CTA Report, Draft 1, ISP Review - US Chemical Safety and Hazard ...

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B.3 Minimum Ignition Energy The minimum ignition energy (MIE) test is useful to determine whether combustible dust/air mixtures are ignitable by a high-voltage spark. Ignition energies determined by this method can be compared to determine the relative hazard of ignition by sources such as electrostatic discharges, electrical equipment sparks, and friction sparks. Test results provide a relative measure of the ignition sensitivity of a dust cloud. The values obtained are specific to the sample, test method, and test equipment. MIE values are not to be considered intrinsic material constants. Any change in particle size, shape, or volatility alters MIE results. MIE tests were performed per ASTM E2019-99, Standard Test Method for Minimum Ignition Energy of a Dust Cloud in Air (1999), using a 1.2-liter clear plastic Hartmann tube. Figure B-4 shows MIE test results for a Durite SD-52SS dust cloud in air. Results indicate that the phenolic resin is very easy to ignite, requiring only 3 millijoules (mJ) of energy to initiate an explosion. 300 250 200 MIE (mJ) 150 100 50 0 3 60 300 Cornstarch Pittsburgh Pulverized Coal Dust SD-52SS + Carbon Black #2 Figure B-4. Minimum ignition energy of Durite SD-52SS compared with other common combustible dusts. 106
B.4 Propagating Brush Discharge Ignition Test During the handling of bulk powders, a propagating brush discharge may ignite dust. A sufficient charge built up on the powder surface can break down in the form of a propagating brush discharge. Unlike a spark discharge, which is localized between two conductive points, a propagating brush discharge is a surface phenomenon. Consequently, it poses the potential hazard of being a delocalized multipoint ignition source. The force of the charge breakdown is sufficient to disperse dust deposited on the surface into the air. B.4.1 Test Setup and Procedure The test apparatus consisted of a high-voltage power supply (Hipotronics Model 250D) connected to a multipoint corona generator. The base of the apparatus was an 8.5-inch sheet metal disk, which is connected to the ground. An 8.5- by 11-inch plastic sheet, with a thickness of 0.0075 inch, was placed on top of the disk. A grounded 2-inch-diameter ball electrode was used to initiate the propagating brush discharge. To estimate the energy of the discharge, a Monroe Electronics Model 282 electrostatic fieldmeter was used to measure the change in electrostatic field (i.e., electrical potential of the surface by extension) before and after the discharge. To produce a charge on the surface of the plastic sheet, 30 to 50 kilovolts were supplied to the multipoint corona generator centered over the sheet metal disk surface at a height of 25.4 millimeters. After a charging time of 60 seconds, the generator was moved away from the surface of the plastic sheet and the power supply was turned off. The field meter was positioned above the surface of the plastic sheet to measure the electrostatic field. The spherical grounding electrode was then lowered to the plastic surface. A propagating brush discharge was produced as the electrode was lowered but before it touched the surface. 107
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KEY ISSUES: U.S. CHEMICAL S AFETY A
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5.1.2 Line 405 Oven Temperature Con
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9.1 FM Global Guidelines...........
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Figures 1 Simplified Layout of CTA
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ACC American Chemistry Council Acro
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Executive Summary A February 20, 20
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1.0 Introduction At approximately 7
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2.0 Key Findings 1. Combustible phe
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3.0 Facility Description 3.1 CTA Ac
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eams. Nonload-bearing masonry block
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Thirteen-foot-high freestanding enc
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4.0 Process Description The product
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4.1.2 Mat-former and Baghouse In th
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Circulating fans and dampers direct
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• Manually striking baghouse bags
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5.0 Incident Description 5.1 Pre-In
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• The line was one week past due
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forklift with a semi-enclosed cab d
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panels and lights down inside the b
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occurred in the southeast corner of
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5.3.3 Firefighting Activities 5.3.3
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5.4 Incident Aftermath The CTA inci
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6.0 Understanding Combustible Dust
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As depicted in Figure 11 (Eckhoff,
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Figure 12. Mechanism for a dust fir
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7.0 Reconstructive Analysis To dete
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urned clean but otherwise intact an
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Page 97 and 98: BY THE U.S. Chemical Safety and Haz
Page 99 and 100: Lawson, Robert G., 1984. Beverly Hi
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Page 121 and 122: APPENDIX E: HMIS Rating System The
Page 123 and 124: APPENDIX F: Simplified Organization
Page 125 and 126: Subtree A Second dust explosion abo
Page 127: Subtree C Most CTA personnel had a
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