Nine Control Fundamentals

I came across the following nine control fundamentals according to Mark Coughran, a consultant on Emerson’s Advanced Applied Technology team. These are based up his years of experience working with process manufacturers to optimize their performance. You may recall Mark from earlier posts on planning plant turnarounds and turbomachinery pressure control.

His fundamentals include:

  1. Make the process as linear as possible
  2. Minimize dead time
  3. Choose the PID controller to compensate for the process
  4. Avoid resonance or amplification of disturbances
  5. Use process capacity to absorb variability
  6. Decouple the interactions by tuning if possible
  7. Help the PID feedback controller with control strategy
  8. Cascade, ratio, feedforward; a.k.a. advanced regulatory controls
  9. Use Fuzzy, Neural, MPC if the above are insufficient

Although there is a lot behind each one, it’s a way to think through the process of solving control performance issues.

Mark cited an example of a Good Automated Manufacturing Practice (GAMP) facility with eight reactors. All of the controls cycled strongly. As a result, steam was being wasted on the up cycle, and cooling water was being wasted on the down cycle. Thinking through the control fundamentals above, Mark recommended changes in the master controller parameters including tuning, jacket controller tuning, split range strategy, and control valve calibrations.

By implementing these changes on three of the eight reactors steam usage for the facility was reduced 10% reducing the plant’s energy bills.

Posted Monday, February 12th, 2007 under Process Optimization, Variability Management.

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