SA Instrumentation & Control - Control Loop

Control Loop

Control loop question answered
June 2019, Michael Brown Control Engineering, Editor's Choice
Control loop expert Michael Brown recently received a question from reader, Hansell Williams. The question relates to applying neural network and machine learning concepts to plant automation and control. ...

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Case History 166: Feel and understanding, or lack thereof
May 2019, Michael Brown Control Engineering, Motion Control & Drives
I was present at a very interesting discussion the other day with people who are leaders in the automation and control industry. The subject was how jobs would disappear over the next decade or two as ...

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Case History 165: Interesting tests on loop problems show how much can be deduced from the results.
March 2019, Michael Brown Control Engineering, Motion Control & Drives
I have published many articles showing problems in control loops with figures showing the tests conducted to determine the problems. This time, by way of a change, I would like to suggest that readers ...

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Case History 164: More on valves that do not control properly.
January 2019, Michael Brown Control Engineering, Motion Control & Drives
I often publish articles showing valve problems. One of the reasons is that I do not think many people understand that valves are generally responsible for 75-80% of all control loop problems. When it ...

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Case History 163: Control limitations on mineral processing plants
November 2018, Michael Brown Control Engineering, Motion Control & Drives
I was recently asked to conduct a control loop audit on a mineral extraction processing plant which was fairly old and had been acquired by new owners. A new and very modern control system had been installed ...

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Case History 162: Optimising an interesting temperature control.
September 2018, Michael Brown Control Engineering, Editor's Choice
I have often written about the huge advantages of using cascade control on processes with very slow dynamics. It is particularly useful when it comes to most temperature related processes, which are normally ...

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Case History 161: Differences between PLCs and DCSs – a discussion from a practical control point of view
July 2018, Michael Brown Control Engineering, Motion Control & Drives
Eliakim Musikiti read one of my articles in SA Instrumentation and Control and emailed me to ask what the differences are between PLCs and DCSs. I started replying to him and then thought that it would ...

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Case History 160: More problems with control
May 2018, Michael Brown Control Engineering, Editor's Choice, Motion Control & Drives
In a recent assignment to sort out problems being experienced in a petrochemical refinery, I came across the following two examples:       Drum pressure misbehaving The first was with the control of an ...

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Case History 159: Bad valves again hampering control.
March 2018, Michael Brown Control Engineering, Editor's Choice
It still fascinates me that so many control problems are caused by poor operation of control valves. I have encountered and recorded hundreds of cases of such problems. What is amazing is that many plant ...

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Case History 158: Report on temperature control of an autoclave
January 2018, Michael Brown Control Engineering, Editor's Choice, Motion Control & Drives
I was recently asked to help with a client who treats a product in an autoclave and was complaining that they always got overshoot on a step setpoint change to holding temperature. The following is taken ...

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Case History 157: Positive lead integrator tuning ‘party trick’.
November 2017, Michael Brown Control Engineering, Editor's Choice
Control loop optimisation has always fascinated me. In most cases when I am called into a plant to sort out a problem, it is something that they have been trying to fix for a long time without success. ...

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Case history 156: All problems can be sorted by tuning
September 2017, Michael Brown Control Engineering, Editor's Choice
People often battle for long periods trying to tune a controller to eliminate problems. As I have often said, one of the biggest fallacies found in plants when it comes to control is that “all problems ...

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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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