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OCR for page 1
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
1
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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 f atalities, 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 Eli..-
immediately, some require retrofitting, and others may be impose. 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 f unctions 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~.
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3
8'
A permanent, professionally recognized and accepted, objective
investigating body would not be hampered by some of the problems faced by
the investigating aubpanel. 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.
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This report deacribes the type of investigation that is envisioned for a
permanent body to conduct.
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Representative terms from entire chapter:
dust explosions
