Overview

In modern control systems, expert system technology is playing an ever-increasing role in assisting the operator in the detection and management of abnormal situations in a plant. With the introduction of distributed control systems in the late 1970's, the basic control systems of many process plants went through major changes in organization and operation. In many cases, the introduction of distributed control allowed control functions to be concentrated into a few control rooms. The traditional control panels for operator interface to the process were replaced with keyboards and monitors. There were few limits on the amount of information that could be accessed and displayed at these operator stations. These systems allowed an operator to make changes and see the process alarms associated with his area of responsibility. In some cases, the system was designed to allow all information about the plant to be accessed from any terminal within the system ^[5.1]. As a result of this technology change, and the increasing pressure on companies to increase productivity, the scope of control that an operator was responsible for changed dramatically.

In one pulp and paper mill the introduction of a distributed control system allowed three control rooms to be consolidated into one and for one operator to do the job formerly done by three ^[5.2]. In some process areas an operator is responsible for as many as thousands of measurements and hundreds of motors and control loops in addition to various subsystems in a process area. Thus,...