Last data update: May 06, 2024. (Total: 46732 publications since 2009)
Records 1-19 (of 19 Records) |
Query Trace: Shahan M[original query] |
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Laboratory results of foam application testing for longwall shield dust control in a simulated environment
Reed WR , Shahan MR , Zheng Y , Mazzella A . Int J Coal Sci Technol 2021 8 (2) 217-227 There were 37 longwall faces operating in mines in the United States in 2019. The average panel width for these longwalls was approximately 368.5 m (1209 ft). This translates to a range of approximately 170–240 shields per longwall, depending upon the width of shield. The movement of longwall shields is a significant contributor to respirable dust overexposures to longwall operators. Foam is expected to have the potential to reduce this shield dust generation. The foam is applied to the area on the roof between the coal face and the shield tip after the shearer passes. In this study, the longwall shield dust simulator was used to test three foam agents for their ability to control dust from longwall shield movements. Results showed that at low-velocity ventilation (≈ 3.0 m/s (600 fpm)) all foam agents were able to produce dust reduction levels of at least 45%. At high-velocity ventilation (≈ 5.1 m/s (1000 fpm)), the reductions were lower and more variable, ranging from being undeterminable for one foam agent to having 46%–63% reductions for the other two foam agents, with one instance of an increase in dust concentration. Overall, the use of foam agents can provide longwall shield dust control. Important factors are roof coverage and the ability of foam to remain on the roof for extended time periods. |
Field testing of roof bolter canopy air curtain operating downwind of the continuous miner
Reed WR , Shahan M , Gangrade V , Ross G , Singh K , Grounds T . Min Metall Explor 2020 38 (1) 581-592 Roof bolter canopy air curtains (CACs) are gaining acceptance as a respirable dust control device that can provide roof bolter operators with protection from overexposure to respirable coal mine dust. Both lab and field studies on the effectiveness of roof bolter CACs have been published. Field studies have shown the effectiveness to be variable. However, in all previous field studies, none has been conducted when the roof bolting machine operates downwind of the continuous miner (CM)—a scenario for which the CAC was designed to provide respirable dust control. This study, performed by researchers from the National Institute for Occupational Safety and Health (NIOSH), was conducted to test a CAC on a roof bolter machine operating downwind of the CM. The results of testing demonstrated that the roof bolter CAC can effectively provide respirable dust protection for roof bolter operators with dust control efficiencies ranging from 11 to 40%. |
Field comparison of a roof bolter dry dust collection system with an original designed wet collection system for dust control
Reed WR , Shahan M , Ross G , Blackwell D , Peters S . Min Metall Explor 2020 37 1885-1898 Dust collectors for roof bolting machines generally use a dry box to collect the roof bolting material. Recently, an underground mining operation converted a dry box dust collector to a wet box dust collector with a unique exception from MSHA for testing purposes. Water is routed to the roof bolter from the main water line of the continuous miner. The wet box utilizes a water spray to wet the incoming material. Testing was conducted comparing the two different collector types. Respirable dust concentrations surrounding the roof bolter with the different collection boxes were similar. The main difference in respirable dust concentrations occurred when cleaning the dust boxes. The average respirable dust concentration during cleaning of the wet box was 0.475 mg/m3, and during the cleaning of the dry box, the average respirable dust concentration was 1.188 mg/m3, a 60% reduction in respirable dust concentration. The quartz content of the roof material was high, ranging from 28.9 to 52.7% during this study. The results from this study indicate that using the wet box as a collector reduced exposure to respirable dust up to 60% when cleaning the collector boxes. |
Design of a water curtain to reduce accumulations of float coal dust in longwall returns
Seaman CE , Shahan MR , Beck TW , Mischler SE . Int J Min Sci Technol 2020 30 (4) 443-447 Accumulation of float coal dust (FCD) in underground mines is an explosion hazard that affects all underground coal mine workers. While this hazard is addressed by the application of rock dust, inadequate rock dusting practices can leave miners exposed to an explosion risk. Researchers at the National Institute for Occupational Safety and Health (NIOSH) have focused on developing a water curtain that removes FCD from the airstream, thereby reducing the buildup of FCD in mine airways. In this study, the number and spacing of the active sprays in the water curtain were varied to determine the optimal configuration to obtain peak knockdown efficiency (KE) while minimizing water consumption. |
Characterization of aerosols in an underground mine during a longwall move
Bugarski AD , Hummer JA , Vanderslice S , Shahan MR . Min Metall Explor 2020 37 (4) 1065-1078 A study was conducted in an underground mine with the objective to identify, characterize, and source apportion airborne aerosols at the setup face and recovery room during longwall move operations. The focus was on contributions of diesel- and battery-powered heavy-duty vehicles used to transfer equipment between the depleted and new longwall panels and diesel-powered light-duty vehicles used to transport personnel and materials to various locations within the mine. Aerosols at the setup face were found to be distributed among diesel combustion-generated submicrometer and mechanically generated coarse aerosols. According to the data, the submicrometer aerosols downstream of the setup face were sourced to diesel exhaust emitted by vehicles operated inside and outside of the panel. Depending on the intensity of the activities on the panel, the outby sources contributed between 12.5 and 99.6% to the average elemental carbon mass flow at the setup face and recovery room. Extensively used light-duty vehicles contributed measurably to the elemental carbon concentrations at the setup face. The number concentrations of aerosols downstream of the setup face were associated with aerosols generated by combustion in diesel engines operated in the shield haulage loop and/or outside of the longwall panels. Entrainment of road dust by diesel or battery-powered load-haul-dump vehicles operated near the measurement site appears to be the primary source of mass concentrations of aerosols. The findings of this study should help the underground mining industry in its efforts to reduce exposures of miners to diesel and coarse aerosols. |
Field study results of a 3rd generation roof bolter canopy air curtain for respirable coal mine dust control
Reed WR , Shahan M , Klima S , Ross G , Singh K , Cross R , Grounds T . Int J Coal Sci Technol 2019 7 (1) [Epub ahead of print] A 3rd generation roof bolter canopy air curtain (CAC) has been developed and constructed by J.H. Fletcher & Co., Inc. As with the previous generation of the CAC, this design uses the principle of providing uniform airflow across the canopy area as recommended by the National Institute for Occupational Safety and Health. The new modifications include a plenum that is constructed of a single flat aluminum plate, smaller-diameter airflow openings, and a single row of perimeter nozzles designed to prevent mine air contaminated by respirable dust from entering the CAC protection zone. Field testing was conducted on this new 3rd generation design showing reductions in coal mine respirable dust exposure for roof bolter operators. Dust control efficiencies for the CAC for the left bolter operator (intake side) ranged from approximately 26%-60%, while the efficiencies for the CAC for the right bolter operator (return side) ranged from 3% to 47%. |
The design of a laboratory apparatus to simulate the dust generated by longwall shield advances
Shahan MR , Reed WR . Int J Coal Sci Technol 2019 6 A laboratory apparatus (shield dust simulator) was designed and constructed to simulate the dust generated during the advance of longwall hydraulic roof supports, or shields. The objective of the study was to develop a tool that could be used to test the hypothesis that foam applied to a mine roof prior to a shield advance could be used to reduce the respirable dust generated during shield advances. This paper will outline the design parameters for the development of the system, as well as describe baseline testing of coal and limestone dust. Results show that the average instantaneous respirable dust concentrated during simulated shield advance. Confidence intervals were calculated from the instantaneous respirable dust data to determine the repeatability of the data produced by the device. |
Field investigation to measure airflow velocities of a ram dump car using circular routing at a Midwestern underground coal mine: a case study
Reed WR , Shahan M , Ross G , Singh K , Cross R , Grounds T . Environ Monit Assess 2019 191 (8) 515 Due to the successful application of roof bolter canopy air curtains (CACs) to protect roof bolter operators from high levels of coal mine respirable dust, a shuttle car CAC is currently being developed. Since a shuttle car consistently trams from the continuous miner to the feeder and back at a speed up to 9.66 kph (6 mph) or 2.68 m/s (528 fpm), it is thought that the shuttle car may encounter very high air velocities (mine ventilation air velocity + max shuttle speed (2.68 m/s (528 fpm)). Past research and preliminary lab testing showed that CAC protection in high interference air velocities is difficult to achieve. Therefore, testing was conducted at a Midwestern US coal mine to determine the air velocities their shuttle car actually encounters. This mine used ram dump cars as their shuttle cars. Results showed that coal mine dust exposure is generally very low at the feeder and when tramming. Elevated concentrations are encountered at the ram dump car operator position when the car is being loaded by the continuous miner. Recorded air velocities while tramming did not reach the max air velocity of mine ventilation air velocity + 2.68 m/s (528 fpm) calculated as 3.32 m/s (653 fpm). High velocities, while encountered, were of low frequency and associated with low respirable coal mine dust concentrations. Therefore, using this new information, designing the shuttle car CAC for maximum interference air velocity may not be as important as previously thought. |
Evaluation of roof bolter canopy air curtain effects on airflow and dust dispersion in an entry using blowing curtain ventilation
Zheng Y , Reed WR , Shahan MR , Rider JP . Min Metall Explor 2019 36 (6) [Epub ahead of print] Roof bolter operators may be exposed to high respirable dust concentrations on continuous miner sections with blowing face ventilation when bolting is performed downwind of the continuous miner. One solution to reduce the high respirable dust concentrations is to use a canopy air curtain (CAC) to deliver clean air from a filtered blower fan directly to the bolter operators under the canopies. The influence of CAC installation in the airflow and dust dispersion around the location of the roof bolter operator can be evaluated by using computational fluid dynamics (CFD). This study, performed by the National Institute for Occupational Safety and Health (NIOSH), considers two scenarios: (1) a roof bolting machine in the center of the entry for installation of the fifth row of bolts from the face, and (2) a roof bolting machine positioned close to the face for the installation of the last row of bolts. In both scenarios, the bolting machine is placed in an environment which contains 6.0 mg/m3 of respirable dust and is ventilated by a blowing curtain with 3000 cfm (1.42 m3/s) of air. This environment is used to simulate the roof bolter machine operating downstream of a continuous mining machine. Two operation positions are simulated at the same bolting location: dual drill heads in the inward position for two inside bolts and dual drill heads in the outward position for two outside bolts. The influence of the CAC on airflows and dust dispersion is evaluated with the CAC operating at 250 cfm (0.12 m3/s). |
Laboratory results of a 3rd generation roof bolter canopy air curtain for respirable coal mine dust control
Reed WR , Joy GJ , Shahan M , Klima S , Ross G . Int J Coal Sci Technol 2019 6 (1) 15-26 Testing was completed on an earlier roof bolter CAC that used slots to provide a perimeter airflow. NIOSH tested it due to its unique design that differed from canopies that provided uniform airflow. Based upon NIOSH recommendations from the earlier testing, a 3rd generation roof bolter CAC has been developed by J.H. Fletcher & Co. The changes to this CAC involve design modifications to the plenum outlets, using a single row of outlets on the perimeter and a different material for the plenum. This laboratory testing was a continuation of the original perimeter slotted CAC design. Using gravimetric and instantaneous sampling of respirable dust concentrations underneath and outside of the CAC, the laboratory testing was completed using three different blower fans that delivered differing airflows. The maximum plenum airflow velocities ranged from 2.34 to 3.64 m/s (460–716 fpm). Results showed plenum respirable dust concentrations ranging from 34.6% to 49.3% lower than respirable dust concentrations outside the plenum protection zone, thus showing an improvement in protection for the roof bolter operators. |
A field study of a roof bolter canopy air curtain (2nd generation) for respirable coal mine dust control
Reed WR , Klima S , Shahan M , Ross GJH , Singh K , Cross R , Grounds T . Int J Min Sci Technol 2019 29 (5) 711-720 A 2nd generation roof bolter canopy air curtain (CAC) design was tested by National Institute for Occupational Safety and Health (NIOSH) at a Midwestern underground coal mine. During the study, the roof bolter never operated downwind of the continuous miner. Using a combination of personal Data Rams (pDR) and gravimetric samplers, the dust control efficiency of the roof bolter CAC was ascertained. Performance evaluation was determined using three methods: (1) comparing roof bolter operator concentrations underneath the CAC to roof bolter concentrations outside the CAC, (2) comparing roof bolter operator concentrations underneath the CAC to the concentrations at the rear of the bolter, and finally, (3) using the gravimetric data directly underneath the CAC to correct roof bolter operator concentrations underneath the CAC and comparing them to the concentrations at the rear of the bolter. Method 1 dust control efficiencies ranged from −53.9% to 60.4%. Method 2 efficiencies ranged from −150.5% to 52.2%, and Method 3 efficiencies ranged from 40.7% to 91%. Reasons for negative and low dust control efficiencies are provided in this paper and include: incorrect sampling locations, large distance between CAC and operator, and contamination of intake air from line curtain. Low dust concentrations encountered during the testing made it difficult to discern whether differences in concentrations were due to the CAC or due to variances inherent in experimental dust measurement. However, the analyses, especially the Method 3 analysis, show that the CAC can be an effective dust control device. |
An alternative approach to relapse analysis: using Monte Carlo methods and proportional rates of response
Friedel JE , Galizio A , Berry MS , Sweeney MM , Odum AL . J Exp Anal Behav 2018 111 (2) 289-308 Relapse is the recovery of a previously suppressed response. Animal models have been useful in examining the mechanisms underlying relapse (e.g., reinstatement, renewal, reacquisition, resurgence). However, there are several challenges to analyzing relapse data using traditional approaches. For example, null hypothesis significance testing is commonly used to determine whether relapse has occurred. However, this method requires several a priori assumptions about the data, as well as a large sample size for between-subjects comparisons or repeated testing for within-subjects comparisons. Monte Carlo methods may represent an improved analytic technique, because these methods require no prior assumptions, permit smaller sample sizes, and can be tailored to account for all of the data from an experiment instead of some limited set. In the present study, we conducted reanalyses of three studies of relapse (Berry, Sweeney, & Odum, ; Galizio et al., ; Odum & Shahan, ) using Monte Carlo techniques to determine if relapse occurred and if there were differences in rate of response based on relevant independent variables (such as group membership or schedule of reinforcement). These reanalyses supported the previous findings. Finally, we provide general recommendations for using Monte Carlo methods in studies of relapse. |
Field investigation to measure airflow velocities of a shuttle car using independent routes at a central Appalachian underground coal mine
Shahan M , Reed WR , Yekich M , Ross G . Min Eng 2018 70 (11) 41-47 Canopy air curtains on roof bolting machines have been proven to protect miners from respirable dust, preventing their overexposure to dust. Another desired application for canopy air curtains is in the compartments of shuttle cars. The challenges faced in developing the design of canopy air curtains for shuttle cars include mine ventilation rates in tandem with the shuttle car tram speeds. The resulting cab airspeeds may exceed 182 m/min (600 fpm), as found in the present study conducted in a central Appalachian underground coal mine by U.S. National Institute for Occupational Safety and Health (NIOSH) researchers. Prior research and laboratory testing had indicated that successfully protecting a miner in high air velocities is difficult, because the clean air from the canopy air curtain is unable to penetrate through the high-velocity mine air. In this study, the dust concentrations to which a shuttle car operator was exposed were measured, and air velocities experienced by the operator were measured as well using a recording vane anemometer. The results indicate that the highest exposure to respirable dust, 2.22 mg/m3, occurred when the shuttle car was loading at the continuous miner, where the average airspeed was 48 m/min (157 fpm). While tramming, the operator was exposed to 0.77 mg/m3 of respirable dust with an average airspeed of 62 m/min (203 fpm). This study indicates that a canopy air curtain system can be designed to greatly reduce an operator's exposure to respirable dust by providing clean air to the operator, as the majority of the operator's dust exposure occurs in air velocities slower than 61 m/min (200 fpm). |
Open-air sprays for capturing and controlling airborne float coal dust on longwall faces
Beck TW , Seaman CE , Shahan MR , Mischler SE . Min Eng 2018 70 (1) 42-48 Float dust deposits in coal mine return airways pose a risk in the event of a methane ignition. Controlling airborne dust prior to deposition in the return would make current rock dusting practices more effective and reduce the risk of coal-dust-fueled explosions. The goal of this U.S. National Institute for Occupational Safety and Health study is to determine the potential of open-Air water sprays to reduce concentrations of airborne float coal dust, smaller than 75 microm in diameter, in longwall face airstreams. This study evaluated unconfined water sprays in a featureless tunnel ventilated at a typical longwall face velocity of 3.6 m/s (700 fpm). Experiments were conducted for two nozzle orientations and two water pressures for hollow cone, full cone, flat fan, air atomizing and hydraulic atomizing spray nozzles. Gravimetric samples show that airborne float dust removal efficiencies averaged 19.6 percent for all sprays under all conditions. The results indicate that the preferred spray nozzle should be operated at high fluid pressures to produce smaller droplets and move more air. These findings agree with past respirable dust control research, providing guidance on spray selection and spray array design in ongoing efforts to control airborne float dust over the entire longwall ventilated opening. |
Comparison of the CAS-POL and IOM samplers for determining the knockdown efficiencies of water sprays on float coal dust
Seaman CE , Shahan MR , Beck TW , Mischler SE . J Occup Environ Hyg 2017 15 (3) 0 Float coal dust, generated by mining operations, is distributed throughout mine airways by ventilating air designed to purge gases and respirable dust. Float coal dust poses an explosion hazard in the event of a methane ignition. Current regulation requires the application of inert rock dust in areas subjected to float coal dust in order to mitigate the hazard. An alternate method using water sprays, which have been effective in controlling respirable dust hazards, has been proposed as a way to control float coal dust generated on longwall faces. However, the knockdown efficiency of the proposed water sprays on float coal dust needs to be verified. This study used gravimetric isokinetic Institute of Occupational Medicine (IOM) samplers alongside a real-time aerosol monitor (Cloud Aerosol Spectrometer with polarization; CAS-POL) to study the effects of spray type, operating pressure, and spray orientation on knockdown efficiencies for seven different water sprays. Because the CAS-POL has not been used to study mining dust, the CAS-POL measurements were validated with respect to the IOM samplers. This study found that the CAS-POL was able to resolve the same trends measured by the IOM samplers, while providing additional knockdown information for specific particle size ranges and locations in the test area. In addition, the CAS-POL data was not prone to the same process errors, which may occur due to the handling of the IOM filter media, and was able to provide a faster analysis of the data after testing. This study also determined that pressure was the leading design criteria influencing spray knockdown efficiency, with spray type also having some effect and orientation having little to no effect. The results of this study will be used to design future full-scale float coal dust capture tests involving multiple sprays, which will be evaluated using the CAS-POL. |
Experimental study on foam coverage on simulated longwall roof
Reed WR , Zheng Y , Klima S , Shahan MR , Beck TW . Trans Soc Min Metall Explor Inc 2017 342 (1) 72-82 Testing was conducted to determine the ability of foam to maintain roof coverage in a simulated longwall mining environment. Approximately 27 percent of respirable coal mine dust can be attributed to longwall shield movement, and developing controls for this dust source has been difficult. The application of foam is a possible dust control method for this source. Laboratory testing of two foam agents was conducted to determine the ability of the foam to adhere to a simulated longwall face roof surface. Two different foam generation methods were used: compressed air and blower air. Using a new imaging technology, image processing and analysis utilizing ImageJ software produced quantifiable results of foam roof coverage. For compressed air foam in 3.3 m/s (650 fpm) ventilation, 98 percent of agent A was intact while 95 percent of agent B was intact on the roof at three minutes after application. At 30 minutes after application, 94 percent of agent A was intact while only 20 percent of agent B remained. For blower air in 3.3 m/s (650 fpm) ventilation, the results were dependent upon nozzle type. Three different nozzles were tested. At 30 min after application, 74 to 92 percent of foam agent A remained, while 3 to 50 percent of foam agent B remained. Compressed air foam seems to remain intact for longer durations and is easier to apply than blower air foam. However, more water drained from the foam when using compressed air foam, which demonstrates that blower air foam retains more water at the roof surface. Agent A seemed to be the better performer as far as roof application is concerned. This testing demonstrates that roof application of foam is feasible and is able to withstand a typical face ventilation velocity, establishing this technique's potential for longwall shield dust control. |
Characterization of airborne float coal dust emitted during continuous mining, longwall mining and belt transport
Shahan MR , Seaman CE , Beck TW , Colinet JF , Mischler SE . Min Eng 2017 69 (9) 61-66 Float coal dust is produced by various mining methods, carried by ventilating air and deposited on the floor, roof and ribs of mine airways. It deposited, float dust is re-entrained during a methane explosion. Without sufficient inert rock dust quantities, this float coal dust can propagate an explosion throughout mining entries. Consequently, controlling float coaf dust is of critical interest to mining operations. Rock dusting, which is the adding of inert material to airway surfaces, is the main control technique currently used by the coal mining industry to reduce the float coal dust explosion hazard. To assist the industry in reducing this hazard, the Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health initiated a project to investigate methods and technologies to reduce float ooal dust in underground coal mines through prevention, capture and suppression prior to deposition. Field characterization studies were performed to determine quantitatively the sources, types and amounts of dust produced during various coal mining processes. The operations chosen for study were a continuous miner section, a longwall section and a coal-handling facility. For each of these operations, the primary dust sources were confirmed to be the continuous mining machine, longwall shearer and conveyor belt transfer points, respectively. Respirable and total airborne float dust samples were collected and analyzed for each operation, and the ratio of total airborne float coal dust to respirable dust was calculated. During the continuous mining process, the ratio of total airborne float ooal dust to respirable dust ranged from 10.3 to 13.6. The ratios measured on the longwall face were between 1B.5 and 21.5. The total airborne float coal dust to respirable dust ratio observed during belt transport ranged between 7.5 and 21.8. |
Opto-dielectrometric sensor for measuring total incombustible content in underground coal mines
Mahdavipour O , Jain A , Sabino J , Wright P , White RM , Shahan MR , Seaman CE , Patts LD , Paprotny I . IEEE Sens J 2017 17 (9) 6443 - 6450 Coal dust produced during underground coalmining, i.e. float dust, which deposits throughout the coal mine can be feedstock for coal dust explosions. To prevent these explosions, inert rock dust (limestone dust) is applied to roof, floor, and ribs areas of a coal mine. The ratio of incombustible mass (rock dust + incombustible content of coal dust) divided by total mass of the deposited dust is defined as the Total Incombustible Content (TIC) of the deposited dust within the mine. Regulations require that a minimum TIC ratio (80%;) to be maintained for safe working conditions inside the mine. This paper presents design, fabrication and experimental results for a real-time sensing module which uses continuous optical and dielectrometry methods to measure the TIC of the deposited float dust/rock dust. The optical sensor determines the TIC of the deposited dust based on optical reflection which is described by modified Beer Law. We present an extension of the Bouguer-Beer-Lambert Law to find the relation between the reflectivity of a layer of known thickness (obtained by interdigital dielectrometry sensor) of a dust mixture to the ratio of each constituent. We also present the experimental results from testing the sensor prototypes in a realistic laboratory test bed that is subjected to the deposition of the coal dust/rock dust mixture. The sensor performance and stability at different humidity levels is evaluated and the accuracy of the results are compared to the currently established best practices for measuring TIC in underground coal mines. |
Legislation and other legal issues relevant in choosing to partner with a service dog in the workplace
Glenn MK , Foreman AM , Shahan KM , Meade BJ , Wirth O , Thorne KL . J Rehabil 2017 83 (2) 17-26 Objective. Decisions to use a service dog for employment impacts more than just the workplace. It extends into housing, transportation, and public access. Findings from an exploratory study of the use of service dogs in the workplace revealed a need for clarification and dissemination of relevant laws and resulting regulations associated with living and working with a service dog (Glenn, 2013). This investigation sought to respond with a review of legislation and case law that may impact a person's ability to live and work independently with a service dog. Method. A search of the regulations and case law in the United States related to the use of a service dog in various environments was conducted, focusing on examples of legal precedents that have arisen at the federal, state and local levels. Results. Federal law and resulting regulations, as well as local and state case law, were presented for Disability Support and Accommodation: service animal definitions, use of service animals in different environments to include housing, public access, transportation, and employment, rights to privacy, and responsibility to maintain control of the dog. Conclusions. Two themes needing attention emerged: (1) discrepant interpretations of service animal in the law and by the general population and (2) among service dog handlers and allies there exists a lack of accurate information and ability to inform others of their rights, the laws and associated requirements related to service dog teams. |
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