Terry Blevins

Author's details

Date registered: April 19, 2011

Biography

Terry Blevins has been actively involved in the application and design of process control systems throughout his career. For more than 15 years, he worked as a systems engineer and group manager in the design and startup of advanced control solutions for the pulp and paper industry. Terry was instrumental in the establishment of Emerson Process Management's Advanced Control Program. From 1998-2005, Terry was the team lead for the development of DeltaV advanced control products. He is the Fieldbus Foundation™ team lead for the development and maintenance of the Function Block Specification and editor of the SIS Architecture and Model Specifications. In this capacity, Terry is involved in the movement of Fieldbus Foundation function block work into international standards. Terry is the U.S. expert to the IEC SC65E WG7 function block committee that is responsible for the IEC 61804 function block standards. He is a voting member and chairman of ISA104-EDDL (Electronic Device Description Language) committee and is the technical advisor to the United States Technical Advisory Group (USTAG) for the IEC65E subcommittee. He is also a member of the USNC TAG (IEC/SC65 and IEC/TC65). Terry authored "An Overview of the ISA/IEC Fieldbus," Section 11, Standards Overview, Fifth Edition of the Process/Industrial Instruments and Controls Handbook and coauthored four sections in the Fourth Edition of the Instrumentation Engineer's Handbook, Process Control and Optimization. He coauthored the ISA bestselling book Advanced Control Unleashed. He has 36 patents and has written over 65 papers on process control system design and applications. Terry received a Bachelor of Science in Electrical Engineering from the University of Louisville in 1971 and a Master of Science in Electrical Engineering from Purdue University in 1973. In 2004, he was inducted into Control Magazine's Process Automation Hall of Fame. Presently, Terry is a principal technologist in the future architecture team of DeltaV Product Engineering at Emerson Process Management.

Latest posts

  1. Surge Tank Control — May 20, 2013
  2. Easy to Apply Tuning Rules — May 13, 2013
  3. On-demand Tuning Example — May 6, 2013
  4. Selecting Control Response — April 29, 2013
  5. Capturing Process Dynamics — April 22, 2013

Most commented posts

  1. Control Basics and Terminology — 1 comment
  2. Basics of Advanced Control — 1 comment

Author's posts listings

May
20

Surge Tank Control

Surge Tank Level Control

Intermediate liquid storage tanks (surge tanks) are commonly installed between processing areas of the plant. Under normal operating conditions, these storage buffers allow each process area to be operated independently of the other process areas. Any imbalance in the area production rates within a plant will be reflected by a change in level of the …

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May
13

Easy to Apply Tuning Rules

Tuning PI Controller

Older control systems may not include tools that allow the PID tuning to be automatically established. In such cases, the following procedure outlined in Chapter 12 of Control Loop Foundation – Batch and Continuous Processes may be quickly applied to determine the tuning of a self-regulating process for PI control. In Chapter 4 of Advanced …

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May
06

On-demand Tuning Example

On-Demand Tuning Example

Control system manufacturers have adopted different technologies to implement on-demand tuning. Because these tools are designed to work in a noisy process measurement environment, the tuning results are usually better than those achieved through manual tuning techniques. To illustrate the features that may be included in on-demand tuning capability, the on-demand tuning capability of the …

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Apr
29

Selecting Control Response

After the process characteristics are identified, the information is then used to calculate the recommended loop tuning. The tuning rules used to derive controller parameters from process characteristics can be chosen as appropriate for the specific process and the desired speed of response. As addressed in Chapter 4 of Advanced Control Foundtion – Tools, Techniques, …

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Apr
22

Capturing Process Dynamics

Structuring On-demand Tuning

When the on-demand tuning application resides in a DCS workstation, communications between the controller and the workstation can introduce variable delay and jitter in the observed process response. As addressed in Chapter 4 of Advanced Control Foundation – Tools, Techniques, and Applications, the process may be more accurately identified by distributing the on-demand tuning functionality …

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Apr
15

On-Demand Tuning

Self Regulating Response

During the commissioning of feedback control based on the PID algorithm, the PID tuning parameters (that is, the proportional, integral, and derivative gain) must be set to specific values to achieve the best controller response to setpoint and disturbance input changes. To minimize process variations and the response time to setpoint and disturbance input changes …

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Apr
09

Performance Monitoring Tools

Performance Monitoring Overview

Many control system manufacturers and third party companies now offer tools that are designed to monitor process control and instrumentation performance. In addition to providing on-line information that summarizes control utilization, the user may access other information that may be helpful in determining the cause of, and solution to, poor control utilization. In section 3.4 …

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Apr
01

Addressing Loop Interaction

Interactive Loop Example

In some cases, the manipulated parameter of one control loop can impact the controlled parameter of another control loop as illustrated below. To allow both loops to operate in automatic mode, loop interaction is most often addressed by simply detuning one of the control loops by reducing the proportional gain. The valve (or another final …

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Mar
25

Split Range Setup

Split Range Control

One of the most common ways of addressing multiple process inputs is split range control. A splitter block, which appears as one valve to the PID block, can be used in the control strategy to define a fixed relationship between the controller output and each manipulated process input. In Advanced Control Foundation – Tools, Techniques, …

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Mar
18

Impact of Changing Process Gain

non-linear valve characteristics

From a control perspective, it is highly desirable that the process gain is constant. If the process gain is constant, then the same proportional gain can be used over the entire operating range of the control loop. Using a control valve as an example, if the valve characteristic was not properly selected based on the …

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