In mineral processing plant, The control of any crushing operations starts with the control of the feed system. Sinonine has summarized the disturbances in a crusher as:
1.Ore properties (size and hardness),
2.Ore feed rate,
3.Crusher settings (close and open settings) — alterations due to wear and tear,
4.Surge in feed load and plant power draw.
The control loops of a gold crushing plant are shown in Fig. 1.
Fig1. Control of gold ore crushing plant
Two regulatory control loops and a supervisory control loop are shown. The function of one regulatory loop (shown within dotted lines) is to control the feed tonnage on the feeder conveyor and the other to regulate the crusher power which in turn regulates the feed. The supervisory loop is a cascade loop which deals with any imbalance between the two regulatory loops through level changes in the feed hopper.
The basic instrumentation involved would include a transducer to monitor the closed side setting (and or open side setting), an A/D connection to the controller and a D/A connection to the level indicator.