• Journal of the Korean Geosynthetics Society
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• v.17 no.4
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• pp.81-92
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• 2018

Recently, the use of natural gas has steadily increased due to its economical advantage and increased demand of clean energy uses. Accordingly, construction of LNG storage tanks is also increased. Secure of the stability of LNG tanks storage requires high technology as natural gas is stored in a liquid state for efficiency of storage. When a cryogenic LNG fluid leaks on ground due to a defect in LNG tank, damage is expected to be significant. Many researchers evaluated the critical and negative effects of LNG leakage, but there is limited research on the effect of cryogenic fluid leakage on the ground supporting LNG tanks. Therefore, in this study, the freezing expansion of the ground during cryogenic LNG fluid leakage was evaluated considering various outflow situations and ground conditions. The LNG leakage scenarios were simulated based on numerical analyses results varying the surcharge load, temperature boundary conditions, and soil types including freeze-sensitive soil. Consequently, short and long term ground temperature variations after LNG leakage were evaluated and the resulting ground behavior including vertical displacement behavior and porosity were analyzed.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.5
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• pp.487-494
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• 2011

The safety valve used in LNG/LNG-FPSO ships plays an important role in maintaining a fixed level of pressure by emitting LNG gas out of the pipes in the LNG piping system. The discharge coefficient is regarded as the most important factor in the valve performance. To satisfy the ship's classification, the discharge coefficient of the safety valve must usually be over 0.8. Despite the importance of understanding the flow phenomena inside the safety valve, the valve design is usually based on experience and experiments. We carried out a computational fluid dynamics (CFD) investigation using the ANSYS-CFX software. We observed the flow phenomena inside the valve and measured the discharge coefficients according to changes in the valve lift, which is the distance between the exit of the nozzle and the lower part of the disc plate. We verified our CFD results for the discharge coefficients using available experimental data.

• Journal of the Korean Institute of Gas
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• v.5 no.3 s.15
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• pp.73-79
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• 2001

The corner protection which is consist of insulation and $9\%$ nickel liner is designed to mitigate the high hoop tension at the corner of LNG storage tank by LNG leakage. So the design loads depend on thermal and liquid pressure from leaked LNG In this paper design conditions are suggested as operating, major and minor leak conditions. And in order to check integrity of comer protection for the design conditions by appendix 4 in ASME section VIII div.2, acceptability checking process that have stress categorization and finite element analysis is explained.

• Plant Journal
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• v.16 no.3
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• pp.42-46
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• 2020

In the large LNG process in FLNG or FSRU, sudden temperature drops of the steel in the event of LNG leaks may cause brittle fracture of the structure. In this paper, we investigate the principle and process of forming a cryogenic fluid on a steel plate through a cryogenic spillage experiment, and analyze the correlation of the temperature distribution of the steel plate according to the distance from the nozzle and exposure time. Two types of cryogenic fluids were used: LN2 and LNG. The cyogenic liquid was released on the steel plate at 1.6L/min for LN2 and 1.5L/min for LNG. For the steel, DH was used and the temperature was measured at 10 points in total. The Leidenfrost effect was observed on the steel plate, and the temperature distribution of the steel was varied according the flow path and the heat of evaporation of the fluid.

• Journal of the Korean Institute of Gas
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• v.6 no.4 s.18
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• pp.33-39
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• 2002

[ $9\%$ ] nickel steel LNG storage tank have double containments that can store cryogenic LNG independently. Inner tank material is used as $9\%$ nickel steel and outer tank is constructed by concrete. Comer protection which is installed on inner surface of concrete corner is consist of $9\%$ nickel steel liner and form glass insulator that make reduce tension at corner when LNG is leaked from inner tank. It is very difficult to design corner protection because expansion and contraction of liner make stress state complex. Corner protections of operating tank in KOGAS are designed by Japanese engineering company such as TKK, KHI and England company of WHESSOE. This paper is mainly focused on the integrity comparison of them according to requirements of Appendix 4 in ASME Section VIII Div. 2 by using FEM.

• Journal of the Korean Institute of Gas
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• v.13 no.1
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• pp.40-44
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• 2009

This is a comparative structural analysis for a steel roof LNG storage tank that has some advantages relatively in designing larger scale tanks and construction cost, etc. compared with a conventional concrete roof LNG storage tank as the capacity of LNG storage tanks is bigger. Structural analysis was performed on a 200,000$k{\ell}$ steel roof LNG storage tank and a concrete of the same capacity in condition of three critical load combination cases, a normal operation, a LNG spillage and seismic case by using finite element method. And comparative structural safety evaluation was carried out by using strength ratio in places of concrete wall, foundation and roof with a quantitative method.

• Fire Science and Engineering
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• v.18 no.3
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• pp.57-73
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• 2004

Quantitative safety analysis through a fault tree method has been conducted for a fire broken out over the spilling LNG from a pilot LNG tank, which may have 4 types of scenarios causing potentially risky results. When we consider LNG release from venting pipelines as a first event, any specific radius of Low Flammable Limit(LFL) has not been built up. The second case of LNG outflow from the rupture of storage tank which will be the severest has been analyzed and the results revealed various diffusion areas to the leaking times even with the same amount of LNG release. As a third case LNG leakage from the inlet/outlet pipelines was taken into consider. The results showed no significant differences of LFL radii between the two spilling times of 10 and 60 minutes. Hence, we have known the most affecting factor on the third scenario is an initial amount of LNG release. Finally, the extent of LFL was calculated when LNG pipelines around the dike area were damaged. In addition, consequence analysis has been also performed to acquire the heat radiation and flame magnitude for each case.

• Journal of Ocean Engineering and Technology
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• v.28 no.6
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• pp.517-526
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• 2014

The leakage of cryogenic LNG through cracks in the insulation membrane of an LNG carrier causes the hull structure to experience a cold spot as a result of the heat transfer from the LNG. The hull structure will become brittle at this cold spot and the evaporated natural gas may potentially lead to a hazard because of its flammability. This paper presents a computational model for the LNG flow and heat diffusion in an LNG insulation panel subject to leakage. The temperature distribution in the insulation panel and the speed of gas diffusion through it are simulated to assess the safety level of an LNG carrier subject that experiences a leak. The behavior of the leaked LNG is modeled using a multiphase flow that considers the mixture of liquid and gas. The simulation model considers the phase change of the LNG, gas-liquid multiphase interactions in the porous media, and accompanying rates of heat transfer. It is assumed that the NO96-GW membrane storage is composed of glass wool and plywood for the numerical simulation. In the numerical simulation, the seepage, heat diffusion, and evaporation of the LNG are investigated. It is found that the diffusion speed of the leakage is very high to accelerate the evaporation of the LNG.

• Journal of the Korean Institute of Gas
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• v.9 no.1 s.26
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• pp.44-50
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• 2005

This paper presents integrated control and safety management system for a LNG storage tank. This system is for collecting and analyzing the temperature, pressure, and vibration signals in which are used to control and guarantee the system safety and leakage control from the inner gas tank. Based on the investigations of LNG tank related failures and accidents, we strongly recommend the modification and new development of current safety related measuring and control systems because the LNG tank is constructed bigger and bigger in recent years for the efficiency and safety increments. Thus, this paper presents newly developed integrated control and safety management system for a large LNG storage tank. This system provides the enhanced measuring and control systems, and new displacement based safety system, which may detect and control the deformation properties of tank structures. In addition, we recommend that the new integrated control and safety management system should be coupled by process integrated innovation system (PIIS) for an increased safety, efficiency, and productivity of LNG tanks.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.95-98
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• 2006

Many LNG ships will be constructed in Korea and the demand of safety valves is increasing. The most important performance of the developed safety relief valves for LNG ship is flow capacity. Flow capacity tests for 8 sizes of developed safety valves were conducted in the high pressure gas flow standard system in KRISS. The initial spring force adjustment was important for setting pressure of the safety valve. The procedure of data reduction and evaluation of the safety valve performance are suggested. This procedure was approved by French Bureau Veritas and Lloyd's Register.