AS 4156.1.1 pdf download

AS 4156.1.1 pdf download.Coal preparation
2.1  Sample mass
Samples for float and sink testing shall be obtained and prepared according to the requirements of relevant Standards (AS 2519, AS 2617, ISO 13909 series) and relevant sections of this Standard. The sampling requirements stated in this Standard shall take precedence. For samples undergoing float and sink testing, the mass of the size fraction on which float and sink testing is being conducted shall be as listed in Table 1. NOTE  Appendix B provides further information and example calculations in order to determine the bulk sample mass necessary to achieve masses in individual size fractions for float and sink testing (as shown in Table 1). As a general rule, the number of discrete particles in any size fraction shall be not less than 2000. When coals exhibit low yields in any fraction, to obtain sufficient sample for analytical requirements, the sample mass shall not be less than 20 g and not less than 10 particles in each relative density fraction. If these requirements cannot be met, this fact shall be noted in the test report. NOTE 1  This is particularly relevant to float and sink testing of bore core samples. NOTE 2  Samples with different particle sizes will contain particles with different proportions of mineral matters and organic matters, which will produce different washability (different float and sink distribution). Consequently it is critical that a representative sample of the relevant size distribution is provided for float and sink testing. NOTE 3  It is assumed that square-mesh particle sizes are used; if wedge-wire or round-hole sizes are used, this fact should be reported. NOTE 4  The mass of the sample to be taken for any given purpose will determine to a large extent the accuracy of the test. In turn, the sample mass will be governed by the purpose for which the test is being carried out.NOTE 5  When a bulk sample is being taken, it is better to over-sample than to have insufficient material. For testing on the top sizes shown in Table 1, the bulk sample mass may weigh up to 20 t, and for other sizes the amounts should be reduced according to the decrease in nominal topsize. The importance of sufficient sample mass and a method for the determination of the required mass of a bulk sample is given in Appendix B.
Many coal samples, such as strip samples and bore core require pre-treatment to better simulate the size distribution of the raw coal feed to a coal preparation plant. This ensures more accurate representation of fines content, which in turn affects washability results. The pre-treatment process shall involve any or a combination of the following: (a) Drop shatter — The picking up and dropping of a sample onto a steel plate under specific conditions. Refer to AS 4156.8. (b) Top size reduction — This process requires oversize material to be reduced to pass a nominated screen, with a minimal amount of fine material being produced. Top-size reduction does not simulate the size distribution of coal preparation plant feed, because the coal particles are not selectively broken. Various methods can be utilized to perform this procedure, including the following: (i) Jaw crusher — The sample is choke-fed to the crusher with the aim of producing the nominated size. (ii) Hand knapping — The sample is broken using hand-held implements. Done carefully, this procedure can yield the least amount of fine material. Hammermill type crushers shall not be used for size reduction, due to the excess amount of fine material produced. (c) Dry tumbling — The sample is tumbled end over end in a drum under specified conditions. (d) Wet tumbling — The sample is tumbled end over end after the addition of water and under specified conditions. NOTE  See Appendix E for more information.