Adapting to the dual hazardous area classification system

Twenty-five years after it was first proposed and after five years of heated debate, the 1996 National Electrical Code (NEC) includes a new way to classify hazardous areas contained in Article 505 “Class I Zones 0, 1, & 2 Locations”. This article provides an alternative path to classify hazardous areas as Zones 0, 1 and 2 instead of the traditional Division 1 and 2     

One company's approach to cord-connected safety

One major US chemical manufacturing site has implemented a safety initiative dealing with cord-connected electrical equipment that exceeds regulatory requirements. The program includes mandatory use of GFCI devices for all 120-Vac equipment used in the plant, as well as annual inspections and visually discernable exterior bonding requirements for higher voltage cord-connected equipment. Receptacle outlets with voltages greater than 120 Vac were also placed on an annual inspection program, as well as many 120-Vac explosionproof outlets. Annual safety awareness training was mandated for all users of cord-connected equipment.     

Global hazardous area requirements

This article highlights those improvements and serves as a short tutorial into current international codes for the implementation of sometimes hazardous electrical components. It focuses on North American engineers working on non-U.S. projects. Included is a general subject overview and in particular, a discussion of similarities and differences between the codes. IEEE recommended the practice of 303 auxiliary devices for rotating electrical machines in Class I, Division 2 and Zone 2 locations. It is now expanded to include the Canadian Electrical Code (CEC), International Electrotechnical Commission (IEC), European Committee for Electrotechnical Standardization (CENELEC), and Standards Australia/New Zealand (AN/NZS) regulations     

危险区域分级和危险区域电工设备的选用

危险区域电工设备由于使用条件比一般条件更为苛刻 ,因而在设计中应考虑更多的因素。对危险区域的分级、设备的要求及评价作了分析和对比 ,以供设计危险区域的电工设备时参考。     

危险区域分级和危险区域电工设备的选用

危险区域电工设备由于使用条件比一般条件更为苛刻,因而在设计中应考虑更多的因素。对危险区域的分级、设备的要求及评价作了分析和对比,以供设计危险区域的电工设备时参考。     

火炸药危险场所爆炸参数研究分析

针对火炸药自身的性能、特点及生产、使用的危险场所存在的安全隐患，就进行的火炸药粉尘爆炸参数的研究，进行了详细的论述，为确定用于火炸药危险场所电气设备的防爆型式和结构参数提供参考依据。     

Practical considerations of area classification: how for toclassify

Defining the classification of a location or facility (class, group, and division), while often a difficult and time-consuming task, is only the first of three separate and distinct tasks that must be performed by those who provide electrical area classification. This first task defines the kinds of materials that are present in the location using the terms class, group, and division. The second task is to choose electrical equipment and installation techniques appropriate to the class, group, and division decisions assigned to the location in the first task. The third and final task in electrical area classification is to determine the physical boundaries or extent of the areas that are influenced by the class, group, and division decisions reached in the first task. The NEC and RP 500 are both used in this final task of electrical area classification. This article concentrates on the methods used in the third task to determine the physical boundaries or extent of classified areas. The author concentrates on the third task, with the intent of providing the skills and insights that are necessary to properly determine the physical boundaries of classified areas consistent with personnel and facility safety. Only Class I, Division 2 locations are examined     

Industrial facilities gain new area classification guidelines

Both the United States National Electrical Code (NEC) and the Canadian Electrical Code (CEC) provide special rules for installing electrical equipment in hazardous (classified) locations. Hazardous locations are those locations where fire or explosion hazards may exist due to flammable gases or vapors, flammable liquids, combustible dust, or easily ignitible fibers or flyings. Only Class I materials (gases and vapors) are within the scope of American Petroleum Institute (API) RP500 and RP505. These recommended practices offer those in the petroleum industry an opportunity to standardize area classification drawings-both for drawings using the Division method of area classification and for drawings using the Zone method of area classification. Good engineering judgment must be used with RP500 and RP505, but guidelines provided should minimize differences of classifications by qualified individuals classifying the same or similar locations. This article provides an overview of the two recommended practices including outlines of tables of content, but primarily emphasising the substantive changes and additions     

蓄电池的危险特性检验

依据《关于危险货物运输的建议书》对蓄电池的分类和规定,讨论了分类需要的实验项目和分类流程,为蓄电池危险特性检验提供了完善的方法。根据试验结果,蓄电池可不分类为危险货物,可以作为普通货物进行包装运输。     

High interrupting capacity equipment for hazardous locations

There are numerous methods of handling high fault currents in the modern industrial facility. When it comes to hazardous locations, however, questions abound as to the equipment and systems required to survive these conditions without causing ignition of the surrounding atmosphere. Many opinions, and in some cases misconceptions, exist over what actually is suitable for such an application. Two alternatives are presented here; one using a system approach, the other regarding explosion-proof equipment designed for this application     

Selection of electrical equipment for hazardous areas

When an electrical apparatus is to be installed in areas where dangerous concentrations and quantities of flammable gases, vapors,mists, ignitable fibers, or dusts may be present in the atmosphere, protective measures are applied to reduce the likelihood of explosion due to ignition by arcs, sparks, or hot surfaces produced either in normal operation or under specified fault conditions. The following International Electrotechnical Commission (IEC) standards are relevant for the correct selection and installation of electrical apparatus in hazardous areas: · IEC Standard 60079-14: Electrical Apparatus for Explosive Gas Atmospheres, Part 14: Electrical Installations in Hazardous Areas (Other Than Mines) · IEC Standard 61241-14: Electrical Apparatus for Use in the Presence of Combustible Dust, Part 14: Selection and Installation. In this article, we discuss IEC Standard 60079-14, which was revised in 2007. The changes to the standard and the consequences of these changes for the installers and users are discussed. Special emphasis is accorded to critical components, such as flameproof cable entries and cable selection. Tests carried out by the Germany's Federal Institute of Physics and Metrology (PTB) with direct entries into flameproof enclosures using various cable types and the results are presented. It has been found practical to classify hazardous areas into zones according to the likelihood of an explosive gas atmosphere being present (see IEC Standard 60079-10 for definitions). Such classification allows appropriate types of protection to be specified for each zone. In the ATEX directive 94/9/EC, the new idea "Criteria Determining the Classification of Equipment-Groups into Categories" now defines different levels of safety for the electrical apparatus against the possibility of becoming a source of ignition. Therefore, the user can have a second selection criterion for choosing the correct product for a given application.     

基于DS证据理论的SVM分类模糊域数据修正

在介绍支持向量机(SVM)和DS证据理论的基础上,提出了一种利用DS证据理论对SVM分类模糊域数据进行分类修正的方法。该方法首先利用SVM对测试样本进行分类,对SVM分类输出模糊域的样本使用隶属度函数将SVM的输出距离转换成样本对各状态的隶属度;其次利用DS证据理论融合其他传感器信息,对各状态下的隶属度进行适度修正,从而实现该区域数据的重新合理排布;最后将该方法应用于高压断路器故障诊断,以验证其诊断性能。大量的实验结果表明,该方法可以利用断路器操作线圈电流数据,合理修正振动数据分类结果,实现断路器机械故障的准确检测。     

一种基于包长和时间间隔的网络流量分类方法

关于流分类,流量统计特性的种类繁多,流量分类的方法复杂多样,综合准确率和效率,提出了1种基于包长和时间间隔的流量分类方法.首先,对抓取的数据包的包长和包到达的间隔时间这两个流量特性进行统计,然后将统计的数值建立出相应流量的特性模型,运用矢量量化的数学方法对未知流量进行处理,得出结论.测试结果表明提出的基于包长和时间间隔...     

The load characteristics classification and synthesis of substations in large area power grid

It is very difficult to build load model for every substation since there are numerous substations in large area power grid. A practical method is to classify the substations into several classes, pick out a typical substation from each class and build its load model, then generalize it to other substations of the same class. In this paper, a new method based on SOM (Self-Organization Map) neural network is presented for load characteristics classification and synthesis of substations in large area power grid. SOM neural network is a clustering method with self-organizing characteristics and mapping capability that can classify different input patterns automatically. Besides, the trained SOM neural network can discriminate the new input pattern conveniently without retraining. Therefore, the new substations can be discriminated with the existing classification result unchanged. The effectiveness of the proposed method is verified by a simulation of 183 220 kV substations in Shandong power grid using MATLAB Neural Network Toolbox. At first, the load composition rate in each substation is chosen as the feature vector, then SOM neural network is introduced to the classification and synthesis of the load characteristics of substations. At last, the synthetic load characteristic of each class is derived from the cluster center. The result is satisfactory since the method not only decreases the randomness and subjectivity of the load characteristic classification and synthesis of substations, but also improves the effectiveness and efficiency of load modeling. The method offers a new way for practical load modeling.     

危化品运输监控系统的设计与实现

为改善危化品安全生产运输环境,确保危化品运输行业安全、健康、持续发展,在总结常见危化品运输监控系统的基础上,提出了一种基于GPS、GIS、GPRS相结合的危化品运输监控系统,并从软件工程的角度分析了监控系统的设计与实现,详细阐述了监控系统的组成和工作原理.通过对系统进行多种测试,结果表明系统能满足危化品运输行业的要求....     

Investigation of plasma treatment for hazardous wastes such as fly ash and asbestos

Hazardous wastes such as fly ash and asbestos can be melted by plasma treatment to convert them into blocks of vitrified slag resulting in a volume reduction by 49 to 65%. Vitrified slag of fly ash containing such heavy metals as Zn, Cu, and Fe has an extremely high resistance to water. Electric conductivity of the elution of 18.8 g of slag in 700 ml of distilled water is nearly the same as that of pure distilled water, being only about 0.1% of the electric conductivity of the solution of fly ash in distilled water. The surface of the molten asbestos becomes a hard shell without needlelike fibers, thus rendering asbestos safe for human health. As a result, plasma waste treatment can become a powerful tool for environmental protection. © 1999 Scripta Technica, Electr Eng Jpn, 126(3): 73–82, 1999     

Mechanisms for formation of inorganic byproducts in plasma chemicalprocessing of hazardous air pollutants

Plasma chemical behavior of hazardous air pollutants (HAPs) (Cl ₂C=CCl₂, Cl₂C=CHCl, Cl₃C-CH ₃, Cl₂CH-CH₂Cl, CH₃Cl, CH ₃Br and benzene), their molecular probes (CH₄, CH ₃-CH₃, and CH₂=CH₂), and carbon oxides (CO_x) was investigated with a ferroelectric packed-bed plasma reactor to obtain information on the formation of CO _x and N₂O. It has been shown that the oxidation of CO to CO₂ is a slow reaction in plasma, and that CO and CO ₂ mainly result from different precursors. Simultaneous achievement of complete oxidative decomposition of HAPs in plasma and recovery of CO as a chemical feedstock could be favorable. The process of N₂O formation is affected by HAP structures and oxygen concentration. In the decomposition of olefinic HAPs, such as Cl₂ C=CCl₂ and Cl₂C=CHCl, high-power short-residence-time operations are effective in suppressing N₂ O formation. In the cases of CH₃Cl and CH₃Br, low specific energy density operations could be necessary to reduce N₂O concentrations. The yields and selectivities of CO, CO₂ and N₂O change drastically by adding only 2% of oxygen to N₂, and oxygen concentration is not a good factor to control these inorganic oxides     

面向船舶工业新闻的文本分类

由于船舶工业领域中的新闻内容篇幅较长且专业性较强,同时包含大量船舶领域专业词汇,目前针对该领域新闻文本分类的研究较少且缺少相应的船舶工业新闻语料。构建了一个船舶工业新闻语料库,并提出了一种新的面向船舶工业新闻的文本分类算法,首先基于文档频率、卡方统计量及主题模型LSA进行特征选择和特征降维,将文档-词矩阵映射成文档-主题矩阵后,最终对处理后的特征采用支持向量机进行文本分类。通过新闻文本分类的实验表明,所提出的算法能够有效解决文本向量的高维度、高稀疏性问题,在小样本集和类别有限的前提下相比传统方法具有较好的分类效果。     

对居民实行一户一表改造后低压线损的分析

随着国家电力体制改革的深化,国家加大对城网、农网的改造,城乡居民一户一表改造工程是其中的一项重要内容。实施户表改造后,在给用户解决了实际问题的同时也给供电部门的线损带来影响。     

危化品管道非介入式声波泄漏监测传感节点设计

面向危化品输送管道的非介入式声波泄漏检测,介绍了一种基于无线传感网络的非介入式声波泄漏监测传感节点设计方法.传感节点包括传感器及信号调理模块、多节点时间同步模块、数据采集及处理模块和能量捕获模块.利用STM32F407单片机内部基于DMA方式的ADC数据采集和数据串行通信,结合GPS授时实现多节点信号同步采样和定时器校正;利用单片机内部的浮点运算单元实现小波数据压缩,与数据错时发送相结合实现无线数据可靠传输,避免多节点大数据量同时发送导致网络堵塞和数据丢包.测试结果表明:传感节点数据采集准确、通信稳定可靠,为危化品输送管道的非介入式实时泄漏监测提供了一种有效的技术手段.