Ball Mill Loading - Wet Milling
Ball Mill Loading (wet milling)
When charging a ball mill, ceramic lined mill, pebble mill, jar mill or laboratory jar use on a jar rolling mill it is important to have the correct amount of media and correct amount of product.
Charging a Wet Mill – The general operation of a grinding mill is to have the product impacted between the balls as they tumble. Unlike dry milling, wet milling is more straight forward and more forgiving in terms of charging the product. As with dry milling there should be at least 25% liquid to fill the void space plus a bit more to insure the balls are striking product and not each other. Of course the surface tension of the liquid used will greatly affect the ability of the solids to be both suspended in the liquid and to form a film on the grinding media.
Product viscosity in a factor in wet milling. The more viscous the liquid the slower the media velocity (Stokes Law) and, therefore, the less energy imparted into the product. Again following Stokes Law, the smaller the media, and the greater it surfaces area to and the slower its velocity falling through the fluid.
Common starting points for the viscosity limits:
< 1000 cps for alumina media
< 2000 cps for steel media
The starting point for ball mill media and liquid charging is generally as follows:
- 50% media charge
- Assuming 26% void space between spherical balls (non-spherical, irregularly shaped and mixed-size media will increase or decrease the free space)
- 50% x 26% = 13% free space
- Add to this another 45% to 50% above the ball charge for total of 58% to 63% product loading.
This level of liquid loading should leave some air space above the liquid to allow for expansion of the liquid as it heats up during the milling process.
So as a rule of thumb we use a maximum of 60% liquid loading.
See our Size Reduction Options
