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When available, use the work index form a grindability tost at the desired grind for Wi in equation 5. For equation 7, use either the work index from an impact test or a rod mill grindability test, whichever is higher. For equation 8, use the work index from a red mill grindability test, since this more represents the coarse fraction of the feed; if not available then use the ball mill grindability test results.
Without grindability test results, finding the proper work index figure to use in equation 5 is a trial and error calculation which can be programmed for a computer. Using this approach, the work index used in equation 5 should equal the Wioc obtained, after applying EF4 to the work index calculated from operating data. |
