The Kendrick gazette. [volume] (Kendrick, Idaho) 1892-1968, 1915-06-25
Thresher Fires

The many explosions and fires in
threshing machines in the North
west last summer have led the Unit
ed States Department of Agriculture
to take up this question in connec-
ton with it's investigation of grain
dust explosions in cereal mills, eleva-
tors, and similar places. Nearly
300 threshing machines were
destroyed last year in eastern Wash
ington, eastern Oregon, and North
ern Idaho. The total loss was estimat-
ed at 81 900, 900. Insurance compan-
les refused to insure the machines,
arousing acute alarm throughout
the wheat-growing industry of that
section. In some quarters there was
a disposition to attribute these oc-
currences to disgruntled farm hands
or tramps, but specialists in the
department now believe that they
were accidental explosions and that
under certain conditions such explo-
sions are liable to occur wherever
quantities of dust from grain or straw
accumulate. Since it is probable,
therefore, that there will be addi-
tional accidents of the same charac-
ter this season, the department has
assigned investigators to the terri
tory in question and earnestly re-
quests that full reports of all ex-
plosions be sent to the United States
Department of Agriculture, Wash
lngton, DC.
In connection with the study of
explosions in grain mills and eleva-
tors it has been definitely establish
ed that when the air is filled with
fine particles of vegetables dust,
this dust can be ignited and an ex-
plosion follow, much as mixture
of gasoline and air is exploded in
the cylinder of an automobile. 1t
is also known that last year there
was high percentage of smut dust
in the wheat crop in the Pacific
Northwest and preliminary expert
ments have also indicated that this
dust is both highly inflammable and
has great explosive force.
From the accounts of explosions
already received, it appears that the
occurrence originated at or near the
cylinder of the threshing machine,
where the dust was thickest, and
flashed through the entire machine
instantly. In some instances the
fire spread to grain stacked near by.
In grain mills where similar explo-
sions have occurred two reports have
commonly been heard. The first is
a sharp quick sound, followed by a
report of a rumbling nature which
lasts longer time. The second re-
port is usually followed by fire. 1t
is supposed that the first report is
due to small quantity of very fine
dust suspended in air, having been
ignited by some source of heat and
thus exploded. This first explosion
produces sufficient conclusion to dis
lodge the dust settled near by, and
this when shaken into the air and
mixed is ignited by the heat of the
first explosion.
There are a number of ways in
which dust may be ignited, but in
the case of threshing machines it
appears probable that static electri-
city, generated by the operation of
the machine, is chiefly responsible.
The generation of sufficient supply
of "static" would result in the dis
charge of spark which, under the
proper conditions, would serve to ig-
mite the explosive mixture of dust
and air. In this connection it has
been observed that belts slipping on
pulleys will generate considerable
quantities of static electricity.
In view of these facts the depart.
ment recommends the grounding OF
all cylinder shafts on threshing ma
chimes. This can be done by dry
brush contact with the cylinder and
wires run to an iron rod driven into
damp ground. The grounding OF
grinding machines in mills has prov.
ed effective in preventing these dust
explosions and similar precautior
can be adopted advantageously with
threshers.