ABSTRACT
Process control systems involve industrial operations for the manufacture or transformation of energy and chemical products in a continuous stream through the interaction of mass and energy. They include, on the large scale, operations such as the manufacture of chemicals, oil refining and electrical power production, whether using fossil or nuclear energy; and on the small scale processes such as pasteurization and domestic heating and air conditioning. Processes that bear some similarities to process control but which are sufficiently different include discrete manufacturing, transportation systems and systems such as hospitals, although under certain conditions and assumptions aspects of the human factors of process control can be applied to these latter. For general descriptions of the human factors of process control see Rasmussen (1986), Woods (1986), Rasmussen et al. (1995) and Moray (1997a, b)
Process control systems have characteristics in common which cause difficulties for operators and other personnel. Typically they involve the interchange of large volumes or masses of physical substance, the feedstock, and the exchange of large quantities of energy. These exchanges are frequently on a scale which, if uncontrolled, give rise to considerable hazard, to which the events at Bhopal and Chernobyl bear witness. Control of rates of reaction, and mass-energy balances are central to process control operations. Frequently the products, by-products, or waste products include materials which are toxic, and which therefore must be controlled.
