• 한국가스학회지
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• 제20권5호
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• pp.96-103
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• 2016

도시가스 배관의 손상부에 대한 적절한 보수방법은 안전한 가스이송 및 가스 배관의 파손으로 인한 경제적 손실을 줄일 수 있는 중요한 요소이다. 육성용접, type-A 슬리브, type-B 슬리브 그리고 복합재료 슬리브와 같은 보수 방법들이 현재 도시가스 배관 보수에 사용되고 있다. 본 연구에서는 여러 보수방법중 비교적 손쉬운 보수절차로 인해 작업자의 숙련도에 의존하지 않으며 쉽고 경제적으로 보수 할 수 있는 복합재료 슬리브를 이용한 보수방법에 관한 연구를 수행하였다. 특히 탄소섬유 프리프레그를 사용한 복합재 보수방법과 그 결과에 대해 논의하였다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제7권3호
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• pp.435-451
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• 2015

Evaluation of the performance of aging structures is essential in the oil and gas industry, where the inaccurate prediction of structural performance can have significantly hazardous consequences. The effects of structure failure due to the significant reduction in wall thickness, which determines the burst strength, make it very complicated for pipeline operators to maintain pipeline serviceability. In other words, the serviceability of gas pipelines and elbows needs to be predicted and assessed to ensure that the burst or collapse strength capacities of the structures remain less than the maximum allowable operation pressure. In this study, several positions of the corrosion in a subsea elbow made of API X42 steel were evaluated using both design formulas and numerical analysis. The most hazardous corrosion position of the aging elbow was then determined to assess its serviceability. The results of this study are applicable to the operational and elbow serviceability needs of subsea pipelines and can help predict more accurate replacement or repair times.

• 한국화재소방학회논문지
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• 제18권3호
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• pp.57-73
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• 2004

Pilot LNG Tank에서 LNG가 누출되어 화재가 발생할 경우의 정량적 안전성 평가를 고장수목법을 이용하여 4가지 형태의 주요 시나리오를 도출하고 이에 대한 분석을 수행하였다. 첫째 방출관에서 누출할 경우에 특정 Low Flammable Limit(LFL)반경은 형성하지 않았으며, 둘째는 탱크파손으로 인한 LNG 유출이라는 최악의 시나리오 분석을 수행하였고, 그 결과를 살펴보면 총 누출량이 같더라도 시간에 따라 여러 가지 확산범위가 나타남을 확인할 수 있었다. 셋째는 inlet/outlet파이프의 손상으로 인한 누출로 10달과 타분 두 경우에 대해 분석하였으나, 각각의 경우 LFL의 반경은 큰 차이를 보이지 않았다. 따라서, 이와 같은 LNG누출 사고의 경우 초기 방출량의 크기가 확산의 주요 인자임을 알 수 있었다. 넷째는 방류둑에서 LNG배관이 파손될 경우 LFL의 크기를 산출하였다. 한편 복사열 및 불꽃의 크기에 대한 피해결과 분석을 동시에 수행하였다.

• 한국가스학회지
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• 제14권4호
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• pp.18-23
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• 2010

이 논문에서는 실제 설치예정인 도시가스 고압배관에 대하여 정량적 위험성 평가를 실시하고, 평가 결과 위험이 허용영역 밖에 위치하는 경우에는 위험경감조치를 도출하였다. 또한, 도출한 위험경감조치별 위험감소율을 계산하였다. 정량적 위험성 평가결과, 복사열에 의한 사고피해거리는 바람의 속도와 대기안정도에 따라 크게 좌우됨을 알 수 있었다. 위험감소율이 가장 큰 조치는 배관의 부식관리, MOV 설치 및 타공사로 인한 배관손상방지조치를 모두 이행하도록 하는 10번 조치로서 75%의 위험감소효과가 있었다.

• Corrosion Science and Technology
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• 제16권2호
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• pp.85-89
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• 2017

One of the most challenging issues in the oil and gas industry is corrosion assessment and management in subsea structures or equipment. At present, almost all steel pipelines are sensitive to corrosion in harsh working environments, particularly in salty water and sulphur ingress media. Nowadays, the most commonly practiced solution for a damaged steel pipe is to entirely remove the pipe, to remove only a localized damaged section and then replace it with a new one, or to cover it with a steel patch through welding, respectively. Numerous literatures have shown that fiber-reinforced polymer-based composites can be effectively used for steel pipe repairs. Considerable research has also been carried out on the repair of corroded and gouged pipes incorporated with hybrid natural fiber-reinforced composite wraps. Currently, further research in the field should focus on enhanced use of the lesser and highly explored hybrid-biocomposite material for the development in corrosion prevention. A hybrid-biocomposite material from renewable resource based derivatives is cost-effective, abundantly available, biodegradable, and an environmentally benign alternative for corrosion prevention. The aim of this article is to provide a comprehensive review and to bridge the gap by developing a new hybrid-biocomposite with superhydrophobic surfaces.

• 한국가스학회지
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• 제20권4호
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• pp.33-43
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• 2016

미국과 유럽의 가스회사에서는 배관의 보수방법으로 그라인딩, 육성용접, 슬리브덮개용접, 복합재료보수, 핫태핑, 클램프 등 다양한 방법을 사용하고 있으며, 배관에 손상이 발생한 경우 사용적합성 평가를 거쳐 배관보수를 실시하고 있다. 또한, 미국과 영국 등에서는 매설된 도시가스배관이 타공사 또는 부식으로 인해 손상을 입은 경우 손상형태별로 적용 가능한 배관보수방법을 규정하고 있다. 국내의 경우에는 노후된 중압배관에 대하여 정밀안전진단을 하도록 하고 있으며, 정밀안전진단결과 발생된 결함의 종류 및 정도에 따라 배관을 보수, 교체 또는 신설하도록 규정하고 있다. 그러나 보수 및 보강 방법에 대하여는 기준이 마련되어 있지 않아 배관에 손상이 발생한 경우 주로 손상된 배관을 절단한 후 단관(短管)으로 교체하는 방법만을 사용하고 있다. 본 논문에서는 미국, 영국 등 국외의 보수방법 및 기준을 조사하고, 국내의 매설배관 검사 방법 등에 대해 조사하고, 보수방법 시험 결과를 분석한 후 국내 실정에 맞는 배관보수기준(안)을 제시하였다. 개발되는 기준에 따라 도시가스사업자가 정밀안전진단 결과의 후속조치로 배관보수를 하는 경우 가스공급을 중단하지 않아도 되므로 가스의 안정적 공급에 기여할 수 있을 것으로 판단된다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.339-344
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• 2001

The transmission pipeline industry spends many millions of dollars annually performing inline inspections, excavating sites of possible corrosion, and repairing or replacing damaged sections of pipe. New criteria for evaluation the integrity of corroded pipe have been developed in recent years to help in controlling these costs. These new criteria vary widely in their estimates of integrity and the most appropriate criterion for a given pipeline is not always clear. This paper presents an overview, comparison and evaluation of acceptability criteria for corrosion defects in pipelines. By full scale burst tests, this paper have assessed the relative accuracy of each of theses criteria in predicting failure and remaining strength. Many of the criteria appear to be excessively conservative and indicate that defects must be repaired when none is needed, based upon burst test data.

• Journal of Welding and Joining
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• 제14권5호
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• pp.95-105
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• 1996

Korea Gas Corporation has operated high pressure gas transmission line of about 600 kilometers and, therefore, a series of repair welding processes are required in order to cope with external defects such as dent, gouge, cracking usually due to mechanical attacks. Most of gas pipelines repair processes are performed after completely venting remaining gas. However, in some case, though it is very unusual, repairs require without venting gas. For instance, this case is that damaged pipeline is remedied with split sleeve by welding. In this paper, in an effort to confirm a safe application of the split sleeve welding, residual stress, strain and temperature distributions are evaluated by computer simulation and experiments. The results obtained are as follows : 1) Computer modelling is supposed to be reasonable because microstructure changes due to welding is simulated coincidently as compare to that of real condition. 2) The maximal temperature on inside surface of pipeline is 50$0^{\circ}C$ for the repair welding process. 3) The amount of residual stress is estimated as the stress corresponding to 0.8% strain. 4) The repair process employed is determined to be technically preferable because of its avoiding cracks and fractures in the course of welding.

• Journal of Welding and Joining
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• 제14권5호
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• pp.49-58
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• 1996

In Korea Gas Corporation, as one of the pipeline repairing methods, damaged pipelines are sometimes treated with a temporally employment of split sleeve. On conducting the repair process, circumferential fillet and longitudinal groove welding usually must be included. For the case of groove welding, a considerable amount of R&D have been carried out related to property changes, while few study on the property change in fillet welding has been conducted. In this paper, so as to confirm the specification of fillet welding in terms of safety and reliability, properties changed by fillet welding were investigated for two welding processes. Qualifying tests such as reviewing macrostructure and nick-break tests were performed according to API 1104 and ASME section IX. In addition, tensile properties and hardness were evaluated according to KS B0841 and BS 4515. The fillet weld prepared by the qualified procedure showed melting depth of 0.8∼1.3mm and heat affected zone of 2.8∼3.4mm length. No crack and lack of penetration were observed. And the results of hardness and nick-break tests satisfied code requirements. The area crossed by fillet and groove welding line was found to have minimal tensile strength.

• 대한기계학회논문집A
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• 제26권1호
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• pp.203-210
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• 2002

The transmission pipeline industry spends many millions of dollars annually performing inline inspections, excavating sites of possible corrosion, and repairing or replacing damaged sections of pipe. New criteria fur evaluation of the integrity of corroded pipe have been developed in recent years to help in controlling these costs. These new criteria vary widely in their estimates of integrity and the most appropriate criterion fur a given pipeline is net always clear. This paper presents an overview, comparison and evaluation of acceptability criteria for corrosion deflects in pipelines. By full scale burst tests, this paper has assessed the relative accuracy of each of theses criteria in predicting burst pressure. Many of the criteria appear to be excessively conservative and indicate that deflects must be repaired when none is needed, based upon burst test data.