AS 4264.4-1996

Sets out methods for checking and adjusting the precision of sampling, checking the precision of sample preparation and measurement, and testing for bias in the sampling of coal and coke.

This Standard sets out methods for checking and adjusting the precision of sampling, checking the precision of sample preparation and measurement, and testing for bias in the sampling of solid mineral fuels.The procedures described in this Standard apply to sampling of coal and coke from both moving streams and stationary situations, and to the subsequent sample preparation.Experiments to check for precision and bias should be carried out for all sampling programs, whether manual or employing mechanical elements, implemented on a regular basis. Procedures should be repeated whenever significant change in the character of materials being sampled, especially in nominal top size or particle size distribution, has occurred.When a mechanical installation is commissioned or when principal parts are modified, check experiments for precision and bias should be carried out for the installation as a whole. The material to be used for bias tests should be the most variable material that is likely to be sampled. Various parameters, e.g. ash, can be used as measures of the variability of the material. One measure of variability that has been developed is the size-ash index.Where a bias higher than the maximum acceptable bias is detected, checks of individual elements of the system should be made, to determine which part or parts of the installation may require modification.The preferred method of testing for bias (see Clause 8) is by comparison with 'stopped-belt' sampling and using the critical properties in the operation of the sampling system.Design criteria of primary samplers for avoiding bias in a mechanical sampling system are given in AS 4264.1 and AS 4264.2. Reference is made to the geometry of cutter opening design and aperture, cutting speeds, measures for prevention of sample change and contamination, and procedures for examination of the performance of mechanical sampling equipment.

First published as AS K153.1-1964 (being endorsement of BS 1017.1:1960 with Australian Amendment).
Secon edition 1967.
Revised and redesignated AS 1676-1975.
Revised and redesignated AS 2646.8-1984.
Revised and redesignated AS 4264.4-1996.