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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.
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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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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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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 . . ..
Representative terms from entire chapter:
explosive limit
