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!i <br />If Fiaure 4 is compared to Figure 2, the estimated coal ASG derived from the <br />HGC equation is closer to the actual data than the SGS calculated ASG values. <br />Therefore, if the ASG sampling and testing program outlined above fails to <br />provide reasonable results, then the use of the HGC equation might be useful for <br />density estimation If an equation is used to estimate coal ASG, then the drill <br />hole database will be changed to accommodate analyzed and calculated ASG <br />values. <br />SGS, ASTM and Australian density /specific gravity differences <br />SGS employs an internal, but commonly used ASG testing method. The ASTM <br />provides no standard for testing specific gravity for coal. The SGS ASG method <br />uses coal size to 8 -mesh (2.36mm or 0.093 ") and shakes the sample for 20 <br />minutes. The ASH is then calculated by the measured displacement of water. <br />The ASTM does have a standard (D -167) for specific gravity of lump coke, which <br />still uses displacement of water. The coke samples in this test are ground to <br />200 -mesh and are shaken. <br />The Australian Standard AS1038 relative density test uses coal ground to 65- <br />mesh (.212mm or 0.0083 "). To de- aerate the sample AS1038 recommends <br />using a pump desiccator, boiling the samples in a glycerin bath or vibrating the <br />samples with an ultrasonic vibrator. AS1038 also includes the use of dilute <br />wetting agent (methanol) to minimize effects of air - bubbles. The relative density <br />is measured using displacement of water. <br />According to the Preston & Sanders report on Determining In -Situ Relative <br />Density the smaller particle size reduces the affects of internal pore space on the <br />samples. However, the smaller particle size is affected by surface tension of <br />small air - bubbles on the particles. This is why AS1038 mentions several <br />methods for de- aerating the samples. <br />Fr <br />L-A <br />