Greg McMillan

Author's details

Date registered: April 19, 2011


Gregory K. McMillan,CAP, is a retired Senior Fellow from Solutia/Monsanto where he worked in engineering technology on process control improvement. Greg was also an affiliate professor for Washington University in Saint Louis. Greg is an ISA Fellow and received the ISA "Kermit Fischer Environmental" Award for pH control in 1991, the Control Magazine "Engineer of the Year" Award for the Process Industry in 1994, was inducted into the Control "Process Automation Hall of Fame" in 2001, was honored by InTech Magazine in 2003 as one of the most influential innovators in automation, and received the ISA "Life Achievement Award" in 2010. Greg is the author of numerous books on process control, his most recent being Essentials of Modern Measurements and Final Elements for the Process Industry. Greg has been the monthly "Control Talk" columnist for Control magazine since 2002. Presently, Greg contracts as a consultant in DeltaV R&D via CDI Process & Industrial.

Latest posts

  1. Different but the Same — February 22, 2012
  2. Compressor Surge and Stall Detection and Prevention — January 26, 2012
  3. How to Succeed – Part 10 — January 19, 2012
  4. How to Succeed – Part 9 — January 12, 2012
  5. How to Succeed – Part 8 — January 5, 2012

Most commented posts

  1. Unification of PID Controller Tuning Rules — 1 comment
  2. Techniques to Improve pH Measurement Performance — 1 comment

Author's posts listings


How to Succeed – Part 2

Our profession is learned on the job by example and ad-hoc, incidental, or formal mentoring. Experienced APC and E&I engineers have largely left the building. In the new millennium we started a runaway reaction with an accelerating loss of expertise. Are we at a “point of no return?” Is the demise of our profession at …

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How to Succeed – Part 1

The capability of field instrumentation, distributed control systems, and advanced process control (APC) software has dramatically increased. At the same time, energy and environmental requirements and the need for worldwide competitiveness have increased. Production units more than ever need to be able to take advantage of their automation and APC systems. Yet there is a …

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Secondary Flow Loops Offer a Primary Advantage

A secondary flow loop offers opportunities for feedforward control, identification of valve stick-slip and backlash, online metrics, diagnostics, rejection of pressure disturbances, linearization, and modeling. However,  a secondary flow loop can be detrimental when the primary loop has a 63% response time less than 10 seconds. If the 63% response time is greater than 5 seconds, an exceptionally …

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Reactor Cooling and Heating Systems – Part 4

Heat exchangers in a coil or jacket recirculation system are used to provide tempered water. This allows the use of colder or hotter utility streams as inputs to exchangers rather than as inputs to a coil or jacket, moderating temperature extremes  that could cause heat transfer surface coatings or product degradation from localized cold and hot spots …

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Reactor Cooling and Heating Systems – Part 3

Heat exchangers in a process recirculation steam are also used for reactor temperature control. The high velocities on the process side in the exchanger increase the heat transfer coefficient and reduce fouling. For cascade control the reactor temperature PID output is the setpoint of the exchanger outlet temperature. For the exchanger to do its job …

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Reactor Cooling and Heating Systems – Part 2

Whether the secondary loop uses coil or jacket inlet or outlet temperature is often a matter of tradition for a particular company or process industry. The dynamic response of the cascade control system to reactant disturbances such as feed and reaction rate are the same for jacket inlet and outlet temperature control. However, the coil or …

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Reactor Cooling and Heating Systems – Part 1

The cooling and heating system is critical for reactors since temperature plays such a huge role in determining reaction rate and selectivity (formation of desired product).  The limit to what a valve position controller (VPC) can do to increase production rate depends upon the capability of the cooling and heating system. The system can also be the …

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Batch vs. Continuous Control and Optimization – Part 4

Batch and fed-batch reactors are designed so that the product concentration is always increasing in the reaction phase of the cycle whereas continuous reactors are designed to hold a constant product concentration. These fundamental differences have enormous implications in terms of composition control. Conventional control of product concentration in a batch and fed-batch reactor is …

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Batch vs. Continuous Control and Optimization – Part 3

Reactors are the pivotal unit operation that sets plant capacity and efficiency besides product quality. Reactors provide good examples of the common and distinctive opportunities for the PID control of batch, fed-batch, and continuous unit operations. Here we examine pressure, temperature, and endpoint control. The pressure control of batch, fed-batch, and continuous reactors may have …

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Batch vs. Continuous Control and Optimization – Part 2

Batch and continuous temperature loops can have vastly different responses. Fortunately, temperature loops have a characteristic early in the response that enables a fast identification of the process dynamics. The resulting models can be used for process control improvement, tuning, and rapid deployment of models for plantwide simulations. Temperature is the most important common measurement …

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