• Proceedings of the KIEE Conference
• /
• 2006.07b
• /
• pp.643-644
• /
• 2006

자기누설탐상시스템은 지하에 매설된 가스관에서 발생되는 부식이나 크랙 또는 기계적 변형을 탐지하기 위한 방법으로 비파괴검사 방법의 하나이다. 가스관은 Nd자석에 의해 착자가 되고, 가스관에 부식이 발생했을 경우 가스관의 단면적이 작아지게 되어 자기누설이 발생하며, 발생된 자기누설을 홀센서로 검출하여 부식의 유무, 크기, 모양 등을 판별하게 된다. 지하매설 배관은 배관의 직경은 같으나 배관의 두께는 다양하게 존재한다. 특히 30inch의 배관에는 배관의 두께가 11.1, 14.3, 17.5 mm 등이 있다. 자기누설탐상시스템은 배관의 단면적 변화를 감지하는 것이기 때문에 배관의 두께에 따라 그 특성이 변화하게 된다. 또한 두께에 따른 결함의 종류에 따라서 검출신호도 변화하게 된다. 따라서 본 논문에서는 배관의 두께 변화에 따른 검출신호를 분석하였으며, 두께 변화의 영향을 적용하여 검출신호를 보정하기 위한 방법을 제시하였다.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.10
• /
• pp.1131-1137
• /
• 2012

Subsea pipelines have been operated with buried depths of 1.2-4m underneath the seabed to prevent buoyancy and external impacts. Therefore, they have to show resistance to both the soil load and the hydrostatic pressure. In this study, the structural integrity of a subsea pipeline subjected to soil load and hydrostatic pressure was evaluated by using FE analyses. A parametric study showed that the internal pressure increased the plastic collapse depth by increasing the resistance to plastic collapse. The hoop stress increased with an increase in the buried depth for the same water depth; however, the hoop stress decreased with an increase in the water depth for the same buried depth.

• Journal of the Korean Institute of Gas
• /
• v.23 no.2
• /
• pp.28-34
• /
• 2019

A large number of underground pipelines in the Ulsan National Industrial Complex has been constructed to improve the productivity of chemical products and tackle transportation problems. Now, the total of 1,293km of underground pipelines around 62 companies has been installed and operated. Many of underground pipelines have been installed outside of factories. For a past three years, five gas leakage accidents have occurred and the emergency response took up to 8 hours or more. Due to these delay in accidents, second serious accidents might occur and lead to occur damages to adjacent residents. In this study, it is assumed that emergency valve systems are installed under a ground and the efficacy of these is verified. Consequence analysis program was employed to evaluate the mitigation impact of emergency valve systems. The results show that these valve systems are economical and their performances for a mitigation are excellent. The results indicate that the installation of emergency valve systems for underground pipelines should be urgently legislated and performed.

• Journal of the Korean Institute of Gas
• /
• v.20 no.4
• /
• pp.33-43
• /
• 2016

Grinding, weld deposition, type A sleeve, type B sleeve, composite sleeve, hot tapping and clamp are used as the method to repair the buried pipelines in the United States, UK and Europe. In the event of defect to the pipeline, they have repaired the pipeline through the fitness-for-service assessments. In addition, they have guidelines for the possible repair methods to apply to each type of damage, which is occurred due to the 3rd party construction or corrosion. According to the KGS FS551, Safety Validation in Detail including ECDA(External Corrosion Direct Assessment) as one method of integrity management should be carried out for the old pipeline which supply natural gas as the middle pressure in Korea. Where a defect on the pipelines is found, on the result of Safety Validation in Detail, the pipelines should be repaired or replaced by new piping. However, there are no guidelines or regulations regarding the repair and reinforcement of pipeline, so that, cutting the damaged pipeline and replacing it as a segment of new pipe is the only way in Korea until now. We have suggested pipeline repair methods including type A, B sleeve, composite sleeve, after the survey of foreign repair method and standards including the method of United States and the United Kingdom, and after analysis of the results on pipeline repair test including type A, type B sleeve and composite sleeve.

• Journal of the Korean Institute of Gas
• /
• v.4 no.2 s.10
• /
• pp.37-45
• /
• 2000

The underground buried pipelines of Natural gas are relatively safer than any other pipelines of chemical plants, because Natural gas is non-corrosive fluid. But Natural gas is supplied normally the downtown area. So, it may be a disaster because of corrosion which is caused interference facilities, environment and third party accident which is caused facilities construction. Especially, it is very difficult to find out and inspect damages of pipeline because of buried pipelines. Therefore this paper approached to select and manage risk region pipelines according to introduction of underground buried pipeline's risk concept. Risk was indicated three parts - corrosion factor, design and construction factor, maintence and management factor - in this paper, Therefore qualitive risk of pipelines showed score as quantitative number. Also it was thought to be helpful in confidence and safety management that the concept of key index and failure supplementation measures to cost introduces this program. We developed this risk assessment program using visual basic tool and interfaced GIS.

• Journal of the Korean Institute of Gas
• /
• v.21 no.6
• /
• pp.8-14
• /
• 2017

One of the main causes of gas pipeline accidents is mechanical impact(third party damage). The majority of high pressure gas pipelines buried in major domestic industrial complexes are old pipes which have being operated over 20 years. Therefore, if an accident occurs, there will be a full scale accident because there is no additional inspection and reinforcement time. In this study, the defects on the piping during the mechanical impact were studied through the third party damage(excavation) experiments. Experiments were carried out using the 21 ton excavator which is operated in the actual excavation work and the type of pipe to be struck are ASTM A106 Grade.B and ASTM A53 Grade.B. As a result, when the bucket used during excavator operation is a sawtooth bucket, the defect is more bigger. And the smaller the diameter of the pipe, the smaller the depth and length of the defect. Also, it was confirmed that the impact height had no effect on the defects on the buried pipe, during the excavation work.

• Journal of the Korean Institute of Gas
• /
• v.2 no.2
• /
• pp.18-25
• /
• 1998

According to the requirements of ANSI B3l.8, the pipe thickness is determined with hoop stress resulted from internal pressure. And the other loads induced by soil, vehicle, thermal expansion, ground subsidence, etc shall be evaluated rationally. There are two ways of calculating stress of buried gas pipeline. The first is FEM. FEM can calculate the stress regardless of the complexity of pipeline shape and boundary conditions. But it needs high cost and long time. The second is the way to use equation. The reliable equations to calculate the stress of buried gas pipeline was developed and have been used in designing pipeline and evaluating pipeline safety, But these equation are very difficult to understand and use for non-specialist. For easy calculation of non-specialist, the new computer program to calculate stress of buried natural gas pipeline have been developed. The stress is calculated by the equations and extrapolation of the graph resulted from FEM. The full paper is consist of series I and II. In this paper, series I, the calculating equation of the program is explained in detail.

• Journal of the Korean Society for Environmental Technology
• /
• v.19 no.6
• /
• pp.576-585
• /
• 2018

Systematic management during the whole life cycle from construction to operation and maintenance is very important for the seven underground pipelines (waterworks, sewerage, electricity, telecommunications, gas, heating, oil including waterworks and sewerage). Especially, it is the construction process that affects the whole life cycle of underground buried pipeline. In order to construct a new city or to maintain different underground pipes, it is always necessary to dig the ground and carry out construction and related work. There is a possibility that secondary and tertiary breaks frequently occur in the pipeline construction process after the piping constructed first in this process. To solve this problem, a system is needed which can monitor damage in real time. However, the supply of electric power for continuous operation of the system is limited according to the environment of underground buried pipelines, so it is necessary to develop a stable electric power supply system using natural energy rather than existing electric power. In this study, we developed a system that can operate the pipeline monitoring system for long time (24 hours and 15 days) using natural energy using wind and solar light.

• 월간 기계설비
• /
• no.4 s.201
• /
• pp.49-52
• /
• 2007

정부가 도입하려 하는 원콜시스템(EOCS: Excavation One Call System)은 원콜센터에 전화 한통화를 하면 현장에서 만나 도시가스 매설배관을 지면에 표시해 주기 때문에 신청서 작성이 필요없고 곧바로 업무처리가 가능하다. 이 시스템 도입은 관계부처 협의를 거쳐 법제처 심사를 앞두고 있으며 올 하반기쯤 시행될 예정이다.

• Journal of the Korean Institute of Gas
• /
• v.14 no.6
• /
• pp.1-6
• /
• 2010

River crossing pipelines have been being operated with buried depth of 1.2~4m underneath river bottom to prevent buoyance and external impact. River crossing pipelines have to show resistance to soil load and hydrostatic pressure. In this study, structural integrity of the river crossing pipeline subjected to soil load and hydrostatic pressure was evaluated by using FE analyses. Hoop stress increased with increasing buried depth under identical water height in case of without concrete encasement, however, hoop stress decreased with increasing water height under identical buried depth.