• 유체기계공업학회:학술대회논문집
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• 2005.12a
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• pp.200-204
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• 2005

A few intake stations have vibration problems caused by pumps, motors and pipes. The vibration transffered from pumps, motors and pipes excites buiding severely. Therefore, the crack is generated on building wall and people who work at intake station are damaged. In this paper, the vibration and noise have been measured and analyzed for pumps, motors, pipes and building at intake station. Also, the cause of vibration and noise is identified. Finally, the reference of vibration and noise is established using results of measurement.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.33 no.3
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• pp.194-201
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• 1997

Recently with the rapid development in the industries such as an iron mill and chemical plants, these are enlarged by the use of the piping. This piping was encountered the stress corrosion cracking(SCC) because of stress by water pressure and residual stress of welding etc. under industrial water. In this paper, the behaviour of stress corrosion cracking on the weld zone of steel pipe piping water(SPPW) were investigated according to pre-heat before welding in natural seawater(specific resistance : 25$\Omega$-cm). The main results obtained are as follows :1) The stress corrosion cracking for SPPW and SB 41 is most ready to propagate in heat affected zone of weldment. 2) The SCC sensitivity of SPPW on weldment is more susceptible than that of SB 41. 3) The stress corrosion cracking growth of heat affected zone is delayed by the preheat and dry of base metal and electrode before welding.

• Proceedings of the KWS Conference
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• 2005.11a
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• pp.38-40
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• 2005

Fracture mechanics evaluation of stress corrosion cracking (SCC) in the dissimilar metal weld (DMW) for the nuclear piping system is performed; simulating the transition joint of the ferritic nozzle to austenitic safe-end fabricated with the Inconel Alloy A82/182 buttering and welds. Residual stresses in the DMW are computed by the finite element (FE) analyses Then, to investigate the SCC in the weld root under the combined residual and system operation stresses, the fracture mechanics parameters for a semi-elliptical surface crack are evaluated using the finite element alternating method (FEAM). As a result, it is found that the effect of weld residual stresses on the crack-driving forces is dominant, as high as three times or more than the operation stresses.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.10
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• pp.568-572
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• 2013

The main components, such as a reactor vessel, in commercial nuclear power plants have been welded to pipes with dissimilar metal in which Primary Water Corrosion Cracking (PWSCC) has been occurred. PWSCC has become a worldwide issue recently. This paper addresses the results of experimental and numerical analysis to prevent PWSCC by changing the stress profile that is tensile stress to compressive stress at interesting regions with plastic deformation generated by mechanical pressure. Based on the results of experimental and numerical analysis with a 6 inch pipe and dissimilar metal welded pipes, compressive stress 68~206 Mpa is generated at all locations of inner surface in the heat affected zone.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.2 s.257
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• pp.190-196
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• 2007

A few intake stations have vibration problems caused by pumps, motors and pipes. The vibration transferred from pumps, motors and pipes excites building severely. Therefore, the crack is generated on building wall and people who work at intake station are damaged. In this paper, the vibration has been measured and analyzed for pumps, motors, pipes and building at intake station. Also, the cause of vibration is identified. Finally, the solution of structural vibration is established using the results of measurement.

• Journal of the Korean Society of Safety
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• v.25 no.2
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• pp.7-11
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• 2010

Difficulties associated with full-scale pipe tests are rather obvious. That is, it is not only difficult to perform them but also very expensive and it requires lots of experience. And the process of the fracture test for the pipe specimen is very difficult and complicated. Because the pipe specimen, the test jig and the test equipment are very large and heavy, it requires lots of costs and times. In this study, to easily perform the fracture toughness test for a pipe specimen, load line displacement data was obtained using the image processing method.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.16 no.1
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• pp.42-48
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• 2020

The effect of improving the tensile and J-R fracture toughness properties of SA508 Gr.1a on the LBB margin for the main steam pipe is investigated. The material properties and microstructure images of the existing main steam piping material SA106 Gr.C used in domestic nuclear power plants and the newly selected material SA508 Gr.1a were compared. For each material, LBB margins were calculated and compared through finite element analysis and crack instability evaluation. The LBB margin of the improved SA508 Gr.1a is found to be greatly improved compared to that of the existing SA106 Gr.C and SA508 Gr.1a. This is because of the increased material's strength and J-R fracture toughness compared to the previous materials. In order to analyze the effect of physical property change on the LBB margin, the sensitivity of each LBB margin according to the variation of tensile strength and J-R fracture toughness was analyzed. The effect of the change in tensile strength was found to be greater than that of the change in fracture toughness. Therefore, an increase in strength significantly influenced the improvement of the LBB margin of the improved SA508 Gr.1a.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.16 no.1
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• pp.74-83
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• 2020

A number of so-called 'Type IV' cracking was reported to occur at the welded joints of the P91 steel or P92 steel reheat steam piping systems in Korean supercritical thermal power plants. The reheat steam piping systems are subjected to severe thermal and pressure loading conditions of coolant higher than 570℃ and 4MPa, respectively. In this study, piping analyses and design evaluations were conducted for the piping system of a specific thermal plant in Korea and suggestions were made how structural integrity could be improved so that type IV cracks at the welded joints could be prevented. Integrity evaluations were conducted as per ASME B31.1 code with implicit consideration of creep effects which was used in original design of the piping system and as per nuclear-grade RCC-MRx code with explicit consideration of creep effects. Comparisons were made between the evaluation results from the two design rules. Another approach with modification or reduction of the redundant supports in the piping systems was investigated as a tool to mitigate thermal stresses which should essentially contribute to prevention of Type IV cracking without major modification of the existing piping systems. In addition, a post weld heat treatment method and repair weld method which could improve integrity of the welded joint of P91 steel were investigated.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.7 s.178
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• pp.1817-1825
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• 2000

The purpose of this study is to examine the fracture toughness of the welded pipe from the viewpoint of FATT for the S38 and S42 steels used widely as the pipe material. Post weld heat treatment(PW HT) was carried out like following conditions: temperature of 67$0^{\circ}C$, I hour of holding time and cooling in furnace. Fracture toughness was obtained by measuring the crack opening displacement(COD) of the notched specimens over the range of temperature from -14$0^{\circ}C$ to -$25^{\circ}C$. Hardness values at fusion line near around were the highest and the microstructures at welded zone were coarsened. Regardless of the pipe materials, COD and temperature curves of the as-welds were moved toward higher temperature compared with those of the parents. However, COD and temperature curves of the PWHT specimens were positioned at lower temperature compared with those of the as-welds. The more heat input causes to decrease the COD values at the constant temperature. It was verified through the recrystallization treatment that PWHT was attributed to move toward lower temperature region considerably due to the improved plastic deformation at the same applied COD value of 0.3mm and softening effect. In case of the weldment of S38 steel, cleavage fracture was observed at -105$^{\circ}C$ unlike the structural steels, in which brittle fracture mode was generally shown at - 196$^{\circ}C$.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.6
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• pp.1015-1022
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• 2001

The objective of this paper is to develop an expert system called NPIES for nuclear piping integrity. This paper describes the structure and the development strategy of the NPIES system. The NPIES system consists of 3 part; the data input part, the analysis part and the output part. The data input part consists of the material properties database module and the suer interface module. The analysis part consists of the LEFM, CDFD, J/T, limit load modules and the 12 analysis routines for different cracks and loading conditions are provided respectively. Analysis results are presented to screen, printer and text file in the output part. Several case studies on circumferentially cracked piping were performed to evaluate the accuracy and the usefulness of the code. Maximum piping loads predicted by the NPIES system agreed well with those by the 3-dimensional finite element analysis. In addition, even if the material properties were not fully given, the NPIES system provided reasonable evaluation results with the predicted material properties inferred from the material properties database module.