旺格维利采矿法矿柱合理尺寸数值模拟

为回收瓦厂坪铝土矿边角矿体并提高矿井资源回收率,本文基于简支梁、固定梁及两区约束理论,结合FLAC~(3D)数值模拟软件,对瓦厂坪铝土矿采用旺格维利采矿法回收边角矿体时刀间矿柱的合理尺寸进行模拟分析,得出刀间矿柱随采硐数目增加所受垂直应力和塑性区的变化规律。结果表明:较合理的刀间矿柱尺寸为1.0 m,1.0 m刀间矿柱能够保护当前回采采硐,且靠近工作面的三到四对刀间矿柱部分发生塑性破坏,能起到临时支撑顶板作用。     

无缝钢管成形件偏心的原因和防治方法

结合无缝钢管冲孔 拔伸工艺 ,分析了钢管锻件产生偏心的原因 ,并从工艺和模具结构方面探讨了防治钢管产生偏心的措施 ,可为生产无缝钢管及其他孔径要求较高的长筒形零件的行业提供参考     

GO法进行有共因失效系统可靠性分析的新算法研究

共因失效可能使系统的可靠性大大降低,是系统可靠性分析中的重点和难点。GO法可以对含共因失效的系统进行可靠性分析。为了选取已有算法合适的参数,更为了提高有多个共因失效组系统的GO法可靠性分析效率,进行了相关研究。对关键参数公式进行了理论分析,并就几个算例系统进行了计算试验;对已有算法进行了深入研究,为了改进已有算法对共因失效组逐个处理,提出了将共因失效组中的部件均由本组等效共因失效部件代替的新算法。进而,应用分组法和新算法对一个简单示例系统和外电源备用系统进行了共因失效分析。给出了对已有算法参数选取的建议;通过对比可知分组法与新算法计算结果相近。通过对已有算法参数的合理化选取,可以提高计算结果的准确度;新算法可对所有共因失效组一次性处理,是共因失效分析的有效方法。     

归州河西沿江高切坡变形破坏及稳定性分析

为了掌握归州河以西沿江公路由于升级改造、工程开挖而产生的大量公路高切坡发育分布特征,总结其变形破坏模式,进而对其稳定性进行分析。在野外实地宏观调查、测量的基础上,通过数据处理,运用赤平投影法对调查区高切坡稳定性进行区划,其中不稳定切坡长约3.8km,占比39.6%,多发育在侏罗系遂宁组(J3s)和聂家山组(J1n)中,主要变形破坏模式为滑移型、倾倒型和剥落型,并根据其破坏模式的差异性提出相应防治对策。     

Equipment failures and their contribution to industrial incidents and accidents in the manufacturing industry

Accidental events in manufacturing industries can be caused by many factors, including work methods, lack of training, equipment design, maintenance and reliability. This study is aimed at determining the contribution of failures of commonly used industrial equipment, such as machines, tools and material handling equipment, to the chain of causality of industrial accidents and incidents. Based on a case study which aimed at the analysis of an existing pulp and paper company's accident database, this paper examines the number, type and gravity of the failures involved in these events and their causes. Results from this study show that equipment failures had a major effect on the number and severity of accidents accounted for in the database: 272 out of 773 accidental events were related to equipment failure, where 13 of them had direct human consequences. Failures that contributed directly or indirectly to these events are analyzed.     

Thermal risk in batch reactors: Case of peracetic acid synthesis

The present paper deals with accidents risk in batch reactors. It identifies the conditions for the occurrence of a thermal runaway and develops a probabilistic approach to assess the relevant risk. It investigates also the conditions for optimal synthesis of peracetic acid (PAA) with hydrogen peroxide (HP) and acetic acid (AA). The kinetic model of reversible reaction and side reaction of PAA synthesis is used to predict reactor temperature and molar ratio of PAA by ASPEN PLUS software. A sensitivity analysis is performed under different conditions such as constant temperature or adiabatic process with different concentrations of sulfuric acid. Assuming a prior cooling system failure, the conditions for reaction runaway triggering a thermal accident are identified in the case of PAA synthesis. Monte Carlo simulations are used in order to calculate the conditional probability of accident and optimize the synthesis of PAA.     

A review of quantitative risk assessment of onshore pipelines

This paper reviews and analyses frequency and consequences of failure of onshore pipelines transporting oil, refined products and natural gas. Generally accepted risk levels are indicated and a desirable risk range is proposed.Pipeline failure statistics from the United States (US), Canada, Europe and Brazil are compared. Failure rates for internal and external corrosion, human action and natural forces are analyzed and the expected failure rate for each failure mechanism is indicated. The effects of relevant construction and environmental factors on the failure frequency are studied and mean trends are obtained. Furthermore, the sizes of the holes indicated at different databases are compared and a typical distribution of failure sizes is proposed for each mode of failure. Finally, the frequency of ignition after a loss of containment is studied for gas and liquid pipelines.Historical data on consequences of the accidental loss of containment of onshore pipelines is reviewed. Property damage and environmental reparation costs are evaluated directly from pipeline failure data. Straightforward regression models are proposed to quantify these types of consequence taking into account the released fluid and the characteristics of the environment. Societal impact is evaluated by combining simple fire models, heat versus mortality correlations and population density.Finally, values for the desired risk level are evaluated by three methods: i) a risk value representing the good engineering practice; ii) the risk associated to the most relevant codes and regulations concerning pipeline risk assessment and/or construction and operation; iii) an analytically derived optimal risk level. The risk values obtained by the three methodologies are similar and a desirable risk range is proposed.     

Implementation of failure modes and effects analysis in detergent production companies: A case study

Failure mode and effect analysis (FMEA) is the most important method used by production companies to identify potential risks regarding occupational and health hazards and environmental hazards. This method is also useful in defining preventive actions to reduce the effects of these risks. Detergent production companies continually encounter many occupational and health hazards and environmental hazards, the management and reduction of which requires complex assessment in real‐world applications. This paper presents a framework for application of FMEA for managing and ranking identified risks in detergent production companies. A case study is presented to show the application of an FMEA to investigate the results of its application and the outcomes from the analysis. A risk priority number (RPN) is proposed for each distinct risk. The application of FMEA in the detergent production company resulted in grouping the RPN of the identified risks into four different categories. The main corrective actions, which are determined to reduce the RPNs, are presented in this paper. Improving the RPN of the main risks is observed after executing the corrective actions.     

On the functional extinction of the Passenger Pigeon

The Passenger Pigeon (Ectopistes migratorius) was a social breeder, and it has been suggested that the species experienced functional extinction, defined as a total reproductive failure, prior to its actual extinction in the early years of the 20th century. We applied a novel randomization test based on the relative times of the most recent egg‐ and skin‐specimen sightings (i.e., recorded date of specimen collection) to test for functional extinction. For a total of 6 eggs and 27 skins, the observed significance level was 0.38, which indicated that the species did not become functionally extinct. Thus, proposals to reverse its rapid decline in the late 19th century could have been successful.