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1 OONCLUSTONS Chapter 2 CONCLUSIONS AND RECOMMENDATIONS 1. Numerous reports on explosion prevention in the grain-handling industry have been published over the past 60 years. Many present long lists of actions to be taken with little or no assessment of their feasibility or potential effectiveness or explanation of why they were needed. These reports generally do not consider the influence of human characteristics on explosion prevention, questions requiring research, or methods for disseminating widely the available information on explosions and their prevention. In addition, the existence of these reports appears to be little known. 2. Recent compilations would make it appear that the number of grain-handling facility explosions occurring annually in the Uhited States has increased during the past 20 to 25 years but that much of this apparent increase could be due to better reporting procedures. Nonetheless, it appears that the problem of grain elevator explosions is greater than generally realized. 3. The elevator leg is the most dangerous location with respect to initial or the primary dust explosions. 4. Grain dust is generated in many places in elevators and mills. Of particular concern is the dust in confined spaces that, without proper housekeeping, will accumulate in layers on all surfaces and present a potential for secondary dust explosions. l S. There is a considerable body of documented evidence indicating that electrostatic discharge can ignite dust clouds under the right conditions; however, the panel found no evidence of ignition due to electrostatic discharge in its investigations of explosions. 6. The contribution of human operatives and external factors other than the immediate physical aspects (e.g., people's attitudes, insurance practices, and government regulation) often are a major part of the problem and often are overlooked. 9 1
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10 RECOMMENDATIONS l . . . Given these conclusions, the information obtained during its study and the expertise of its members,'the panel identified a number of actions that can reduce the frequency and severity of explosions in grain-handling facilities. it assessed each of these actions in terms of: 1. The efficacy or degree to which the explosion hazard would be eliminated or controlled by the action; ' 2. The feasibility or acceptability of implementing the action in light of economic, legal, cultural, political, social, and technical considerations; and 3. The efficiency or cost-effectivenegs of the action (i.e., the cost of the action versus the potential dollar JOBS if no action is taken). On the basis of this assessment, the panel grouped its recommended actions in terms of priority--first, second, and third. The panel believes that the first-priority'actions should be implemented in all facilities and that the second- and third-priority actions should be implemented to the extent possible depending on the specific facility. There is no internal ranking within each category. ' ' . . . Some of these recommended actions must be implemented by the grain-handling industry and others by government; still others require cooperative efforts. Further, some of these recommended actions are more appropriate for large facilities and others for small--both existing and new. Recommendations peculiar to mills are given here and discussed in Appendix C. First Priority Actions .e Continue research on methods for reducing the dust concentration in legs to a level below the lower explosive limit.* Establish a housekeeping program involving a mechanical dust collection system supplemented by manual or other means. Conduct rigorous preventive maintenance, especially on all parts of bucket elevators. ' · Use a pre-established and enforced permit procedure whenever welding, cutting, or other open flame work is to be done. * Lower explosive limit used throughout this report is synonymous with minimum explosive concentration.
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~1 Incorporate a system to indicate belt slippage and misalignment. Tncorporate'a method to check frequently the temperature and vibration of critical bearings. ' Use devices to extract foreign materials from the incoming grain stream. ~ Ground all conveying and electrical equipment. Second Priority Actions Examine the overall functions of mill" and elevators to develop a totally new system less subject to the hazards of dust explosions. Control dust generation and airborne dust at all grain transfer and discharge points. Notify all plant managers that safely' is their responsibility. If authority is delegated it must be to an employee who reports directly to the plant manager. Apply state-of-the-art techniques to reduce the concentration of airborne dust in and emanating from elevator legs. Establish an information center to distribute actively all available information on elevator and mill dust explosions and their causes and prevention. , Establish a fire and explosion prevention training program at each facility. Conduct research to develop economic uses for collected grain dust. Locate hammer mills, other grinding equipment, and their dust collection systems separate from the main-facility. · Eliminate,all nonessential horizontal surfaces. Treat the avoidance of dust explosion hazards as an initial design criteria in the construction of new mills and elevators and the modification of existing structures. Continue research on methods for reducing dust concentrations below the lower explosive limit in enclosures other than legs. Investigate and report on explosions in a manner that reflects the recommendations made by 'tine panel in its report, The Investigation of Grain Elevator Explosions,. Report AHAB 367-1.
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1 12 Third Priority Actions · Follow, to the extent practical, the National Fire Protection Aseoc:iation's standard on explosion venting (No. 68) for all enclosures. Concrete structures should be vented by windows or othe r openings of the s ize dictated by this standard . · Establish a government and industry group to aid in developing and updating explosion prevention regulations for elevators and mills.. · Quantify housekeeping standards for cleanliness in grain-handling facilities that will prevent'fires and explosions. · Coat all nonhorizontal surfaces exposed to airborne dust with a material that will prevent the buildup of layered dust. Investigate the effect of electrostatics and absolute humidity on the explosion hazard, including. an examination of conveyor belt conductivity and the charging of ungrounded 'conductive structures Apply state-of-the-art techniques to reduce the concentration of airborne dust.below the rawer explosive limit where possible in enclosure" other than legs . Tf dust is returned to the grain stream do it in the least haze odes manne r . . Use only equipment and installation standards meeting National E1 ectrical Code requirements . . ..
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