The abrasion resistance is expressed as volume loss in cubic millimetres or abrasion resistance index in percent. For volume loss, a smaller number indicates better abrasion resistance, while for the abrasion resistance index; a smaller number denotes poorer abrasion resistance.Abrasion index is an index that shows the abrasive properties (abrasion) of coal on the part of the equipment used to grind the coal before being used as fuel in certain combustion systems. The higher the index the abrasive coal the higher the maintenance costs of the coal grinding equipment.
A coal called abrasive when his abrasive index 400-600, and referred not abrasive when his abrasive index <= 10. Coke has abrasive index in 2500 while having an abrasive sandstone index 1200.
Desired coal buyers must have abrasive index <= 200. If abrasive index its> 200, the price of coal could be cheaper or perhaps is totally rejected.
This index is measured using a device called Abrasion Test Apparatus. This device has 4 blades knives made from carbon steel with a hardness of 160 / - 15 Vickers and dimensions of 38 x 38 x 11 mm (+ / - 0.1mm). At the time of the test will be spinning blade stirs coal sample being tested, with a speed of 1470 / - 30 r / min, 12,000 / - 20 rounds.
Minimum weight of sample needed for this test is 10kg with a top size> 16mm. Prior to testing, the samples must be carefully milled to obtain particle-6.7mm.
Tests carried out on samples of the milling results with a weight of 2 / - 0.1kg for each test.The index unit is milligrams of metal blades that eroded per kilogram of coal samples were used.
