The Bond Abrasion Index, devised by F.C. Bond in the 1940‘s, quantifies the abrasivity of an ore. The index can be used to calculate metal wear rates in crushers and ball consumption rates in ball mills.
Bond’s abrasion test consists of a hardened Cr-Ni-Mo alloy steel paddle (hardness 500 Brinell). 7.62 cm X 2.54 cm X 0.64 cm with 2.54 cm of its length silling inside a rotor. 11.43 cm diameter. The rotor is covered by a concentric steel drum 11.43 cm in length and 30.54 cm in diameter. Both the rotor and the outside drum are mounted on a horizontal shaft. The rotor rotates at 632 rpm while the drum rotates in the same direction at 70 rpm. The initial charge mass is 4(X) g of-19.0 mm + 12.7 mm size material. The rotors are run simultaneously for 15 min. Next, the charge is removed and the process is repeated four times. That is. the spindle is exposed to abrasion for I hour. The charge recovered each time is collected, mixed, sieved dry and the P*, determined. The spindle is also weighed. The loss in mass (in grams) of the spindle gives the abrasion index. A,. The total power used in rotation is noted. The abrasion index thus determined is included in Table 3.5 for selected minerals. Mathematical correlation with the work index has not been reliably established.
The abrasion index is used as an indicator of metal wear and crusher and mill liner life expectancy. A high abrasion index, for example > 0.6. would suggest a preference for a single stage crusher-SAG mill circuit to avoid multiple stages of crushing and costly liner replacement operating costs. For A; values > 0.15 non-autogenous impact crushers are considered uneconomic and for A, values > 0.7 double toggle jaw crushers are preferred to single toggle crushers.
Bond developed a number of correlations between the abrasion index and metal wear in operating plants. Figure 3.20 shows a plot of these relationships.