• 설비공학논문집
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• 제27권4호
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• pp.228-232
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• 2015

The water supply galvanized steel pipes of apartment buildings in Bucheon city constructed with building permission before 1994 have many problems such as leaks, the water containing rust, and low water pressure due to corrosion. Therefore, this study aims to find a way to renew the water supply pipes under investigation through a survey. As a result, when replacing the galvanized steel pipe with the corrosion-resistant pipe, the water supply system should also be changed from the gravity tank system to the booster pump system and the hygienic water storage tank. It is necessary to redraft the long-term repair plan including the replacement of the water supply system. Also, it is necessary to save the allowance reserve according to the modified long-term repair plan.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2010년도 학술발표회
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• pp.1710-1715
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• 2010

상수도시설은 운영관리 환경, 사용범위, 빈도 등 특성에 따라 수명이 달라지며, 현행 법률에서 일률적으로 정하고 있는 내용연수와 차별된 접근이 필요함에 따라, 시설의 파손, 보수이력 등 관리현황 및 시설의 경시적인 변화 상태를 조사 분석하여 기술적 판단을 토대로 한 수명평가 방안이 필요하다. 따라서 본 연구에서는 국내외 내용연수 적용현황과 시설별 내용연수 산정 방안, 외국의 상수도시설물 관리 방법, 기존 관로 상태평가 기준 수립을 위한 현황 등을 조사하고, 매설 상수관로에 현장조사를 수행하여, 상수관로의 물리적인 파손위험성과 사고이력을 기반으로 경제적 가치 기준에 의한 잔존수명 평가 기법을 개발하였다. 또한 기존 우리 공사의 노후도 기법을 물리적인 노후진척에 따른 상태변화와 실측 데이터를 활용하여 통계적인 분석을 통하여 평가항목은 축소하고, 신뢰도는 제고하였으며, 관 상태평가를 통해서 합리적인 개량계획 수립을 추진할 수 있도록 관상태평가 가이드라인을 개발하였다.

• Smart Structures and Systems
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• 제7권4호
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• pp.241-262
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• 2011

Cast iron pipe has been used as a water distribution technology in North America since the early nineteenth century. The first cast iron pipes were made of grey cast iron which was succeeded by ductile iron as a pipe material in the 1940s. These different iron alloys have significantly different microstructures which give rise to distinct mechanical properties. Insight into the non-destructive structural condition assessment of aging pipes can be advantageous in developing mitigation strategies for pipe failures. This paper examines the relationship between the small-strain and large-strain properties of exhumed cast iron water pipes. Nondestructive and destructive testing programs were performed on eight pipes varying in age from 40 to 130 years. The experimental program included microstructure evaluation and ultrasonic, tensile, and flexural testing. New applications of frequency domain analysis techniques including Fourier and wavelet transforms of ultrasonic pulse velocity measurements are presented. A low correlation between wave propagation and large-strain measurements was observed. However, the wave velocities were consistently different between ductile and grey cast iron pipes (14% to 18% difference); the ductile iron pipes showed the smaller variation in wave velocities. Thus, the variation of elastic properties for ductile iron was not enough to define a linear correlation because all the measurements were practically concentrated in single cluster of points. The cross-sectional areas of the specimens tested varied as a result of minor manufacturing defects and levels of corrosion. These variations affect the large strain testing results; but, surface defects have limited effect on wave velocities and may also contribute to the low correlations observed. Lamb waves are typically not considered in the evaluation of ultrasonic pulse velocity. However, Lamb waves were found to contribute significantly to the frequency content of the ultrasonic signals possibly resulting in the poor correlations observed. Therefore, correlations between wave velocities and large strain properties obtained using specimens manufactured in the laboratory must be used with caution in the condition assessment of aged water pipes especially for grey cast iron pipes.

• 상하수도학회지
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• 제32권5호
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• pp.435-443
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• 2018

Most of aged water supply pipes have been replaced by the open cut method. However, this method has some limitations because water pipes, in many cases, are buried together with other underground facilities or are buried in the middle of high-traffic roads or in narrow alleyways where boring machines cannot be used. This research developed a pipe bursting device for small diameter pipes that enables pipe replacement without excavating the ground, by the busting of existing buried pipes followed by the traction and insertion of new pipes. As a results of examining the field applicability of the developed device, PE pipes and PVC pipes required the tractive force of 413.65~665.69 kgf and 457.43~791.35 kgf respectively, plus an additional 30 % tractive force per elbow. The proper number of bursting head was demonstrated that the connection of more than 2 heads could secure a stable bending radius of 15D. The developed device can be improved through field experiments involving various pipe types and pipe diameters, as well as presence/absence of elbow, so as to be utilized regardless of diverse variables according to the conditions of the soils surrounding existing pipes.

• 상하수도학회지
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• 제27권4호
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• pp.413-428
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• 2013

In this study, Ant Colony Algorithm(ACO) was used for optimal model. ACO which are metaheuristic algorithm for combinatorial optimization problem are inspired by the fact that ants are able to find the shortest route between their nest and food source. For applying the model to water distribution systems, pipes, tanks(reservoirs), pump construction and pump operation cost were considered as object function and pressure at each node and reservoir level were considered as constraints. Modified model from Ostfeld and Tubaltzev(2008) was verified by applying 2-Looped, Hanoi and Ostfeld's networks. And sensitivity analysis about ant number, number of ants in a best group and pheromone decrease rate was accomplished. After the verification, it was applied to real water network from S water treatment plant. As a result of the analysis, in the Two-looped network, the best design cost was found to $419,000 and in the Hanoi network, the best design cost was calculated to $6,164,384, and in the Ostfeld's network, the best design cost was found to $3,525,096. These are almost equal or better result compared with previous researches. Last, the cost of optimal design for real network, was found for 66 billion dollar that is 8.8 % lower than before. In addition, optimal diameter for aged pipes was found in this study and the 5 of 8 aged pipes were changed the diameter. Through this result, pipe construction cost reduction was found to 11 percent lower than before. And to conclusion, The least cost design model on water distribution system was developed and verified successfully in this study and it will be very useful not only optimal pipe change plan but optimization plan for whole water distribution system.

• 융합정보논문지
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• 제9권5호
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• pp.21-26
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• 2019

도심지에는 상 하수관로, 가스관, 수소관 등 필요에 따라 여러 가지 배관이 매설된다. 매설된 배관은 시간이 경과됨에 따라 균열 등으로 노후화되면서 폭발, 누수 등의 사고 발생 위험을 가지게 된다. 이러한 위험을 방지하기 위해 많은 노후 배관 수리, 교체되지만, 배관의 위치 또한 변경될 수 있다. 변경된 배관의 위치를 확인하지 못하면 배관을 건드려서 사고가 발생할 수 있다. 본 논문에서는 GPR을 사용하여 지하 단면 영상을 얻고, Faster R-CNN을 활용하여 지하 배관의 위치를 추정해보고, augmentation을 적용하여 부족한 데이터를 늘려서 실험을 진행하였다.

• Journal of Welding and Joining
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• 제31권6호
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• pp.1-7
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• 2013

In nuclear power plants, lined carbon steel pipes or PCCPs (pre-stressed concrete cylinder pipes) have been widely used for sea water transport systems. However, de-bonding of linings and oxidation of PCCP could make problems in aged NPPs (nuclear power plants). Recently at several NPPs in the United States, the PCCPs or lined carbon steel pipes of the sea water or raw water system have been replaced with HDPE (high density polyethylene) pipes, which have outstanding resistance to oxidation and seismic loading. ASME B&PV Code committee developed Code Case N-755, which describes rules for the construction of buried Safety Class 3 polyethylene pressure piping systems. Although US NRC permitted HDPE materials for Class 3 buried piping, their permission was limited to only 10-year operation because of several concerns including the quality of fusion zone of HDPE. In this study, various requirements for fusion qualification test of HDPE and some regulatory issues raised during HDPE application review in foreign NPPs are introduced.

• 상하수도학회지
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• 제33권5호
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• pp.353-366
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• 2019

This research proposes an optimal flushing operation technique in an effort to prevent secondary water pollutions and accidents in aged pipes, and to improve the cleaning effect of unidirectional flushing. Water flow directions were analyzed using EPANET 2.0, while flushing and air scouring experiments in forward and reverse directions were performed in the field. In 42 experiments, average residual chlorine concentration and turbidity were improved after cleaning compared to before cleaning. It was found that even when the same cleaning method was used, further improvement of cleaning effect was possible by applying air injection and reverse direction cleaning techniques. By means of one-way ANOVA(Analysis of variance), it was also possible to statistically verify the need of actively utilizing air injection and reverse direction cleaning. Based on correlation between turbidity and TSS, the total amount of suspended solids removal was estimated for 874 flushing operations and 194 air scouring operations. The result showed that air scouring used more discharge water than flushing by an average of $4.9m^3$ yet with larger amounts of suspended solids removal by an average of 145.9 g. The result of analysis on turbidity values from 887 flushing operations showed low cleaning effect of unidirectional flushing for the pipes with diameters over 300 mm. In addition, the turbidity values measured during cleaning showed an increasing tendency as pipe age increased. The methodology and results of this research are expected to contribute to the efficient maintenance and improvement of water quality in water distribution networks. Follow-up research involving the measurement of water quality at regular time intervals during cleaning would allow a more accurate comparison of discharge water quality characteristics and cleaning effects between different cleaning methods. To this end, it is considered necessary to develop a standardized manual that can be used in the field and to provide relevant trainings.

• 상하수도학회지
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• 제35권6호
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• pp.517-531
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• 2021

The water supply facilities of Korea have achieved a rapid growth, along with the other social infrastructures consisting a city, due to the phenomenon of urbanization according to economic development. Meanwhile, the level of water supply service demanded by consumer is also steadily getting higher in keeping with economic growth. However, as an adverse effect of rapid growth, the quantity of aged water supply pipes are increasing rapidly, Bursts caused by pipe aging brought about an enormous economic loss of about 6,161 billion won as of 2019. These problems are not only worsening water supply management, also increasing the regional gap in water supply services. The purpose of this study is to classify hazard evaluation indicators and to rank the water distribution network hazard by cluster using the TOPSIS method. In conclusion, in this study, the entropy-based multi-criteria decision-making methods was applied to rank the hazard management of the water distribution network, and the hazard management ranking for each cluster according to the water supply conditions of the county-level municipalities was determined according to the evaluation indicators of water outage, water leakage, and pipe aging. As such, the hazard ranking method proposed in this study can consider various factors that can impede the tap water supply service in the water distribution network from a macroscopic point of view, and it can be reflected in evaluating the degree of hazard management of the water distribution network from a preventive point of view. Also, it can be utilized in the implementation of the maintenance plan and water distribution network management project considering the equity of water supply service and the stability of service supply.

• 한국습지학회지
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• 제26권2호
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• pp.139-146
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• 2024

노후된 관거 및 지하구조물의 균열 보수에 아스팔트계 주입재, 우레탄계 주입재, 시멘트계 주입재, 아크릴계 주입재 등 다양한 주입재가 사용되고 있다. 친환경적이고 습윤상태에서 경화가 잘되고 온도변화에 안정적인 물성을 갖는 아크릴계 누수 보수재에 대하여 연구하였다. 개량된 아크릴 누수 보수재와 기존 아크릴레이트 주입재의 성능 비교를 위하여 KS 규격의 실험방법에 준용하여 수중침지 길이변화율 시험, 수중 유실 저항성 시험, 내화학 성능시험을 실시하였다. 비교 실험해 본 결과 개량된 아크릴 누수 보수재는 기존 아크릴레이트 주입재보다 습윤상태, 온도변화, 화학적 반응에 따른 수축변화가 없었고 수중 저항성 실험에서 유실되지 않았다. 또한, 개량된 아크릴 누수 보수재의 환경적 영향성을 알아보기 위해 어류급성독성 실험과 급성경구독성 실험을 진행하여 관찰해 본 결과 실험체의 사망률이 없었고 특별한 유의점이 발견되지 않았다. 본 연구의 실험결과 개량된 아크릴 누수 보수재가 성능적으로 우수하고 환경적으로 안전하고 인체에 무해하다고 판단되었다. 본 연구의 다양한 실험결과 기존의 아크릴레이트 보수재보다 개량된 아크릴 누수 보수재가 관거 및 지하구조물 균열 부위의 보수재로 사용되기 적합하다고 사료된다. 본 연구는 아크릴 누수 보수재에 대한 적용성 평가에 대한 연구로 향후 기술 개발에 활용자료로 제안하고자 한다.