Michael Brown Control Engineering

Email: michael.brown@mweb.co.za
www: www.controlloop.co.za
more information about Michael Brown Control Engineering

Reminiscences of a life in control
February 2024, SAIMC

Reminiscences from Michael Brown on a long and rich journey in the world of automation together with SAIMC.
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Loop signatures 21: You cannot control if your measurement is incorrect.
January 2024, Editor's Choice

The first law of process control could be stated as saying that you cannot control if your measurement is incorrect. We all know this law. However do we all remember it in the heat of the moment?
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Case History 190: Measurement problem ruins level control.
November 2023, Editor's Choice, Fieldbus & Industrial Networking

The widely held belief in many plants that tuning will solve all base layer control problems is completely fallacious. Bad tuning is generally not the main reason for loops to perform badly. It is important when performing optimisation that all elements in a loop are considered, in addition to the control strategy, before even thinking of tuning.
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Loop signatures 20: The great deceivers.
October 2023, Editor's Choice

It is generally better to live with noise rather than filtering it out, provided it does not cause the final control element to jump around excessively.
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Case history 189: Poor furnace temperature control.
September 2023, Editor's Choice, PLCs, DCSs & Controllers

Many process engineers do not appreciate the importance of flow loops in their unit controls. A senior process engineer once told me that flow loops need not be tuned well, as they generally have little effect on the more important and much slower loops like temperatures and pressures.
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Loop signatures 19: Noise – nuisance or enemy?
August 2023, Editor's Choice, Fieldbus & Industrial Networking

This Loop Signature series of articles would not be complete without sections on the problems of noise and filtering, which are two of the most misunderstood areas in process control.
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Case History 188: Process gain – an important dynamic.
July 2023, Editor's Choice

When analysing a control loop, one of the important things that one must do is to determine the dynamics of the process.
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Digital controllers: Part 9 - Integral or reset windup
June 2023, Editor's Choice

The integral or I term in a controller is a brilliant thing. It is an extremely elegant and simple solution for eliminating offset in control. However, like everything else in this world, virtually everything good has its bad side as well.
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Case History 187 - Integrating or self-regulating or both?
May 2023, Editor's Choice

It is vital, when optimising a control loop, to establish at the outset if the process is self-regulating or integrating, as not only do these two process types behave completely differently, but also they are tuned very differently.
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Loop Signatures 17 - How to make a bad valve into a good valve.
April 2023, Editor's Choice, PLCs, DCSs & Controllers

People often have little realisation as to how badly a faulty valve can affect the performance of the control of the loop. So how can one make a real valve with its problems into a perfect valve? The answer is simple. One makes use of a technique called cascade control, whereby a second controller is used to control the flow of fluid through the valve.
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Case history 186: Don’t always trust valve position feedback signals
March 2023, Editor's Choice, PLCs, DCSs & Controllers

I recently encountered an interesting problem in a minerals recovery processing plant. The loop in question was a gas flow control to a burner. The operators reported that the loop cycled badly in automatic, and was very difficult to control manually. The C&I technicians had tried all sorts of tunings without any improvement.
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Loop Signatures 16 - Digital controllers: Part 8: The full PID controller and response to setpoint or load changes.
February 2023, Editor's Choice, PLCs, DCSs & Controllers

The full PID controller and response to setpoint or load changes.
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