The Ball Charge in SAG- and Ball Mills, the fraction of the mill volume constituted by balls, has a significant impact on the performance of a mill and the greater Grinding circuit. Running at the wrong Ball Charge would adversely impact not only the process's throughput but the consistency of the product particle size (P80) as well.

A prominent problem is that plant personnel are often unsure what the ball charge levels in their mills are. Meaning that they don't have accurate feedback on when to add balls into their mill, apart from when they stop the mill to see.

In other words: either impact your mill performance by doing more mill stoppages (to measure ball charge) or by not knowing what the ball charge is.

Our Solution's Grinding Application solves this problem with its Ball Charge Virtual Sensor and its accompanying Alert.
The Grinding Application's Ball Charge Model tracks the level of the ball charge in the mill in real-time. It uses AI and first-principle modelling of ball wear and -ejection in order to accurately predict changes in the ball charge levels during the mill's operation. The model tracks multiple factors including ball additions, ore properties, ball hardness, mill operational regimes, discharge grate design, etc.

The resulting real-time Ball Charge Virtual Sensor gives Operators and Metallurgists immediate and direct feedback on their Ball Charge of each mill. These Virtual Sensors are delivered in as an Alert, which compares the Virtual Sensor value with desired/optimal operating bands (minimum & maximum limits) for the particular mill. Whenever the Ball Charge moves outside of these ranges, Operators are alerted to correct it by adjusting their ball addition schedule/control.

This Virtual Sensor can also be used historically by Metallurgists to do root-cause analyses, and see which ball charge ranges gave the best performance over a given period or for a given ore type.


Stabilising the Ball Charge in your Mills and ensuring close tracking of your optimal Ball Charge setpoints will increase your mill throughput and improve your P80 stability. Additionally, it will mean you can stop your mill less often (for ball measurements) and avoid unnecessary ball breakage and mill liner damage.

Dashboard Example

This Grinding Application Virtual Sensor and Alert are delivered to Operators and Metallurgists via Below is an example of a Dashboard showing the Ball Charge Virtual Sensor with other key Mill variables, and an Alert showing that the Ball Charge is low:

  1. Navigate to SAG Mill Ball Charge dashboard.

  2. Select LIVE mode in the time picker.

  3. Observe the Line graph to ensure the ball charge remains within the desired range.

  4. See the bar chart to know about the current ball size distribution.

  5. Adjust your ball addition schedule as required to achieve the desired ball size distribution.

  6. Record the ball addition via the Data Input Widget (if not on your SCADA system).

  7. See the total volume taken up by balls (Jb).

For more info, please do reach out to us via Intercom. We'd be happy to help!

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