• Proceedings of the KSME Conference
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• 2003.04a
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• pp.670-677
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• 2003

Although Gas Tungsten Arc Welding (GTAW or TIG welding) is considered as high quality and precision welding process, it also has demerit of low melting rate. Narrow-gap TIG welding which has narrow joint width reduces the groove volume remarkably, so it could be shorten the welding time and decrease the overall shrinkage in heavy wall pipe welding. Generally Narrow-gap TIG welding is used as orbital welding process, it is important to select the optimum conditions for the automatic control welding This paper looks at the application and metallurgical properties on Narrow-gap TIG welding joint of heavy wall large austenitic stainless steel pipe to determine the deposition efficiency, the resultant shrinkage and fracture toughness. The fracture toughness depends slightly on the welding heat input.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.807-812
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• 2001

This paper represents the wall thinning analysis results for secondary side piping of two types of domestic nuclear power plants based on the DB establishment and F AC analysis study for NPP secondary system piping. CHECWORKS code utilized in this study has been applied world widely to wall thinning analyses for secondary side piping and its reliability has also been proved. The predicted wear rates for several piping systems of a pressurized water reactor NPP are compared with those of a pressurized heavy water reactor NPP and with the measured wear rates. On the basis of comparison results of the predicted and measured wear rates, the analysis results can be effectively applied to the development of a standard thinned pipe management program targeted all domestic nuclear power plants.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.4
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• pp.368-377
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• 2013

The Urea-SCR system commercialized shows a remarkable performance to reduce NOx emission in heavy duty diesel engines. However, Urea-water solution injected upstream a mixer, which is set up inside a exhaust pipe to promote exhaust gas-atomized droplet mixing, bumps up against the wall of a exhaust pipe as the droplets flow downstream through the exhaust gas. The urea deposited on the wall of the exhaust pipe is changed into the Urea-salt, resulting in the decreased life-time of the SCR catalysts. Therefore, the development of the urea deposition avoidance technologies is being treated as an important issue of the Urea-SCR systems. An experimental study was carried out to investigate the effects of the wall flow characteristics around the mixer-housing assembly with the variation of the mixer housing surrounding and supporting the mixer, which is designed to increase the wall flow and then to reduce droplet deposition. The flow characteristics was investigated by using a hot-wire anemometry for 2-D simplified duct model, and the housing tilt angles and the position of the mixer were changed : angle of $0^{\circ}$, $1^{\circ}$, $2^{\circ}$, $3^{\circ}$, and mixer positions of 0L, 0.5L, 1L. The results showed that the wall flow onto the exhaust pipe was improved with changing the tilt angle of the mixer housing, and the wall flow improved more when the position of the mixer was on 1L.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.4
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• pp.79-84
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• 2020

Induction bending via high-frequency heating is widely used for manufacturing pipe and section steel bends. It allows productivity improvement, unit cost reduction, delivery time compliance, and good mechanical properties. The recent increase in high-end vessels and offshore plants has raised the demand for high-frequency bending, which should improve the product quality and reduce the costs by simplifying the fabrication process; therefore, the characteristics and performance of this technique must be studied and proper design technology is required. During hot pipe bending via induction heating, the outward wall thickness of the pipe is thinned due to tensile stress and this thickness reduction cannot exceed 12.5%. This study focused on pipe bends with a bending curvature of 5D and their optimization design; in particular, the conditions that can both improve the productivity of the high-frequency bending process and keep the maximum thickness reduction below 12.5% were determined.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.25 no.5
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• pp.261-268
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• 2013

Technologies for preventing contaminants deposition are a key issue in a modern duct system. When particulate matters deposit inside the exhaust pipes, which are widely used in the Urea-SCR system to reduce $NO_x$ emission from heavy duty diesel engines, many problems arise associated with increased flow resistance and corrosion. Therefore, the development of the urea deposition avoidance technologies is being treated as an important issue of the Urea-SCR system. An analytical study was carried out to investigate the effects of the wall flow around the mixer with the variation of the mixer housing surrounding and supporting the mixer, which is designed to increase the wall flow and then to reduce droplet deposition. The housing angles and the position of the mixer were changed：angles of $0^{\circ}$, $1^{\circ}$, $2^{\circ}$, and $3^{\circ}$, and mixer positions of 0 L, 0.5 L, and 1 L. The axial velocity distributions, maximum velocity, the half-width, and momentum distribution of the wall flow were investigated to examine the effect of the mixer-housing assembly geometry.

• Journal of Korean Society of Steel Construction
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• v.16 no.1 s.68
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• pp.43-49
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• 2004

With building structures becoming higher and having longer spans, new structural steel with better strength, thicker plate, and performance may be required rather than conventional structural steel. TMC steel is widely used in building structures largely due to its excellent seismic performance, superior weldability, and design strength that is not affected by plate thickness. To make use of TMC steel in pipe structures with large diameter and heavy wall, however, the this study, the degradation of material properties in submerged are welded SM520TMC steel pipes and tubes was evaluated using variable fabrication process and material change. Degradation test results showed that the yield and ultimate strength increased and elongation decreased regardless of the mode of fabrication, i.e., through roll bending or press forming, or steel used, i.e., domestic SM520TMC steel or SM520TMC steel from Japan.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.4
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• pp.307-314
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• 2004

A circumferential guided wave method was developed to detect the axial crack on the bent feeder pipe. Dispersion curves of circumferential guided waves were calculated as a function of curvature of the pipe. In the case of thin plate, i.e. infinite curvature, as the frequency increases, the $S_0$ and $A_0$ mode coincide and eventually become Rayleigh wave mode. In the case of pipe, however, as the curvature increases, the lowest modes do not coincide even in the high frequencies. Based on the analysis, a rocking technique using angle beam transducer was applied to detect an axial defect in the bent region of PHWR feeder pipe. Based on the analysis of experimenal data for artificial notches, the vibration modes of each signal were identified. It was found that the notches with the depth of )0% of wall thickness can be detected with the method.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.2
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• pp.136-141
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• 2004

A torsional guided wave mode was applied to detect a crack in a pipe. An array of electromagnetic acoustic transduce. (EMAT that can generate and receive torsional guided ultrasound with the frequency of 200kHz was designed and fabricated for testing a pipe of 2.5 inch diameter Artificial notches with various depths were fabricated in a bent feeder pipe mock-up and the detectability was examined from the distance of 2m of the specimen. The axial notches with the depth of 5% of wall thickness were successfully detected by a torsional mode (T(0,1)) generated by the EMAT However, it was found that the depth of defects was not related to the signal amplitude.

• Journal of Welding and Joining
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• v.32 no.5
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• pp.21-25
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• 2014

Oil and gas fields were left unexploited which deemed too deep and sour. New developing markets are emerging in this part and pipe manufacturers need demanding requirements in the combination of sour service requirements with heavier wall thickness required to cope with increasing water depths. Whilst, the strength and fracture toughness needed to meet the strict requirements In order to deliver the optimum sour properties in the final pipe, attention needs to be paid to each stage throughout the process from steel making. The main key during steel making is strengthening, securing mechanical properties and suppression of center segregation by adding proper chemical elements and controlling water cooling and plate rolling. Additionally in welding, it is required to prevent HAZ softening by high heat input during welding of heavy thick pipes and hydrogen assisted cracking in high strength steels with hard phases. In this paper, we introduce markets of sour resistant linepipe steels and in response to this, have a look in the development trend of sour resistant linepipe steels and its sour characteristics in welded joints.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.3
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• pp.313-318
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• 2012

In CANDU, feeder pipes supply heavy water to pressure tube and steam generator. Under service conditions, Flow-Accelerated Corrosion (FAC) produces local wall-thinning in the feeder pipes. The wall-thinning in these pipes affects the integrity of the piping system, as verified in previous research. This paper provides limit loads for wallthinned feeder pipes with $45^{\circ}$ and $60^{\circ}$ bend angles, and proposes an equation that predicts the limit loads for wallthinned feeder pipes with arbitrary bend angles. On the basis of finite element limit analyses, limit loads are obtained for wall-thinned feeder pipes under in-plane bending and internal pressure. There are two cases of in-plane bending: the in-plane closing direction and the in-plane opening direction. The material is considered the effect of the large deformation, so an elastic-perfectly-plastic material is assumed in the calculations.