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Sample splitters and reducers
Gross samples, if not too large, may be
reduced to test sample size by one or more
passes through a sample splitter or Jones
type riffle, which will divide a sample in
half while maintaining the particle size
distribution of the original sample. By
repeated passes, the sample can be split
into quarters, eighths, and so on until the
size of the sample desired is obtained. For
larger gross samples, sample reducers are
available which will select a representative
1/16 part with a single pass. After just two
passes
through
representative one pound sample can be
obtained from an original 256 pounds.
Three passes will give a one pound sample
from two tons of material.
sure that the passages in the splitter or
reducer are at least three times the size of
the largest particle in the sample. Do not
attempt to arrive at exactly the amount of
material specified for the test.
gram sample is desired, arrive as near to
this amount as practicable, because it will
make no difference in the test percentage
results whether the sample is slightly
larger or smaller. In attempting to arrive
at an exact weight, the tendency is to
discriminate by the removal of sizes that
are not representative of the whole, thus
destroying the representative quality of the
sample.
Size of Sample in the Test
There is a natural tendency, although
incorrect, to use an excessively large
sample in the test. In most cases, a
smaller
sample
accurate analysis. Beware, however, that
the more you split, the greater the chance
of error. Testing sieves are a go or no go
gauge; if the sample is too large it will not
permit each of the particles an opportunity
to
present
themselves
surface.
Often the limiting factor for
reducing the sample size is the accuracy of
the weighing device used to determine the
amount of material retained on the sieve.
Generally a 25 to 100 gram sample is
recommended. However, if it is necessary
to establish the correct sample size, utilize
the following procedure: Using a sample
splitter, reduce samples to weights (i.e. 25,
50, 100, 200 grams).
such
a
unit,
Always make
If a 50
will
provide
a
to
the
screen
Analyze these
a
more
various sample sizes on a selected nest of
sieves
preferably using a mechanical sieve shaker.
If the test with the 100 gram sample shows
approximately
passing the finest sieve as the 50 gram
sample, whereas the 200 gram sample
shows a lower percentage, this would
indicate that the 200 gram sample is too
large and the 100 gram samples would be
satisfactory.
sample on the same set of sieves for the
same time period to see if repetitive results
are obtainable.
for
a
period
of
the
same
Then run the 100 gram
five
minutes
percentage
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