• 한국가스학회:학술대회논문집
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• 한국가스학회 2001년도 추계학술발표회 논문집
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• pp.45-57
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• 2001

An alternating current (AC) corrosion using coupon has been studied. Coupons were applied in terms of AC voltage from high value to low value through the survey of AC voltages on buried gas transmission pipeline over the country. Parameters such as AC current density of coupon, AC voltage, cathodic protection potential, soil resistivity and frequency were monitored continually. Corrosion induced by AC was observed even under cathodically protected condition that met cathodic protection criterion(: below -850mv vs. CSE). Corrosion rate was affected mainly not by AC voltage but by both of frequency and AC current density. An experimental corrosion rate relationship could be obtained statistically, in which AC corrosion rate increased linearly with effective AC current density and its slope was 0.619.

• 한국안전학회지
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• 제13권2호
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• pp.54-64
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• 1998

This study was initiated to examine the stress and deformation characteristics of the pipelines which were subjected to various environmental conditions in order to confirm their integrity. As the part of them, this paper presents the analysis results for the effect of ground subsidence combined with main loads on buried natural gas pipelines. The ground subsidence which can occur for buried gas pipeline has been classified to the three cases. Finite element method was used to analyze the effect of ground subsidences on pipeline of 26 inch(0.660 m) and 30 inch(0.762 m) diameter used as high pressure ($70 kg_f/cm^2(6.86 MPa)$) main pipelines of KOGAS. This paper shows the result of stress analysis for the pipelines subjected to those three case ground subsidence. Comparing these results with safety criterion of KOGAS(0.9 $\sigma_y$), maximum allowable settlement and loads have been calculated.

• 한국안전학회지
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• 제33권3호
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• pp.33-38
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• 2018

Defects in piping caused by corrosion or external impact of underground piping can lead to high risk of rupture of the piping due to high pressure. Flammable gas can be immediately ignited when discharged from piping, causing a jetfire. The damage of the radiant heat not only threatens the health of the workers who work in the industry but also the health of the people living in the neighboring residential areas. It is important to prevent and prepare before an accident occurs. In this study, three types of flammable gas underground piping accident scenarios were investigated, and the ranges of influence were determined using Phast ver7.2. and finally regression models were formulated to predict the ranges using excel and Matlab.

• 동력기계공학회지
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• 제17권1호
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• pp.36-41
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• 2013

A study of the possible axisymmetric modes that propagate at low frequencies in buried, water-filled pipes is presented. It is well known that for a vacuum-pipe-vacuum system the sole non-torsional axisymmetric mode that exists at low frequencies is the fundamental L(0,1) mode. When a pipe is filled with water and still surrounded by a vacuum it is also known that another mode then appears which at low frequencies is characterized by predominantly axial water-borne displacements. In addition to these modes. this paper explores two other, less well known axisymmetric modes whose exitence depends on the acoustic properties of the outer medium that surrounds a pipe. The predicted characteristics of these modes are presented and the likelihood of them propagating over any significant distance in a buried water pipe is discussed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 심포지엄 논문집 정보 및 제어부문
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• pp.346-348
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• 2007

Underground pipe is an instrument to transport rapidly and safely a lot of fluid like gas, oil, water supply and drain system. It acts like blood vessels of human body in a modern industry. As in this country, the pipe facilities have been constructing since 1970's. The pipes constructed for a long time ago are already starting to reveal the problem like corrosion and most of them are built underground. So for companies, the managing of the underground pipes is very hard because it needs high technology and a lot of money. So we made a new robot system to repair and maintain the pipes at a low price. This new robot is devised using pressing wall type to work inside 700${\sim}$900(mm) size pipe. And it has good carrying and working power.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 A
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• pp.349-351
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• 2001

Because of the continuous growth of energy consumption and also the tendency to site power lines and pipelines along the same route, the close proximity of power lines and buried metallic pipelines has become more and more frequent. Therefore there has been and still is a growing concern about possible hazards resulting from the influence of power lines on metallic pipelines. When a ground fault occurs in an electrical installation the current flowing through the earthing electrode produces a potential rise of the electrode and of the neighbouring soil with regard to a remote earth. This paper analyzes the effects of ground faults when the current will flow into the soil from the foot of 345kV transmission line tower.

• Corrosion Science and Technology
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• 제11권6호
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• pp.225-231
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• 2012

Fitness-for-Service is a useful technology to determine replacement timing, next inspection timing or in-service when nuclear power plant's buried pipes are damaged. If is possible for buried pipes to be aged by material loss, cracks and occlusion as operating time goes by. Therefore Fitness-for-Service technology for buried pipe is useful for plant industry to perform replacement and repair. Fitness-for-Service for buried pipe is studied in terms of existing code and standard for Fitness-for-Service and a current developing code case. Fitness-for-Service for buried pipe was performed according to Code Case N-806 developed by ASME (American Society of Mechanical Engineers).

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 전기설비
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• pp.61-63
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• 2005

In present, most of underground metallic structures, especially gas pipeline, have adopted in order to protect against a corrosion. If a coating defect is be on the surface of gas pipeline, the pitting corrosion is occur normally. So, in the corrosion field, investigation of coating defect is very important activity. In this paper, DCVG(Direct Current Voltage Gradient) method which is can detect a coating defect of gas pipeline is introduced. And also, the assesment of coating defect position according to the position of temporary anode of ICCP(Impresed Current Cathodic Protection) system is presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 추계학술대회 논문집 전기설비전문위원
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• pp.53-55
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• 2005

Because of the continuous growth of energy consumption and also the tendency to site power lines and pipelines along the same route, the close proximity of power lines and buried metallic pipelines has become more and more frequent. The lightning strokes collected by an electric substation or power line tower might cause arcing through the soil to an adjacent gas pipeline. This paper gives the review of the breakdown mechanism and the standards of separation distance between lower and pipelines.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1273-1275
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• 2003

Corrosion of metallic structures arises when an electric current flows from the metal into the electrolyte such as soil and water. The potential difference across the metal-electrolyte interface, the driving force for the corrosion current, can emerge due to a variety of temperature, pH, humidity etc.. In this paper we analyze P/S potential and axial current of the pipeline with CP systems using BEM and DC traction stray current influences on buried pipelines.