Monthly Archive: March 2009

Mar
30

What Have I Learned? – Ratio Control (Part 1)

Ratio control provides coordination of multiple flows. One flow is an “independent flow” that is used to set production rate. Sometimes this flow is also termed a “wild flow” when the availability of this flow is not determined by the production unit. In a ratio control system, the process variable (PV) or set point (SP) …

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Mar
25

Application Notes

MPC Implementation Methods for The Optimization of a Slow MV with Good Load Rejection by a Fast MV, September 22, 2005 (970KB PDF) MPC Implementation Methods for the Optimization of the Response of Control Valves to Reduce Variability, January 3, 2007 (463KB PDF) Compensation of Dead Time in PID Controllers, December 6, 2006 (4,074KB PDF) …

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Mar
24

What Have I Learned? – Manipulation of Multiple Flows (Part 3 – MPC)

In this final part of this series, we look at what model predictive control (MPC) can do for the following applications: (1) Extend rangeability (2) Improve resolution (3) Enable preferential use of flows based on cost (4) Send flows to multiple destinations possibly based on priorities (5) Provide counteracting effects MPC is the more powerful …

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Mar
16

What Have I Learned? – Manipulation of Multiple Flows (Part 2 – Valve Position Control)

If you have manipulated flows with counteracting effects (application 5), such as steam and coolant or acid and base reagents, your most straightforward solution is split range control because split ranged control prevents a loss in efficiency from both streams flowing at the same time if there is no overlap at the split range point …

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Mar
09

What Have I Learned? – Manipulation of Multiple Flows (Part 1 – Split Ranged Control)

When there is more than one manipulated flow, split range control is commonly used, the subject of Part 1. In succeeding parts to this series we will see how regulatory control connoisseurs use valve position control and advanced control enthusiasts have gotten increasingly innovative in the use of model predictive control. The manipulated flows are …

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Mar
04

What Have I Learned? – Cascade Control (Part 3)

We conclude with a ten step implementation procedure for helping you get the most out of your cascade control system. (1) Pick a fast secondary measurement with enough rangeability to correct for nonlinearities and disturbances. Flow is the most popular secondary measurement because it is relatively fast and can compensate for nonlinear valve characteristics and …

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