Design practice for extinguishing barrier systems

An extinguishing barrier comprises an optical flame sensor and a HRD-Suppressor located downstream of the detected flame front. The effectiveness of an extinguishing barrier is based on its ability to detect an explosion in a pipeline by means of an optical flame detector whose tripping signal is amplified and then very quickly actuates the detonator-actuated valves of the pressurized HRD-Suppressors. Extensive practice-related tests in pipelines, having different cross sections and length, in pipelines connected with different vessels, have shown that extinguishing barriers can be used without reservation to halt or stop an explosion in practice. The amount of suppressant agent required depends on the nature of the combustible dusts, the nominal diameter of the protected pipeline, the explosion velocity and the maximum reduced explosion overpressure in the vessel. Most significantly, the theoretical understanding of explosion propagation and extinguishing has led to computer design guidance which has simplified system design. Explosions can be combated effectively in pipelines up to diameter 2500 mm.     

Deflagration suppression of high Kst dusts

Deflagration suppression is one of several means of explosion protection for process volumes. This paper presents a discussion of some of the variables which influence the final pressure obtained upon suppression of a process deflagration. In particular the discussion focuses on suppression of the deflagrations of fast burning dusts, i.e. dusts with high K_st values. The discussion is amplified using recently obtained data from deflagration and suppression tests on three flammable dusts representing the St-2 and St-3 deflagration classes. It is shown that the relationship between post-suppression pressure and K_st value is not always as expected. The underlying reason for this result relates to differences in the burning characteristics of the subject dusts in the relevant stages of the deflagration.     

Increased fire hazard of N-heterocyclic compounds substituted by S-containing group

Release of CS₂ and/or H₂S caused by friction is demonstrated on two N-heterocyclic compounds carrying S-atom containing substituents. Because of the generation of electrostatic charge and creeping discharge, simultaneously brought about by friction, ignition and possible explosion of the released gaseous products of decomposition could occur. The tested compounds proved not to be sensitive to impact. Nonetheless, fire and explosion hazard of dusts must not be judged by their sensitivity to impact only. It is necessary to test their sensitivity to friction as well.     

Laboratory and large-scale dust explosion research

This paper describes dust explosibility research in full-scale experimental mines and a 20-L laboratory chamber at the U.S. Bureau of Mines and in a 1-m³ laboratory chamber at Fike Corporation. The purpose of this research is to improve safety in mining and other industries that manufacture, process, or use combustible dusts. As part of this work, carbonaceous dusts with a wide range of volatilities and various particle size distributions were studied. Laboratory data on the minimum explosible concentrations of predispersed dusts were comparable to mine data for nominal dust loadings that were dispersed by the aerodynamic disturbance from a gas ignition zone. Recommendations are given on the limitations of small-scale testing such as “overdriving” by too strong of an ignitor. The effect of dust particle size on explosibility data is illustrated for coal and aluminum dusts. For both dusts, the finest sizes were the most hazardous. The inerting requirements for preventing explosions were also measured in both laboratory and large-scale systems. All the data show relatively good agreement between the laboratory and the large-scale tests.     

Pressure venting of dust explosions in large vessels

The validity of the dust explosion venting nomograph D in NFPA 68 was examined in tests with vessels having volumes from 2.4 to 250 cubic meters and with dusts of classes St 1 and St 2.     

Turbulence effects on dust explosion venting

The ability to estimate the intensity of accidental dust explosions is an essential prerequisite of methodologies intended to provide design guidelines for the protection of equipment and buildings where combustible dusts are being handled. In general, the severity of an explosion depends on the type of dust involved, its physical properties (such as particle size and moisture content), the characteristics of the interested volume (size, shape, presence of vents, and blockages), the strength and type of the ignition source, and the conditions of the environment (air flow, turbulence).     

Deflagration protection of pipes

The potential for gas and dust explosions in the process industries has been historically recognized. Potentially explosible materials, both organic and inorganic, are handled in large quantities on a daily basis. These hazardous materials are processed in vessels and/or pipes: that is volumes with small length to diameter (L/D) ratios or volumes with large length to diameter ratios. It has also been historically recognized that explosions have different characteristics in different volumes. This difference becomes critically important when explosion protection methods are being designed.     

Case histories of dust explosions

Three dust explosion incidents that occurred within Monsanto Europe are discussed. The company carries out a wide range of operations involving powdered solids, and the incidents illustrate the range of situations that can cause dust explosions. The design approaches used now, covered by guides such as the NFPA 68 and 69 usually prevent major losses, but there are some lessons to be learned from the three incidents described. The most basic one is that there are so many different ways of igniting flammable dusts that we should never use elimination of ignition sources as the sole method of protection. The other lesson is a very old one: the need to maintain all our equipment and safety systems in operational condition at all times. This is particularly difficult in practice because these systems are not required for day-to-day production, but still must operate effectively when they are needed.     

Price Competition and Market Structure: The Impact of Cartel Policy on Concentration in the UK

This paper examines the impact of firms' conduct on market structure. It studies the evolution of concentration in UK manufacturing following the abolition of cartels using a theoretical framework based on Sutton's theory of market structure and a panel data set of four-digit industries over 1958–1977. The econometric results suggest that the intensity of price competition has a positive effect on concentration in exogenous sunk cost industries as well as in advertising-intensive and R&D-intensive industries. The concentration-market size relationship, while negative in exogenous sunk cost industries, breaks down in industries with high advertising or R&D intensity.     

Dust entrainability and its effect on explosion propagation in elongated structures

Two apparatuses have been developed to characterize the entrainability of dust deposits. The minimum aerodynamic wall shear stress required for dust removal (Critical Shear Stress), measured by the first apparatus, is an indicator of the ease with which dust particles can be removed from a layer. The second apparatus measures the settling velocity distribution of dust clouds, which is an important factor controlling the extent of dispersion as well as the time period during which the entrained dust cloud can remain suspended. Testing has shown that the critical shear stress depends not only on the nature of the dust, but on the way the dust deposit is formed. Therefore, a portable version of this apparatus was developed to allow field testing of dust deposits. This methodology has also been used to evaluate the effect of oil treatment sometimes used in the grain handling industry to reduce dust emission. Simulated explosion tests have demonstrated the importance of critical shear stress on dust entrainability. A simple model calculating unsteady dust concentration in elongated structures has been developed. The model shows that flammable dust concentrations induced in a gallery by a primary explosion exist over a finite length and time period. Therefore, the probability of a secondary explosion depends not only on the dust and layer properties, but on the details of the primary explosion and of the enclosure geometry. A simple criterion for transmission of a primary explosion into an adjoining elongated structure is discussed in the paper.     

地下综合管廊混凝土爆灰检测及加固

针对某市钢筋混凝土地下综合管廊的现浇顶板、侧壁出现的混凝土爆灰质量缺陷,为确保管廊结构的安全使用,采用钻心法、超声波法、沸煮试验、爆灰物质的化学成分分析等检测方法,对爆灰现象进行了检测。结果显示,混凝土中存在的块状氧化钙与水熟化后体积增大1倍~2.5倍,使得混凝土在强度未达到设计抗拉强度前在块状氧化钙体积膨胀应力作用下被拉裂,导致了此类质量缺陷的发生。分析了质量缺陷对管廊结构的影响,并对管廊结构进行了加固设计及处理,满足了结构的正常安全使用要求。研究结果可为类似爆灰缺陷的设计及处理提供参考。     

西南地区制造业专业化与产业同构及对策研究

为了解西南地区制造业专业化水平与产业同构程度,提高市场一体化水平,文章利用克鲁格曼指数和区位熵衡量了20个制造业2002～2014年的地区专业化水平,结果表明西南地区间专业化水平与地区间一体化水平偏低,且13年来无明显提高;各省市存在较严重的产业同构但有缓解趋势;优势产业主要体现在资源和劳动密集型的传统产业和重工业,高新技术产业较缺乏。基于分析,提出了加快实现行政区经济向市场化区域经济转变,建立健全区域产业合作利益分享与补偿机制,强化西南地区协同产业定位,加快具有优势的传统产业和重工业的优化升级,实现传统主导优势产业裂变或内涵式转型升级等发展对策。     

模糊事故树法在贵州某煤矿瓦斯爆炸事故分析中的应用研究

贵州省是煤矿瓦斯事故的高发地区,瓦斯事故通常会有大量人员伤亡,造成煤矿重大经济损失,本论文运用安全系统工程的知识,把事故树和模糊数学相结合,以贵州省某煤矿瓦斯爆炸事故为案例,建立煤矿瓦斯爆炸事故分析模型,分析煤矿瓦斯爆炸事故。     

FCC organizational structure and regulatory convergence

Convergence of information industries has led to the emergence of services that cross industry boundaries. Changes in these industries have caused the organization of regulatory institutions to become inadequate. An exploratory analysis of orders issued by bureaus of the US Federal Communications Commission shows overlap in the issues on which each provides rulings. Rather than organizing into traditional industries such as common carrier, cable, and mass media, bureaus could be re-organized into functions such as oversight of rates, spectrum allocation, and universal service provision. Using theories of bureaucracy and organization, this paper proposes an explanation for the difficulties that the FCC has had in adapting to converging information industries.     

Ultimate capacity of blast loaded structures common to chemical plants

There has been a great deal of investment in development of design criteria and design and construction of heavily reinforced, blast-resistant control rooms. This remains the best option for protective construction against severe blast loading experienced close in to a vapor cloud or other explosion hazard. However, most structures encountered at chemical plants and contemplated for future construction are conventional steel frame, metal clad buildings. In this paper we look closely at the response of such buildings to explosion loads and their ability to undergo large deformations without structural failure. The types of structural elements evaluated include metal decking of various gauge and shape along with a variety of girt and purlin sections. Building frames or bents are also evaluated, although the date base for these is much more limited. The work is based on observations made during investigations of large explosion accidents along with analytical predictions and test measurements. To conclude, we offer specific design criteria and connection recommendations for enhancing the overall strength of a building through the use of conventional components in unconventional construction.     

矿用瓦斯爆炸阻隔技术研究与发展

近年来煤炭生产任务加重,矿井开采深度增加,导致矿井瓦斯事故频发,本文对国内外瓦斯爆炸及阻隔爆技术进行了总结概述,分析了现阶段广泛应用于我国矿山的阻隔爆设施的优缺点,对一些国内外的先进阻隔爆研究成果进行了分析介绍,这些阻隔爆技术及材料能够在一定程度上为我国瓦斯灾害防治工作提供新思路、新方法。     

中国制造业知识特性、规模、经济效益比较分析

本文建立了知识要素对制造业发展的影响模型，并根据模型建立起评价制造业知识特性的指标体系，进而分析了在知识经济条件下，中国制造业的产业结构特征，建立起知识与产业规模，知识与产业经济效益的分类准则，并以此标准对29个制造业进行了分类，揭示了产业知识水平对产业发展的重大影响。     

分类适度管制：放松管制背景下的我国政府管制结构重构

伴随着西方放松管制改革的浪潮,国内学术界也开始呼吁放松管制,但目前我国的政府管制面对的主要是行政垄断问题以及管制结构的不合理。因此,我国政府管制改革,不是“放松管制”的问题,而是管制结构重构的问题：一方面要消灭原来计划体制的管理体制、管理办法和管理方式,消除行政垄断,另一方面要转变管制重点实行分类管制,即根据垄断性产业的业务进行划分实施放松管制的政策;根据不同产业以及同一产业不同时期实施放松管制政策。     

Supply chain environmental investments in dynamic industries: Comparing investment and performance differences with static industries

Research linking investments in environmental practices to firm performance has matured over the past years. However, empirical research is still ambiguous on how and whether investments in environmental practices improve a plant's performance. We believe that contingency factors, especially the industry in which plants act has a significant role in the success of environmental investments. Using empirical data collected across a wide range of industries our results indicate that plants competing in dynamic industries such as apparel do on average invest less in supply chain environmental practices compared to plants in static industries. In addition, these environmental investments do not significantly improve operational performance in dynamic industries in terms of cost, quality, delivery and flexibility. However, in static industries environmental investments do significantly improve a plant's operational performance in terms of cost, quality and flexibility.     

Characteristics and diffusion of technological innovations

The paper examines fourteen post war innovations; five in the flour milling industry, four in the malting industry, and five in the dairy industry. The major work has been carried out in the flour milling industry, with supportive studies in the malting and dairy industries. Examination is made of the characteristics of the innovations as perceived by technical managers who are in a position to influence adoption or non-adoption. The research sets out to study the relationship between the perceived characteristics of the innovations and their diffusion times. It is hoped that the results will be of value to engineering designers and marketing managers in the capital equipment manufacturing industries by enabling them to develop a clearer understanding of adoptors and non-adoptors of innovations and also to study the inter-relationships between different sectors of the industries which they serve. Two forms of profiles of the characteristics of innovations are presented.