Ep16 Why SAG milling triumphed over AG milling

Autogenous grinding (AG) of ores dates back to the early 1900's and predates Semi-autogenous grinding (SAG) by several decades. The first modern SAG mills appeared in the late 1960's and early 1970's, and often these SAG mills were originally installed as AG mills which failed to deliver the grinding performance that the mines needed. These were quickly modified by adding grinding balls, giving birth to the current SAG mill. In other words, SAG milling was a response to the failure of AG milling in these projects. Very few fully autogenous milling projects are being proposed now; the SAG mill (and its accompanying ball charge) is the base case for a lot of new mining projects, with the HPGR and ball milling circuit a distant second place in popularity. This presentation will explore why SAG mills are so superior to AG mills for most projects and why the costs of the grinding balls consumed in the SAG mill will be offset by improved project financial returns.