5.1 Although the determination of the washability characteristics of coal is not an exact science, this washability test method can be used to investigate the cleaning characteristics of coarse- and fine-coal fractions. However, especially with the fine-coal fractions, this test method may not be applicable for low-rank coals for reasons explained in 1.2.

5.2 The usefulness of this test procedure and the usefulness of the results derived from washability testing are directly related to the care exercised in developing and following the sampling regime while taking into consideration the desired degree of precision. For more exacting work, it will be necessary to know the general washability characteristics of the material in question. This can be done only through pilot testing as described in 9.6 and Annex A3.

5.3 This test method, in conjunction with the advice of experts and with knowledge of the particle size analysis (see Test Method D4749), is used for the engineering design of coal preparation facilities.

5.4 This test method is also used to assist in process control and to determine the efficiency of operating preparation plants.

5.5 This test method is used in core studies to determine the quality washability characteristics of coal reserves; however, in these instances the typical mass of raw coal from Table 1 may be neither applicable nor practical. For this reason, core diameter should be as large as possible and subdivision of the core section by any means or for any purpose prior to washability testing should be avoided. Care must be exercised in the design of the coring programs, including the consideration of appropriate geostatistics, in order that the potential recovery and quality of the coal reserves, as defined by the washability analysis of the cores, have any practical significance.

Size Fraction

Mass of Material Needed for Washability Analysis of that Size Fraction,
kg (lb)

200 mm × 100 mm (8 in. × 4 in. round)

2720 (6000)

100 mm × 50 mm (4 in. × 2 in. round)

 910 (2000)

50 mm × 25 mm (2 in. × 1 in. round)

225 (500)

25 mm × 12.5 mm (1 in. × ¹/₂ in. round)

 90 (200)

12.5 mm × 6.3 mm (¹/₂ in. × ¹/₄ in. round)

25 (50)

6.3 mm × 2.36 mm (¹/₄ in. × No. 8 USA Standard)

 9 (20)

2.36 mm × 1.40 mm (No. 8 × No. 14 USA Standard)

 5 (10)

1.40 mm × 600 μm (No. 14 × No. 30 USA Standard)

2 (5)

600 μm × 300 μm (No. 30 × No. 50 USA Standard)

1 (2)

300 μm × 150 μm (No. 50 × No. 100 USA Standard)

0.5 (1) 

150 μm × 75 μm (No. 100 × No. 200 USA Standard)

0.5 (1) 

1.1 This test method describes procedures for determining the washability characteristics of coarse-coal fractions and fine-coal fractions. Each sample being tested can have more than one coarse-coal size fraction and more than one fine-coal size fraction (see Annex A1). Each such size fraction has an upper size limit and a lower size limit, neither of which overlaps with the next larger nor smaller size fraction. (See Test Method D4749.)

1.2 While, in general, this test method has useful application in determining the washability characteristics of low-rank coals, in the strictest sense, it is not necessarily the most technically correct test method to determine washability characteristics of low-rank coals because of problems relative to the loss of moisture through drying during sample preparation and analysis. Methods that are directly applicable to low-rank coals are to be developed.

1.3 The values stated in SI units are to be regarded as the standard. The values shown in parentheses are for information only.

1.4 This standard does not purport to address the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, see Section 8 and Appendix X1.