Coal Age

DEC 2012

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rock dust continued the CFR is 4% or less. Figure 1 shows the distribution of samples with respect to FCS content. As shown, only 17 of the samples exceeded 4%, resulting in 93.5% of the samples meeting the allowable level specified in the CFR. Fifteen samples exceeded 4% FCS but were less than 5%, so they could potentially be approved for use by the Secretary of Labor. Two of the samples (0.8%) contained more than 5% FCS and would not meet the requirements in the CFR. XRD analysis was conducted with a PANalytical X'Pert Pro diffractometer (PANalytical Inc., Westborough, Mass.) to quantify crystalline silica content using modified NIOSH Analytical Method 7500. Figure 2 provides a summary of the XRD analysis for crystalline silica content in the Company Profile - Paid Advertisement Since inventing the original bearing isolator in 1977, Inpro/Seal has upheld our commitment to deliver innovative sealing solutions and superior customer service; the right technology, right when you need it. Premature and unnecessary bearing failure on rotating equipment, such as pillow blocks, motors, pumps, and gearboxes, can contribute to costly downtime and maintenance headaches along with labor, safety and environmental concerns in the coal industry. Ineffective sealing on the bearing housing of rotating equipment allows for the passage of lubrication out of the equipment and contamination into the bearing housing. Contaminants entering the bearing housing will mix with the lubrication and create an abrasive environment for the bearings to operate while lubrication loss causes the bearings to seize up when the oil or grease level gets to low. 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To alleviate the high cost of downtime, our outstanding customer service and streamlined production process allow for same day shipments on most products, including new designs. www.inpro-seal.com 50 www.coalage.com rock dust samples. It should be noted that none of the analyzed samples contained cristobalite or tridymite, with all of the reported crystalline content resulting from quartz. The sample distribution shows that 69% of the rock dust samples contained 1% or less quartz, while 97.3% contained 2% or less quartz. These levels are well below the 5% quartz threshold 3 that is used to determine reduced respirable dust standards in the current coal mine dust regulations [30 CFR § 70.101]*. However, if the rock dust contains significant levels of respirable-sized dust, mine worker exposure to airborne rock dust would increase the potential for exposure to respirable quartz dust. As previously mentioned, at least 15 samples were analyzed for each of six different producers. However, the number of samples from these producers ranged from 15 to 65 samples. The data from each producer was used to calculate a mean and standard deviation for FCS and quartz. The standard deviation was then used to calculate a 95% confidence interval (CI) around the mean. Figures 3 and 4 illustrate the results for FCS and quartz, respectively. As expected, variation occurred in the confidence intervals for FCS and quartz from one producer to the next, but this variation was not uniform. It does not appear that the variation is correlated with the levels of FCS or quartz that are present nor with the number of samples. Also, relative size of the confidence interval for FCS appears to be independent of the confidence interval for quartz. For example, the smallest CI for FCS was observed for producer F, but this producer did not have the smallest CI for quartz. Likewise, the largest CI for FCS was found for producer C, but this producer did not have the largest CI for quartz. These results were not surprising, since the rock dust could be produced from multiple quarries that have different rock types. Silica content was also examined based upon the type of packaging for the rock dust. Rock dust that was delivered in 40- or 50-lb bags was classified as bag dust, while dust delivered in super-sacks/mega bags or bulk mode was classified as bulk. As shown in Figure 5, the difference in FCS was less than 0.1% for three of the producers, with a maximum difference of 0.5% for producer C. Similarly, the difference in quartz was December 2012

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