• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.1070-1072
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• 2003

In this paper, Firstly, it is shown that the high vibration source of piping system is the pulsation transmission of pipe line element ,such as, orifice plate, valves and the control valve is a broad band source and the branch wall and the cavity have vortex frequency Secondly, in order to decrese the turbulence vibration of piping system, the practical analysis of piping flow by EFD have been developed and its effectiveness is investigated as applying it at piping system practically.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1990.10a
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• pp.113-124
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• 1990

Tap lines are small branch piping generally less than two inches in diameter. They typically branch off of header piping having a much larger diameter. An example of a common tap line is a 3/4 inch size high point vent or low point drain. Most tap lines have at least one valve near the header tap connection to provide isolation. Two valves are often required for double isolation. A light water reactor(LWR) nuclear power plant will have several hundred tap lines. These lines come in many sizes and shapes and serve numerous functions. A single process piping valve may have three different tap lines associated with it (figure 1). Table 1 delineates the different categories of tap lines. Vibration failures of tap lines are a common occurrence in all industrial plants including nuclear and fossil power plants. These types of failures constitute a significant percentage of all piping related failures. An unscheduled plant shutdown or outage resulting from the failure of a tap line decreases plant reliability and may have a detrimental effect on plant safety. Most tap line vibration failures can be avoided through the use of appropriate routing and support techniques. Standardized designs can be developed for use in a myriad of applications. These designs will not only minimize failures but will also reduce the necessary analysis and installation efforts.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.322-327
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• 2001

The internal leaks of RCS pressure boundary valves may cause thermal fatigue crack because of the TASCS in RCS branch line. After experienced unisolable piping failures in several PWR plants, many studies have peformed to understand these phenomena and various methods were applied to ensure the structural integrity of piping. In this paper, the cause of unisolable piping failures and the alternatives to prevent recurrence of failure were reviewed. Also, the severity of piping failure including susceptibility of valve leaks was evaluated for the Westinghouse 2-loop plant. The length of turbulent penetration on RHR inlet piping was measured and, thermal fluid analysis and fatigue analysis was performed for this piping. As a means of ensuring the structural integrity, temperature monitoring and specialized UT and other alternatives were compared for the further application.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.7 no.3
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• pp.40-47
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• 2011

KSNPs(Korea Standard Nuclear Power Plant) have been applied the break exclusion criteria to the high energy lines passing through containment penetration area to ensure that piping failures would not cause the loss of containment isolation function, and to reduce the resulting dynamic effects. Systems with the criteria are the Main Steam system, Feed Water system, Steam Generator Blowdown system, and Chemical & Volume Control system. In accordance with FSAR(Final Safety Analysis Report), a 100% volumetric examination by augmented in-service inspection of all pipe welds appled the break exclusion criteria is required for the break exclusion application piping. However, it is difficult to fully satisfy the requirements of inspection because 12", 8" and 6" weldolet weldments of Main Steam pipe line have complex structural shapes. To resolve the difficulty on the application of conventional UT(Ultrasonic Testing) technique, realistic mock-ups and UT calibration blocks were made. Simulations of conventional UT were performed utilizing CIVA, a commercial NDE(Nondestructive Examination) simulation software. Phased array UT experiments were performed through mock-up including artificial notch type flaws. A phased array UT technique is finally developed to improve the reliability of ultrasonic test at main steam line pipe to 12", 8" and 6" branch connection weld.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.12 no.2
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• pp.25-33
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• 2016

The thermal stratification phenomenon in the nuclear power plant can cause abnormal deformation of the piping, contact with the support, damage to the support system. Repetition of the thermal stratification phenomenon or variation of the thermal boundary layer can cause thermal fatigue. Thermal stratification phenomenon in nuclear power plants is still an ongoing issue and active research has been carried out. In this paper, the current situation in Korean nuclear power plants is described, followed by the status of research and the future problems on the thermal stratification phenomenon in Korea.

• Journal of the Korean housing association
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• v.19 no.5
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• pp.111-120
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• 2008

The aim of this study is to present the design methods about manifold location being installed and size and to draw out the proper piping size as comparing the fluctuation of discharge with manifold size and residence size through the piping network analysis, when using the same faucet in accordance. The findings are summarized as follows, 1) an appropriate header main body pipe diameter was deemed to be $32{\sim}50\;mm$. 2) the research presented design measures for the application of appropriate water supply inlet pipe diameters according to residential buildings with various sizes. 3) the header direct branch piping method is ideal for small and medium-sized residential complexes, and the header branching and semi header methods are deemed to be more favorable for large residential complexes. 4) this study offered design measures for appropriate header system main body pipe diameters, water supply inlet pipe diameters, header system piping methods, application methods for functional auxiliary equipment units, and header system installation spaces and location.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.8 no.3
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• pp.307-316
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• 1996

The objective of present study is to obtain information on the stenosis effects in the branch tubes for industrial piping system and atherogenesis processing in human arteries. Numerical solutions for flows of Newtonian and non-Newtonian fluids in the branch tubes are obtained by the finite volume method. Centerline velocity and pressure along the bifurcated tubes for water, blood and aqueous Separan AP-273 solution are computed and the numerical results of blood and the Separan solution are compared with those of water. Flow phenomena in the stenosed branch tubes are discussed extensively and predicted effectively. The effects of stenosis on the pressure loss coefficients are determined.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.652-657
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• 2000

In this paper, Firstly, it is shown that the high vibration source of piping system is the pulsation transmission of pipe line element, such as, orifice plate, valves and the control valve is a broad band source and the branch wall and the cavity have vortex frequency. Secondly, in order to decrese the high vibration of piping system, some practical Friction damper with high damping have been developed and its effectiveness is investigated as installing it at piping system practically.

• Transactions of the Korean Society of Pressure Vessels and Piping
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• v.4 no.2
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• pp.40-45
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• 2008

There exist many types of pipe and component fatigue through vibrations, thermal fatigues or shifting. In some cases of thermal stratification/thermal fatigue, pipes & components are receiving thermal stress by means of material expansion and shrinkage by continuous thermal repetitive variation. Small cracks initially occur on the inside surface by thermal stress. These cracks grow in depth the pipe wall and finally come to a rupture. Pipe parts of susceptibility to thermal stratification and thermal fatigue are now being examined by conventional UT(ultrasonic test) as volumetric examination. It is difficult to fully satisfy the code & standards requirements because 3" weldolet weldments of RCS 16" pipe to 3" branch connection lines have complex structural shape. To solve the problems of conventional UT examination, we made a realistic mock-up and UT calibration block. We performed a simulation of phased array UT utilizing CIVA as NDE(Non-Destructive Examination) simulation software. Also we designed phased array UT transducer and wedge, optimal frequency by using simulation data. We performed phased array UT experiment through mock-up including artificial flaws(notch). The phased array UT technique is finally developed to improve the reliability of ultrasonic test at RCS 16" pipe to 3" branch connection weld.

• Journal of Advanced Marine Engineering and Technology
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• v.22 no.3
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• pp.275-284
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• 1998

Standard on the carbon dioxide extinguishing system was prepared by the committed of the national fire protection assocition(NFPA)in USA on 1980. And this code is also applied to the design of a marine fire extinguishing system The most important problem in design is the uniform discharge of $CO_2$ through each nozzle from the high pressure $CO_2$ storage facility. The purpose of this paper is to develop the computer software to design the marine fire protection piping system. By solving the continuity equation energy equation and Bernoulli's equation simulataneously the flowrate in branch pipelines and discharge nozzles can be calculated.