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Fastest grinding occurs where there is just sufficient
material in a batch to fill all voids and slightly cover
the grinding media. The material should never be allowed
to drop below the surface of the grinding media, because
when this happens, excessive wear occurs to the mill
and grinding media and contaminates the material itself.
The largest size batches should not exceed 60% of total
mill volume.
We should establish the batch size consistent with
the allowable running time. It is recommended to do
a little experimentation with the batch size to try
to develop a system that will work out best under particular
grinding conditions. The one principal rule to remember
is that the grinding media must be covered with material.
Viscosity - The most important element in wet grinding
is the viscosity of the batch. Low viscosity materials
permit the grinding media to move with excessive
speed and this may cause abnormal wear, contamination
and heat build-up. If the low viscosities cannot be
avoided then it is imperative that small grinding media
be used.
With high viscosities free movement of the grinding
media is impeded. This can cause a carrying over and
"throw" of the media resulting in inefficiencies
and contamination.
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