Are Your Process Variables Under Control?

Printable Version (PDF)

 

KEY PROCESS VARIABLES

Key Process Variables

There is no doubt that minimizing variation in key process variables improves recovery. Optimizing the control of any process variable requires knowledge of:

With a first-class training program, your operators can become expert on each of these requirements!

FIGURE 2
GRINDING CIRCUIT

Grinding Circuit Training Program

CONTROL LOOP

Control Loop Training Program

Block Diagram Training Program

Once the operators have a good grasp of the process and the particular control loop, trainees would be taught to troubleshoot process variable problems logically, by drawing on their knowledge of the process equipment, flows, and control methodology. Operators must often check to see if the process controller output makes sense based on the deviation between the variable and set point. For example, addressing an issue with a sump level controlled by a discharge control valve, may involve the following steps:

Once the details of the process and control methodology, as well as control loop troubleshooting techniques are covered in the classroom, simulation drills can be conducted by the instructor with the operator trainees.

For example, the instructor might say that the field operator in the ball mill area has just reported that the mill discharge slurry appears to be very thick (high slurry density). The target slurry density is 60 percent solids, but the calculated discharge is running at about 70 percent solids and seems to be increasing. The trainee group would then discuss the symptom of the problem and, given their classroom knowledge of the process and control methodology, tell the instructor what they would do. For example, they will know from the training that there is a ratio control loop that modulates process water flow rate into the mill in proportion to the solids entering the mill. The trainee team might say that they would check the ratio controller and the output to the process water control valve. The instructor would then explain what they would see regarding the flow controller set point and output to the flow control valve. This back-and-forth process goes on until the trainee group finds the answer. The instructor can then critique the troubleshooting methods used by the trainees.

With proper training on the layout of the plant equipment, the process flow, process control methodologies, and troubleshooting techniques, variation in key process variables can be significantly reduced, optimizing the process and increasing mineral recovery and profits.