An orifice is used widely as a flow meter or a contraction device in pipeline systems in hydro-power plants, thermal power plants, and chemical plants because of its simple construction, high reliability, and low cost...An orifice is used widely as a flow meter or a contraction device in pipeline systems in hydro-power plants, thermal power plants, and chemical plants because of its simple construction, high reliability, and low cost. However, it is well known that flow-accelerated corrosion (FAC) occurs on the pipe wall downstream of the orifice. Some of the authors have examined FAC through experimental and numerical analyses and have reported that one of the major governing parameters of FAC for single-phase water flow is the pressure fluctuation p’ on the pipe wall, and also that pipe wall thinning rate TR can be estimated by p’. In addition, they have presented the effects of the ori-fice geometry on p’ or TR, and have described a method for suppressing p’ or TR. In the present study, FAC for a two-phase air-water bubble flow is examined and compared with the single-phase water flow experimentally. Further, it is shown that because p’ is also considered a governing parameter of FAC for a two-phase air-water bubble flow, TR can be estimated using p’. It is also indicated that, by using a downstream pipe with a smaller diameter than that of the upstream pipe, p’ or TR can be suppressed.展开更多
Aiming at the high temperature corrosion in a coal-fired boiler,the effect of H2S and SO2 on the corrosion of 12 CrlMoV under the water wall condition has been investigated by experiments.The results indicate that H2 ...Aiming at the high temperature corrosion in a coal-fired boiler,the effect of H2S and SO2 on the corrosion of 12 CrlMoV under the water wall condition has been investigated by experiments.The results indicate that H2 S can promote the corrosion significantly,and the coarse porous oxide film formed cannot stop the progress of corrosion.While SO2 presents little effect on the corrosion.The main composition of the surface of 12 CrlMoV corrosion products is Fe2 O3.With H2S in the atmosphere,the corrosion gradually develops into deeper layers by forming FeS,FeO and Fe2 O3 alternately.The corrosion rate is doubled for every 50℃ inerease in temperature at 400-500℃.展开更多
Effects of Mo, Nb, Ti on mechanical properties and corrosion resistance of 22.5% Cr ferritic stainless steel were investigated. The results show that Mo exists in ferritic stainless steel mainly in the solution treatm...Effects of Mo, Nb, Ti on mechanical properties and corrosion resistance of 22.5% Cr ferritic stainless steel were investigated. The results show that Mo exists in ferritic stainless steel mainly in the solution treatment condition, and it can enhance steel＇ s strength through solid solution strengthening. In Ti ＋ Nb dual-stabilized ferritic stainless steel, the steel＇s toughness decreases obviously because coarse TiN particles form and some metallic compounds precipitate along the grain boundaries. In Nb single-stablized ferritic stainless steel, Nb exists either in the solution treatment condition or in the form of dispersed precipitates Nb（C, N）, which will act as the nuclei of precipitation of the fine （r phase. As a result, the precipitation of the coarse σ phase along the grain boundary can be inhibited, leading to significant improvement in steel＇ s toughness at a low temperature. Based on these, high corrosion-resistant ferritic stainless steel B445R was developed for the building cladding system. Test results show that B445R has a superior corrosion resistance to austenitic 316 L in chloride solution. Besides, it has a good forming property and weldability. All these make it an ideal decorating material for the building cladding system in severe coastal regions.展开更多
The fluoride volatility method (FVM) is a technique tailored to separate uranium from fuel salt of molten salt reactors. A key challenge in R&D of the FVM is corrosion due to the presence of molten salt and corros...The fluoride volatility method (FVM) is a technique tailored to separate uranium from fuel salt of molten salt reactors. A key challenge in R&D of the FVM is corrosion due to the presence of molten salt and corrosive gases at high temperature. In this work, a frozen-wall technique was proposed to produce a physical barrier between construction materials and corrosive reactants. The protective performance of the frozen wall against molten salt was assessed using FLiNaK molten salt with introduced fluorine gas, which was regarded as a simulation of the FVM process. SS304, SS316L, Inconel 600 and graphite were chosen as the test samples. The extent of corrosion was characterized by an analysis of weight loss and scanning electron microscope studies. All four test samples suffered severe corrosion in the molten salt phase with the corrosion resistance as: Inconel 600>SS316L>graphite>SS304. The presence of the frozen wall could protect materials against corrosion by molten salt and corrosive gases, and compared with materials exposed to molten salt, the corrosion rates of materials protected by the frozen wall were decreased by at least one order of magnitude.展开更多
A number of piping components in the secondary system of nuclear power plants are exposed to aging mechanisms such as FAC (Flow-Accelerated Corrosion), cavitation, flashing, SPE (Solid Particle Erosion), LDIE (Liquid ...A number of piping components in the secondary system of nuclear power plants are exposed to aging mechanisms such as FAC (Flow-Accelerated Corrosion), cavitation, flashing, SPE (Solid Particle Erosion), LDIE (Liquid Droplet Impingement Erosion), etc. Those mechanisms may lead to thinning, leak, or rupture of the components. Due to the pipe ruptures caused by wall thinning in Surry unit 2 of USA in 1986 and in Mihama unit 3 of Japan in 1994, the pipe wall thinning management has emerged as one of the most important issues in nuclear power plants. To manage the pipe wall thinning in the secondary system, Korea has used a foreign program since 1996. As using the foreign country’s program for long term, it was necessary to improve from the perspective of the users. Accordingly, KEPCO-E & C has started to develop the 3D-based pipe wall thinning management program (ToSPACE, Total Solution for Piping And Component Engineering management) from eight years ago, and the development was successful. This paper describes the major functions included in ToSPACE program, such as 3D-based DB (Database) buildup, development of FAC and erosion evaluation theories, UT (Ultra-sonic Test) data reliability analysis, field connection with 3D, automatic establishment of long-term inspection plan, etc. ToSPACE program was developed to allow site engineers performing the selection of inspection quantity at each refueling outage, UT data reliability analysis, UT evaluation, determination of next inspection timing, identification of the inspecting and replacing components in 3D drawings, etc., to access easily.展开更多
Currently, Living Wall Systems (LWSs) are assuming great importance in the built environment, due to environmental and aesthetic advantages, as well as the use of urban residual space and underutilized surfaces of bui...Currently, Living Wall Systems (LWSs) are assuming great importance in the built environment, due to environmental and aesthetic advantages, as well as the use of urban residual space and underutilized surfaces of buildings. However, the maintenance and the durability of the materials used have been a challenge for architects and professionals in the field. The aim of this paper is to evaluate the anti-corrosion performance of a steel framing profile, galvanized carbon steel (55% Al-Zn), a sustainable material with easy assembly, to apply LWS in the hot and humid tropical climate of Niterói (Rio de Janeiro, Brazil). In order to create the conditions of the tests, “X” cut were made in Al-Zn coating, sanding, and application of epoxy and glass fiber-reinforced polyester. After the experiments that lasted four months, the 55% Al-Zn coating was analyzed using Scanning Electron Microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The results of the tests were promising for the use of this galvanized steel for application as a support for green vertical facades. 55% Al-Zn coatings are recommended for marine atmospheres due to their good anti-corrosion performance.展开更多
文摘An orifice is used widely as a flow meter or a contraction device in pipeline systems in hydro-power plants, thermal power plants, and chemical plants because of its simple construction, high reliability, and low cost. However, it is well known that flow-accelerated corrosion (FAC) occurs on the pipe wall downstream of the orifice. Some of the authors have examined FAC through experimental and numerical analyses and have reported that one of the major governing parameters of FAC for single-phase water flow is the pressure fluctuation p’ on the pipe wall, and also that pipe wall thinning rate TR can be estimated by p’. In addition, they have presented the effects of the ori-fice geometry on p’ or TR, and have described a method for suppressing p’ or TR. In the present study, FAC for a two-phase air-water bubble flow is examined and compared with the single-phase water flow experimentally. Further, it is shown that because p’ is also considered a governing parameter of FAC for a two-phase air-water bubble flow, TR can be estimated using p’. It is also indicated that, by using a downstream pipe with a smaller diameter than that of the upstream pipe, p’ or TR can be suppressed.
基金supported by the National Key Research and Development Plan of China (No. 2018YFB0604203)
文摘Aiming at the high temperature corrosion in a coal-fired boiler,the effect of H2S and SO2 on the corrosion of 12 CrlMoV under the water wall condition has been investigated by experiments.The results indicate that H2 S can promote the corrosion significantly,and the coarse porous oxide film formed cannot stop the progress of corrosion.While SO2 presents little effect on the corrosion.The main composition of the surface of 12 CrlMoV corrosion products is Fe2 O3.With H2S in the atmosphere,the corrosion gradually develops into deeper layers by forming FeS,FeO and Fe2 O3 alternately.The corrosion rate is doubled for every 50℃ inerease in temperature at 400-500℃.
文摘Effects of Mo, Nb, Ti on mechanical properties and corrosion resistance of 22.5% Cr ferritic stainless steel were investigated. The results show that Mo exists in ferritic stainless steel mainly in the solution treatment condition, and it can enhance steel＇ s strength through solid solution strengthening. In Ti ＋ Nb dual-stabilized ferritic stainless steel, the steel＇s toughness decreases obviously because coarse TiN particles form and some metallic compounds precipitate along the grain boundaries. In Nb single-stablized ferritic stainless steel, Nb exists either in the solution treatment condition or in the form of dispersed precipitates Nb（C, N）, which will act as the nuclei of precipitation of the fine （r phase. As a result, the precipitation of the coarse σ phase along the grain boundary can be inhibited, leading to significant improvement in steel＇ s toughness at a low temperature. Based on these, high corrosion-resistant ferritic stainless steel B445R was developed for the building cladding system. Test results show that B445R has a superior corrosion resistance to austenitic 316 L in chloride solution. Besides, it has a good forming property and weldability. All these make it an ideal decorating material for the building cladding system in severe coastal regions.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Science(No.XDA02030000)
文摘The fluoride volatility method (FVM) is a technique tailored to separate uranium from fuel salt of molten salt reactors. A key challenge in R&D of the FVM is corrosion due to the presence of molten salt and corrosive gases at high temperature. In this work, a frozen-wall technique was proposed to produce a physical barrier between construction materials and corrosive reactants. The protective performance of the frozen wall against molten salt was assessed using FLiNaK molten salt with introduced fluorine gas, which was regarded as a simulation of the FVM process. SS304, SS316L, Inconel 600 and graphite were chosen as the test samples. The extent of corrosion was characterized by an analysis of weight loss and scanning electron microscope studies. All four test samples suffered severe corrosion in the molten salt phase with the corrosion resistance as: Inconel 600>SS316L>graphite>SS304. The presence of the frozen wall could protect materials against corrosion by molten salt and corrosive gases, and compared with materials exposed to molten salt, the corrosion rates of materials protected by the frozen wall were decreased by at least one order of magnitude.
文摘A number of piping components in the secondary system of nuclear power plants are exposed to aging mechanisms such as FAC (Flow-Accelerated Corrosion), cavitation, flashing, SPE (Solid Particle Erosion), LDIE (Liquid Droplet Impingement Erosion), etc. Those mechanisms may lead to thinning, leak, or rupture of the components. Due to the pipe ruptures caused by wall thinning in Surry unit 2 of USA in 1986 and in Mihama unit 3 of Japan in 1994, the pipe wall thinning management has emerged as one of the most important issues in nuclear power plants. To manage the pipe wall thinning in the secondary system, Korea has used a foreign program since 1996. As using the foreign country’s program for long term, it was necessary to improve from the perspective of the users. Accordingly, KEPCO-E & C has started to develop the 3D-based pipe wall thinning management program (ToSPACE, Total Solution for Piping And Component Engineering management) from eight years ago, and the development was successful. This paper describes the major functions included in ToSPACE program, such as 3D-based DB (Database) buildup, development of FAC and erosion evaluation theories, UT (Ultra-sonic Test) data reliability analysis, field connection with 3D, automatic establishment of long-term inspection plan, etc. ToSPACE program was developed to allow site engineers performing the selection of inspection quantity at each refueling outage, UT data reliability analysis, UT evaluation, determination of next inspection timing, identification of the inspecting and replacing components in 3D drawings, etc., to access easily.
文摘Currently, Living Wall Systems (LWSs) are assuming great importance in the built environment, due to environmental and aesthetic advantages, as well as the use of urban residual space and underutilized surfaces of buildings. However, the maintenance and the durability of the materials used have been a challenge for architects and professionals in the field. The aim of this paper is to evaluate the anti-corrosion performance of a steel framing profile, galvanized carbon steel (55% Al-Zn), a sustainable material with easy assembly, to apply LWS in the hot and humid tropical climate of Niterói (Rio de Janeiro, Brazil). In order to create the conditions of the tests, “X” cut were made in Al-Zn coating, sanding, and application of epoxy and glass fiber-reinforced polyester. After the experiments that lasted four months, the 55% Al-Zn coating was analyzed using Scanning Electron Microscope (SEM) and energy dispersive X-ray spectroscopy (EDS). The results of the tests were promising for the use of this galvanized steel for application as a support for green vertical facades. 55% Al-Zn coatings are recommended for marine atmospheres due to their good anti-corrosion performance.
