AS ISO 12742:2021 pdf free.Copper, lead and zinc sulfide concentrates一Determination of transportable moisture limits一Flow-table method.
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 5 and 6) the flow moisture point.
To check the main flow moisture point graphically, three more samples (samples 7 to 9), 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 be used to validate the main flow moisture point.
7.2 Preparation of test portions
7.2.1 General
Sample 1 shall be prepared in accordance with ISO 10251. Proceed to 7.7.
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;
c) 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.AS ISO 12742 pdf download.