• Title/Summary/Keyword: corrosion assessment

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Sedimentary Environment Change in Mid-channel Bar of the Lower Geum River Using Multi-temporal Satellite Data (다중시기 영상자료를 이용한 금강하류의 하중도 퇴적환경 변화)

  • Hong, Ki-Byung;Jang, Dong-Ho
    • Journal of Environmental Impact Assessment
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    • v.18 no.3
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    • pp.171-183
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    • 2009
  • This study aims to analyze the sedimentary environment change in mid-channel bar of the lower Geum river basin after the construction of the estuary barrage using multi-temporal satellite data and GIS. The sedimentary environment changes were observed in mid-channel bar areas. The mid-channel bar F was found to have been newly formed for 10 years(1996-2006), whereas the mid-channel bar B located between mid-channel bar A and C has disappeared by erosion during the same periods. When examined by section, the areas of the mid-channel bar in the upper stream section from the Yipo's reference point generally increased due to the prevailing sedimentary environments, and those of the downstream section decreased where corrosive environments are dominant. In ternms of the centroid movement, the mid-channel bars grew up toward the downstream by switching erosion and accumulation, as sedimentation was prevailing in the downstream area of mid-channel bars and corrosion was dominant in the upper stream. Through grain size analysis, the study areas are divided into three sections according to the average grain size. In Section I, the mid-channel bars were formed as a result of sedimentary process of tides in the past. In Section II, the mid-channel bars were formed partly through the sedimentary process of rivers although the sedimentary process of tides is prevailing. In Section III, the mid-channel bars were formed mainly through the sedimentary process of rivers, even if it showed the sedimentary process of tides in the past.

Material Life Cycle Assessment of Extrusion Process of A7003 (A7003 알루미늄 합금 압출공정의 MLCA 산정기술)

  • Jo Huyng-ho;Cho Hoon;Kim Byung-min;Kim Young-jig
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 2002.11a
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    • pp.43-49
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    • 2002
  • A7003 alloy has characteristics of their excellent weldability, high corrosion resistance and superior plastic working however the broadening of application for the alloy has been hampered by the lower extrudability associated by Mg content. For improvement of extrudability and enhanced recovery efficiency during Al scrap recyeling, it has been generally practiced to reduce Mg content in A7003 alloy. Therefore, it is necessary to investigate the influence of Mg content on mechanical strength and extrudability of A7003 alloy. For efficient material processing which has small amounts, life cycle assessment in material processing(MLCA) is evaluated. The quantitative analysis of energy requirements and $CO_2$ emission for production of A7003 extruded bar are estimated with different Mg content and billet pre-heating process (heating source by light oil or LPG). In particular, the estimation of energy requirements was performed within shipping and gating range (except the mining and extraction stages)to investigate the influence of the variables on energy requirements and $CO_2$ emission in detail. As Mg content increased, the flow stress and the extrusion pressure for A7003 alloy increased. It has been thought that an increment in extrusion pressure with increasing Mg content is caused by the solid solution hardening of Mg atoms in the matrix and increment in volume fraction of intermetallic compound, $Mg_2Si$. The extrudability and the tensile strength are equal to, or above that of conventional A 7003 alloy even the content of Mg varied from $1.1wt.\%\;to\;0.5wt.\%$ alloy. This means that minimizing the content of Mg in A7003 alloy can enhance recovery efficiency during Al scrap recycling. It can be quoted that rather than Mg content energy source for billet heating is a prime factor to determine the atmospheric $CO_2$ emission.

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A Study on the Integrity Evaluation Method of Subclad Crack Under Pressurized Thermal Shock (가압열충격 사고시 클래드 하부균열 안전성 평가 방법에 관한 연구)

  • Kim, Yeong-Jin;Kim, Jin-Su;Gu, Bon-Geol;Choe, Jae-Bung;Park, Yun-Won
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.7
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    • pp.1139-1146
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    • 2001
  • The reactor pressure vessel(RPV) is usually cladded with stainless steel to prevent corrosion and radiation embrittlement, and a number of subclad cracks have been found during an in-service-inspection. These subclad cracks should be assured for a safe operation under normal conditions and faulted conditions such as pressurized thermal shock(PTS). Currently available integrity assessment procedure for an RPV, ASME Code Sec. XI, are built on the basis of linear fracture mechanics (LEFM). In PTS condition, however, thermal stress and mechanical stress give rise to high tensile stress at the cladding and elastic-plastic behavior is expected in this area. Therfore, ASME Code Sec. XI is overly conservative in assessing the structural integrity under PTS condition. In this paper, the fracture parameter (stress intensity factor, K, and RT(sub)NDT) from elastic analysis using ASME Sec. XI and finite element method were validated against 3-D elastic-plastic finite element analyses. The difference between elastic and elastic-plastic analysis became significant with increasing crack depth. Therfore, it is recommended to perform elastic-plastic analysis for the accurate assessment of subclad cracks under TPS which causes plastic deformation at the cladding.

An Experimental Study on the Fire Risk Assessment & Calculation Breakthrough Time through Permeation Test of Chemical Protective Clothing (화학보호복의 화재위험성 및 화학적 투과시험을 통한 파과시간산정에 관한 실험적 연구)

  • Ko, Jae-Sun;Park, Pyoung-Kyu
    • Fire Science and Engineering
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    • v.24 no.2
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    • pp.21-30
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    • 2010
  • We have test chemical resistance and flame retardant properties of chemical protective clothing Fabrics by the ASTM and ISO standard methods. The flame retardant test results show that polyethylene is poor in flame resistance but fluoroelastomer add to decabrom is excellent in flame resistance. Especially, nowadays heat protective clothing for firefighters, which is aluminized film layers laminated to aramid fabric, show the excellent flame resistance. However, the chemical resistance test results show that aluminium is high corrosive in 4M NaOH solution alone. The problem of corrosion can be overcome by employing multiple barrier film. Also, based on the result of flame retardant test, duel skin of polymer barrier film add to aluminum film and single skin of fluorinated rubber with flame retardant materials seems to be fit for the chemical protective clothing. Also the thermal protection and heat transfer test results show that TPP and HTI is increased assured that the continued study on fire risk assessment & chemical resistance of chemical protective clothing fabrics will contribute to the upgrade the performances of chemical protective clothing fabrics.

Influence of Carbonation and Freezing-thawing on the Chloride Diffusion in Concrete (탄산화 및 동결융해 현상이 콘크리트 중의 염소이온 확산에 미치는 영향 연구)

  • Kim, Dong-Baek;Kwon, Ki-Jun;Jung, Sang-Hwa;Bok, Hoon
    • Journal of the Korean Society of Safety
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    • v.22 no.3 s.81
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    • pp.57-64
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    • 2007
  • Recently, the corrosion of concrete structures has received great attention related with the deterioration of sea-side structures, such as new airport, bridges, and nuclear power plants. In this regards, many studies have been done on the chloride attack in concrete structures. However, those studies were confined mostly to the single deterioration due to chloride only, although actual environment is rather of combined type. The purpose of the present study is, therefore, to explore the influences of carbonation and freezing-thawing action to chloride attack in concrete structures. The test results indicate that the chloride penetration is more pronounced than the case of single chloride attack when the carbonation process is combined with the chloride attack. It is supposed that the chloride ion concentration of carbonation region is higher than the sound region because of the separation of fixed salts. Though the use of fly ash pronounces the chloride ion concentration in surface, amounts of chloride ion penetration into deep region decreases with the use of fly ash. The small reduction of relative dynamic elastic modulus induced from freezing-thawing increases the chloride ion penetration depths much. The present study allows more realistic assessment of durability for such concrete structures which are subjected to combined attacks of both chlorides and carbonation or freezing-thawing but the future studies for combined environment will assure the precise assessment.

A Study on Damage Effects Assessment for Asphyxiation Accident due to Malfunction of Gas Type Fire Extinguishing System (가스계 소화설비 오작동으로 인한 질식사고의 피해영향 평가)

  • Kim, Eui-Soo
    • Journal of the Korean Institute of Gas
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    • v.24 no.2
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    • pp.36-43
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    • 2020
  • Gas system fire extinguishing equipment is a very economically useful facility, but if it is not used for a long period of time after installing the equipment, there is possibility of rupture due to corrosion of containers and operation errors of equipment systems, and this is very dangerous. However, it is impossible to experiment to check whether the equipment is operating normally. If gas is temporarily released into the enclosed space due to rupture and malfunction, it can cause serious human damage due to gas suffocation. In this study, based on the suffocation death accident of gas system fire extinguishing facility, the inflow path of released gas and the possibility of death and time to death were estimated using a 3D scan and FLACS.

Reliability Assessment for Corroded Pipelines by Separable Monte Carlo Method (Separable Monte Carlo 방법을 적용한 부식배관 신뢰도평가)

  • Lee, Jin-Han;Jo, Young-Do;Kim, Lae Hyun
    • Journal of the Korean Institute of Gas
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    • v.19 no.5
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    • pp.81-86
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    • 2015
  • A deterministic stress-based methodology has traditionally been applied in pipeline design. Meanwhile, reliability based design and assessment (RBDA) methodology has been extensively applied in offshore or nuclear structures. Lately, the release of ISO standard on reliability based limit state methods for pipelines ISO16708 indicates that the RBDA methodology is one of the newest directions of natural gas pipeline design method. This paper presents a case study of the RBDA procedure for predicting the time-dependent failure probability of pipelines with corrosion defects, where separable Monte Carlo (SMC) method is applied in the reliability estimation for corroded pipeline instead of traditional, crude Monte Carlo(CMC) Method. The result shows the SMC method take advantage of improving accuracy in reliability calculation.

Risk Reduction Rate for Each Risk Mitigation Measure on High Pressure Urban Gas Pipelines Proposed by Quantitative Risk Analysis (정량적 위험성 평가를 통해 제안된 도시가스 고압배관의 위험경감조치별 위험감소효과)

  • Ryou, Young-Don;Jo, Young-Do;Park, Young-Gil;Lee, Su-Kyung
    • Journal of the Korean Institute of Gas
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    • v.14 no.4
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    • pp.18-23
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    • 2010
  • After conducting QRA(quantitative risk assessment) for the high pressure urban gas pipelines planned to be installed, RMMs(risk mitigation measures) when the societal risk is outside the acceptable region have been derived in this paper. Also risk reduction rates are calculated for each RMM. As a result of QRA, we find out that damaged distance caused by radiational heat is largely dependent upon the wind velocity and the atmospheric stability. The measure that has the highest risk reduction effect is No. 10 which includes pipeline corrosion monitoring, MOV(motor operated valve) installation and the method to protect pipeline damage caused by third-party mechanical interference, and which shows 75 % of risk reduction effect.

Ultrasonic characterization of exhumed cast iron water pipes

  • Groves, Paul;Cascante, Giovanni;Knight, Mark
    • Smart Structures and Systems
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    • v.7 no.4
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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.

Evaluation of TiN-Zr Hydrogen Permeation Membrane by MLCA (Material Life Cycle Assessment) (물질전과정평가(MLCA)를 통한 TiN-Zr 수소분리막의 환경성 평가)

  • Kim, Min-Gyeom;Son, Jong-Tae;Hong, Tae-Whan
    • Clean Technology
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    • v.24 no.1
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    • pp.9-14
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    • 2018
  • In this study, Material life cycle evaluation was performed to analyze the environmental impact characteristics of TiN-Zr membrane manufacturing process. The software of MLCA was Gabi. Through this, environmental impact assessment was performed for each process. Transition metal nitrides have been researched extensively because of their properties. Among these, TiN has the most attention. TiN is a ceramic materials which possess the good combination of physical and chemical properties, such as high melting point, high hardness, and relatively low specific gravity, high wear resistance and high corrosion resistance. With these properties, TiN plays an important role in functional materials for application in separation hydrogen from fossil fuel. Precursor TiN was synthesized by sol-gel method and zirconium was coated by ball mill method. The metallurgical, physical and thermodynamic characteristics of the membranes were analyzed by using Scanning Electron Microscope (SEM), Energy Dispersive X-ray (EDS), X-ray Diffraction (XRD), Thermo Gravimetry/Differential Thermal Analysis (TG/DTA), Brunauer, Emmett, Teller (BET) and Gas Chromatograph System (GP). As a result of characterization and normalization, environmental impacts were 94% in MAETP (Marine Aquatic Ecotoxicity), 2% FAETP (Freshwater Aquatic Ecotoxicity), 2% HTP (Human Toxicity Potential). TiN fabrication process appears to have a direct or indirect impact on the human body. It is believed that the greatest impact that HTP can have on human is the carcinogenic properties. This shows that electricity use has a great influence on ecosystem impact. TiN-Zr was analyzed in Eco-Indicator '99 (EI99) and CML 2001 methodology.