• The KSFM Journal of Fluid Machinery
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• v.16 no.4
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• pp.5-9
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• 2013

An experimental investigation has been carried out in order to evaluate characteristics of wetted-type multi-path ultrasonic flowmeters. The multi-path ultrasonic flowmeters were installed at various entrance and exit locations for several cases of pipe fitting(straight, $90^{\circ}$ double elbow) and valve(gate valve, butterfly valve). We measured the flow-rate at each location. The measurement data of test flowmeter were compared with the measured data of reference flowmeter. The uncertainties of reference flowmeter and test flowmeter are 0.3 %, 0.4 %, respectively. The results demonstrate the effects of flowmeter location as well as the measurement errors in flow rate. The distance between the flow disturbance factor and a flowmeter was an important element of the test.

• Journal of Ocean Engineering and Technology
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• v.33 no.5
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• pp.479-485
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• 2019

As exhaust gas systems of ships become more complicated, it is necessary to calculate an accurate pressure loss at their design stage. If the dynamic loss coefficients of non-standard fittings mainly used in exhaust gas pipe (EGP) are well-documented, it would be possible to calculate precise pressure loss more readily than using the conventional method that analyzes the entire system. In the case of a ship's EGP, the flow rates and temperatures of exhaust gas are determined by engine specifications, and the range of the flow rate and temperature is limited according to operating conditions. In addition, as it is possible to define non-standard fittings frequently used in an EGP, a database can be easily constructed and effective. This paper illustrates effective parameters and analysis cases of several types of non-standard fittings mounted in ship EGPs. The analysis procedure proposed in this paper is verified using existing research results on HVAC fittings. The numerical procedure, which is minimally affected by manpower and grid, is established such that it can be applied at the industry level.

• Journal of the Korean Institute of Gas
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• v.27 no.2
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• pp.79-85
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• 2023

Recently, in the semiconductor process, large companies are seeking process changes from memory semiconductors to the foundry due to the increase in demand due to the 4th industry. industry is expanding. The characteristics of special gases and precursors, which are raw materials used to produce these semiconductor chips, are toxic, pyrophoric, inflammable, and corrosive. These semiconductor raw materials are operated in a closed system and do not leak to the outside during normal times, but when leaked, they spread to the inside of the gas box, and when proper ventilation is not provided inside the gas box, they spread to the outside, causing fires, explosions, or toxic substances. It can lead to major accidents such as leakage. Recently, there have been cases of accidents in which hazardous materials leaked from the closed system of the semi conductor process and spread to the inside and outside of the gas box. . In this study, we propose preventive measures based on the case of an accident in which raw material leaked from the VCR fitting, which is the connection part of the semiconductor raw material transfer pipe, and spread to the outside of the gas box.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.3
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• pp.307-313
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• 2010

In this study, alternative designs for the bends used in district heating pipes are investigated. The district heating pipes, which are subjected to temperatures of 10 to $120^{\circ}C$ and a water pressure of $16\;kgf/cm^2$, have to withstand thermomechanical cyclic loads when in use. These pipes comprise three concentric tubes: a steel pipe (internal), polyurethane (PUR) insulator (middle), and a high-density polyethylene (HDPE) case (external). In addition, the bends in the district heating pipe system are covered with foam pads that cause aging. In this study, an alternative bend design that does not involve the use of a foam pad is proposed to overcome the aging problem in the bends. In the proposed design, "shear rings" are added to the surface of a bend, and its dimensions are determined by a combination of the statistical (Taguchi) method and FEM. The geometrical parameters such as thickness, height, and number of the rings significantly affect the design optimization, and hence, they affect the results of the FEM.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.10
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• pp.1612-1620
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• 2004

This study presents methods to estimate elastic-plastic crack opening displacement (COD) fur circumferential through-wall cracked pipes for the Leak-Before-Break (LBB) analysis of pressurized piping. Proposed methods are based not only on the GE/EPRI approach but also on the reference stress approach. For each approach, two different estimation schemes are given, one for the case when full stress-strain data are available and the other fur the case when only yield and ultimate tensile strengths are available. For the GE/EPRI approach a robust way of determining the Ramberg-Osgood (R-O) parameters is proposed, not only fur the case when detailed information on full stress-strain data is available but also for the case when only yield and ultimate tensile strengths are available. The COD estimates according to the GE/EPRI approach, using the R-O parameters determined from the proposed R-O fitting procedures, generally compare well with the published pipe test data. For the reference stress approach, the COD estimates according to the method based on both full stress-strain data and limited tensile properties are in good agreement with pipe test data. In conclusion, experimental validation given in the present study provides sufficient confidence in the use of the proposed method to practical LBB analyses even though when information on material's tensile properties is limited.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.05a
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• pp.189-194
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• 2006

The internal construction industry is not situation of cost reduction based on low wages anymore by the increase in wages as insufficient supply of stilled workers. Recently remodeling constructions that only need to change facilities as to stay the existing structures are on the increase. Now the method of piping facility used to remodeling construction needs stilled workers, large work space and a variety of tools. These complex construction process have a difficulty of high-quality and economical construction. In addition it have the hish incidence of warranty and a problem of cost increase as a commitment of manpower by warranty repair. In order to solve these problems it is necessary for appropriate new technology to the internal construction environment. Piping fittings by Insert & Coupling Joint is a method that unskilled workers can be easily constructed though one touch set up and it is convenient to maintain for repair work of piping facility. This technology show the effect of 3 percentages labor cost reduction as compared with piping fittings by press joint on apartment 500 households. Therefore this technology is supposed that attain a cost reduction though the technical and economical construction and a client satisfaction though the high-quality construction on the present construction market.

• Geomechanics and Engineering
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• v.32 no.4
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• pp.411-426
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• 2023

Soft clay is widely distributed in the southeast coastal areas of China. Many large underground structures, such as subway stations and underground pipe corridors, are shallow buried in the soft clay foundation, so the dynamic characteristics of the soft clay must be considered to the seismic design of underground structures. In this paper, the dynamic characteristics of saturated soft clay in Shanghai under the bidirectional excitation for earthquake loading are studied by dynamic triaxial tests, comparing the backbone curve and hysteretic curve of the saturated soft clay under different confining pressures with those under different vibration frequencies. Considering the coupling effects of the confining pressure and the vibration frequency, a fitting model of the maximum dynamic shear modulus was proposed by the multiple linear regression method. The M-D model was used to fit the variations of the dynamic shear modulus ratio with the shear strain. Based on the Chen model and the Park model, the effects of the consolidation confining pressure and the vibration frequency on the damping ratio were studied. The results can provide a reference to the earthquake prevention and disaster reduction in soft clay area.

• Journal of Energy Engineering
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• v.23 no.4
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• pp.247-255
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• 2014

The present study was conducted to elucidate the characteristics of temperature at the inlet and outlet pipes of a refrigerator drain condenser and suggest the method to predict the temperature of the refrigerant at the inlet and outlet pipes of the drain condenser. For this purpose, a built in style refrigerator was installed in a constant temperature chamber to measure temperatures at the inlet and outlet pipes of the drain condenser. From the results of the present analysis, it could be seen that the measured temperatures changed from $37^{\circ}C$ to $46^{\circ}C$ and the actual refrigerant temperatures were higher than the measured temperatures with the difference magnitude of $8^{\circ}C$ to $22^{\circ}C$. The present study suggested that the temperatures of the refrigerator could be calculated with the measured temperatures by introducing curve fitting of the measured temperature. The predicted refrigerant temperatures by the present study had the accuracy within 6% error of the actual refrigerant temperatures.

• Corrosion Science and Technology
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• v.3 no.5
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• pp.216-221
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• 2004

The operating experience showed that the fatigue is one of the major piping failure mechanisms in nuclear power plants (NPPs). The pressure and/or temperature loading transients, the vibration, and the mechanical cyclic loading during the plant operation may induce the fatigue failure in the nuclear piping. Recently, many fatigue piping failure occurred at the socket weld area have been widely reported. Many failure cases showed that the gap requirement between the pipe and fitting in the socket weld was not satisfied though the ASME Code Sec. III requires 1/16 inch gap in the socket weld. The ASME Code OM also limits the vibration level of the piping system, but some failure cases showed the limitation was not satisfied during the plant operation. In this paper, the fatigue behavior of the socket weld in the nuclear piping was estimated by using the three dimensional finite element method. The results are as follows. (1) The socket weld is susceptible to the vibration if the vibration levels exceed the requirement in the ASME Code OM. (2) The effect of the pressure or temperature transient load on the socket weld in NPPs is not significant because of the very low frequency of the transient during the plant lifetime operation. (3) 'No gap' is very risky to the socket weld integrity for the specific systems having the vibration condition to exceed the requirement in the ASME OM Code and/or the transient loading condition. (4) The reduction of the weld leg size from $1.09*t_1$ to $0.75*t_1$ can affect severely on the socket weld integrity.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.121-127
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• 2018

A system for diagnosing surface defects of long and large pipe inner overlay welds, 1m in diameter and 6m in length, was developed using a Liquid Penetrant Test (PT). First, CATIA was used to model all major units and PT machines in 3-dimensions. They were used for structural strength analysis and strain analysis, and to check the motion interference phenomenon of each unit to produce two-dimensional production drawings. Structural strength analysis and deformation analysis using the ANSYS results in a maximum equivalent stress of 44.901 MPa, which is less than the yield tensile strength of SS400 (200 MPa), a material of the PT Machine. An examination of the performance of the developed equipment revealed a maximum travel speed of 7.2 m/min., maximum rotational speed of 9 rpm, repeatable position accuracy of 1.2 mm, and inspection speed of $1.65m^2/min$. The results of the automatic PT-inspection system developed to check for surface defects, such as cracks, porosity, and undercut, were in accordance with the method of ASME SEC. V&VIII. In addition, the results of corrosion testing of the overlay weld layer in accordance with the ferric chloride fitting test by the method of ASME G48-11 indicated that the weight loss was $0.3g/m^2$, and met the specifications. Furthermore, the chemical composition of the overlay welds was analyzed according to the method described in ASTM A375-14, and all components met the specifications.