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a | Chapter 13 Overview of Control System Design General Requirements 1. Safety. It is imperative that industrial plants operate safely so as to promote the well-being of people and equipment within the plant and in the nearby communities. Thus plant safety is always the most important control objective and is the subject of Section 10.5. 2. Environmental Regulations. Industrial plants must comply with environmental regulations concerning the discharge of gases liquids and solids beyond the plant boundaries. 3. Product Specifications and Production Rate. In order to be profitable a plant must make products that meet specifications concerning product quality and production rate. 1 Chapter 13 4. Economic Plant Operation. It is an economic reality that the plant operation over long periods of time must be profitable. Thus the control objectives must be consistent with the economic objectives. 5. Stable Plant Operation. The control system should facilitate smooth stable plant operation without excessive oscillation in key process variables. Thus it is desirable to have smooth rapid set-point changes and rapid recovery from plant disturbances such as changes in feed composition. 2 Chapter 13 Steps in Control System Design After the control objectives have been formulated the control system can be designed. The design procedure consists of three main steps 1. Select controlled manipulated and measured variables. 2. Choose the control strategy multiloop control vs. multivariable control and the control structure e.g. pairing of controlled and manipulated variables . 3. Specify controller settings.
