ASTM D720-91 pdf free.Standard Test Method forFree-Swelling Index of Coal.
Mechanical or electronic devices may be used todetermine the standard profiles if they give results equivalent tothose obtained with measurement techniques described in 7.2.1and 7.2.2.If the residue is coherent but nonswollen, place it on aflat surface and carefully place a 500-g weight on the button. If the button disintegrates,report the swelling index as one half.If the button supports the weight or merely cracks into two orthree hard coherent pieces, report the number as one.Report the average swelling index of a series of threebuttons expressed to the nearest one-half unit. If this testmethod is to be used for International Classification of hardcoal by type, make five buttons.Report the swelling index aszero if the residue from the test sample is noncoherent.
9.The relative precision of this test method forthe determination of free-swelling index covers the index rangefrom one to nine.View each coke button through the sight tube andcompare it with the series of standard profiles shown in Fig.4.Place the standard profile with which a button is to becompared exactly in the center of the field of vision as viewedfrom the top of the tube. Place the button on the profile androtate it on its axis until, viewed with the eye placed immedi-ately over the top of the tube, the maximum cross-sectionalarea is obtained. Record the number of the standard profilemost nearly matched by the maximum cross-sectional area ofthe button as the swelling index.If any button deviates by morethan one unit from the other two buttons，make a newdetermination.Some coals give buttons that do not conform in shapeto the standard profiles. For such coals， measure the maximumcross-sectional areas of the buttons and determine the indexfrom the relationship of the areas of the standard profiles toswelling indexes as shown in Fig. 5. For measuring thecross-sectional areas, mount the buttons on graph paper ruledinto square centimetres and square millimetres，and trace theoutlines of the buttons on the paper while viewing through thesight tube shown in Fig. 1. The buttons may be mountedconveniently by means of modeling clay.The squares insidethe outline may be counted, and fractions of squares along theboundary line estimated.ASTM D720 pdf download.