules for the Stable Operation of the Flexible Riser in a Deep-Seabed Mining System (심해저 채광 시스템에서 유연관의 안정적인 운용을 위한 부력재 배치 설계)

  • Oh, Jae-Won;Min, Cheon-Hong;Lee, Chang-Ho;Hong, Sup;Bae, Dae-Sung;Lim, Jun-Hyun;Kim, Hyung-Woo
    • Ocean and Polar Research
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    • v.37 no.2
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    • pp.119-125
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    • 2015
  • This paper focuses on the efficient arrangement plan of buoyancy modules, which plan is used to secure the safe operation and structural stability of a marine riser. The marine riser is connected between a vessel and seabed devices. The movement of the vessel and the seabed devices are affected by the motion of the riser. The riser of a deep-seabed integrated mining system exerts a strong influence on the healthy transfer of minerals. So, buoyancy modules must be equipped to compensate for the problem which is the structure stability and the dynamic motion. Installation locations and quantities of the buoyancy modules are determined by real sea experiments. But this is not easy to do because in real sea experimental conditions the cost is expensive as well as being, time-consuming and dangerous. Therefore, the locations and quantities should be determined by numerical simulation. This method is called simulation-based design. The dynamic analysis models of the riser and the buoyancy modules are built into the commercial software of DAFUL.

Nonlinear Dynamic Analysis of Steel Lazy Wave Riser using Lumped Mass Line Model (집중질량 라인모델을 이용한 Steel Lazy Wave Riser의 비선형 동적 해석)

  • Oh, Seunghoon;Jung, Jae-Hwan;Park, Byeongwon;Kwon, Yong-Ju;Jung, Dongho
    • Journal of Ocean Engineering and Technology
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    • v.33 no.5
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    • pp.400-410
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    • 2019
  • In this study, the numerical code for the 3D nonlinear dynamic analysis of an SLWR (Steel Lazy Wave Riser) was developed using the lumped mass line model in a FORTRAN environment. Because the lumped mass line model is an explicit method, there is no matrix operation. Thus, the numerical algorithm is simple and fast. In the lumped mass line model, the equations of motion for the riser were derived by applying the various forces acting on each node of the line. The applied forces at the node of the riser consisted of the tension, shear force due to the bending moment, gravitational force, buoyancy force, riser/ground contact force, and hydrodynamic force based on the Morison equation. Time integration was carried out using a Runge-Kutta fourth-order method, which is known to be stable and accurate. To validate the accuracy of the developed numerical code, simulations using the commercial software OrcaFlex were carried out simultaneously and compared with the results of the developed numerical code. To understand the nonlinear dynamic characteristics of an SLWR, dynamic simulations of SLWRs excited at the hang-off point and of SLWRs in regular waves were carried out. From the results of these dynamic simulations, the displacements at the maximum bending moments at important points of the design, like the hang-off point, sagging point, hogging points, and touch-down point, were observed and analyzed.

Computer Aided Design of a Pattern and Risers for Casting Processes(I) (주형의 전산기 원용 설계(I) -목형과 압탕부의 설계-)

  • 박종천;이건우
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.1
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    • pp.72-78
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    • 1990
  • An interactive computer program has been developed to design a pattern and risers for the production of castings of high quality. In our system, the user models the shape of a final product by using the system's modeling capability, a pattern is generated in a three dimensional model by eliminating the holes and adding shrinkage allowances and drafts, the proper riser is created automatically, and they are united together to yield the three dimensional model of the portion of a mold assembly. The mold can be completed after the runners and the gating systems are designed, modeled, and united, which will be described in part 2 of this work. The unique feature of this work is a realization of an automatic design of the pattern and risers by integrating the modeling capabilities and the design equations used in the real practice.

DESIGN STUDY OF AN IHX SUPPORT STRUCTURE FOR A POOL-TYPE SODIUM-COOLED FAST REACTOR

  • Park, Chang-Gyu;Kim, Jong-Bum;Lee, Jae-Han
    • Nuclear Engineering and Technology
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    • v.41 no.10
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    • pp.1323-1332
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    • 2009
  • The IHX (Intermediate Heat eXchanger) for a pool-type SFR (Sodium-cooled Fast Reactor) system transfers heat from the primary high temperature sodium to the intermediate cold temperature sodium. The upper structure of the IHX is a coaxial structure designed to form a flow path for both the secondary high temperature and low temperature sodium. The coaxial structure of the IHX consists of a central downcomer and riser for the incoming and outgoing intermediate sodium, respectively. The IHX of a pool-type SFR is supported at the upper surface of the reactor head with an IHX support structure that connects the IHX riser cylinder to the reactor head. The reactor head is generally maintained at the low temperature regime, but the riser cylinder is exposed in the elevated temperature region. The resultant complicated temperature distribution of the co-axial structure including the IHX support structure may induce a severe thermal stress distribution. In this study, the structural feasibility of the current upper support structure concept is investigated through a preliminary stress analysis and an alternative design concept to accommodate the IHTS (Intermediate Heat Transport System) piping expansion loads and severe thermal stress is proposed. Through the structural analysis it is found that the alternative design concept is effective in reducing the thermal stress and acquiring structural integrity.

Fatigue performance of deepwater steel catenary riser considering nonlinear soil

  • Kim, Y.T.;Kim, D.K.;Choi, H.S.;Yu, S.Y.;Park, K.S.
    • Structural Engineering and Mechanics
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    • v.61 no.6
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    • pp.737-746
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    • 2017
  • The touch down zone (TDZ) and top connection point of the vessel are most critical part of fatigue damage in the steel catenary riser (SCR). In general, the linear soil model has been used to evaluate fatigue performance of SCRs because it gives conservative results in the TDZ. However, the conservative linear soil model shows the limitation to accommodate real behavior in the TDZ as water depth is increased. Therefore, the riser behavior on soft clay seabed is investigated using a nonlinear soil model through time domain approach in this study. The numerical analysis considering various important parameters of the nonlinear soil model such as shear strength at mudline, shear strength gradient and suction resistance force is conducted to check the adoptability and applicability of nonlinear soil model for SCR design.

Application of Solidification Analysis considering Volumetric Contraction to Riser Design of Steel Castings (주강품 압탕 설계에 체적 수축을 고려한 응고해석의 적용)

  • Kim, Ji-Joon;Kim, Ki-Young;Choi, Jeong-Kil;Hong, Chun-Pyo
    • Journal of Korea Foundry Society
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    • v.15 no.5
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    • pp.494-506
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    • 1995
  • Test castings in plate, disc, and cubic shaped castings for 0.2wt.% carbon and stainless steel have been poured to examine the effects of the riser dimensions including riser neck on the casting soundness. Three empirical methods were chosen in risering of steel castings. A computer program of solidification analysis considering liquid and solidification contraction was developed to apply for riserdesign calculated by using their methods in plate, disc, and cubic shaped castings, and to calculate the position and dimension of shrinkage cavity in complex shaped casting. The potential of present method has been successfully demonstrated by comparing predicted cavity shapes with those obtained in a series of experimental castings. Three empirical methods can be used in a practical way to make a rapid estimation of tie minimum riser diameter, but they can not provide a criterion of casting soundness with shape and material on all occasions. The shape and position of shrinkage cavity can be successfully predicted both using the present method and using risering calculated by their methods regardless of the shape and cast material.

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Prediction of Axial Solid Holdups in a CFB Riser

  • Park, Sang-Soon;Chae, Ho-Jeong;Kim, Tae-Wan;Jeong, Kwang-Eun;Kim, Chul-Ung;Jeong, Soon-Yong;Lim, JongHun;Park, Young-Kwon;Lee, Dong Hyun
    • Korean Chemical Engineering Research
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    • v.56 no.6
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    • pp.878-883
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    • 2018
  • A circulating fluidized bed (CFB) has been used in various chemical industries because of good heat and mass transfer. In addition, the methanol to olefins (MTO) process requiring the CFB reactor has attracted a great deal of interest due to steep increase of oil price. To design a CFB reactor for MTO pilot process, therefore, we has examined the hydrodynamic properties of spherical catalysts with different particle size and developed a correlation equation to predict catalyst holdup in a riser of CFB reactor. The hydrodynamics of micro-spherical catalysts with average particle size of 53, 90 and 140 mm was evaluated in a $0.025m-ID{\times}4m-high$ CFB riser. We also developed a model described by a decay coefficient to predict solid hold-up distribution in the riser. The decay coefficient developed in this study could be expressed as a function of Froude number and dimensionless velocity ratio. This model could predict well the experimental data obtained from this work.

Analytical and numerical analysis for unbonded flexible risers under axisymmetric loads

  • Guo, Yousong;Chen, Xiqia;Wang, Deyu
    • Ocean Systems Engineering
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    • v.6 no.2
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    • pp.129-141
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    • 2016
  • Due to the structural complexity, the response of a flexible riser under axisymmetric loads is quite difficult to determine. Based on equilibrium conditions, geometrical relations and constitutive equations, an analytical model that can accurately predict the axisymmetric behavior of flexible risers is deduced in this paper. Since the mutual exclusion between the contact pressure and interlayer gap is considered in this model, the influence of the load direction on the structural behavior can be analyzed. Meanwhile, a detailed finite element analysis for unbonded flexible risers is conducted. Based on the analytical and numerical models, the structural response of a typical flexible riser under tension, torsion, internal and outer pressure has been studied in detail. The results are compared with experimental data obtained from the literature, and good agreement is found. Studies have shown that the proposed analytical and numerical models can provide an insightful reference for analysis and design of flexible risers.

A Study on the Design of Optimum Dimension of Staircase -Focused on the Minimum Dimension of Riser, Tread and Slope for Safety on Staircase- (계단의 적정치수 계획에 관한 연구 -계단에서의 안전을 위한 단높이, 단너비, 경사도의 최소치수를 중심으로-)

  • 김용환
    • Journal of the Korean housing association
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    • v.14 no.5
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    • pp.105-116
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    • 2003
  • The purpose of this study is to suggest the method of prevention of staircase accidents, and to make housing environment better through researching the dimension of a housing staircase for Korean. The scope and method of this thesis is to investigate the dimension limits of a staircase (slope, minimum width of tread, maximum height of riser), and to analyze the characteristics of foot condition (jutting rate, foot angle, ball joint, nosing clearance, clearance distance) using the experiment which takes a photograph of foot motion during walking stairs. The results of this thesis are as follows. The slope of a staircase in house is $32.3^{\circ}$$^{\circ}$-$42.1^{\circ}$$^{\circ}$. The riser should be less than 190 mm. The minimum size of tread is 210 mm and proper size is 270 mm.

Casting Simulation on the Integrated Twin-Scroll Turbine Housing with Exhaust Manifold

  • Kang, Ho-Jeong;Yun, Pil-Hwan;Cheon, Joo-Yong;Kim, Hyo-Jung;Kim, Chung-Min;Park, Jin-Young
    • Journal of Korea Foundry Society
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    • v.37 no.6
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    • pp.173-180
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    • 2017
  • In this paper, the casting design of the integrated twin-scroll turbine housing with exhaust manifold using stainless steel is investigated. Due to the complexity in its geometry and the poor castability of stainless steel, it is more crucial to set up the appropriate casting design to avoid casting defects. Gas porosity and shrinkage formation with the changes of gating systems (one-/two-side), riser conditions and pouring temperatures are examined via casting simulation and virtual castings. Simulation results show that two-side gating system produced better quality casting than that of one-side gating system, minimizing the gas content of the castings and it is also verified by X-ray analysis for the virtual castings. For the changes of riser conditions and pouring temperatures in the two-side gating system, it is found that the change of the height of two risers plays an important role in obtaining the best quality by reducing shrinkage defects.