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Chapter 1 INTRODUCTION Dust explosions have occurred with considerable frequency in grain processing facilities since the inception of the industry. All grain- handling facilities that receive and transfer grain, from country elevators collecting directly from the farm to huge export terminals, have been susceptible to explosions. A number of explosions near the end of 1977 and in early 1978, which caused many fatalities and tens of millions of dollars worth of damage, prompted action on the part of federal agencies to look for ways to reduce the frequency of explosions. Part of this action was the convening of a panel under the auspices of the National Materials Advisory Board (NMAB) of the National Research Council to study causes of grain elevator explosions and recommend ways to prevent them. The charge of this panel included conducting on-site investigations of explosions occurring during the panel's tenure. The purpose of the investigations was both to determine the causes of the explosions and to develop investigative methodology. The panel's investigation subpanel went to a number of explosion sites generally soon after the the occurrence of the explosions. Substantial expertise was developed by the subpanel members, some of whom were already familiar with explosion investigation, and they identified the probable sequence of events in all but one of the incidents investigated. The panel has published three reports on its study (National Materials Advisory Board 1980, 1982a, 1982b). The purpose of this report is to relate the methodology and philosophy of investigation based on the experience of the investigation subpanel and to describe some typical explosion scenarios. Chapter 2 of this report discusses the investigation methodology and philosophy; Chapter 3 contains a summary of reports on some of the explosion events that the team investigated, and the Appendix contains more detail on those incidents. In each investigation the purpose was to determine the most plausible initiation and sequence of events, not to place blame for the explosion. The intent of this effort is to help identify the generic elements that lead to dust explosions in grain elevators and, thus, provide additional insight and knowledge to those in the industry so that explosions may be prevented. Considerable literature has been developed in recent years on the causes of grain elevator explosions. One very extensive study (Verkade and Chiotti 1976) identified 126 explosions and reported that for 40 percent of them the causes were unknown. Many in the industry still believe that a large
percentage of explosions are not explainable. However, the investigating subpanel believes that the causes of previous explosions were not identified either because there was no investigation or because there was no effective effort to determine the patterns of the explosions. There are various reasons for the lack of investigation of individual explosions. In some cases management may not be committed to finding the cause. Insurance companies may simply pay off the loss without serious investigation due either to their own internal policies, the lack of time, or not being able to provide enough experienced investigators at the site. People not directly associated with the elevator often have no motivation to learn exact details other than to submit a report to a state agency on the most likely cause. Many times state or local agencies have no real commitment to ferret out the precise cause. The grain industry in its dedication to determining the general causes and improving the preventive measures that are necessary to reduce the number of explosions could benefit from procedures established by other industries. For example, the chemical industry has always shared information concerning accidents that caused fatalities, injuries, and property damage. That sharing requires the willingness to expose to their fellow industry members those scenarios and events that could happen in other locations. It has helped the chemical industry to establish a safety record that is commendable. The grain industry is only beginning to look upon this sharing as a valuable procedure. "Prevention of Grain Elevator and Mill Explosions" (National Materials Advisory Board 1982a) describes the major causes of grain dust explosions and recommends preventive measures based in part on investigations of the type described in this report. Many of the causes can be eliminated immediately, some require retrofitting, and others may be impossible to eliminate without rebuilding entire structures. Many of the major causes that now are repeated year after year (for example, overheating of bearings) could soon become minor causes. For example, microprocessors are now available to monitor even some of the simplest functions in a grain elevator, including whether or not belts are moving at proper speeds or are properly loaded or that bearings or bins are overheating, etc. In the near future, even small elevators will be able to afford some sort of micro- processor sensing. Already a small system can be installed for under $10,000. Nevertheless, the investigation of causes of grain dust explosions must be a continuing endeavor as all causes cannot be totally eliminated. The panel hopes that in the near future a suitably placed, permanent investigating capability will be established to continue the work of grain elevator investigation and provide the industry and government with reports on incidents as they occur. The panel has already presented a positive recommendation for such an action (National Materials Advisory Board 1980).
A permanent, professionally recognized and accepted, objective investigating body would not be hampered by some of the problems faced by the investigating subpanel. For example, because of their professional commitments, the subpanel members were not always able to respond immediately when notified of an explosion. Also, although the subpanel assured grain elevator managers that its sole purpose was to seek causes and identify ways to prevent future explosions and not to place blame, some managers viewed the subpanel's activities as harassment. This report describes the type of investigation that is envisioned for a permanent body to conduct.