Click for next page ( 2


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 1
1 BACKGROUND Chapte r 1 TNTRODUCT TON 1 Explosions in grain elevators and mills have been documented for over 100 years but probably have occurred ever since structures for handling grain in large quantities were developed. Although long recognized as an industrial hazard, elevator explosions received wide national attention recently when during an eight day period in 1977 beginning on December 21 and ending on December 28, five explosions occurred resulting in 59 deaths and 4 8 injuries (U. S. Department of Agriculture 1980) . In the past, explosion prevention efforts in the grain processing industry were concentrated on mills, mainly flair and starch. The federal government first gave attention to the dangers of grain dust explosions following the explosion of a feed mill in 1913, and the continuing emphasis on mills may have been due to the very large number of fatalities that occurred in early mill explosions (e.g., 43 fatalities and 30 injuries in a starch mill explosion in Cedar Rapids, Iowa, in 19191. However, the danger of explosions due to collections of grain dust in elevators had not been totally ignored (U.S . Department of Agriculture 1918, U.S . Grain Corporation 19 20a and b} . In Ju ly 1978, at the request of the Department of Agriculture, the National Academy of Sciences conducted an international symposium on -train elevator explosions (National Materials Advisory Board 19781. Shortly after the symposium the Occupational Safety and Bealth Administration (OSHA) of the Department of Labor requested that the National Academy of Sciences form a group to study the causes and make recommendations for the prevention of grain e levator explos ions . In November 1978, the Panel on Causes and Prevention of Grain Elevator Explosions was for~d under the Academy's National Materials Advisory Board. The panel is part of the Board's Canunittee on Evaluation of Industrial Hazards. The Nonmember panel is composed of experts in systems analysis, explosion dynamics, investigations and prevention, instrumentation, grain handling and processing, agricultural insurance practices, employee relations, dust control methods, and aerodynamics. Its objectives were to: 1. Study the federal government's investigation of grain elevator explosions and make recommendations for improvement, 2. Investigate grain elevator explosions selected by OSHA occurring during the panel's tenure and determine their causes, 1

OCR for page 1
2 3. Recommend actions to be taken to reduce the occurrence of. explosions ingrain elevators and mills and to identify any needed research and development, - 4.. Produce a handbook on dust collection methods and systems for grain elevators and mills, and 5. Develop a methodology for investigating explosions in grain-handling facilities based on the panel's experience. RISK MANAGEMENT METHODOLOGY . . . . Explosions in grain elevators and mills have been studied from many viewpoints in the pant. However, none of these studies has considered all aspects of explosions in relation to one another simultaneously. The panel undertook to overcome these deficiences by employing a systematic approach to risk management that permits all aspects of a situation to be considered simultaneously rather than separately or sequentially (Maritime Transportation Research Board 19811. In applying the systems approach, the panel attempted to identify every possible hazard that contributes to grain dust explosions in elevators and mills. Preventive or corrective actions for each identified hazard were then proposed, and the costs of these actions were estimated. It was then possible to evaluate each identified hazard in teems of its severity, probability, and cost of hazard elimination or control so that a ranking of significance to explosion potential could be established. This ranking then formed the basis for the panel's recommendations. Figure 1-shows the functions of risk management (Grose Or' item guided the panel's efforts to be systematic in their study of grain dust explosions. Activities related to all five functions were conducted by the panel and illustrate how this method could be applied by the grain-handling industry. Administration of Risk-Related Tasks . . The first step in managing risk is to define the situation or location where risks are to be controlled. The panel therefore had to identify clearly and precisely all functions (tasks or activities) performed in a grain elevator or mill. me most c ammo n means of displaying these functions is a functional flow block diagram (baud) that depicts functions in separate boxes or blocks connected by arrows to indicate their order of occurrence. Using such a diagram helps to avoid a random or piecemeal attempt to identify explosion hazards. The FFBD for a grain elevator is shown in Figure 2. Note that it does not indicate who, why, where, or how; it simply describes what is being done. me inputs to any task or activity are shown 1

OCR for page 1
3 / / FINANCING \ f Uncontrolled Risk \/ 1 / ADMINISTRATION ~: \of Risk-Related Task,/ \ \ CONTROL \of Significant Risk FIGURE: 1 Functions of risk management. /IDENTIFICATION of Risk Exposure - EVALUATION of Identified Risk /

OCR for page 1

OCR for page 1
s on the left and the outputs appear on the right. Thus, the FFBD shows graphically the interdependence of all tasks or activities taking place in the facility. Since it is one single and complete display of all essential functions, the probability of overlooking any factor related to an explosion is vastly reduced. Identification of Risk Exposure The primary mechanism used by the panel to identify the caused of grain dust explosions was the hazard scenario. Every accident is comprised of many elements--not just some singular, isolated event, and the hazard scenario is a brief description of the combined causative factors that could lead to an explosion. Hazard scenarios are not an end in themselves in that they identify only facets of exposure to risk {Grose 1982~. However, one of the major values of hazard scenarios is that they can describe explosions that have not yet occurred but that are possible. Thus, they serve to emphasize the need for preventive or corrective actions. Appendix A presents a representative sample of the more than 150 scenarios that were prepared by the panel. Some of them describe actual occurrences investigated by panel members while others are hypothetical possibilities proposed by employees of the grain-handling industry experienced in elevator operations. Early in their attempt to identify causal factors for grain elevator explosions, the panel concluded that existing data were insufficient to permit the identification of needed preventive actions. Therefore, a team of panel members was formed to investigate significant explosions that occurred during the panel's tenure. The primary function of the investigation team was to obtain data that identified the hazards leading to a grain elevator explosion. A secondary function was to establish and refine investigative techniques for identifying and analyzing causal factors at the scene of an explosion.* The team was staffed with panel members and liaison representatives who had diversified professional specialties. Evaluation of Identified Risk Identifying the many and varied explosions risks in a grain elevator, whether by means of hazard scenarios or on-site investigations of expicsions, is a difficult process. It is especially important that hazard identification not be inhibited by any initial concern for the significance of an individual identified hazard; if it is, many subtle hazards probably will be overlooked. * A report entitled, The Investigation of Grain Elevator Explosions,. NMAB 367-1, 1980, National Academy of Sciences, Washington, D.C., was issued.

OCR for page 1
6 Ultimately, however, all identified hazards must be evaluated for their significance because there are never enough resources available to prevent or correct every hazard that can be identified. The panel ranked all identified hazards into a hierarchy of importance using three measures--the severity of the hazard, its frequency or probability of occurrence, and the amount of' resources required to control it. Each scenario was assigned three letters--one for severity, one for probability, and one for control resources as described in Appendix A. Since historical data for many of the scenarios did not exist, the panel's judgment was important in this ranking. ' Once the three letters-were assigned to each scenario, all the scenarios could be evaluated by the panel to determine their relative hazard significance. This r'anking procedure can be used in the future by grain elevator owners and operators. Using this decision-making tool, they can judge the significance of all identified hazards on the same basis and efficiently allocate resources for the reduction or control of explosions e Control of Significant Risk Once the evaluation of all identified risks revealed those that were most significant, the panel sought expert counsel on how such hazards might be best controlled. This counsel was of several types. Knowledgeable experts in grain dust control, elevator design,'environmental protection, grain economics, and grain handling were invited to address the panel on dust explosion prevention. Other groups and spokesmen met with the panel to offer control measures. (See Preface for a list of those contributing to this effort.) Individual panel members also visited selected grain-handling sites to review specific preventive actions for explosion scenarios. Financing of Uncontrolled Risk - There are three classes of uncontrolled hazards: (a) those for which there is no effective preventive action, {b) those considered insignificant but which turn out to be consequential, and (c) those that were unforeseen. While the panel has made no recommendations regarding the various options for financial coverage of bosses due to these three classes of risk, the economic impact due to dust explosions was ' of constant concern. Among the options discussed were loss write-off, assumption of debt, self-insurance, and other means of transferring the risk of loss.

OCR for page 1
1 7 REFERENCES Grose, V.L., Converting health hazard control from moralism to management, Professional Safety 25~3) March (1980, :31-40. Grose, V.L., Managing medical malpractice risk via system science, Journal of Medical System 6~) (1982) :89-103. . . . Maritime Transportation Research Board, Research needs to reduce maritime collisions, ratings, and groundings, National Academy Press, Washington, D .C., May 19 81 . Nationa1 Materials Advisory Board, International Symposium on Grain Elevator Explosions, Proceedings, Volume 2, Report AHAB 353-2, Washington, D.C., July 11-12, 1978. U.S. Department of Agriculture, Prevent grain dust explosions and fires, USDA Circular, 1918. U.S. Department of Agriculture, Prevention of Dust Explosions in Grain Elevators An Achievable ~1, USDA, Washington, D.C., 1980. U.S. Grain Corporation, Grain dust explosion prevention, (in cooperation with the Bureau of Chemistry, U.S. Department of Agriculture), New York, 1920a. U.S. Grain Corporation, Proceedings of Conference of Men Engaged in Grain Dust Explosion and Fire Prevention campaign, (in cooperation with the Bureau of Chemistry, U.S. Department of Agriculture), July 1920b. 1

OCR for page 1