AS 2806.5 pdf download – Aluminium ores—Sampling Part 5: Methods for checking the precision of sampling
4 General conditions 4.1 General The dctcrmination of prccision of sampling is based on duplicatc sampling from lots. If samplc prcparation and analysis is also carried out in duplicate, it is possible to determine the errors associated with those parameters in addition to the errors due to sampling.
4.2 Number of lots for the experiment In order to reach a reliable conclusion，it is rec- ommended that the experiment be carried out on more than 20 lots of the same type of aluminium ore. However. if this is impracticable, at least 10 lots should be covered and each lot shall be divided into several perts to produce more than 20 parts for the experiment. Thc cxperiment shall be carried out on cach part, considering cach part a3 a separate lot in accordance with ISO 8685.
4.3 Number of increments and number of gross samples The minimum number of increments required for the experiment shall be twice the ununnber specilieu in IsO 8685. Thus, if the number of increments required for the routine sampling is n and one gross sample is constitutcd, the minimum number of increments re- quired for the experiments shall bc 2n and two gro3s samples shall be constituted.
NOTE 2 If this is impracticable. n increments may be taken and divided into two parts, each corprising n/2 inr orements.
4.4 Sample preparation and testing The preparation of samples shall be in accordance with IsO 6140 and the testing of samples shall be carried out in accordance with the methods pre- scribed in the relevant International Standards.
4.5 Replication of experiment It is recommended that, even after a series of exper- imcnts has bccn conducted, the experiments should be repeated at regular intcrvals and when there is a change in ore quality. The experiment should also be repeated when there is a change in equipment or of ore supplier. Because of the large amount of work involved in this method, it is recommended that the procedure should be carried out as a part of routine work of sampling and measurcment.
5.1 Duplicate samples Fach alternate primary increment is set aside in order to form gross samples A and B. The number of div- ided increments per primary increment Is the same as that taken for routine sampling An example of a sampling plan for gross samples A and B is shown in figure 1
5.2.2 Division-testing type 2 (see figure 3)
5.2 Sample division and testing The tWo gross samples A and B taken in accordance with 5.1 shall be divided separately and subjected to either type 1, type 2 or type 3 testing as described in 5.2.1, 5.2.2 or
5.2.3 respectively. 5.2.1 Division-testing type 1 (see figure 2)
220.127.116.11 The two gross samples A and B shall be divided separately to prepare two final samples.
18.104.22.168 The four final samples A1, A2 and B, B2 shall each be tested in duplicate. A total of eight tests shall be run in random order. NOTE 3 In type 1 testing. the standard deviations of sampling, preparatlon and measurement are obtained separately.
22.214.171.124 The gross sample A shall be divided to pre- pare two final samples, A1 and A2. and from the gross sample B, one final sample shall be prepared.
126.96.36.199 The final sarmple A, shall be tested in dupi- cate and the other final sarmples A2 and B shall be tested individually.
NOTE4 In type 2 testing, the standard deviations of sampling，preparation and measurement are obtainable separately. However, the precision for estimating the stan- dard deviations Of sampling. preparation and measurement will be luwer Uhan lial allainable in type 1 testing.
5.2.3 Division-testing type 3 (see figure 4)
188.8.131.52 From each of the two gross samples A and B, one final sample shall be prepared.