Greg McMillan shares ways to address slow valves and different time constants between primary and secondary loops. Recorded deminar (demo/seminar) available for viewing at: http://www.screencast.com/t/YWYxZGUw

1. Interactive Opportunity Assessment Demo and Seminar (Deminar) Series for Web Labs – PID Control of Slow Valves and Secondary Loops May 12, 2010 Sponsored by Emerson, Experitec, and Mynah Created by Greg McMillan and Jack Ahlers

3. The Latest on Unleashing PID Power for Batch Processes Chapter 3 Features: PID Types and Structures Positive Feedback Integral Mode Dynamic Reset Limiting Cascade Loops Full Throttle Startup Appendix C Features: Unification of Tuning Methods

9. Volume Booster with Integral Bypass (Furnace Pressure and Surge Control Signal from Positioner Air Supply from Filter-Regulator Air Loading to Actuator Adjustable Bypass Needle Valve

10. Booster and Positioner Setup (Furnace Pressure and Surge Control) Port A Port B Supply ZZZZZZZ Control Signal Digital Valve Controller Must be functionally tested before commissioning! 1:1 Bypass Volume Booster Open bypass just enough to ensure a non-oscillatory fast response Air Supply High Capacity Filter Regulator Increase air line size Increase connection size Terminal Box

12. Ramping Response of Actuator for a Large Step or a Large Actuator Multiply time by 10 for large actuator without volume booster Time (sec) Stroke (%)

13. Exponential Response of Actuator for a Small Step or a Small Actuator Stroke (%) Time (sec)

15. Positive Feedback Implementation of Integral Mode with Dynamic Reset Limit   SP   proportional derivative  Gain     Rate    CO filter filter CV filter Filter Time   Rate Time  filter Filter Time = Reset Time ER is external reset (e.g. secondary PV) Dynamic Reset Limit ER Positive Feedback

17. Cascade Control Benefit (self-regulating process)  i   o   i   o   i   o   i  inner loop process time constant  o  outer loop process time constant  i  inner loop process deadtime  o  outer loop process deadtime

19. Cascade Control Benefit (integrating process)  i   o   i   o   i   o   i  inner loop process time constant  o  outer loop process time constant  i  inner loop process deadtime  o  outer loop process deadtime

21. Effect of Slow Secondary Loop (cascade control integrating process) Secondary loop slowed down by a factor of 5 Secondary SP Secondary CO Primary PV Secondary SP Primary PV Secondary CO

27. Summary of Demos Demo Sec PID Mode Secondary Dynamic Reset Primary Dynamic Reset Valve Slew Rate Secondary Process Response Primary Process Type 1 CAS Disabled Disabled Fast Fast Self-Reg 2 AUTO Disabled Disabled Slow Fast Self-Reg 3 AUTO Enabled Disabled Slow Fast Self-Reg 4 CAS Disabled Disabled Fast Slow Self-Reg 5 CAS Disabled Disabled Fast Slow Self-Reg 6 CAS Disabled Disabled Fast Fast Integ 7 CAS Disabled Disabled Fast Slow Integ 8 CAS Disabled Enabled Fast Slow Integ

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30. QUESTIONS?