Tumbler tests

The drop shatter test indicates the resistance of a coal or coke to breakage on impact (see D440). A sample is dropped in a standard way a number of times from a specified height. Eor the tumbler test or abrasion index (ASTM D441), the coal or coke is rotated in a dmm to determine the resistance to breakage by abrasion (18). 

Other Tests. The so-called tumbler tests are usually used for testing material like coke, coal, iron ore pellets or tablets. They can be divided into drum tests and ball mill type tests. The latter type is used to derive both the Hardgrove Index and the Bond s Work Index, which are often used to classify the material friability as described in Sec. 3. They are generally more suited to coarse material. The Hardgrove Grindability test requires an initial size range form 595 to 1190 microns. 

ASTM D-441. Standard Test Method of Tumbler Test for Coal. 

ASTM D-3402. Standard Test Method for Tumbler Test for Coke. 

The second test, known as the tumbler-test method, also forms one of the tentative A.S.T.M. standards (A.S.T.M. Designation D 441 -37 T). The apparatus for this test consists of a 7V4-in. diameter pebble mill in which a 1000-g sample is rotated at a speed of 40 rpm. No pebbles or balls are used in the jars. Three lifting shelves 120 deg apart, mounted on a removable circular frame, are provided the frame is fastened to the jar during the test. The jar (four jars containing the same sample are usually run simultaneously on one machine) is turned for one hour at the speed indicated. 

In conducting the tumbler test for friability, great care must be taken in selecting and preparing the sample. Since the procedure for friability determinations requires the use of 1.5- to 1.05-in. coal, it is necessary that samples be selected from this size range. It is also necessary that each lump be free from cracks or any indications of faults which might bias the results. The lumps selected are carefully screened through a 1.5-in. screen and those sizes retained on the 1.05-in. screen to the amount of 1000 g are placed in the pebble mill and turned as described above. 

D 441 - 37 T. Tentative method of tumbler test for coal. Part III, 575-579. E 11 -39. Standard specifications for sieves for testing purposes. (Wire cloth sieves, round-hole and square-hole screens or sieves.) Part III, pp. 535-541. 

ASTM tumbler test, 36 balling circuit control, 75 balling drums, 78... 

Apart from the impact and vibration tests dealt with previously, there are several other tests of friability, some of which appear in British Standards dealing with specific materials. Such tests include mixer tests, jet impingement tests, shear tests, tumbler tests and fluidized bed tests. Of these, the shear tests and tumbler tests are only considered worth mentioning here, with more details available from another BMHB publication54. 

Tumbler tests, and more specifically drum tests have been probably most popular and there are at least two British standards describing the procedures, one for testing of coal and coke15 (the MICUM test) and another for iron ore63, with some American standards also available (ASTM D3402, D4058-81 and E278). 

It is clear from this short review of some standard tumbler tests that this area is well served by national standards. Each caters for a specific material and has been developed for a specific index... 

The tumbler test for measuring coal friability (ASTM, 2011f) employs a cylindrical porcelain jar mill (7.25 in. [18.4 cm] in size) fitted with three lifters that assist in tumbling the coal. A 1000 g... 

ASTM. 201 If. Method for Tumbler Test for Coal (ASTM D441). Annual Book of ASTM Standards, Section... 

Size of Coal, Designating from its Screen Analysis Sulfur in Coal Ash Sulfur, Forms of, in Coal Tumbler Test for Coal... 

ASTM E279-97 (2005) Standard Test Method for Determination of Abrasion Resistance of Iron Ore Pellets and Sinter by the Tumbler Test ASTM C421-05 Standard Test Method for Tumbling Friability of Preformed Block-Type Thermal Insulation... 

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