The Continuous Flow Industries: Feedback Control and Computerisation

Continuous flow industries process bulk raw materials into finished or intermediate products by physical or chemical means to produce a finished product with the desired attributes (Laspe 1957: 420). Although many process industries operate around the clock, others produce in very large batches or in near-continuous systems. It is a very diverse group. The classic examples are oil refining, the petrochemicals industry, and parts of the iron and steel industry, but branches of the building materials and food processing industries had been making the transition to continuous processing from the late nineteenth century; the dividing lines between very large batch and continuous operation were often indistinct. Production processes in these industries were transformed during the twentieth century by two major developments. First, these industries tended to become more scientifically-based, with attempts to understand more clearly the basic science of the reactions upon which production depended. Secondly, as scientists understood the chemical and physical processes of production, they needed increasingly sophisticated and robust measuring devices to monitor changes in an increasing array of chemical and physical properties and intricate servomechanisms to move controls by precise amounts. By these means closed loop feedback controls allowed the chemical reactions to be monitored and controlled much more closely, often with dramatic consequences for the industry concerned.1 The business histories of these industries and of the giant businesses that dominated them have done much to explain the scientific research and development work but it is essential to turn to the automation literature of the 1950s for insights into the development of instrumentation, control mechanisms and the rapid expansion of automatic control.