Testwork: Bond abrasion index

Testwork: Bond Abrasion Index

Test name

Bond Abrasion Index

Abbreviation Alternate Forms Ai

Typical F80 size Typical P80 size 19 000 µm n/a

Models

Steel wear calculation

The Bond Abrasion Index is a measure of how readily a rock sample will wear away steel that comes into contact with it. It is conventionally used to estimate the liner and media wear rate in rod mills, ball mills and crushers.

This is a batch test and returns a result in units of grams (the amount of metal that wears off the test coupon).

Sample Requirements

The minimum sample consists of 2 kg of material in the -19 mm by +13.5 mm size fraction. Sample finer than 13.5 mm cannot be used and should be excluded from the 2 kg sample weight measurement.

Test Inputs

Not applicable

Test outputs

The laboratory will report

• Ai value, in grams. The test product particle size distribution is commonly provided, but is rarely used for performing calculations.

The test consists of measuring the weight of a standard steel paddle before and after contact with the ore sample in a tumbling mill with a specific geometry. The reported Ai value is the quantity of mass (measured in grams) lost by the paddle during the test.

Extra field available for modelling

• synthetic indicates whether this is a real test result, or just a synthetic one that should only be used for modelling. If this column contains a value of '1' (boolean=true) for a test, then that test is understood to not be a real test result and is therefore not shown on the testwork comparison charts. Synthetic values are available when running circuit model simulations and do show up in the list of model results.

Modelling

Abrasion Index is not used directly in any of the power models. It is used in secondary calculations to estimate the wear of mill liners and media.

The original wear formulae are widely published, including Page 752 of the "Mineral Processing Plant Design, Practice, and Control Proceedings", Volume 1, SME 2002. These equations were based on the ball and liner metallurgy of the mid 20^th century and may be obsolete for more advanced steel alloys.

The ball wear equations in SAGMILLING.COM use a newer calibration formula that uses the Bond Abrasion Index was published by Carlos Rabanal & Levi Guzmán of Moly Cop Andesur (Procemin 2013). This model is referred to as the "Improved Benavente" equation and computes the 'specific wear constant' $k^{E}_{d}$ measured as µm of ball wear per kWh/t of net mill power.

$k^{E}_{d} = 1.36 \left [ \left ( \frac {Ai - 0.05}{0.20} \right ) ^{0.166} \left ( \frac {F_{80}}{5000} \right ) ^{0.069} \left ( \frac {pH}{10} \right ) ^{-0.243} \right ]$

Discussion

The Bond Abrasion Index is related to wear estimates by formulae generated by Fred Bond at Allis-Chalmers in the 1950's. The relationships are entirely empirical and were calibrated to the liner and media metallurgy of that era. Large-scale SAG milling was not included in the process operations that Bond surveyed (they wouldn't appear in their modern form for another twenty years), and no widely-accepted formula for estimating liner or ball wear in SAG mills using Abrasion Index has been published.