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

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have escaped through an open oven door (Section 5.1.2), or the dust cloud may have entered the oven and ignited. 7.1.1.3 Other Possible Ignition Sources CSB considered other potential sources of ignition at the point of origin, as noted below, but concluded that they were unlikely: • Electrical equipment: Several electrical boxes containing switches and relays were located in the area of origin and might have produced electrical sparks. The boxes were not dust- tight, and such sparks would have been capable of igniting a combustible dust cloud. CSB contractors examined the electrical boxes and concluded that—though they were fire- damaged—there were no indications that the spark-producing electrical equipment inside provided an ignition source (Appendix C). • Lube oil system: The lube oil system and pump for the oven flights were also examined. The piping for the high-temperature oil had no moving parts and was found to be free of leaks. The oil pump was pneumatically operated. • Static electricity: CSB also eliminated static electricity as an ignition source. Interviews with line crews revealed that electrostatic discharges occurred frequently when the mat- former was cleaned of phenolic resin. However, no one interviewed could recall an instance when the phenolic resin ignited. Tests conducted by a CSB contractor confirmed that the static energy in a propagating brush discharge 17 (PBD) was incapable of igniting the resin because it did not produce enough energy (Appendix B). 17 PBDs are lightning-like electrostatic discharges. They are the most energetic of all types of electrostatic discharges, with spark energies approaching 1 joule. 54
7.1.2 Other Possible Initiating Events 7.1.2.1 Natural Gas Explosion A natural gas supply line and the piping manifold were located in the area of origin. CSB considered the possibility that the incident resulted from the ignition of leaking natural gas, but determined that scenario unlikely. The natural gas supplied to CTA contained a mercaptan odorant. If there is a leak, the odor of the gas is readily detectable by smell at one-fifth of the LEL of the gas. 18 None of the employees working on line 405 reported smelling natural gas during the night shift or on the morning of the incident. CSB received reports from a few employees who had smelled natural gas in other areas and believed that leaking gas might have provided fuel for the explosions. The gas company and insurance investigators conducted a natural gas header leak test after the explosion. No significant leaks were detected. Also, a CSB contractor tested the piping and components of the line 405 natural gas fuel manifold (Appendix C). The results of these tests showed no leaks in the natural gas supply or vent piping that would have caused gas to enter the building. 7.1.2.2 Ignition of Flammable Vapors on Line 403 Another possible initiating event considered by CSB was an explosion caused by the ignition of accumulated flammable vapor in the vent line to the roof incinerator on line 403. Overpressure in the line connecting to the oven had caused a flange to separate, and inspection doors on the vent line were partially blown outward. Burn patterns on the incinerator stack indicated that it had been on fire. 18 The MSDS for natural gas supplied by Delta Natural Gas Company, Winchester, Kentucky, dated December 20, 1991, states that the lower explosive limit is approximately 4.5 percent by volume in air. 55
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KEY ISSUES: U.S. CHEMICAL S AFETY A
Page 3 and 4: 5.1.2 Line 405 Oven Temperature Con
Page 5 and 6: 9.1 FM Global Guidelines...........
Page 7 and 8: Figures 1 Simplified Layout of CTA
Page 9 and 10: ACC American Chemistry Council Acro
Page 11 and 12: Executive Summary A February 20, 20
Page 13 and 14: 1.0 Introduction At approximately 7
Page 15 and 16: 2.0 Key Findings 1. Combustible phe
Page 17 and 18: 3.0 Facility Description 3.1 CTA Ac
Page 19 and 20: eams. Nonload-bearing masonry block
Page 21 and 22: Thirteen-foot-high freestanding enc
Page 23 and 24: 4.0 Process Description The product
Page 25 and 26: 4.1.2 Mat-former and Baghouse In th
Page 27 and 28: Circulating fans and dampers direct
Page 29 and 30: • Manually striking baghouse bags
Page 31 and 32: 5.0 Incident Description 5.1 Pre-In
Page 33 and 34: • The line was one week past due
Page 35 and 36: forklift with a semi-enclosed cab d
Page 37 and 38: panels and lights down inside the b
Page 39 and 40: occurred in the southeast corner of
Page 41 and 42: 5.3.3 Firefighting Activities 5.3.3
Page 43 and 44: 5.4 Incident Aftermath The CTA inci
Page 45 and 46: 6.0 Understanding Combustible Dust
Page 47 and 48: As depicted in Figure 11 (Eckhoff,
Page 49 and 50: Figure 12. Mechanism for a dust fir
Page 51 and 52: 7.0 Reconstructive Analysis To dete
Page 53: urned clean but otherwise intact an
Page 57 and 58: Table 3 Borden Chemical Black Pheno
Page 59 and 60: 7.3 Line 405 Equipment Testing CSB
Page 61 and 62: determine if those products are haz
Page 63 and 64: that the phenolic resin could explo
Page 65 and 66: A 1998 internal Borden Chemical mem
Page 67 and 68: • Characterize new and existing p
Page 69 and 70: CTA that phenolic resins, when susp
Page 71 and 72: CTA department supervisors were res
Page 73 and 74: 8.5 Work Practices 8.5.1 Production
Page 75 and 76: operating the oven with the doors o
Page 77 and 78: 8.7 Incident Investigations The inc
Page 79 and 80: • Excessive accumulations of comb
Page 81 and 82: Data Sheet 6-9 also states: Clean o
Page 83 and 84: Table 5 Insurance Company Dust Issu
Page 85 and 86: standards (Appendix D). Kentucky OS
Page 87 and 88: 10.2.2 Division of Building Codes E
Page 89 and 90: 11.0 Combustible Dust Hazard Study
Page 91 and 92: 4. The Borden Chemical product stew
Page 93 and 94: 13.0 Recommendations CSB developed
Page 95 and 96: Kentucky Office of Occupational Saf
Page 97 and 98: BY THE U.S. Chemical Safety and Haz
Page 99 and 100: Lawson, Robert G., 1984. Beverly Hi
Page 101 and 102: APPENDIX A: Fire and Explosion Dama
Page 103 and 104: APPENDIX B: Laboratory Testing of P
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B.2 Minimum Explosible Concentratio
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B.4 Propagating Brush Discharge Ign
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Material Corona Charge Voltage (kV)
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APPENDIX C: Equipment Testing Line
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II controllers, only manufactured a
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Therefore, at any given time, it wa
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APPENDIX D: NFPA Guidelines In prom
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D.2 Other Pertinent NFPA Codes D.2.
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APPENDIX E: HMIS Rating System The
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APPENDIX F: Simplified Organization
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Subtree A Second dust explosion abo
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Subtree C Most CTA personnel had a
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