交流干扰下管道最佳保护准则探究

为了探究交流干扰下抑制管道发生腐蚀的最佳保护准则,通过试验确定交流干扰下达到最佳保护状态时的阴极保护电位,首先验证经典的-0.85 V[vs饱和硫酸铜参比电极(CSE)]阴极保护电位准则和负向偏移100mV阴极保护准则在交流干扰下是否还具有良好的保护效果;接着探究阴极保护电位对保护效果的影响,确定保护效果较好时保护电位的范围.在此基础上,再结合保护程度和保护效率2个评价指标全面分析,找出最佳保护状态下的阴极保护电位取值.结果表明:存在交流干扰时,经典的-0.85 V(vs CSE)阴极保护电位准则和负向偏移100 mV阴极保护准则已经失效;在-1.20 V(vs CSE)以内,阴极保护电位负向升高,对交流干扰下的腐蚀抑制作用会增强;综合腐蚀速率、保护程度和保护效率3个因素,得到交流电流密度在50 A/m2以内时,建议采用-1.00 V(vs CSE)的保护电位;交流电流密度大于50A/m2时,建议采用-1.10 V(vs CSE)的保护电位.     

金属储罐外底面阴极保护电位分布的预测模型及其精准性

为了掌握金属储罐基础厚度、土壤电阻率对储罐阴极保护的影响,建立了20钢储罐底板外侧阴极保护电位分布的数学模型。利用FLUENT软件模拟计算了不同影响因素下金属储罐底板外侧的阴极保护电位,研究了不同厚度沥青砂层、砂垫层和土壤电阻率对其阴极保护电位分布的影响。结果表明:沥青砂层的厚度对保护电位分布影响较小,土壤电阻率对保护电位分布影响较大,砂垫层越厚越有利于阴极保护电位的均匀分布。本模型的模拟结果与实测结果相近,可以用于金属储罐阴极保护效果的预测。     

非均质土壤中油井套管外加电流阴极保护的数值仿真

为了解决深井套管阴极保护的井底保护效果评价问题,针对延长油田西区采油厂正171号丛式井阴极保护系统项目,采用边界元方法,以非均匀电阻率和分段极化曲线的方法模拟实际工况,通过Beasy软件利用数值模拟技术计算不同阳极埋深对阴极保护电位分布的影响,评价了外加电流阴极保护对井底的保护效果。结果表明,采用边界元方法可快速准确地模拟油井套管在非均质土壤中的阴极保护电位分布。正171号丛式井阴极保护方案为阳极埋深100 m,水井保护电位范围为-998~-1 023 m V(vs SCE),油井保护电位范围为-961~-1 192m V,井组各油井底部均能得到良好的保护。     

海底生物燃料电池中304不锈钢(06Cr19Ni10)阴极腐蚀保护作用研究

以304不锈钢(06Cr19Ni10)作为阴极构建海底生物燃料电池装置,研究了该电池对其海水腐蚀的阴极保护作用。自然腐蚀状态下不锈钢电位为-260 mV,阴极保护试样为-340 mV。荧光显微镜(FM)和扫描电镜(SEM)观察结果表明,两组试样的表面微生物附着情况差别不大,阴极保护试样表面腐蚀程度较低。电化学阻抗法及极化曲线测试表明,通电保护试样的阻抗值随时间增加逐渐增大,腐蚀电流密度Icorr逐渐减小,保护试样的抗腐蚀能力增强,电池装置对不锈钢阴极起到一定的保护作用。     

牺牲阳极阴极保护在沿海挡潮闸中的应用

沿海工况下的水工钢闸门易遭受腐蚀破坏,为减轻腐蚀延长使用寿命,对射阳河挡潮闸35扇钢闸门采取了牺牲阳极阴极保护措施.保护系统运行近10 a,对钢闸门进行保护效果检查和保护电位检测.结果表明:钢闸门表面无锈蚀,阴极保护电位均满足规范要求且分布均匀,镁阳极适用于淡海水环境介质中且保护效果优异,由于闸门两侧及底部因其他构件吸收电流较多,阳极消耗较快,保护电位偏正;为使闸门表面达到同寿命保护,可在两侧及底部适当增加阳极数量或增加阳极质量.     

铁基材料用于海水中铜管材的阴极保护

通过测试在海水中的自腐蚀电位、工作电位以及驱动电位,分析了2种铁基材料用于海水中紫铜阴极保护的可行性,确定了紫铜在海水中的最小保护电位。利用实验室阴极保护模拟实验对保护效果进行了测试。结果表明,在海水中铁基阳极工业纯铁、35钢对紫铜具有良好的保护效果,失重率减小达90%以上,海水中紫铜阴极极化电位稳定-680 m V左右,超过紫铜最小保护电位。     

热镀锌钢材的电偶腐蚀行为-划痕型缺陷

使用锌-碳钢异材质丝柬电极技术,模拟并研究了锌/钢电偶腐蚀不同阶段的电位和电流密度的空间分布.结果表明,在锌丝与钢丝面积比为10:1的情况下,锌丝能给钢丝提供足够的阴极保护,且锌丝之间存在明显的电位、电流分布不均现象;钢丝之间也存在电化学参数分布不均现象,而且在受到保护的同时钢丝表面有氢析出.     

X80管线钢在近中性环境中阴极保护下的应力腐蚀敏感性

目前,对管线钢在外加电位下的应力腐蚀开裂的研究尚不全面.应用慢应变速率拉伸、扫描电镜(SEM)观察和动电位极化测试方法,研究了在近中性模拟土壤溶液(NS4)中,不同阴极保护电位下X80管线钢的应力腐蚀开裂(SCC)行为.结果表明:X80管线钢的SCC行为与阴极保护电位密切相关;在-850,-1000,-1 200 mV(相对饱和硫酸铜电极)3个保护电位下,阴极过程析氢反应起主要作用,随着阴极保护电位的负移,X80管线钢的脆性逐渐增大;在-1 200 mV条件下SCC敏感性系数最高,形变硬化指数最低,SCC现象最为严重.     

某气田集输管线阴极保护检测与优化设计

多管线共用阳极阴极保护系统中,不同管线保护电位存在差异,长距离管线末端欠保护,提高电流输出可造成其他联合保护管线过保护.为了准确获取真实电位分布状况,对多管线联合保护阴极保护电位进行模拟计算,研究了不同阳极地床布置方式对各管线阴极保护电位的影响.结果 表明:模拟计算结果与实际测量结果吻合性良好;新建阳极与其他阴极保护系统的管线及阳极之间距离越远,阴极保护系统间干扰越小,越有利于阴极保护电位的均匀分布.     

油田套管阴极保护技术的应用

油田套管腐蚀是油气开采过程中普遍存在的问题.套管一般深埋于地下,所处的地下环境较为复杂,阴极保护技术可使钢质套管得到保护,从而延长套管的使用寿命.通过一套完整的阴极保护系统技术设计,给出了完整的阴极保护施工方法.通过Beasy软件利用数值模拟技术计算不同阳极埋深对阴极保护电位分布的影响,评价了外加电流阴极保护对井底的保护效果.仿真结果表明:阳极安装在井组中间距离井组横向距离12 m,埋深为100 m,井组可得到良好保护.该技术防腐蚀效果明显,套管腐蚀现象得到显著改善,能满足不同条件下的防腐蚀需求,可在油田开展进一步推广应用.     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

The Research of Anti-Wear Properties of Organomolybdenum Compounds in the Engine Oils

A four-ball tester was used to evaluate the anti-wear performance of three kinds of organomolybdemun compounds in the engine oils, i. e., molybdenum dialkyldithiophosphate (MoDDP), molybdenum dialkyldithiocarbamate ( MoDTC), and sulphur and phosphorus freeorganomolybdeum (Molybdate). The results indicate that a low concentration of MoDDP doesn' t improve the anti-wear properties of the commercial engine oils, but a high concentration of MoDDP can obviously improve the anti-wear properties and the load-carrying capacity of the engine oils. MoDTC doesn' t improve the antiwear properties of the engine oils, but worsens the anti-wear properties of the oils. Signifi can timprove ment of frictional and wear characteristics is obtained with Molybdate added in the commercial engine oils and the formulated oils.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Certification Becomes Important for the I Quality; and Safety Supervision of the Chinese Liquor Sector

The end of 2007, over 200 unit products of more than 80 Chinese firms have passed the quality grade certification for liquor products. These products involve distilled spirits, beer, wine, yellow wine, fruit syrup wine and others, and cover over 80% of the national top-branded liquor products.……     

Deposition and Coating Properties on CVD Tungsten

Surface characterization and microstructure studies are performed on chemical vapor deposited (CVD) tungsten coating. There is about 2 μm thickness diffusion layer of tungsten in the molybdenum substrate. The thermal shock test shows tungsten coating has good adhesion with molybdenum substrate, but the elements of oxygen and carbon in the tungsten coating have the bad affection to the adhesion. The result of high-temperature diffusion experiment is the diffusion rate from molybdenum substrate to tungsten coating is faster.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Analysis of marine hydrobiont lipid extracts as possible cryoprotective agents

We studied a combined effect of the cryoprotectants both of lipid and carbohydrate origin at the presence of DMSO or without it on cell viability and the RNA synthesis in the embryonic mollusc and echinoderm cell cultures obtained at different developmental stages. Cryoprotective properties of exogenous lipids correlated with their thermotropic behavior. Lipid extracts from marine hydrobiontes, which thermal transitions are characterized by relatively small part of calorimetric thermogram area lying at temperatures above 0 °C (6–18%), were found to possess a considerable cryoprotective activity. The results are discussed in relation to the prediction of the cryoprotective activity of lipid extracts for marine animal cells. In addition, it was found that marine invertebrate cells can be cryopreserved without DMSO at the presence of trehalose and lipid extracts of some marine hydrobiontes.     

Low-Temperature Properties of Silver

Pure silver is used extensively in the preparation of high-temperature superconductor wires, tapes, films, and other configurations in which the silver not only shields the superconducting material from the surrounding materials, but also provides a degree of flexibility and strain relief, as well as stabilization and low-resistance electrical contact. Silver is relatively expensive, but at this stage of superconductor development, its unique combination of properties seems to offer the only reasonable means of achieving usable lengths of conductor. In this role, the low-temperature physical (electrical, thermal, magnetic, optical) and mechanical properties of the silver all become important. Here we present a collection of properties data extracted from the cryogenic literature and, to the extent possible, selected for reliability.