Example: PID controller adjusts heat to control temperature
Consider the case where a PID controller adjusts heat to control temperature. In this case: the lower the temperature setpoint, the less heat is required, on average. The less heat, the less costs! Hence, after you tuned the PID optimally, the temperature variations will reduce, and you can lower the setpoint while still guaranteeing the same minimum temperature level.
This sounds like a nice way to increase profitability, if the loop is controlling quality, or adjusting some energy related input like heat or electricity. However, some control loops do not fall in this category, and even if they do, the payback on this is not always that much. So, you may wonder, what then is the main argument for going though the process of tuning loops in order to increase profitablity? That is discussed next!
Going through the tuning process allows to check for hidden problems
In a lot of cases, going through the tuning process brings up hidden problems, like:
- the controlled process variable (of the loop) does not respond to the manipulated variable (like a valve) at all!
- the controlled process variable (of the loop) responds much slower to the manipulated variable then previously!
- the controlled process variable responds in a non-smooth way , indicating sensor or software programming problems
- after PID tuning, the loop's closed loop response is much slower than predicted by the model, or
- after PID tuning, the loop's closed loop response is unstable (in contrast to what was expected of course)
All of these above mentioned issues, that can be detected with the PID Tuner, have a major impact on the plant's production quality, throughput and profitability. In addition, those problems make it harder for operators to do their work properly. Alarms are popping up on operator's HMIs way too often, due to control loop limits that are exceeded. Operators are constantly firefighting and resolving the most urgent issues. Obviously, that does not lead to world class production.
Investigations indicate that, in practice, in most plants 30% of the control loops are in manual ! Another 25% (or so) of the loops shows oscillatory behavior.
All in all, there is a huge potential to increase plant's profitability, but the results can be hard to calculate .
In the 'case studies' we show actual examples where the use of the PID Tuner created considerable increase of profits.
Click here to read those stories
 G. Buckbee, ‘How to Improve Performance Of Process Control Assets’, brochure, Expertune, 2011
 N. Vatanskia, S-L. Jämsä-Jounelaa, A. Rantalac, T. Harjub, 'CONTROL LOOP PERFORMANCE MEASURES IN THE EVALUATION OF PROCESS ECONOMICS', IFAC 2005