SA Instrumentation & Control - Control Loop

Control Loop

Case History 155: Control with unstable tuning
July 2017, Michael Brown Control Engineering, Motion Control & Drives
I have come across quite a few control loops that were doing a reasonable job of control and which were in fact completely unstable, and in some cases were working much better than if the loop had been ...

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Case History 154: What happens to the process if the valve jumps?
May 2017, Michael Brown Control Engineering, Editor's Choice, System Integration & Control Systems Design
I recently wrote a Case History about control problems in a minerals extraction plant in Portugal, which was experiencing great difficulty with the control on their flotation banks. I have also written ...

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Case History 153: Why is the control so terribly erratic?
March 2017, Michael Brown Control Engineering, Editor's Choice, Motion Control & Drives
I was recently asked to advise on a bad pH control problem in a water treatment plant. A new carbonisation bay had been installed at the plant: Figure 1 shows the layout of the bay and controls. Raw water ...

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Case History 152: Control problems with airflows in flotation banks
January 2017, Michael Brown Control Engineering, System Integration & Control Systems Design
I have written quite a few articles specifically dealing with control problems in mineral processing plants that are largely due to poor understanding, and apparently complete lack of concern of control ...

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Case History 151: The myths surrounding deadtime dominant processes
November 2016, Michael Brown Control Engineering, Editor's Choice, System Integration & Control Systems Design
The practice of industrial feedback control is one of the most misunderstood engineering disciplines in the world. The theory was developed by eminent mathematicians in the early 1900s and was based on ...

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Case History 150: Mystery in distillation column temperature control.
September 2016, Michael Brown Control Engineering, Editor's Choice
The longer I work in the field of control loop optimisation, the more I learn that things often do not work the way one expects. I have spent over 30 years optimising literally thousands of feedback control ...

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Case History 149: Classic examples of badly optimised loops.
July 2016, Michael Brown Control Engineering, Editor's Choice
Problems on a flow control loop    The first example is that of a flow control loop on a liquid flow. Figure 1 shows a closed loop test with a step change of setpoint.    Three problems immediately stand ...

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Case History 147: Why base-layer feedback control is needed
April 2016, Michael Brown Control Engineering, Editor's Choice, System Integration & Control Systems Design
A friend of mine was appointed to start an advanced control and optimisation group in a very large chemical plant and he hired a group of academically highly qualified young APC (advanced process control) ...

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Case History 146: What makes control loop optimisation worthwhile?
February 2016, Michael Brown Control Engineering, Editor's Choice, System Integration & Control Systems Design
In this article we look at three cases where great success was achieved through optimisation. The work was all done in a petro-chemical refinery.       Case study 1 The first example is of a reactor feed ...

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Case History 145: Control problems in a zinc mine
December 2015, Michael Brown Control Engineering, System Integration & Control Systems Design
As a break from the problem reports presented in the last few Case Histories, this article will discuss some problems I encountered recently at a zinc mining plant in Europe where I carried out a base ...

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Case History 144: Report after optimisation exercise – part 5
October 2015, Michael Brown Control Engineering, System Integration & Control Systems Design
This is the fifth article taken from a report which was prepared for various departments in a process company after some optimisation work was performed for them. (The other four articles were published ...

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Case History 143: Report after optimisation exercise – Part 4.
August 2015, Michael Brown Control Engineering, System Integration & Control Systems Design
This is the fourth article taken from a report which was prepared for various departments in a process company after some optimisation work was performed for them. (The other three articles were published ...

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Case History 142: Report after optimisation exercise – Part 3.
June 2015, Michael Brown Control Engineering, System Integration & Control Systems Design, Editor's Choice
This is the third article taken from a report which was prepared for various departments in a process company after some optimisation work was performed for them. (The other two articles were published ...

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Case History 141: Report after optimisation exercise - Part 2
April 2015, Michael Brown Control Engineering, System Integration & Control Systems Design
The first part of a report, published in Case History 140 (February), showed successes obtained and problems uncovered in an optimisation exercise in a particular process plant that takes optimisation ...

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