• Journal of Drive and Control
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• v.18 no.4
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• pp.28-34
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• 2021

Among the currently available types of fuel, LNG emits a relatively small amount of nitrogen oxide and carbon dioxide when it burns in the engine. However, since LNG is a flammable material, leakage during bunkering can lead to accidents, such as fires. Therefore, it is necessary to install a remote operation emergency shut-down (ESD) valve to block the flow and leakage of LNG in an emergency situation that occurs during bunkering. The ESD valve uses a hydraulic driving device consisting of a hydraulic control valve and a hydraulic motor to control globe valve disc displacement, which regulates the flow path for LNG transfer. At this time, there are various nonlinearities in hydraulic driving devices; hence, it is necessary to design a controller with robust control performance against these uncertainties. In this study, modeling of the ESD valve was carried out, and a sliding mode controller to control the displacement of the globe valve disc was designed. As a result, it was confirmed that the designed control performance could be achieved by overcoming nonlinearity characteristics using the designed controller.

• Journal of Yeungnam Medical Science
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• v.31 no.2
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• pp.144-147
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• 2014

Despite the necessity of surgical aortic valve replacement, many patients with symptomatic severe aortic stenosis (AS) cannot undergo surgery because of their severe comorbidities. In these high-risk patients, percutaneous transcatheter aortic valve implantation (TAVI) can be safely accomplished. However, no study has shown that TAVI can be performed for patients with severe AS accompanied by acute decompensated heart failure. In this case report, 1 patient presented a case of severe pulmonary hypertension with decompensated heart failure after diagnosis with severe AS, and was successfully treated via emergency TAVI. Without any invasive treatment, acute decompensated heart failure with severe pulmonary hypertension is common in patients with severe AS, and it can increase mortality rates. In conclusion, TAVI can be considered one of the treatment options for severe as presented as acute decompensated heart failure patients with pulmonary hypertension.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.3
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• pp.309-314
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• 2015

A sunken ship often involves an oil spill. This paper was carried out to minimize environmental and cost damages stemming from oil spil of sunken shipl. Through the analysis of both the standards of the oil tank system and installation, we have identified potential oil spill sites and proposed a remedy of prevention. The result of study, the air pipes of the oil tank are a vulnerable point for oil spill. Also, the remote control devices of emergency shut-off valve have poor accessibility at abandon ship, making it difficult to shut off the emergency shut-off valve. Thus, we propose the addition of a remote quick closing valve in the air pipe and the building of a central control system.

• Journal of the Korean Institute of Gas
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• v.23 no.2
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• pp.28-34
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• 2019

A large number of underground pipelines in the Ulsan National Industrial Complex has been constructed to improve the productivity of chemical products and tackle transportation problems. Now, the total of 1,293km of underground pipelines around 62 companies has been installed and operated. Many of underground pipelines have been installed outside of factories. For a past three years, five gas leakage accidents have occurred and the emergency response took up to 8 hours or more. Due to these delay in accidents, second serious accidents might occur and lead to occur damages to adjacent residents. In this study, it is assumed that emergency valve systems are installed under a ground and the efficacy of these is verified. Consequence analysis program was employed to evaluate the mitigation impact of emergency valve systems. The results show that these valve systems are economical and their performances for a mitigation are excellent. The results indicate that the installation of emergency valve systems for underground pipelines should be urgently legislated and performed.

• Journal of Drive and Control
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• v.8 no.3
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• pp.44-47
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• 2011

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.949-958
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• 2024

In contrast to all-time flooded small modular reactor (SMR) systems, an in-kind flooding safety system (FSS) has been proposed as a passive safety system applicable to small modular reactors (SMRs) that adopt a metal containment vessel (MCV). Under transient conditions, the FSS can provide emergency cooling to dry reactor cavities and sustain long-term coolability using re-acquired evaporated steam in the reactor building on demand. When designing an FSS, the effect of the flooding flow area is vital as it affects the overall accident sequence and safety. Therefore, in this study, a MELCOR model of a reference SMR is developed and numerical analysis is performed under postulated accident scenarios. Without flooding, the MCV pressure of the reactor module exceeds the design pressure before core damage. To prevent core damage, an emergency flooding strategy is devised using various flow path parameters and requirements to ensure an adequate emergency coolant supply before the core damage is investigated. The results indicate that a flow area exceeding 0.02 m2 is required in the FSS to prevent MCV overpressure and core damage. This study is the first to report a strategic analysis for appropriately sizing an FSS flooding valve applicable to innovative SMRs.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.19 no.8
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• pp.843-849
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• 2009

The reliable operation of a swing check valve in the main feed water system of a power plant is most essential for successful shout-down process. A failure to close the valve at proper time often leads to the instability of the main feed water system, or even to an emergency stop of the power plant. In reality it is a very difficult task to monitor the behavior of a swing check valve. Furthermore it is impossible to see the motion of the valve. In this work two measurements were carried out simultaneously to determine the precise valve closure time. The dynamic pressure measurements were made at the inlet and outlet regions of the swing check valve. The transient vibration of the valve housing in the direction of water flow was also measured, which enabled the measurement of the transient vibration of the valve housing near valve closure. By comparing the results produced from these measurements the precise valve closure time could be determined. By carrying out order tracking technique using the dynamic pressure signals and pump rpm signal, the complicated dynamic problems inside the main feed water system can be more easily dealt with. This measurement scheme might be implemented in a power plant on a real-time basis without much difficulty. If this could be implemented, valuable information essential for shut-down operations can readily be passed on to the main control room. The feasibility of this implementation was demonstrated by this experimental work.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.3
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• pp.202-210
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• 2006

In the nuclear power plant, emergency core coolant system (ECCS) is furnished at reactor coolant system (RCS) in order to cool down high temperature water in case of emergency. However, in this coolant system, thermal stratification phenomenon can be occurred due to coolant leaking in the check valve. The thermal stratification produces excessive thormal stresses at the pipe wall so as to yield thermal fatigue crack (TFC) accident. In the present study, when the turbulence penetration occurs in the branch pipe, the maximum temperature differences of fluid at the pipe cross-sections of the T-branch with thermal stratification are examine.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.1
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• pp.124-134
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• 1996

In this paper the pressures and flowrate distributions in the loading/unloading piping system of LNG carrier have been investigated in the case of unsteady flow state as well as steady one. Under emergency situation the main cargo pumps are forced to fail, and the ESD(Emergency Shut Down) valves and Stop valves are closed within set-time. The surge pressures according to the variations of valve closing time have been computed to recognize the surge phenomenon due to sudden decrease of flowrate. By means of these analysis results, the most important factors on the in-pipe surge phenomenon of cargo loading/unloading piping system of LNG Carrier are the type of ESD and Stop valves, valve closing time, and the pipe arrangements.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.593-598
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• 2000

Experimental study is conducted to clarify the pneumatic characteristics of brake system for freight train. Empty-load and diaphragm brake systems are mainly installed in the freight trains owned by KNR(Korean National Railroad). Experimental train set is composed of sixteen freight train and one diesel locomotive that are now in use. From the experimental results, in case of commercial brake, empty-load brake system responds to the brake command more slowly than the diaphragm brake system. But, in case of release command, the response time of diaphragm brake system is shorter than that of empty-load one. In the emergency brake test, the decreasing rate of brake pipe pressure of tenth car is almost same that of decreasing rate of commercial brake service.