Copper, lead, zinc and nickel concentrates

BS ISO 12743:2021 pdf free.Copper, lead, zinc and nickel concentrates – Sampling procedures for determination of metal and moisture content.
7.2.3 Sample cutter
The following cutters may be used for taking primary increments:
a) a falling-stream cutter whose cutting speed is constant during the course of handling the entire lot;
b) a falling-stream cutter whose cutting speed is constant while cutting the stream but can be regulated, primary increment by primary increment, corresponding to the flow rate of the concentrate on the conveyor belt;
c) a cross-belt cutter.
7.2.4 Taking of primary increments
Each primary increment shall preferably be taken by a single traverse of the sampling device, so that a full cross-section of the concentrate stream is taken. However, in manual-sampling cases where it is not possible to obtain a complete cross-section in one operation, increments may be taken systematically across the concentrate stream so that, when they are combined, they represent the full cross-section of the stream (see 9.7).
The first primary increment shall be taken ata random mass, less than the mass interval m determined in 7.22. Thereafter, the required number of primary increments shall be taken at fixed mass intervals ofm, and this interval shall not be changed during the entire course of sampling the lot.
If the planned number of primary increments has been taken and handling has not been completed, additional primary increments shall be taken at the same mass interval until the handling operation is completed.
7.2.5 Constitution of subsamples and lot samples
If the coefficient of variation of primary increment masses is 20 % or less, primary increments may be combined into subsamples or a lot sample. either as taken or after having been processed individually to a particular stage. Subsamples shall preferably comprise equal numbers of consecutive primary increments.
However, if the coefficient of variation of primary increment masses exceeds 20 %, either:
a) each primary increment shall be subjected separately to division (according to the rules of division) and determination of its quality characteristics; or
b) primary increments shall be subjected to constant mass division, prior to combining into subsamples or a lot sample.
Primary increments and subsamples should not be combined into a single sample for the lot, unless the composite sample can be adequately mixed (see 15.3).
For the determination of moisture content, it is recommended that a moisture subsample be constituted for each sub-lot. This will not only reduce the total variance but will also minimize loss of moisture and hence bias.
7.2.6 Types of division
Two types of division are applicable to mass-basis sampling:
a) Constant-mass division, which is a method of obtaining divided increments, subsamples or lot samples with almost uniform mass, regardless of the variation in the masses to be divided. Cutter- type dividers with variable cutting frequencies can be used for this type of division (see 15.4.6).
b) Proportional division, which is a method of obtaining divided increments, subsamples or lot samples with masses proportional to the varied masses to be divided. Rotary sample dividers can be used for this type of division (see 15.4.5).
Cutter-type dividers can lead to moisture loss, so are not recommended for division of moisture samples.
72.7 Division of increments
Where increments require division and subsamples or a lot sample are constituted from the divided increments, division shall be carried out as follows (see Table 4):
a) If the coefficient of variation of the increment masses is 20 % or less, either constant-mass or proportional division shall be used.
b) If the coefficient of variation of the increment masses is greater than 20%, division shall be carried out on an increment-by-increment basis using constant-mass division.
7.2.8 Division of subsamples
Where subsamples are divided and a lot sample is constituted from the divided subsamples, division shall be carried out as follows (see Table 4):
a) If the coefficient of variation of the subsample masses is 20% or less, and the subsamples consist of an equal number of increments, either constant-mass or proportional division shall be used.
b) If the coefficient of variation of the subsample masses is greater than 20 %, and the subsamples consist of an equal number of increments, constant-mass division shall be used.
c) lithe subsamples consist of different numbers of increments, proportional division shall be used.
7.2.9 Division of lot samples
When a lot sample is divided, either constant-mass or proportional division shall be used.
7.3 Time-basis systematic sampling
7.3.1 General
Time-basis sampling involves the fllowing steps:
a) Distributing the required number of primary increments on a uniform time basis throughout the lot to be sampled.
b) For each time interval, taking increments of mass proportional to the concentrate flow rate at the time of taking the increment.
The time interval between primary increments should be rounded down to the nearest second, to ensure that the number of primary increments taken will be larger than the minimum number required.
7.3.3 Sample cutter
The following cutters may be used for taking primary increments:
a) A falling-stream cutter whose cutting speed is constant during the course of handling the entire lot.
b) A cross-belt cutter.
7.3.4 Taking of primary increments
Each primary increment shall preferably be taken by a single traverse of the sampling device, so that a full cross-section of the concentrate stream is taken. However, in manual-sampling cases where it is not possible to obtain a complete cross-section in one operation, increments may be taken systematically across the concentrate stream so that, when they are combined, they represent the full cross-section of the stream over time (see 91).
The first primary increment shall be taken at a random time less than the time interval tt determined in 7.32. Thereafter, the required number of primary increments shall be taken at fixed time intervals of t, and this interval shall not be changed during the entire course of sampling the lot.
If the planned number of primary increments has been taken and handling has not been completed, additional primary increments shall be taken at the same time interval, until the handling operation is completed.
7.3.5 Constitution of subsamples and lot samples
Subsamples or lot samples may be constituted in either of the following ways:
a) primary increments, as taken, shall he combined into subsamples or a lot sample, irrespective of the variation of masses of primary increments; or
b) primary increments shall be divided by proportional division; subsamples or lot samples shall then be constituted by combining divided increments.
Where subsamples are analysed to determine the quality characteristics for the lot, the mass of the sub- lot from which the subsample was taken shall be determined, in order to obtain the weighted average of the quality characteristic for the lot.
Primary increments and subsamples should not be combined into a single sample for the lot, unless the composite sample can be adequately mixed (see 15.3).
For the determination of moisture content, it Is recommended that a moisture subsample be constituted for each sub-lot. This will not only reduce the total variance, but will also minimize loss of moisture and hence bias.
7.3.6 Types of division
Both constant-mass and proportional division are applicable to time-basis sampling (see 7.2.6).
7.3.7 Division of increments and subsamples
Increments and subsamples shall be divided by proportional division (see Table 4).
7.3.8 Division of lot samples
When a lot sample is divided, either constant-mass or proportional division shall be used (see Table 4).BS ISO 12743 pdf download.Copper, lead, zinc and nickel concentrates