CWi vs DWi

What is the difference between CWi and DWi: WiC measures fracture strength in coarse rocks, DWi measures matrix competence in medium-size rocks.

Bond Rod Mill Work Index Equipment & Apparatus Review

Commentary on the apparatus of the Bond rod mill Work Index by Alex Doll December, 2015 alex.doll@sagmilling.com The Bond “Third Theory” of comminution was originally divided into three size classes reflecting the varieties of comminution equipment common during the time period when Bond (and his collaborators) were gathering the information to calibrate comminution models.  The … Read more

Peripheral Discharge Ball Mills -Theory and Practice

These notes are based on observations made while on a recent trip through the West, for the purpose of studying the practical operation of the ball-mill. The writer takes this opportunity to express his thanks for courtesies extended at the many plants visited as well as for the valuable data received. While there are several … Read more

Rock Crushing Theory and Formula using Kick & Rittinger’s Law

Rittinger’s theory and law of the energy expended in crushing of rock is that the work of crushing is proportional to the reduction in diameter; or, as I have more fully expressed it: “The work done in crushing is proportional to the surface exposed by the operation; or, better expressed for this purpose, the work … Read more

Rittinger and Kick’s Laws of Crushing

I happen to be one of those who believe that Rittinger probably meant what he said when he wrote what Stadler has quoted, “the increase of the surfaces exposed is directly proportional to the force required for reducing” “and therefore also to the work absorbed in effecting the separa­tions.” (The italics are now mine instead … Read more

Calculating DWi from Axb Drop Weight Test Results

The drop weight test is a common laboratory measurement used to determine the comminution characteristics of rock samples. A common metric derived from a drop weight test is a value “A×b”. Another common metric that is derived from the SMC Test™ variant of a drop weight test is a “Drop Weight Index”, abbreviated as DWi. … Read more

Standard Bond Ball Mill Grindability Test Method-Procedure

Here is the old Allis-Chalmers Bond Work Index Grindability Test Procedure. The standard feed is prepared by stage crushing to all passing a 6 mesh sieve, but finer feed can be used when necessary. It is screen analyzed and packed by shaking in a 1000-cc graduated cylinder, and the weight of 700 cc is placed … Read more

Methods to Estimate AG/SAG Mill Power Requirements

A linkedin.com group was recently discussing this by asking:  I’ve tried to estimate AG/SAG Mill power requirements using several different methods: (1) Using the results of SMC data (2) Using SAG Power Index (SPI) data (3) Using the 1989 Barratt method updated on Alex Doll’s Web site (February 16, 2015) (3) Using Don Burgess’ method (11th … Read more

Table of Bond Abrasion Index for Varied Minerals-Materials

The Bond Abrasion Test determines the Abrasion Index, which is used to determine steel media and liner wear in crushers, rod mills, and ball mills. Bond developed the following correlations based on the wear rate in pounds of metal wear/kWh of energy used in the comminution process.   Determining rock abrasivity in the laboratory ref