1.1 Flow table test procedure
The flow table is generally suitable for mineral concentrates
or other fine material with a maximum grain size of 1 mm. It may also
be applicable to materials with a maximum grain size up to 7 mm. It
will not be suitable for materials coarser than this and may also
not give satisfactory results for some materials with high clay content.
If the flow table test is not suitable for the material in question,
the procedures to be adopted should be those approved by the authority
of the port State.
The test described below provides for determination of:
.1 the moisture content of a sample of cargo,
hereinafter referred to as the test material;
.2 the flow moisture point (FMP) of the test material
under impact or cyclic forces of the flow table apparatus; and
.3 the transportable moisture limit of the test
.2 Flow table mounting (ASTM Designation (C230-68)
– see 3).
.3 Mould (ASTM Designation (C230-68) – see
.4 Tamper (see figure
220.127.116.11): the required tamping pressure may be achieved by
using calibrated, spring-loaded tampers (examples are included in
figure 18.104.22.168) or some other suitable design of tamper that allows
a controlled pressure to be applied via a 30 mm diameter tamper head.
.5 Scales and weights (ASTM Designation (C109-73)
– see 3) and suitable sample containers.
.6 Glass graduated measuring cylinder and burette
having capacities of 100-200 ml and 10 ml, respectively.
.7 A hemispherical mixing bowl approximately 30
cm diameter, rubber gloves and drying dishes or pans. Alternatively,
an automatic mixer of similar capacity can be used for the mixing
operations. In this case, care should be exercised to ensure that
the use of such a mechanical mixer does not reduce the particle size
or consistency of the test material.
.8 A drying oven with controlled temperature up to
approximately 110°C. This oven should be without air circulation.
Temperature and humidity
It is preferable to work in a room where the samples will
be protected from excessive temperatures, air currents and humidity
variations. All phases of the material preparation and testing procedure
should be accomplished in a reasonable space of time to minimize moisture
losses and, in any event, within the day of commencement. Where possible,
sample containers should be covered with plastic film or other suitable
The quantity of material required for a flow moisture test
will vary according to the specific gravity of the material to be
tested. It will range from approximately 2 kg for coal to 3 kg for
mineral concentrates. It should be collected as a representative sample
of the cargo being shipped. Experience has shown that more accurate
test results will be obtained by ensuring that the moisture content
of the test sample is increased rather than decreased towards the
Consequently, it is recommended that a preliminary flow
moisture test should be conducted, generally in accordance with the
following, to indicate the condition of the test sample, i.e. the
quantity of water and the rate at which it is to be added or whether
the sample should be air-dried to reduce its moisture content before
commencing the main flow moisture test.
22.214.171.124 Preparation of the test sample
The representative sample of test material is placed in
the mixing bowl and thoroughly mixed. Three subsamples (A), (B) and
(C) are removed from the mixing bowl as follows: about one fifth of
the sample (A) should be immediately weighed and placed in the drying
oven to determine the moisture content of the sample “as received”.
Two further subsamples, each of about two fifths of the gross weight,
should then be taken, one (B) for the preliminary FMP test and the
other (C) for the main FMP determination:
Filling the mould. The mould is
placed on the centre of the flow table and filled in three stages
with the material from the mixing bowl. The first charge, after tamping,
should aim to fill the mould to approximately one third of its depth.
The quantity of sample required to achieve this will vary from one
material to another, but can readily be established after some experience
has been gained of the packing characteristics of the material being
The second charge, after tamping, should fill the mould to about two
thirds of its depth and the third and final charge, after tamping, should reach to
just below the top of the mould (see figure 1.1.4-2).
Tamping procedure. The aim of
tamping is to attain a degree of compaction similar to that prevailing
at the bottom of a shipboard cargo of the material being tested. The
correct pressure to be applied is calculated from:
Tamping pressure (Pa) = Bulk density of cargo
Bulk density can be measured by a single test, using the
Proctor C apparatus described in ASTM Standard D-698 or JIS-A-1210,
on a sample of the cargo at the proposed moisture content of loading.
When calculating the tamping pressure, if no information
concerning cargo depth is available the maximum likely depth should
Alternatively, the pressure may be estimated from table 126.96.36.199.
The number of tamping actions (applying the correct, steady
pressure each time) should be about 35 for the bottom layer, 25 for
the middle and 20 for the top layer, tamping successively over the
area completely to the edges of the sample to achieve a uniformly
flat surface for each layer.
Removal of the mould. The mould
is tapped on its side until it becomes loose, leaving the sample in
the shape of a truncated cone on the table.
Bulk density (kg/m3)
Maximum cargo depth
||Tamper pressure (kPa)
|Iron ore concentrate
|Lead ore concentrate
|(values in parenthesis are equivalent kgf when applied via a
30 mm diameter tamper head)
188.8.131.52 The preliminary flow moisture test
.1 Immediately after removing the mould, the flow
table is raised and dropped up to 50 times through a height of 12.5 mm at a rate
of 25 times per min. If the material is below the FMP, it usually crumbles and
bumps off in fragments with successive drops of the table (see figure 1.1.4-3).
.2 At this stage, the flow table is stopped and the
material returned to the mixing bowl, where 5-10 ml of water, or possibly
more, is sprinkled over the surface and thoroughly mixed into the material, either
with rubber-gloved fingers or an automatic mixer.
The mould is again filled and the flow table is operated
as described in 184.108.40.206.1 for up to 50 drops. If a flow state is not
developed, the process is repeated with further additions of water
until a flow state has been reached.
Identification of a flow state. The impacting action of the flow table
causes the grains to rearrange themselves to produce compaction of the mass. As a
result, the fixed volume of moisture contained in the material at any given level
increases as a percentage of the total volume. A flow state is considered to have
been reached when the moisture content and compaction of the sample produce a
level of saturation such that plastic deformation occursfootnote. At this stage, the moulded sides of the sample may
deform, giving a convex or concave profile (see figure 1.1.4-4).
With repeated action of the flow table, the sample continues
to slump and to flow outwards. In certain materials, cracks may also
develop on the top surface. Cracking, with the appearance of free
moisture, is not, however, an indication of development of a flow
state. In most cases, measurement of the deformation is helpful in
deciding whether or not plastic flow has occurred. A template which,
for example, will indicate an increase in diameter of up to 3 mm in
any part of the cone is a useful guide for this purpose. Some additional
observations may be useful. For example: when the (increasing) moisture
content is approaching the FMP, the sample cone begins to show a tendency
to stick to the mould. Further, when the sample is pushed off the
table, the sample may leave tracks (stripes) of moisture on the table.
If such stripes are seen, the moisture content may be above the FMP:
the absence of tracks (stripes) is not necessarily an indication of
being below the FMP.
Measuring the diameter of the cone, at the base or at half
height, will always be useful. By addition of water in increments
of 0.4% to 0.5% and applying 25 drops of the flow table, the first
diameter increase will generally be between 1 and 5 mm and after a
further increment of water the base diameter will have expanded by
between 5 and 10 mm.
.4 As an alternative to the procedure described
above, for many concentrates a fast way of finding the approximate
FMP is as follows:
When the moisture content is definitely beyond the FMP,
measure the diameter after 25 drops, repeat the test after adding
a further increment of water, measure the diameter and draw a diagram
as illustrated in figure 1.1.4-1,
showing increase in diameter plotted against moisture content. A straight
line drawn through the two points will cross the moisture content
axis close to the FMP.
Having completed the preliminary FMP test, the sample for
the main test is adjusted to the required level of moisture content
(about 1% to 2%) below the flow point.
220.127.116.11 Main flow moisture test
When a flow state has been reached in the preliminary test, the moisture
content of subsample (C) is adjusted to about 1% to 2% less than the last value which
did not cause flow in the preliminary test (this is suggested simply to avoid starting
the main test too close to the FMP and then having to waste time air-drying it and
starting again). The final test is then carried out on this adjusted sample in the same
manner as for the preliminary test, but in this case with the addition of water in
increments of no more than 0.5% of the mass of the test material (the lower the
“preliminary” FMP, the smaller the increments should be). After each stage, the whole
moulded sample should be placed in a container, weighed immediately and retained for
moisture determination if required. This will be necessary if the sample flowed or if
the next, slightly wetter, sample flows. If not required, it may be returned to the
When a flow state has been reached, the moisture content
should be determined on two samples, one with moisture content just
above the FMP and the other with moisture content just below the FMP.
The difference between the two values should then be 0.5% or less,
and the FMP is taken as the mean of these two values.
18.104.22.168 Determination of moisture content
It should be noted that, for many materials, there are recognized
international and national methods for determining moisture content. These methods, or
ones that have been established to give equivalent results, should be followed.
Concentrates and similar materials
It is clearly important that the samples should be dried to a constant mass.
In practice, this is ascertained after a suitable drying period at 105°C by weighing the
sample successively with an interval of several hours elapsing. If the mass remains
constant, drying has been completed, whereas if the mass is still decreasing, drying
should be continued.
The length of the drying period depends upon many variables, such as the
disposition of the material in the oven, the type of container used, the particle size,
the rate of heat transfer, etc. It may be that a period of five hours is ample for one
concentrate sample, whereas it is not sufficient for another. Sulphide concentrates tend
to oxidize, and therefore the use of drying ovens with air circulation systems is not
recommended for these materials, nor should the test sample be left in the drying oven
for more than four hours.
The recommended methods for determination of the moisture content are those
described in ISO 589-1974, “Hard Coal – Determination of Total Moisture”. This method,
or ones that have been established to give equivalent results, should be followed.
Calculation of moisture content, FMP and transportable moisture limit:
as the exact mass of the subsample “as received” (see 22.214.171.124),
as the exact mass of the “as received” subsample, after drying,
as the exact mass of the sample just above the flow state (see 126.96.36.199),
as the exact mass of the sample just above the flow state, after drying,
as the exact mass of the sample just below the flow state (see 188.8.131.52),
as the exact mass of the sample just below the flow state, after drying,
.1 The moisture content of the concentrate “as
.2 The FMP of the material is:
.3 The transportable moisture limit of the material
is 90% of the FMP.
For all peat moss, determine the bulk density, using either the ASTM or CEN
(20 L) method.
Peat should be above or below 90 kg/m3 on a dry weight, basis in
order to obtain the correct TML.
As indicated in 1.1.1, the following should be determined:
.1 the moisture content of a sample of cargo
.2 the flow moisture point (FMP);
.3 the transportable moisture limit (TML). The TML
will be determined as follows:
.3.1 for peat with a bulk density of greater
than 90 kg/ m3 on a dry weight, the TML is 85% of the FMP;
.3.2 for peat with a bulk density of 90 kg/
m3 or less on a dry weight, the TML is 90% of the FMP.