# Grinding & Classification Circuits

Grinding & Classification Circuits2018-06-17T09:51:34-04:00
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## Table of Bond Work Index (2 replies and 1 comment)

isqui
1 year ago
isqui 1 year ago
 Hello, I was checking the Table of Ball Mill Index. Regarding the source 1 (Bond), I checked the source and the values are different. I thought the reason was that the values reported by Bond were in short ton instead of metric ton. However, I tried to calculate one value and I still get different results. For instance basalt for Bond is 20.41 kWh/short ton, which multiplied by 1.1 short ton/metric ton gives a higher value (22.45) than the one reported on the website (18.9). Where am I wrong? Thank you!
Alex Doll
1 year ago
Alex Doll 1 year ago

Hi Isqui

I've got a copy of the 1953 work index tabulation by Bond (available from here: http://www.OneMine.org/document/abstract.cfm?do
cid=33579 )

The Andesite is given as 18.25 kWh/st; 18.25 × 1.1023 = 20.12

The 911 tabulation says Andesite is 20.1 kWh/t, which is correct.

Cement clinker in Bond's list is 13.56 kWh/st; 13.56 × 1.1023 = 14.947

The 911 tabulation says 15.0 kWh/t; also correct.

So it looks like the Source 1 column of the 911 tabulation is correct.

isqui
1 year ago

Hello Alex,

Thank you very much for your reply. We might have a different version of Bond's work then. I checked the values on "Crushing and Grinding Calculations - Part II" from 1961 on Table IIIA. I don't have access to the link you sent. From the paper, the value for Andesite is 22.13.

Best regards

RayMartin
1 year ago
RayMartin 1 year ago

The number from Fred C in 1961 was an average of 10 determinations and the Table has the rider that values can vary for the same material from different sources.  Therefore it is only a guidline.

The later values from Metso's "Basics in Mineral Processing 2015" (Bond worked for All-Chalmers, which is now Metso) gives the value for basalt as 17.10. All kwh/st.

For a particular application or project to size a mill circuit it would be prudent to have the Work Index (also for abrasion or crushing) determined at a mineral processing laboratory.

I work in the Iron Ore industry and Wi can vary widely between ore types and even within the same pit.

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