4.6.1 It is not practicable to specify a single
method of sampling for all consignments since the character of the
material and the form in which it is available will affect the selection
of the procedure to be used. In the absence of internationally or
nationally accepted standard sampling procedures, the following sampling
procedures for concentrate stockpiles may be used to determine the
moisture content and the TML of mineral concentrates. These procedures
are not intended to replace sampling procedures, such as the use of
automatic sampling, that achieve equal or superior accuracy of either
moisture content or TML.
4.6.2 Subsamples are taken in a reasonably uniform pattern,
where possible from a levelled stockpile.
4.6.3 A plan of the stockpile is drawn and divided into
areas, each of which contains approximately 125 t, 250 t or 500 t, depending on the
amount of concentrate to be shipped. Such a plan will indicate the number of subsamples
required and where each is to be taken. Each subsample taken is drawn from approximately
50 cm below the surface of the designated area.
4.6.4 The number of subsamples and sample size are given by
the competent authority or determined in accordance with the following scale:
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Consignments of not more than 15,000 t:
One 200 g subsample is taken for each 125 t to be shipped.
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Consignments of more than 15,000 but not more than 60,000
t:
One 200 g subsample is taken for each 250 t to be shipped.
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Consignments of more than 60,000 t:
One 200 g subsample is taken for each 500 t to be shipped.
4.6.5 Subsamples for moisture content determination are
placed in sealed containers (such as plastic bags, cans or small metallic drums)
immediately on withdrawal for conveyance to the testing laboratory, where they are
thoroughly mixed in order to obtain a fully representative sample. Where testing
facilities are not available at the testing site, such mixing is done under controlled
conditions at the stockpile and the representative sample placed in a sealed container
and shipped to the test laboratory.
4.6.6 Basic procedural steps include:
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.1 identification of consignment to be sampled;
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.2 determination of the number of individual
subsamples and representative samples, as described in 4.6.4, which are
required;
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.3 determination of the positions from which to
obtain subsamples and the method of combining such subsamples to arrive at a
representative sample;
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.4 gathering of individual subsamples and placing
them in sealed containers;
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.5 thorough mixing of subsamples to obtain the
representative sample; and
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.6 placing the representative sample in a sealed
container if it has to be shipped to a test laboratory.