In the chemical process industries (CPI), dust can present an issue far more menacing than a housekeeping nuisance. Combustible dust is in fact, much too often listed as a cause of serious, and even fatal accidents.
In January of this year, the U.S. Chemical Safety Board (CSB; Washington, D.C., www.csb.gov) issued its report on the U.S. Ink plant flash fire that burned seven workers. This incident, which occurred in October 2012 in East Rutherford, N.J., was found to have resulted from the accumulation of combustible dust inside a dust-collection system that had been put into operation four days prior to the accident. One of the key findings in the report is that while the dust-collection system was designed for dust collection, it was modified to include a housekeeping function, which caused insufficient flowrates. The CSB report notes that the volume of air flow and the air velocity were below industry recommendations.
In 2006, the CSB issued a comprehensive report on combustible dust hazards that was based on investigations of three major industrial explosions that occurred in the U.S. in 2003 alone. The three incidents, in North Carolina, Kentucky and Indiana, cost 14 lives and numerous injuries. In that 2006 study, the CSB identified 281 combustible-dust incidents that occurred in the previous 25 years and claimed 119 lives with over 700 injuries. Since 2006, the CSB documented 50 combustible-dust incidents that resulted in 29 fatalities and 161 injuries. These include the 2008 Imperial Sugar disaster near Savannah, Ga., and three incidents over a six-month period in 2011 at a powdered-metal plant in Gallatin, Tenn.
Standards and regulations
What is striking in the reports about dust explosions is that at least in some cases, known engineering controls may have been preventative. In its 2006 investigation report “Combustible Dust Hazard Study,” the CSB recommended that the Occupational Safety and Health Admin. (OSHA; Washington, D.C.; www.osha.gov) issue a standard to prevent combustible-dust fires and explosions based on standards already available from the National Fire Protection Agency (NFPA; Quincy, Mass.; www.nfpa.org). The CSB reiterates this recommendation in numerous subsequent reports including its most recent one issued in January. While standards exist, they are voluntary and not enforced through federal regulations. In 2013, the CSB designated a comprehensive general industry standard for combustible dust as its first “Most Wanted Chemical Safety Improvement.”
In the meantime, a wealth of information about combustible dust is available. The CSB website contains many lessons learned from incident investigations in both report and video format. The NFPA offers a number of relevant standards. OSHA offers various resources, including information on its Combustible Dust National Emphasis Program (NEP). And numerous articles, such as the Feature Report in this issue (Prevent Combustible Dust Explosions With Nitrogen Inerting, p. 64) help to share knowledge and insight into this important issue.■