AS ISO 12742:2021 – Copper, lead and zinc sulfide concentrates-Determination of transportable moisturelimits – Flow-table method.
5.10 Drying trays or pans, having dimensions that permit the sample to be spread to a thickness of less than 30 mm.
The trays shall be made of corrosion-resistant and heat-resistant material, such as stainless steel, glass or enamel plate.
5.11 Drying oven, ventilated, with forced circulation of air or inert gas, regulated at a temperature of
5.12 AIrtight containers.
6 Sampling and sample preparation
6.1 General
TML figures are required to be updated on a periodic basis, usually six-monthly, or when there Is a known change to the process used to produce the material. The reported figure should be the mean of samples taken during the period.
To ensure that the TML result is representative, increments of the material shall be taken in accordance with ISO 12743. either:
a) while a stockpile is being built up or broken down: or
b) while loading or discharging a vessel.
These increments are combined to form the sample used to determine TML.
The sample used to determine TML should not be used to determine moisture content.
Stationary sampling of stockpiles should never be used for the determination of TML. This method of sampling can only be used to provide an indicative moisture value for use during the planning of shipping schedules.
6.2 Laboratory sample
Samples for the determination of TML shall be taken in accordance with ISO 12743. The laboratory sample shall not weigh less than 12 kg. To minimize changes to the flow characteristics of the sample, it shall not be oven-dried or ground during Its preparation, although partial drying as described In 7.4.4 is allowed.
6.3 Sample preparation
Homogenize the laboratory sample as quickly as possible to prevent moisture losses. Take nine test samples as follows:
a) Sample I
Take not less than 2 kg from the laboratory sample. This sample is to he used for determining the moisture content of the sample as received. Place this sample on a drying tray or pan.
b) Sample 2
Take approximately 1.2 kg from the laboratory sample. This sample is to be used for the preliminary TML test Store this sample in an appropriately labelled airtight container.
c) Samples 3 to 6
7 Procedure
7.1 General
Copper, lead and zinc concentrates can undergo rapid changes in moisture when exposed to air, so all stages of the test should be accomplished In the shortest time period and shall be completed within the day of commencement. Where possible, sample containers should be covered with plastic film or any other suitable airtight cover.
The moisture result from sample 1 provides information about how far the material under test is from the flow moisture point.
As more accurate results are obtained when the moisture of the test portion is close to the flow moisture point, a preliminary test is carried out (sample 2). The result of this test is used to adjust the moisture of the final test portion to 1 % to 2 % relative below (samples 3 and 4) and above samples S and 6) the flow moisture point.
To check the main flow moisture point graphically, three more samples (samples 71o9, having moisture values higher than the flow moisture point, are tested. The flow moisture point Is the extrapolation to zero of the least squares linear regression of the test portions showing a measurable displacement. The value obtained this way will he used to validate the main flow moisture paint.
7.2 Preparation of test portions
7.2.1 General
Sample 1 shall be prepared in accordance with ISO 10251. Proceed to 77
Samples 2 to 9 shall be prepared in accordance with 7.2.2 to 7.2.6.)
7.2.2 FillIng the mould
Place the mould on the centre of the flow table and fill It In three stages with the test portion as follows:
a) the first charge, after tamping, shall aim to fill the mould to approximately one-third of its depth; b) the second charge, after tamping, shall fill the mould to about two-thirds of its depth;
cJ the third and final charge, after tamping, shall reach to just below the top of the mould (see Figure 1).
The quantity of test portion required to achieve each of these stages will vary from one material to another, but is readily established after experience has been gained on the packing characteristics of the material being tested.