What is a control? What is a control system? What is variability and how can it be improved? Can operators identify problems with controls before they stop working? How does better knowledge of these subjects by operators help them improve operations? This course answers these questions.
Often, from an operator's perspective, controls are black boxes that keep the process running - and when they don't - a call is made to E&I. However, controls can be “working” but not in a manner that provides any benefit to the operation. Data shows that often over 50% of the controls in a manufacturing facility are not operating properly and that in many cases, process performance would improve if the control was turned off.
This course gives operators the tools to understand how process control works, what their process displays look like when the controls are optimized, and what the displays look like when the controls are not working properly. With this knowledge they can know when and who to look for help when there is a problem and how to improve their interactions with the controls system when there are no problems. As a result, the plant should see improved performance in the areas of throughput and quality.
This lesson will describe some basic definitions used when talking about controls. The focus is on how a control affects operations. The definitions provided here are: control, average value, and variability
The last lesson finishes with a discussion of variability. This lesson continues the discussion, but within the context of process capability. A brief overview of Statistical Process Control is a natural progression of the variability discussion. This forms the basis for discussions on controls vs. process capabilities in later lessons. Exercises for the student include some simple SPC applications.
Lesson 3 – Proportional Control
PID control is defined and then proportional control is discussed. A comparison is drawn between SPC and P control. Strengths and weakness of pure proportional control are reviewed.
Lesson 4 – Proportional Integral Control
This lesson combines the learnings from lessons 2 and 3. In lesson 2 the student learned the problems with over control when basing current control actions solely on current error, rather than considering the history of the error and the process capability. Lesson 3 looked at how proportional control works and importantly how it does not make use of the error history. In this lesson, the integral component is added to the control to account for the error history. A comparison is drawn between the SPC in lesson 2 and the PI control of this lesson. Finally, PI control introduces the subject of loop stability.
Lesson 5 – Proportional Integral Control Continued
This lesson continues the discussion of the previous lesson. The focus now is on the more practical aspects of PI control, including dead time, stability, over control, loop tuning, variability reduction, and other aspects of PI loop operation.
Lesson 6 – Proportional Integral Derivative Control and Loop Tuning.
The concept of derivative control is introduced. Given the rarity of this type of control only an overview is provided here. In lesson 5 many issues with PI loops were presented. In this lesson the loop tuning process and how a tuned loop can improve variability is described.
Lesson 7 – Cascade control
Many loops are combined into a cascaded controls scheme. Although operators do not often adjust the inner loops of these schemes, high variability in one of the inner loops can cause overall variability of the output. The student will learn how cascaded controls operate and some sources of output variability.
Lesson 8 – Model Based Control and Troubleshooting
PID control has been the focus of this course, but many examples of advanced model based controls are seen in manufacturing plants. These controls are examined from the context of how they resolve some issues seen in PID control of variability. The final section addresses the troubleshooting that an operator can perform to determine if controls are working adequately.
The Controls for Operators course is designed to help operators understand how controls operate and how they can be optimized. A key focus is how controls reduce variability and what patterns operators might see that indicate problems.
The course is delivered as an online course with simulations. Instructor led courses are available if desired. The online modules should take about 24 hours to complete.
If you have any questions or comments - please contact us at 253.333.6685