Hardness

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 middle size class, represented by rod milling, is fitted to a tumbling test, referred to as the Bond rod mill work index (WiRM, or RWi).  The apparatus used to determine this work index was described in

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By | 2017-03-19T03:06:49+00:00 March 31st, 2016|Categories: Hardness, Laboratory Procedures, Rod Mills|Comments Off on Bond Rod Mill Work Index Equipment & Apparatus Review

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 types of ball-mill on the market, particular attention will here be given to the diaphragm type (Peripheral Discharge Ball Mills ), as the open-trunnion type, especially the conical mill, has been thoroughly discussed here.

There is a prevailing impression that the ball-mill

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By | 2017-03-17T19:31:07+00:00 March 14th, 2016|Categories: Ball Mills, Hardness, Laboratory Procedures|Comments Off on Peripheral Discharge Ball Mills -Theory and Practice

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 done on a given mass of rock is proportional to the reciprocal of the diameter of the final product, assuming that all the mass has been reduced to one exact size, which is only theoretically possible.”

Kick’s law is: “The energy required for producing analogous changes

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By | 2017-03-19T03:48:31+00:00 March 11th, 2016|Categories: Crushing & Screening, Hardness, Laboratory Procedures|Comments Off on Rock Crushing Theory and Formula using Kick & Rittinger’s Law

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 of Rittinger’s or Stadler’s.)

Our difficulty lies in not understanding just what occurs at the so called “elastic limit.” Up to this point the energy applied to the body is absorbed by it uniformly in proportion to volume. At the so-called elas­tic

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By | 2017-03-19T04:16:15+00:00 March 8th, 2016|Categories: Crushing & Screening, Hardness|Comments Off on Rittinger and Kick’s Laws of Crushing

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. This work looks at a public database of test results to determine a relationship for DWi as a function of A×b.

by Alex Doll @ SAGMilling.com

Method

A database of publicly published grindability test results has been collected by the Author. This database includes just over

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By | 2017-03-19T05:58:43+00:00 February 1st, 2016|Categories: Crushing & Screening, Hardness|Tags: |Comments Off on Calculating DWi from Axb Drop Weight Test Results

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 in the mill and ground dry at 250 per cent circulating load.

The mill is 12 in. x 12 in. with rounded corners, and a smooth living except for a 4 in. x 8 in. hand hole door for charging. It has a revolution counter and runs at 70 rpm.

The grinding charge consists of 285 iron balls weighing

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By | 2017-03-19T07:13:56+00:00 December 14th, 2015|Categories: Concentrator Manuals/Procedures, Grinding, Hardness|Comments Off on Standard Bond Ball Mill Grindability Test Method-Procedure

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 Mill Operators Conference 2012)

They seem to give very different predictions for guiding the selection of SAG mill sizes.

I tend to favor the updated Barratt method in terms of the rationale behind the approach, but I don’t have access

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By | 2017-03-19T12:58:01+00:00 October 20th, 2015|Categories: Grinding, Hardness|0 Comments

Table of Bond Abrasion Index for Varied Minerals-Materials

Table Abrasion Index of Minerals

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.

Bond_Abrasion_Test_determines_the_Abrasion_Index SGS

Determining rock abrasivity in the laboratory

ref

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By | 2017-03-19T13:08:37+00:00 October 8th, 2015|Categories: Grinding, Hardness|0 Comments