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     

Toward alignment of safety levels concerning electricalinstallations in the EU

The European Standard EN 50110-1 “Operation of Electrical Installations” is applicable to all operation of and work activity on, with, or near electrical installations. In Europe, there are many national laws, standards and internal rules dealing with the matters coming within the scope of this standard, and these practices have been taken as a basis for this standard. The standard is believed to be a first decisive step to the gradual alignment in Europe of the safety levels associated with electrical installations. This article acknowledges the present different national requirements for safety, summarizes Standard EN 50110-1's definitions and terms, and compares these definitions and terms with those adopted in the IEEE Standard 902     

Instructional overview of IEEE 1349-2001-guide for the application of electric motors in class I, division 2 hazardous (classified) locations

This work presents an overview of IEEE 1349-2001, a Guide that assists individuals, organizations, and suppliers with the application of motors in Class I, Division 2 locations, where flammable gases and vapors may occasionally be present. Three-phase and single-phase ac synchronous and induction electric motors in sizes from fractional horsepower through 10 000 hp and beyond are covered in the Guide. Primary emphasis is on the use of general-purpose enclosures and precautions against excessive surface temperatures and sparking of rotor bars and enclosure joints. The Guide also provides guidance for maintaining the life-cycle integrity of motors in Division 2 locations. Existing codes and standards, such as the National Electrical Code, contain cautionary notes for general-purpose motor applications in Division 2 areas. This Guide documents industry experience and established practices for the application of general-purpose motors in Division 2 locations and provides guidance for applying motors in these locations. It is not a specification and is not intended to be used as a specification for purchasing motors installed in Division 2 locations. This paper does not replace the Guide, but should be used to supplement and understand the Guide. Significant motor temperature information is contained in the Guide including maximum recommended Division 2 exposed surface temperatures at full load. Manufacturers, users, and other industry experts worked about eight years to develop this consensus standard. It was approved by the IEEE-SA Standards Board in December 2001 and published in June 2002.     

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.     

尘土颗粒带电对电接触故障的影响

对尘土颗粒的带电特性进行了研究,并探讨了颗粒带电对电接触故障的影响.结果表明,尘土颗粒所带电荷的总体变化趋势可用一个一元三次多项式表示,电荷分布呈现带状区域.对失效的连接器触点进行观察分析发现,电触点接触区附近的污染要高于非接触区的污染,污染物中主要为尘土.尘土污染会造成镀金微孔,并造成微孔腐蚀.     

Implementing electrical safety regulations and standards

Since the creation of OSHA in 1912, there have been continuing changes in regulations, codes and standards impacting work practices and exposure to hazardous electrical energy. These include, but are not limited to, various OSHA regulations, NFPA 70E (1988 & 1995), National Electrical Code and National Electrical Safety Code. These consensus documents are written with the intention to establish lower injury performance expectations, or to offer guidance in developing work practices that lower the risk of personnel injury. In order to have an impact in the workplace, people in the workplace must transform often general or generic expectations or guidance into changes in specific practices that may be unique for their industry, plant or work environment. A successful and effective transformation process typically requires participation and support from management, technology experts, safety professionals, and the work force (whom the changes are intended to protect). This article provides insight in the transformation process used successfully in several companies. While the details may vary from company to company, as well as from different plants within each company, the elements for success are viewed as common     

浅谈火力发电厂输煤系统粉尘治理

粉尘治理工作是火力发电厂输煤系统一项长期重要工作。详细分析了输煤系统粉尘来源的机理,提出了输煤系统粉尘治理的工作重点、技术方案和设备选型,为发电厂输煤系统粉尘的治理提供参考。     

A Wet-Wall Electroinertial Precipitator: A Highly Efficient Air Cleaner for Cotton Dust

A wet-wall electroinertial air cleaner has been developed to control and remove dust generated during the processing of cotton textile fibers. The combination of electrostatic and inertial forces provides for high-efficiency collection of fine cotton dust, and the wet wall is used to continuously flush out the precipitated dust, thus avoiding problems of dust reentrainment or fire hazard. The air-cleaner design consists of a vertical tube equipped with a coaxial charging wire and an air entrance tangential to the periphery of the tube so as to inpart internal rotational flow. Dust entering the tube is charged by corona from the coaxial wire and is attracted to the tube wall by a combination of both the electrical and the centrifugal forces. A film of water introduced at the upper end of the tube flows down the inner wall and washes collected dust down the tube wall to a discharge sump. Data is presented on the efficiencies of a 4-in and an 8-in diameter precipitator operating at upper limits of about 200 ft3/min and 800 ft3/min, respectively, with artificially produced cotton dusts.     

输煤系统粉尘综合治理的应用

输煤系统的粉尘污染问题是燃煤电厂职业环境比较关注的焦点。许多年来,人们一直在探索粉尘治理的妙方,以寻求降低粉尘、改善作业环境,但效果不很理想。该文结合神木发电公司输煤系统粉尘污染的实际情况,有针对性的介绍了输煤系统降尘的一些具体做法,实施后效果明显。     

尘土存在条件下连接器电接触可靠性研究

尘土污染是造成连接器电接触故障的主要原因之一。为进行尘土条件下电接触可靠性评定,设计尘土自然沉积实验,得到尘土沉积密度的时间曲线。以洁净样片200次电阻测试的最大值作为压着尘土颗粒的判据,得到压着概率达到90%以上的危险尘土密度临界值为每平方毫米300个。最后对压着概率和尘土密度进行曲线拟合,得到拟合效果较好的几种函数形式,分析认为四次多项式和幂函数拟合是最符合要求的。     

吸尘器及其电动机的发展前景

吸尘器是家用电器产品中的主要产品之一。文中阐述国内外吸尘器的产销现状,我国吸尘器及其电动机生产技术与先进国家的差距,指出我国吸尘器要占领国内市场,打入国际市场,必须尽快提高产品内在性能,向功能多样化、操作自动化及产品轻便化、配套化发展,而提高吸尘器电机的性能,实现吸尘器电机国产化乃是当务之急。     

纤维对连接器电接触可靠性的影响

尘土是导致连接器电接触故障的重要原因之一。尘土成分包含无机物和有机物两部分,纤维是尘土中常见的有机物,通过静态和动态实验模拟实际环境中纤维对连接器电接触的影响具有重要意义。纤维密度是影响静态接触电阻的主要因素;当接触界面存在纤维时,正压力对静态电阻的影响不明显。在微动过程中,正压力越大,纤维越易被推开;纤维不易进入接触面;纤维对接触面磨损的影响较小。     

灰库污染治理技术及应用

通过对下花园发电厂于除灰灰库的卸灰扬尘问题进行分析,针对引起扬尘的主要原因对干灰设备进行改造。改造后彻底解决了干灰生产过程中粉尘对环境的污染,改善了灰库周围的环境。该治理技术对干灰系统设计和老厂干灰设备改造具有一定的借鉴、指导作用。     

高海拔沙漠化盐渍土地区GIS设备安装的质量控制

在高海拔、沙漠化、盐渍土地区进行750 kV超长全封闭组合电器（GIS）现场安装,目前还没有相对应的技术资料和标准工艺来指导施工。介绍某750 kV输变电工程中GIS设备的组装和对接实践,提出针对大风沙天气的安装环境应采取的防尘、检测及控制措施。采用“盐微粒控制”技术和汇控柜加装 “防沙罩”等措施,以防止硫酸盐对设备元件造成腐蚀,杜绝细粉沙侵入柜内元件。并实施750 kV超长GIS设备供货、安装及试验“一体化”操作流程,以确保GIS设备安装质量优良,进而保证GIS设备安全可靠运行。该项工程的研究与实践可供同行参考和借鉴。     

Safe and sound

When the ATEX Directives were released in 2003, the only clear point was that ex motors with converter supply had to be safe. Otherwise, the requirements in relevant standards were different for the motors depending on the protection type or voltage, and also, the installation standard was adding new guidelines. In addition, each country had its own history and practices, which confuse the end users and manufacturers. These ATEX Directives are the first attempt to harmonize the rules with respect to the past and the actual installed base.     

核电厂安全级(1E)电缆鉴定审查过程中相关问题的探讨

核电厂1E级电缆作为核电厂安全系统在正常工况下和设计基准事件期间及随后的规定时间内执行安全功能所必需的重要设备,必须按照相关的标准制定鉴定大纲和程序,并进行质量鉴定,对1E级电缆的鉴定过程和鉴定文件进行审查是核安全设备审查的重要内容之一.对1E级电缆鉴定样本选择、电缆材料热寿命评定和加速热老化试验条件等三个问题进行了讨...     

Escaping arc danger

The paper presents the arc flash assessment in petrochemical and chemical industry. This article provides the IAS Cement Industry Committee information and references to help apply the expertise in risk and safety management experience for the specific hazard of electrical arc flash. The information and references provided include the following: (1) injury frequency and prediction methods (2) cost information to help in building a business case to enable fact-based management decision on priority and resource allocation (3) comparison of several implementation options, including a recommendation for the best long-term strategy for minimizing both injuries and costs (4) considerations to help assure effective arc hazard analysis (5) examples of control measures that can be implemented based on the results from an arc hazard assessment (6) sources for more information. The author's intent is to aid in accelerating the implementation of technology and work practices proven effective through the technical forums sponsored by the PCIC of the IAS. The harmonization of workplace electrical safety standards biased toward optimizing the integration of inherently safer technology, improved safe work practices, and state-of-the-art safety management systems will improve the electrical safety of workers in all industries.     

华东电网安全文明生产达标的回顾和总结

１９８９年原电力部决定开展安全文明生产达标工作，华东网局根据部的统一部署召开了一系列会议、制订一系列《实施细则》、《考核标准》，并在管辖范围内积极推行。通过９年的实践，由于各级领导重视，依靠广大职工做了大量工作，从而使安全水平不断提高，设备状况逐年转优，经济指标稳步改善，文明生产蔚然成风，成绩显著     

The effect of neutral earthing practices on lightning currentdispersion in a low-voltage installation

Computer modeling with the EMTP code has been applied to several configurations and earthing practices in use in various countries to show the effect of any differences in the dispersion (sharing) of a lightning stroke current among the available paths for the earth-seeking lightning current. Simplifying assumptions have been made to some details of the configurations to focus on the main difference-earthing practices. Identifying such differences provides the necessary perspective on their significance and the strong need to take them into consideration when developing international standards on surge-protective device applications     

Current north american assessment and refurbishment practices of substation grounding systems

A survey was undertaken on the current assessment and refurbishment practices of North American utilities regarding substation grounding systems. The information was gathered using standard survey techniques where all interested parties were requested to fill out a short written survey and return it with the understanding that their responses would be kept anonymous. Survey results show that almost all utilities evaluate the integrity of their ground grids at some point, and have maintenance or engineering standards for determining the integrity. Test equipment is frequently used to evaluate integrity, and ground grids not meeting these standards are commonly upgraded. The results also show that most use high resistivity surfacing material, yet very few test the resistivity of the material at the time it is installed. This paper provides guidance on the recommended best practices based on these survey results, which can be used for benchmarking purposes. It also includes a short discussion on the importance of maintaining the substation grounding system.