This paper focused on the corrosion resistance of cold spray Al–Al_2O_3composite coatings used on carbon steel pipe surfaces under thermal insulation. Al–Al_2O_3coatings were produced on the carbon steel pipe surfac...This paper focused on the corrosion resistance of cold spray Al–Al_2O_3composite coatings used on carbon steel pipe surfaces under thermal insulation. Al–Al_2O_3coatings were produced on the carbon steel pipe surface by cold spray(CS) technology. Experimental apparatus was built to test the corrosion resistance of coatings beneath mineral wool insulation under isothermal, thermal cycling and wet/dry conditions. The results showed that when α-Al_2O_3 was added in spraying powder, the coating could obtain higher hardness and a denser microstructure. From corrosionunder-insulation(CUI) tests, Al–Al_2O_3CS coatings were proven to be efficient in protecting carbon steel pipe from CUI mainly owning to lamellar microstructures of coatings. There was no evidence to show that α-Al_2O_3 might bring any negative effect on corrosion resistance. Al–Al_2O_3CS coatings were sensitive to the chloride ion concentration. When these coatings were exposed to higher concentrations of NaC l, the coating's exhibited faster degradation.展开更多
In-situ tests and numerical manipulations were conducted for comparison of superior/inferior quality of casing-tube-vacuumized insulation and polyurethane insulation of fi＇eezing apparatuses in relation to non-unifor...In-situ tests and numerical manipulations were conducted for comparison of superior/inferior quality of casing-tube-vacuumized insulation and polyurethane insulation of fi＇eezing apparatuses in relation to non-uniform cold distribution in the multi-coil fi＇eez- ing layout and the contradiction between large-coil diameter layout of the freezing holes and stability of the headfi＇ame base. Tests show that： （1） under current technology, vacuumized insulation is of short duration due to lack of appropriate applied vacuum; （2） after the freezing pipe is insulated with polyurethane, the temperature gradient is less than no insulation, and the temperature dif- ference between insulated and non-insulated apparatuses is stable as the freezing period increases. Finally, it is pointed out that polyurethane insulation is quite efficient in present technical freezing construction. Keywords： freezing pipe; insulation effect; polyurethane; energy conservation展开更多
This paper focuses on advanced analysis techniques and design considerations of DC interference generated by HVDC electrodes during normal bipolar and temporary monopolar operations on neighboring metallic utilities, ...This paper focuses on advanced analysis techniques and design considerations of DC interference generated by HVDC electrodes during normal bipolar and temporary monopolar operations on neighboring metallic utilities, with a special emphasis on buried gas and oil pipelines. This study examines the level of pipeline corrosion, the safety status in the vicinity of exposed appurtenances and the impact of DC interference on the integrity of insulating flanges and impressed current cathodic protection (ICCP) systems. Computation results obtained for different soil models show that different soils can lead to completely different DC interference effects. The results and conclusions presented here can be used as a reference to analyze the severity of DC interference on pipelines due to proximate HVDC electrodes.展开更多
基金Supported by innovation program for graduate students in Jiangsu Province of China(CXLX12_0434)
文摘This paper focused on the corrosion resistance of cold spray Al–Al_2O_3composite coatings used on carbon steel pipe surfaces under thermal insulation. Al–Al_2O_3coatings were produced on the carbon steel pipe surface by cold spray(CS) technology. Experimental apparatus was built to test the corrosion resistance of coatings beneath mineral wool insulation under isothermal, thermal cycling and wet/dry conditions. The results showed that when α-Al_2O_3 was added in spraying powder, the coating could obtain higher hardness and a denser microstructure. From corrosionunder-insulation(CUI) tests, Al–Al_2O_3CS coatings were proven to be efficient in protecting carbon steel pipe from CUI mainly owning to lamellar microstructures of coatings. There was no evidence to show that α-Al_2O_3 might bring any negative effect on corrosion resistance. Al–Al_2O_3CS coatings were sensitive to the chloride ion concentration. When these coatings were exposed to higher concentrations of NaC l, the coating's exhibited faster degradation.
基金supported by National S&T Support Program (2006BAB16B01)
文摘In-situ tests and numerical manipulations were conducted for comparison of superior/inferior quality of casing-tube-vacuumized insulation and polyurethane insulation of fi＇eezing apparatuses in relation to non-uniform cold distribution in the multi-coil fi＇eez- ing layout and the contradiction between large-coil diameter layout of the freezing holes and stability of the headfi＇ame base. Tests show that： （1） under current technology, vacuumized insulation is of short duration due to lack of appropriate applied vacuum; （2） after the freezing pipe is insulated with polyurethane, the temperature gradient is less than no insulation, and the temperature dif- ference between insulated and non-insulated apparatuses is stable as the freezing period increases. Finally, it is pointed out that polyurethane insulation is quite efficient in present technical freezing construction. Keywords： freezing pipe; insulation effect; polyurethane; energy conservation
文摘This paper focuses on advanced analysis techniques and design considerations of DC interference generated by HVDC electrodes during normal bipolar and temporary monopolar operations on neighboring metallic utilities, with a special emphasis on buried gas and oil pipelines. This study examines the level of pipeline corrosion, the safety status in the vicinity of exposed appurtenances and the impact of DC interference on the integrity of insulating flanges and impressed current cathodic protection (ICCP) systems. Computation results obtained for different soil models show that different soils can lead to completely different DC interference effects. The results and conclusions presented here can be used as a reference to analyze the severity of DC interference on pipelines due to proximate HVDC electrodes.
