Particle size and surface area effects on explosibility using a 20-L chamber

The Mine Safety and Health Administration (MSHA) specification for rock dust used in underground coal mines, as defined by 30 CFR 75.2, requires 70% of the material to pass through a 200 mesh sieve (<75 μm). However, in a collection of rock dusts, 47% were found to not meet the criteria. Upon further investigation, it was determined that some of the samples did meet the specification, but were inadequate to render pulverized Pittsburgh coal inert in the National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) 20-L chamber. This paper will examine the particle size distributions, specific surface areas (SSA), and the explosion suppression effectiveness of these rock dusts. It will also discuss related findings from other studies, including full-scale results from work performed at the Lake Lynn Experimental Mine. Further, a minimum SSA for effective rock dust will be suggested.     

Post-explosion observations of experimental mine and laboratory coal dust explosions

The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) and the Mine Safety and Health Administration (MSHA) conducted joint research on dust explosions by studying post-explosion dust samples. The samples were collected after full-scale explosions at the PRL Lake Lynn Experimental Mine (LLEM), and after laboratory explosions in the PRL 20-L chamber and the Fike 1 m³ chamber. The dusts studied included both high- and low-volatile bituminous coals. Low temperature ashing for 24 h at 515 °C was used to measure the incombustible content of the dust before and after the explosions. The data showed that the post-explosion incombustible content was always as high as, or higher than the initial incombustible content. The MSHA alcohol coking test was used to determine the amount of coked dust in the post-explosion samples. The results showed that almost all coal dust that was suspended within the explosion flame produced significant amounts of coke. Measurements of floor dust concentrations after LLEM explosions were compared with the initial dust loadings to determine the transport distance of dust during an explosion. All these data will be useful in future forensic investigations of accidental dust explosions in coal mines, or elsewhere.     

Collecting representative dust samples: A comparison of various sampling methods in underground coal mines

Former methods used in the U.S. to assess hazardous and explosible coal dust date back to the 1950s. As mining technologies advanced, so too have the hazards. Given the results of the recent coal dust particle size survey and full-scale experimental mine explosion tests, the National Institute for Occupational Safety and Health (NIOSH) recommended a new minimum standard, in the absence of background methane, of 80% total incombustible content (TIC) be required in the intake airways of bituminous coal mines, replacing the previous 65% TIC requirement. Most important to monitoring and maintaining the 80% TIC is the ability to effectively collect and analyze representative dust samples that would likely disperse and participate in dust explosion propagation. Research has shown that dust suspended on elevated surfaces is usually finer, more reactive, and more readily dispersible while floor deposits of dust are generally coarser and more difficult to disperse given the same blast of air. The roof, rib, and floor portions of the dust samples were collected and analyzed for incombustible content separately and the results were compared to a band sample of the roof, rib, and floor components. Results indicate that the roof and rib dust samples should be kept separate from floor dust samples and considered individually for analyses. The various experimental collection methods are detailed along with preferred sampling approaches that improve the detectability of potentially hazardous accumulations of explosible dust.     

Analysis of “high-dollar” value safety and health citations and orders for the US coal mines

This paper presents an analysis of a “high-dollar” value safety and health citations and orders for the US coal mines using the Mine Safety and Health Administration (MSHA) data. Term “high-dollar” value relates to penalty of $10,000 and more per citation or order. The study was based on historical MSHA data for the period from 01/01/2009 to 12/31/2009. Data shows that there were 1161 “high-dollar” value citations and orders in 2009 with a total penalty of almost $31-million. The most cited standard was 75.400 – “Accumulation of combustible material” with a 259 “high-dollar” value citations and total penalty of almost $5.9-million. Among all US states, the West Virginia coal mines recorded the highest number of citations and the total penalty value. Results of this study can be used by coal mining industry to help in prioritizing resource allocations and determining control strategies.     

A methodology for assessing underground coal mines for high safety-related risk

In 2008 the authors developed a methodology for assessing underground coal mines for high risk for major-hazard events. It focused on major hazard-related violations of safety standards associated with high-risk conditions. Later using the same stratified pilot sample of 31 mines, injury measures and MSHA citation data were combined into a Safe Performance Index (SPI). Using 2009 data, the database was expanded to 107 mines, which is a 30% sampling of all underground coal mines. The SPI was used to assess the relative safety-related risk of mines, including by mine-size category. The methodology can be used to assist companies, the Mine Safety and Health Administration, or state agencies in targeting mines with high risk for serious injuries and elevated citations for remediation of their violation and/or injury experience.     

Pilot sample risk analysis for underground coal mine fires and explosions using MSHA citation data

After three decades of sustained continuous improvement of mine safety performances in the US, mine disasters in 2006 and 2007 compromised an excellent record and presented new challenges and vulnerabilities for the underground coal mining industry. In the aftermath of the incidents, formal investigations and new scrutiny of mine safety by the US Congress and expert study groups followed. The US Congress passed the Mine Improvement and New Emergency Response Act of 2006 (MINER Act), which mandated new laws to address the issues, including those related to mine fires and explosions from which miners must be protected. The National Mining Association-sponsored Mine Safety Technology and Training Commission report highlighted the role of risk analysis and management in identifying and controlling major hazards, such as fires and explosions. In this paper an approach is given for analyzing the risks for fires and explosions based on the Mine Safety and Health Administration citation database. Using 2006 citation data and focusing on subsystem failures, the methodology is applied to a database for a pilot sample of underground coal mines stratified by mine size and state.     

Ignition of methane–air mixtures by laser heated small particles

Optical technologies have progressed rapidly in the past 15 years. One application of laser technology in underground coal mines currently under evaluation is the remote measurement of explosive methane gas. Federal regulations require that atmospheric monitoring systems used in gassy underground mines where permissible equipment is required shall be intrinsically safe. Mine Safety and Health Administration criteria for the evaluation and testing of intrinsically safe apparatus and associated apparatus contain no specific guidance for optoelectronic components such as diode lasers. The National Institute for Occupational Safety and Health is conducting a study to help provide a scientific basis for developing appropriate safety guidelines for optical equipment in underground coal mines. Results of experiments involving ignition of methane–air mixtures by collections of small heated particles of Pittsburgh seam coal and black iron oxide are reported. The inert but more strongly absorbing iron oxide targets consistently ignited methane–air mixtures at lower powers than the coal targets. Minimum observed igniting powers for laser energy delivered by 200, 400 and 800 μm core fiber optic cables and directed onto iron oxide targets in methane–air atmospheres were 0.6, 1.1, and 2.2 W, respectively. Comparisons with the results of other researchers are made. A thermal layer theoretical approach to describing the process is included as an appendix.     

中国煤矿安全技术进展

本文综述了我国在防治矿井瓦斯,矿井火灾和煤矿粉尘三个方面的技术概况。反映了为适应煤炭生产技术的发展,我国在这三方面的技术进展及所取得的效果。矿井瓦斯防治技术方面,主要介绍了矿井瓦斯涌出量的确定,瓦斯抽放工艺及装备,煤与瓦斯突出预测预报和综合防止煤与瓦斯突出技术的情况及成果。矿井火灾防治技术方面,着重介绍了矿井火灾预测预报技术,尤其是煤炭自燃发火早期预测预报技术以及煤矿自然发火防治技术中在灌浆代用材料,惰气防灭火等方面的发展及现状。煤矿粉尘防治技术方面,扼要介绍控制粉尘危险的基本途径,以防尘为中心包括降尘、除尘和防止煤尘爆炸及爆炸传播技术的一整套治理煤矿粉尘的工艺及装备,简要介绍了瓦斯煤尘爆炸的实验能力。通过本文的介绍,可以对我国在防治煤矿安全生产中主要自然灾害的技术对策和取得的成果有一个较全面的了解。     

An analysis of equipment-related fatal accidents in U.S. mining operations: 1995–2005

Despite significant reductions in mining fatalities, the number of these accidents remains high. Based on the number of fatalities per year, a persistent area of concern in mine safety continues to be equipment-related. The study was undertaken in order to more thoroughly characterize equipment-related mining fatalities and to perform an analysis of those that occurred over the last 11-years, from 1995 through 2005. Equipment-related fatalities obtained from the Mine Safety and Health Administration (MSHA) reports are used in this study. Results show that the proportion of total mine fatalities attributable to the equipment ranged from 37% to 88% per year. Among the MSHA equipment subcategories, the greatest proportion of fatalities is related to haul trucks (22.3%), belt conveyors (9.3%), front-end loaders (8.5%), and miscellaneous equipment (36.6%). The relationship between number of equipment-related fatalities and mining experience of the workforce was also examined. Study shows that workers with less than five years of appropriate mining experience constitute 44% of all fatalities that occurred during the period of 1995–2005.     

The potential impact of light emitting diode lighting on reducing mining injuries during operation and maintenance of lighting systems

Research by the US National Institute for Occupational Safety and Health (NIOSH) indicates that light emitting diodes (LEDs) can be used to enhance safety by improving a miner’s ability to see mining hazards and reducing glare. This paper investigates if LEDs provide another benefit by reducing miner exposure to hazards during maintenance and operation of LED lighting. LEDs could provide useful lives up to 50 times longer than incandescent lighting commonly used in mining and could enable design changes to reduce certain hazards. The mining accident records compiled by the Mine Safety and Health Administration (MSHA) were examined to determine the extent and nature of accidents involving the maintenance and operation of mine luminaries. A total of 140 relevant accident records were found for the years 2002–2006. These incidents resulted in 3668 days lost from work with an additional 925 days of restricted activity. The injury narratives were studied to determine if the implementation of LED-based luminaries could reduce injury severity and frequency. The greatest near-term potential impacts appear to be related to reducing maintenance and cap lamp redesign. Longer term (5 years), low-power and lightweight auxiliary LED lighting for surface mines could also have potential impact for improving safety.     

沁海煤矿瓦斯重大灾害及生产动态安全状况诊断

按照《煤矿安全规程》2010版制成安全检查表,运用安全检查表法和系统分析的方法对煤矿的主要系统存在的隐患进行逐项诊断,主要诊断矿井的瓦斯抽放系统、矿井的通风系统、矿井的防尘系统、矿井的防灭火系统以及矿井运输提升系统等。诊断主要是针对瓦斯重大灾害及矿井生产过程中违章违规现象以及矿井自然属性带来的系统固有隐患,对矿井中员工的操作规范情况也进行检查,并对存在的隐患和员工的错误操作提出相应的整改措施,促使煤矿及时对矿井存在的系统固有隐患和人为隐患进行整改,以消除在生产动态过程中查出的隐患,从而预防煤矿事故的发生。消灭了事故隐患,实际上也是把事故消灭在萌芽状态之中,达到防患于未然,提高我国煤矿安全生产水平。     

固体惰性介质对煤粉爆炸压力的影响研究

通过对固体惰性介质在减轻煤粉爆炸作用的实验研究,给出影响固体惰化剂作用效果的主要影响因素。实验分别选用来自加拿大和中国的3种煤粉和石灰石,对每种实验样品的成分、粒度都进行分析。用20L球形容器进行实验,测定煤粉中加入不同含量的石灰石后煤粉爆炸的Pmax和(dp/dt)max值。结果表明,石灰石能够起到减轻煤粉爆炸影响的作用,并且随着煤粉粒度的减小,要达到相同的抑爆效果需要的石灰石的用量将加大。     

采煤工作面粉尘状况与防尘工作重点

本文介绍了近几年来对我国部分煤矿采煤工作面粉尘状况的调查,测试和煤矿粉尘粒度分布分析结果。通过测试分析证明,不同煤种的煤被外部能量破碎时,它的产尘量、产生的粉尘的粒度分布及粉尘中呼吸性粉尘含量不同;各种煤直接破碎产生的粉尘和矿井空气的浮游粉尘的粒度分布均符合罗辛——拉姆勒(Rosin——Rammlar)分布规律;采用一般常规防尘措施(如煤体注水、洒水、喷雾降尘等),对粒度较粗的粉尘有一定降尘效果,可改善粉尘作业环境,而对工人身体健康影响较大的呼吸性粉尘降尘效果不显著,造成矿井浮游粉尘中呼吸性粉尘含量增加。为此,今后防尘工作重点应加强对呼吸性粉尘控制技术的研究,推广、应用对呼吸性粉尘除尘效率高的防尘措施,大幅度降低矿井中呼吸性粉尘.使煤矿尘肺病发病率有较大降低。     

Limiting oxygen concentration for coal dusts for explosion hazard analysis and safety

Investigation of explosion characteristics of coal dust was undertaken as a part of regular research program at CSIR-CBRI, Roorkee, India, for designing explosion safety measures for coal dust handling installations. This paper presents results of detailed experimental work on determination of Limiting Oxygen Concentration (LOC) and influence of reduced oxygen levels on explosion severity data for two types of coals with varying volatile matter as 27.18% (coal A) and 19.69% (coal B) from Jharia coalfield of India determined at ambient conditions with 20-L Spherical Vessel established at CSIR-CBRI. The effects of coal particle size and moisture content were evaluated. Data presented will be used for hazard analysis, designing explosion preventive measures, and explosion severity reduction by involving the use of inert gases for installations handling pulverized coal with similar nature. The importance of ignition source energy in determining LOC data is highlighted. The data collected lead to an extension of the current data for coal dusts as found in the literature. Limiting oxygen concentrations were found as 7% for coal A and 8% for coal B for the size representative to that used in pulverized coal boilers and moisture content ～4%.     

安太堡露天煤矿职业健康安全管理体系绩效分析

通过对安太堡露天煤矿职业健康安全管理体系认证前后安全生产管理基础数据的调查和统计,采用定性和定量的分析方法对该企业的安全管理水平进行了绩效对比分析和模型分析。结果表明,对于露天煤矿企业,建立职业健康安全管理体系有利于提高企业安全管理的水平;同时证明,该绩效分析方法具有分析过程简单、分析结果科学实用等优点。     

Underground coal mining injury: A look at how age and experience relate to days lost from work following an injury

Coal has been mined in the United States since colonial times and coal mining has always been a dangerous occupation. Despite the dangers involved in coal mining, coal is essential to the functioning of our society. Coal provides energy for products, businesses, and homes. Not only is coal mining a dangerous occupation, but, like many other industries, coal mining has also been referred to as a “graying occupation” as many coal miners are reaching retirement age. Younger workers possess certain advantages as older workers may have age-associated decrements in cognitive function, health, and recuperative ability. Although there are documented decreases in health and safety associated with age, there are also benefits at the workplace associated with increasing age. Increasing age brings about more experience and familiarity with the work environment. This study used the Mine Safety and Health Administration’s (MSHA) database on accidents, injury, and illness from the years 2003 through 2007 to examine how age, experience at the current mine, total years experience as a coal miner, and experience in the current job affects injury severity. The results of the data indicated that there was a relationship between age and days lost as well as total mining experience and days lost following an injury. Furthermore, the data indicated an increased risk of overexertion injuries as age increases. These are important findings for the coal mining industry as many miners are more experienced and older.     

考虑煤体粒度的落煤瓦斯涌出预测模型研究*

为了探究不同煤体粒度对于工作面瓦斯涌出的影响规律,以王家岭煤矿为研究对象,通过现场测试分析采落煤与放落煤的粒度分布,采用数值模拟计算不同粒度煤体的瓦斯涌出特征;并推导采落煤和放落煤的瓦斯涌出预测模型,对模型进行现场应用。研究结果表明:王家岭煤矿采落煤粒度分布范围更广,存在较高比例的微小粒度和大粒度煤体;煤体粒度越小,则瓦斯涌出速度越快。采落煤和放落煤的综合涌出强度均可以用指数函数来描述,模型计算结果与现场实际数据误差在合理范围内。     

计算机网络考试系统在山西煤矿安全培训中的应用实践

安全培训在煤矿安全管理中发挥着重要的作用。山西煤炭资源丰富,有包括地方、乡镇在内的煤矿4000余个,更需要通过科学、公正的考核手段保证安全培训质量,提高煤矿企业负责人的素质来保证煤矿的安全生产。传统的安全培训考试由于受到人力、物力和人情关系等主客观因素的影响,难以达到完全的公平、公正。而计算机网络考试通过题库随机出题、标准化判卷等技术手段恰好可以解决这些问题。由山西煤矿安全监察局组织开发的“山西省煤矿安全培训考试系统”,经过一年多安全培训考核的实践,取得良好的效果,基本实现了预期的设想。该系统的开发和应用为安全培训的科学化、规范化,为提高各类煤矿企业负责人的素质作出了有益的尝试。     

Experimental mine and laboratory dust explosion research at NIOSH

This paper describes dust explosion research conducted in an experimental mine and in a 20-L laboratory chamber at the Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH). The primary purpose of this research is to improve safety in mining, but the data are also useful to other industries that manufacture, process, or use combustible dusts. Explosion characteristics such as the minimum explosible concentration and the rock dust inerting requirements were measured for various combustible dusts from the mining industries. These dusts included bituminous coals, gilsonite, oil shales, and sulfide ores. The full-scale tests were conducted in the Lake Lynn experimental mine of NIOSH. The mine tests were initiated by a methane–air explosion at the face (closed end) that both entrained and ignited the dust. The laboratory-scale tests were conducted in the 20-L chamber using ignitors of various energies. One purpose of the laboratory and mine comparison is to determine the conditions under which the laboratory tests best simulate the full-scale tests. The results of this research showed relatively good agreement between the laboratory and the large-scale tests in determining explosion limits. Full-scale experiments in the experimental mine were also conducted to evaluate the explosion resistance characteristics of seals that are used to separate non-ventilated, inactive workings from active workings of a mine. Results of these explosion tests show significant increases in explosion overpressure due to added coal dust and indications of pressure piling.     

Analysis of fatalities and injuries involving mining equipment

INTRODUCTION: Despite significant reductions, the number of injuries and fatalities in mining remains high. A persistent area of concern continues to be equipment-related incidents. METHOD: Mine Safety and Health Administration (MSHA) and Current Population Survey (CPS) data were used to examine equipment-related injuries over the period 1995-2004. Incidents were reviewed to determine which types of mining equipment were most often involved and to identify and characterize trends. RESULTS: Non-powered hand tools was the equipment category most often involved with non-fatal injuries while off-road ore haulage was the most common source of fatalities. SUMMARY: Younger employees had an elevated risk of injury while workers >55 years had an elevated risk for fatality. A large majority of incidents involve workers with <5 years experience. IMPACT ON INDUSTRY: Results should increase hazard awareness and enable mine management to select and prioritize problem areas and safety system weaknesses in both underground and surface mining.