TABLE 3A: COMPARISON BY POWER PER TON (KwH/T)

Eliminating variations in mill circuit feed and product, Table 3B shows the comparison based upon the work index calculated from the operating data (W_io)

TABLE 3B
COMPARISON BY OPERATING WORK INDEX (W_io)

The next comparison eliminates the variations caused by differences in the grindability of the ore. This is the more accurate comparison as it compares grinding circuit performance as referred to a common base or reference. Table 3C gives the comparison based upon: Wioc / Wi

TABLE 3C:
COMPARISON BY GRINDING EFFICIENCY
 FORMULA

Month	68% CS			73% CS
	Mill A	Mill B	Average	Mill C	Mill D	Average
January	1.04	1.22	1.13	1.01	--	1.01
February	0.97	0.91	0.94	0.91	--	0.91
March	1.18	1.01	10.95	0.89	1.10	0.995
April	0.94	0.98	0.96	0.97	0.88	0.925

These two samples were given to show how the Bond work index can be used to evaluate grinding mill performance, record mill operating data and evaluate in-plant grinding studies. In a multi-stage separately as a single mill. If the data does not permit this, consider all stages as a single stage by using the feed to the first stage, the final product size and the total power of all stages in calculating W_io.

It has been determined that the work index obtained from standard Bond Grindability Test cannot be used to determine the power required for grinding in primary autogenous and partial autogenous grinding circuits. (4) However, calculating work indices from operating data is satisfactory for evaluating from corresponding grindability and impact tests, the performance of primary autogenous and partial autogenous circuits can be rated.