Case
No.39
Dust
explosion when flour was fed into a storage hopper by air
pressure
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[Circumstances
of Incident]
A dust explosion occurred within a storage hopper when flour
was fed into a storage hopper.
On the day of the accident, flour
stored within the storage hopper was first put into bags. This bagging
work was completed around 3:00 in the afternoon.
Following this,
the victim confirmed that no flour was left inside the storage hopper by
lowering a shielded electric light inside the storage hopper from the
inspection hatch located at the upper part of the bin.
About one
hour after confirming that the hopper was empty, another worker started
feeding flour into the hopper by air pressure. About 30 minutes after the
start of the feed, the victim noticed an offensive odor around the bin.
While the victim was checking the cause, an explosion occurred in the
upper part of the bin, and the victim suffered burns from hot gases
generated in this explosion.
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[Causes]
The
following can be considered as the causes of this
accident.
- Flour particles being fed into the storage hopper
were 50 microns in size, and therefore highly prone to explosive
combustion when mixed with air in the process of being fed into the bin
by air pressure.
- The incandescent electric lamp used to check the
inside of the storage hopper was left within the hopper and became the
source of ignition.
- As the work manual was not careful enough to cover
all possibilities, a still-lighted incandescent electric lamp was left
inside the storage hopper.
- Safety management structure was not fully
established.
- Safety education concerning dust explosions was
insufficient.
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[Caused by] |
Hazardous
materials, harmful substances, etc. |
[Type of accident]
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Explosion |
[Number of
victims] |
Two
injured (requiring an absence from
work) |
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