Tag Archive: “control system”

Jan
14

Evaluating Control System Performance

Process Control System

The operation of industrial process control systems often involves the control of multiple unit operations with hundreds of measurements and control loops, as illustrated below. Although these systems are designed to automatically archive operational data in an historian, it is time consuming to examine historical data to determine if there has been a change in …

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Dec
17

Future Technology Trends

Karl Astrom

Professor Åström is well known throughout the world for his work in process control. The book he co-authored with Tore Hägglund, Advanced PID Control, is one of the most comprehensive texts on this topic. In the early 1990’s Professor Åström was a consultant to the Emerson team that did the basic research for the development …

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Jul
25

Commissioning Control Systems – Valve Performance

Impact of Sticky Valve on Automatic Control

As addressed in my July 18th blog, when a valve positioner is installed on a valve actuator, as long as it is functioning properly it will automatically increase the actuator pressure until the valve moves to a position that matches that requested by the control system. Feedback of the stem position is used by the …

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Jul
18

Commissioning Control Systems – Valve Positioners

Valve with Electro-Pneumatic Transducer

When commissioning a control system, it is important to be aware of whether a regulating valve is equipped with a positioner. If a valve does not have a positioner, then as part of loop commissioning it may be necessary to install a positioner on the valve to achieve the desired control performance. For various reasons, …

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Jun
20

Duty Cycle Control

Duty Cycle Control Example

As discussed in Chapter 11 of Control Loop Foundation – Batch and Continuous Processes, some field devices used in the process industryrequire that the control system provide a pulsed output interface. For example, in the plastics industry extruders are often used to process plastic pellets into various products. Plastic pellets are fed into the barrel …

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Apr
11

Process Simulation – Part 4

In my March 14, 21, and 28th postings I summarized some of the basics associated with design and implementation of process simulation that are addressed in the book Control Loop Foundation – Batch and Continuous Processes. Simulations based on duplicating the process step response may be effectively used for operator training and control system check. …

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