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회귀분석을 통한 DH순환수 환경 부식인자에 따른 두께 감육량 산출식 도출
소윤식(Yoon Sik So),임정민(Jeong Min Lim),김우철(Woo Cheol Kim),김정구(Jung Gu Kim) 대한설비공학회 2022 대한설비공학회 학술발표대회논문집 Vol.2022 No.6
In order to evaluate the thickness loss due to corrosion of the district heating pipeline, it is necessary to evaluate various factors affecting corrosion. However, it is difficult to evaluate the corrosion property in all variables because the corrosion factors are varied. Therefore, in this study, the relationship between corrosion factors (pH, dissolved oxygen and period of use) and thickness loss was evaluated through an efficient experimental design using Box-Benhken method in the response surface methodology. For an acceleration of corrosion, a galvanostatic test was used. After that, based on the measured thickness loss, multiple-regression analysis was performed to derive the thickness loss equation according to the corrosion factors. Through this equation, it is expected that the long-term corroison of the metal structures can be predicted simply by measuring the corrosion factors present in the environment.
홍민성,소윤식,임정민,김정구 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.94 No.-
The corrosion of district heating (DH) pipelines in the internal environment is carefully controlled,however the long-terms of corrosion induced fracture is still uncertain. The general corrosion of pipelinein the heating water is very moderate, therefore it is almost not affected to initiate fracture. While,localized corrosion in weld zone is very dangerous situation because it can act as a stress concentrationpoint. Therefore, it is significant to analyze using the fracture mechanics whether a fracture actuallyoccurs due to the localized corrosion or not. In this study, the long-term corrosion was simulated using the electrochemical acceleration method. The surface morphology parameter of the accelerated specimen was analyzed using a 3D profiler. Thecrack tip opening displacement (CTOD) was calculated using the corrosion morphology parameters. Consequently, in internal DH environment, general corrosion is the dominant factor in fracture ratherthan localized corrosion. In other words, internal corrosion cannot be a main reason of the DH pipelinefracture.
열수송관에서 pH에 따른 부식생성물이 탄소강의 부식에 미치는 영향
임정민(Jeong Min Lim),소윤식(Yoon Sik So),김우철(Woo Cheol Kim),김정구(Jung Gu Kim) 대한설비공학회 2022 대한설비공학회 학술발표대회논문집 Vol.2022 No.6
pH of district heating water is controlled to prevent a fracture of pipeline by corrosion. However, corrosion behavior of carbon steel is changed by corrosion products. Therefore, in this study, the corrosion behavior of long-term used heat transport pipeline was evaluated as variable of pH in a simulated district heating water. The corrosion behavior was evaluated after accelerating the 10 years corrosion using a galvanostatic test according to pH 5, 7, 9 and 11. As a result, localized corrosion was occurred in pH 5 and 11, and uniform corrosion was shown in pH 7 and 9. In pH 9 and 11, magnetite was formed on the surface of specimen. The high electrical conductivity of magnetite induces galvanic corrosion between carbon steel and magnetite, resulting in localized corrosion. At pH 7 and 9, the corrosion rate was the lowest at pH 9. Therefore, pH of heating water should be managed not to be lower than 5 or higher than 11. Also, it is best to maintain a pH of 9 for a long-term use of the pipeline.