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The History of Test Dust
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INTRODUCTION : Arizona sand
has been used for testing filtration, automotive, and
heavy equipment components for decades. A variety of
names have been applied to Arizona sand including Arizona
Road Dust, Arizona Silica, AC Fine and AC Coarse Test
Dusts, SAE Fine and Coarse Test Dusts, J726 Test Dusts,
and most recently ISO Ultrafine, ISO Fine, ISO Medium
and ISO Coarse Test Dusts. Many military and industrial
specifications require use of Arizona Test Dust and refer
to one or more of the above names. This report will attempt
to describe particle size differences and provide a brief
history of Arizona Test Dust use dating back to 1940.
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HISTORICAL PERSPECTIVE
EARLY HISTORY
Use of Arizona sand as a test contaminant dates back prior to 1940. The
proposed Air Cleaner Test Code, SAE Journal, Volume 47, July 1940 pages
294 to 299 provides an early examination of particle shape, particle
size, and accepted analysis methods used at that time. SAE Handbook,
1943 Edition, Page 716, Air Cleaner Test Code-Preparation of Air Cleaner
Test Dust reads as follows: Due to the absence of definite information
and the almost unanimous lack of agreement on the part of those concerned,
it has not been possible to set up a standard test dust although there
is probably no single element affecting to so great a degree the efficiency
of an air cleaner as the fineness of the dust used for testing. Satisfactory
results in the development of air cleaners having a high degree of field
efficiency have been obtained by preparing dust as follows:
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Raw Material : The material shall
be dust that settles out of the air behind or around
tractors or implements operating in the Salt River Valley,
Arizona. It is recommended that this dust be caught on
a canvas cloth.
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Method of Manufacture :
1-Dry raw dust in oven
2-Sift dust through 200 mesh screen (0.0029 in. width of openings).
3-Discard dust retained on 200 mesh screen
4-Sift dust obtained in section 2 through a 270 mesh screen (0.0021 in.
width opening) until no more will go through.
Screen Analysis (By Weight)
80 per cent through 270 mesh screen. 20 per cent through 200 mesh screen,
but shall be retained on 270 mesh screen.
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Examination of these specifications
reveals;
First - The requirement of air floating results in dust is in every way
comparable with that entering the air cleaner of a tractor when operating
in a field, since the position of the air inlet is such that the greater
part of the dust entering the tractor inlet is actually air floated.
Second - The specifications of sieve
size were arrived at by analyzing samples of dust caught
in the oil cups of a number of cleaners operating in
the extremely dusty conditions in the Southwest.
Third - Examination of air floated dust
from the Salt River Valley of Arizona reveals that it
contains a high percentage of extremely fine particles,
highly abrasive in nature, the size of which is difficult
to arrive at by any screening specifications. To develop
the fallacy of depending solely upon a screen analysis,
an examination has been made of such dust as would pass
through a 270 mesh wire screen. One of these samples
was taken from dust originating in Salt River Valley,
Ariz., the other originating in the Imperial Valley at
Calexico, Calif. An examination of this dust revealed
the following properties;
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Particle Size
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Arizona Dust
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California Dust
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(microns)
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(percent)
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(percent)
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53-44
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17.3
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5.1
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43-24
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54.2
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42.3
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23-6
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15.4
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35.9
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5-0
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13.1
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10.7
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Formulation of Arizona Test
Dust by collecting wind blown topsoil, which required
screening and blending, became impractical as larger
quantities of test dust were needed. It is also conceivable
that significant variation in particle size of wind blown
dusts would occur as a result of changing weather conditions.
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