• Journal of Drive and Control
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• v.13 no.4
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• pp.7-13
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• 2016

This paper presents the meter-out and meter-in speed control characteristics of a pneumatic cylinder with relief valve type cushion device. The piston displacement and velocity are measured to investigate high speed driving performance with variation of the pressure setting in relief valve, air supply pressure, load mass, the supply and exhaust flow rate from the cylinder. Also, the internal pressures and temperatures driving pressure and cushion chamber are measured. The piston displacements and velocities of meter-out and meter-in control are compared experimentally determined data. A comparison experimental data meter-out and meter-in control show that a relief valve type cushion device is suitable for high speed pneumatic cylinders. The desired response characteristics of piston displacement and velocity are satisfactory adjust the pressure setting of a relief valve with varying system parameters such as air supply pressure, load mass and controlled flow rate.

• Journal of the Korean Society of Safety
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• v.35 no.6
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• pp.32-45
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• 2020

The problem of determining the discharge rates of gases from pressurized vessels through pressure relief devices was dealt with comprehensively. First, starting from basic fluid flow equations, detailed modeling procedures were presented for isentropic nozzle flows and frictional flows in a pipe, respectively. Meanwhile, physical explanations were given to choking phenomena in terms of the acoustic velocity, elucidating the widespread use of Mach numbers in gas flow models. Frictional flows in a pipe were classified into adiabatic, isothermal, and general flows according to the heat transfer situation around the pipe, but the adiabatic flow model was recommended suitable for gas discharge through pressure relief devices. Next, for the isentropic nozzle flow followed by adiabatic frictional flow in the pipe, two equations were established for two unknowns that consist of the Mach numbers at the inlet and outlet of the pipe, respectively. The relationship among the ratio of downstream reservoir pressure to upstream pressure, mass flux, and total frictional loss coefficient was shown in various forms of MATLAB 2-D plot, 3-D surface plot and contour plot. Then, the profiles of gas properties and velocity in the pipe section were traced. A method to quantify the relationship among the pressure head, velocity head, and total friction loss was presented, and was used in inferring that the rapid increase in gas velocity in the region approaching the choked flow at the pipe outlet is attributed to the conversion of internal energy to kinetic energy. Finally, the Levenspiel chart reproduced in this work was compared with the Lapple chart used in API 521 Standatd.

• Transactions of the Korean hydrogen and new energy society
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• v.20 no.3
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• pp.188-193
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• 2009

Fuel cell vehicles are equipped with Pressure Relief Devices(PRDs) installed in pressure tank cylinder to prevent the explosion of the tank during a fire. PRDs are safety devices that perceive a fire and release gas in the pressure tank cylinder before it is exploded. But if the PRD does not actuate, because either the PRD fails or can't be surrounded by the flame of a fire, the tank will rupture and produce a blast wave and hydrogen fire ball. In this paper, we observed the fire behavior of actual fuel cell vehicle, comparing with that of gasoline vehicle.

• Journal of Drive and Control
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• v.12 no.4
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• pp.54-59
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• 2015

Due to the tendency to use high speed pneumatic cylinders to improve productivity, cushioning devices are adopted to decelerate the piston motion of pneumatic cylinders to reduce noise, vibration, and impact. This paper presents a comparison of the cushion characteristics of a high speed pneumatic cylinder with a relief valve type cushioning device. The system parameters selected are the damping coefficient, Coulomb friction, heat transfer coefficient, and cracking pressure of the relief valve in the air cushioning device. The integral of the time multiplied square error (ITSE) is used to quantitative measure the cushioning performance to assess the effect of varying these. The cushioning performance achieved good results when the ITSE is a minimum value. In a comparison of the piston displacement and velocity with the variations in system parameters, the heat transfer coefficients are not as significantly affected as the other. Also, the cracking pressure of the relief valve is mainly affected by the pressure and temperature in the cushion chamber.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.1
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• pp.1-6
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• 2017

Surge pressure is created by rapid change of flow rate due to operation of hydraulic component or accident of pipeline. Proper control of surge pressure in distribution system is important because it can damage pipeline and may have the potential to degrade water quality by pipe leakage due to surge pressure. Surge relief valve(SRV) is one of the most widely used devices and it is important to determine proper parameters for SRV's installation and operation. In this research, determining optimum parameters affecting performance of the SRV were investigated. We proposed the methodology for finding combination of parameters for best performance of the SRV. Therefore, the objective function for evaluate fitness of candidate parameters and surge pressure simulation software was developed to validate proposed parameters for SRV. The developed software was integrated into genetic algorithm(GA) to find best combination of parameters.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.6
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• pp.24-30
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• 2013

This paper studies the comparative analysis on two different internal cushion devices (the types of needle and relief valve) used to absorb the energy which is generated when the pneumatic cylinder moves with the load at meter-out speed control system. The effect at varying the piston velocity under same driving condition is mainly investigated. The simulation results on pressure in the cushion chamber and the dynamic behavior of the relief valve type cushion device are compared with the needle valve type. Design and performance are improved with the cushion configuration of better quality at high-speed pneumatic cylinder. Based on the relation between absorbed energy and impact energy at cushion process, cushion performance at pneumatic cylinder is evaluated.

• Journal of the Korean Institute of Gas
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• v.27 no.3
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• pp.35-40
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• 2023

In order to prevent an ammonia container from bursting under conditions such as overcharging and abnormal temperature rise, it is necessary to prepare accident prevention measures through analysis of the operating mechanism of the Thermally Activated Pressure Relief Devices (TPRD) attached to the container. In this study, stress analysis acting on the ammonia container under pressurized conditions, density change analysis according to temperature change, and correlation between container filling amount and temperature and pressure change were presented. In addition, the maximum filling amount of the ammonia container was calculated, and the temperature and pressure at the filling amount were calculated through the phase equilibrium diagram. Based on this, the appropriate melting point of the Thermally Activated Pressure Relief Devices was derived and verified through a melting temperature experiment. Based on the results of this study, conditions for preventing ammonia container rupture accidents were suggested.

• Journal of the Korean Institute of Gas
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• v.13 no.4
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• pp.33-39
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• 2009

This study is intended to experiment performance of pressure relief device and to extend the effective ways to prevent cylinders of NGV from bursting when they are exposed to local fire intensively or when they are overcharged under ambient temperature at fueling stations in summer. In the results of thermal cycling experiments, all products of three companies met the requirements for gas leakage in the qualification criteria between $82^{\circ}C$ and $-40^{\circ}C$. But the o-rings of two companies' specimens among the three companies' specimens got damaged under the accelerated conditions between $135^{\circ}C$ and $-45^{\circ}C$. It took one minute and thirty nine seconds for a glass bulb type of a thermal sensitive type PRD to activate and it took two minutes and thirty one seconds for a fusible plug type of a thermal sensitive type PRD to activate. These results indicated that a glass bulb type of a thermal sensitive type PRD was one minute faster than a fusible plug type of a thermal sensitive type PRD. Under the accelerated condition $135^{\circ}C$, the activation pressure of a pressure sensitive type PRD burst at 32.1 MPa and, under the condition of qualification criteria, it burst from 30.7 MPa to 32.1 MPa.. As a result of the experiment for performance of pressure relief device, in the case of the thermal sensitive type PRD, a glass bulb type is more effective to flame than a fusible plug type. we confirmed that the rupture pressure of a pressure sensitive type PRD could not be affected by temperature and pressure cycling.

• Transactions of the Korean hydrogen and new energy society
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• v.22 no.4
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• pp.520-526
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• 2011

In recent years, it is very important that hydrogen storage system is safe for user in any circumstances in case of crash and fire. Because the hydrogen vehicle usually carry high pressurized cylinders, it is necessary to do safety design for fire. The Global Technical Regulation (GTR) has been enacted for localized and engulfing fire test. High pressure hydrogen storage system of fuel cell electrical vehicles are equipped with Thermal Pressure Relief Device (TPRD) installed in pressured tank cylinder to prevent the explosion of the tank during a fire. TPRDs are safety devices that perceive a fire and release gas in the pressure tank cylinder before it is exploded. In this paper, we observed the localized and engulfing behavior of tank safety, regarding the difference of size and types of the tanks in accordance with GTR.

• The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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• v.14 no.1
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• pp.21-30
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• 1985

One of the problems with the Boiling Water Reactor involves the flow and thermal mixings in the suppression water pool high pressure steam discharge into the pool in case of emergency core relief. Varioos heat sensitive devices and pumps for the reactor core cooling are installed in the middle of the suppression pool. Especially the pumps utilize pool water in order to cool the reactor core in emergency cases. In this case, the water temperature for the reactor cool ins should be below a certain temperature specified by the reactor design. In the present investigation, in other to determine the optimum locations of these pumping devices, numerical solutions have been obtained for the model to determine the f low mixing characteristics. Experimental investigations have also been carried out for the flow mixing and for the thermal mixing in the pool during the discharge. Considering that the discharge steam through the Quenching Device becomes hot water immediately in the water pool, the steam- equivalent hot water has been utilized. Examining these characteristices, it becomes possible to deform me the best locations for RCIC, LPCI , HPCI pumps in the suppression water pool for the emermency reactor core cooling.