Engineering Controls Database
Best Practices for Dust Control in Coal Mining – Longwall Mining Operations – Belt Entry
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Respirable dust exposure has long been known to be a serious health threat to workers in many industries. In coal mining, overexposure to respirable coal mine dust can lead to coal workers’ pneumoconiosis (CWP). CWP is a lung disease that can be disabling and fatal in its most severe form. In addition, miners can be exposed to high levels of respirable silica dust, which can cause silicosis, another disabling and/or fatal lung disease. Exposure to coal mine dust may also increases a miner’s risk of developing chronic bronchitis, chronic obstructive pulmonary disease, and pathologic emphysema. Once contracted, there is no cure for CWP or silicosis. The goal, therefore, is to limit worker exposure to respirable dust to prevent development of these diseases. |
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CWP contributed to the deaths of 10,406 U.S. miners during 1995–2004 [NIOSH 2008]. Pneumoconiosis continues to be a very serious health threat to underground coal mine workers. Longwall workers can be exposed to harmful respirable dust from multiple dust generation sources, including the intake entry, belt entry, stageloader/crusher, shearer, and shield advance. Using the belt entry to complement the intake entry will allow the delivery of more air to the face, providing the potential for better dust and methane dilution. Recent longwall surveys showed that about 40% of the operations were using belt entry air [Rider and Colinet 2007]. Compliance data analyzed by MSHA [1989] showed that mines using belt air to ventilate work areas did not have significantly different respirable dust levels at the designated occupations when compared to the mines not using belt air. Also, studies conducted by the U.S. Bureau of Mines [Potts and Jankowski 1992; Jankowski and Colinet 2000] indicated that any potential addition to dust levels at the longwall face from the belt entry seems to be mitigated as a result of the increased dilution that can be obtained with additional air brought up the belt entry. However, the potential for dust from the belt entry to contaminate the face area has increased in recent years because the quantity of coal being transported by the belt continues to increase. |
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The following practices can help control respirable dust levels in the belt entry: Belt maintenance. Properly maintaining the belts is one of many vital operating practices necessary to keep respirable dust levels low along the belt entry. Missing rollers, belt slippage, and worn belts can cause belt misalignment and create spillage [Organiscak et al. 1986]. Given the increases in the quantity of coal being transported outby the face, operators must be diligent in their efforts to properly maintain the existing belt entry dust suppression controls to keep fugitive dust from being entrained and carried by the ventilation airstream to the face area. Wetting the coal product during transport. If the coal is wetted adequately at the face, less dust will be created during transport at the transfer points. However, with the substantial increase in airflow in the belt entry, the moisture may evaporate and rewetting of the coal may be necessary at multiple intervals along the belt. Flat-fan sprays and full-cone nozzles are typically used for coal wetting along the belt. Water application usually ranges from 1 to 4 gallons per minute (gpm) at operating pressures of about 50 pounds per square inch (psi) [Kost et al. 1981]. Belt cleaning by scraping and washing. Scraping and washing of the belt play an important role in reducing the amount of dust generated by the conveyor belt [Kissell and Stachulak 2003]. Material that adheres to the belt is subject to crushing at the head and tail roller. Often this material dries out and becomes airborne as it passes over the return idlers. The top and bottom of the return belt should be cleaned with spring-loaded or counterweighted scrapers. A low-quantity water spray may be necessary to moisten the belt slightly and complement the belt scrapers. Previous studies [Stahura 1987; Baig et al. 1994] have shown that water sprays in conjunction with belt scrapers significantly reduced airborne respirable dust levels. Use of a rotary brush that cleans the conveying side of the belt. A motor-driven rotary brush [Organiscak et al. 1986] that cleans the conveying side by rotating in the opposite direction of the conveyor belting (Figure 1) will help reduce dust levels along the belt. This brush should be located near the dump point so that the material sticking to the belt is still wet and agglomerated as it is brushed off. As the material gets carried back on the belt return, it can dry and become airborne when dislodged from the belt.  Wetting of dry belts. Studies have shown that wetting the bottom (non-conveying side) belt can significantly reduce dust from a dry belt as it returns from the dump point [Kissell and Stachulak 2003]. A full-cone water spray is directed onto the non-conveying side of the belt (which is the top side as the belt returns), followed by a piece of material such as a foam-backed piece of carpet positioned across the width of the belt to wipe the belt and remove the dust fines (Figure 2).  |
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NIOSH [2010]. Information circular 9517. Best practices for dust control in coal mining. Morgantown, WV: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2010-110. Jankowski RA, Colinet JF [2000]. Update on face ventilation research for improved longwall dust control. Min Eng 52(3):45–52. Kissell FN, Stachulak JS [2003]. Underground hard-rock dust control. In: Kissell FN, ed. Handbook for dust control in mining. Pittsburgh, PA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2003-147, IC 9465, pp. 83–96. Kost JA, Yingling JC, Mondics BJ [1981]. Guidebook for dust control in underground mining. Bituminous Coal Research Inc. U.S. Bureau of Mines contract J0199046. NTIS No. PB 83-109207. NIOSH [2008]. Work-related lung disease surveillance report, 2007. Morgantown, WV: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, DHHS (NIOSH) Publication No. 2008143a. Organiscak JA, Jankowski RA, Kelly JS [1986]. Dust controls to improve quality of longwall intake air. Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, IC 9114. NTIS No. PB 87-167573. Potts JD, Jankowski RA [1992]. Dust considerations when using belt entry air to ventilate work areas. Pittsburgh, PA: U.S. Department of the Interior, Bureau of Mines, RI 9426. Rider JP, Colinet JF [2007]. Current dust control practices on U.S. longwalls. In: Proceedings of Longwall USA (Pittsburgh, PA, June 5–7, 2007). |
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coal miners coal mining mining underground mines |