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ISO 16742-2014 pdf free download
ISO 16742-2014 pdf free download.Iron ores – Sampling of slurries Minerais de fer-Echantillonnage des schlamms.
4.1 Basic requirements
In this International Standard, a slurry is defined as iron ore of nominal top size ‘ci mm that is mixed with water, which is frequently used as a convenient form to transport iron ore by means of pumps and pipelines and under gravity in launders or chutes or through long distances in slurry pipelines. Tailings froni wet plants are also discharged as a slurry through pipelines to tailings dams. In many of these operations, collection of increments at selected sample points is required for evaluation of the iron ore in the slurry.
A gross or partial sample is constituted from a set of unbiased primary increments from a lot. The sample containers and their contained combined increments are weighed immediately after collection to avoid water loss by evaporation or spillage. Weighing is necessary to determine the percentage of solids mass fraction in the gross sample. The gross or partial sample may then be filtered, dried, and weighed. Alternatively, the gross or partial sample can be sealed in plastic bags after filtering for transport and drying at a later stage.
Test samples are prepared from gross or partial samples after filtering and drying, after breaking up any lumps that have formed during drying using a lump breaker, or forcing the sample through a sieve of appropriate aperture. Test portions may then be taken from the test sample and analysed using an appropriate analytical method or test procedure under prescribed conditions.
The objective of the measurement chain is to determine the characteristic of interest in an unbiased manner with an acceptable and affordable degree of precision. The general sampling theory, which is based on the additive property of variances, can be used to determine how the variances of sampling, sample preparation, and chemical analysis or physical testing propagate and hence determine the total variance for the measurement chain. This sampling theory can also be used to optimize mechanical sampling systems and manual sampling methods.
If a sampling scheme is to provide representative samples, all parts of the slurry in the lot must have an equal opportunity of being selected and appearing in the gross sample for testing. Any deviation from this basic requirement can result in an unacceptable loss of trueness. A sampling scheme having incorrect selection techniques. i.e. with non-uniform selection probabilities, cannot be relied upon to provide representative samples,
Sampling of slurries should preferably be carried out by systematic sampling on a time basis (see Clause 7). If the slurry flow rate and the solids concentration vary with time, the slurry volume and the dry solids mass for each increment will vary accordingly. It needs to be shown that no systematic error (bias) is introduced by periodic variation in quality or quantity where the proposed sampling interval is approximately equal to a multiple of the period of variation in quantity or quality. Otherwise, stratified random sampling should be used (see Clause 8).
Best practice for sampling slurries is to mechanically cut free-falling streams (see Clause 9), with a complete cross section of the stream being taken during the traverse of the cutter. ISO 16742-2014 pdf free download.
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