Computers in process control

Course notes from Computers in Process Control FDA Course, March 19-23, 1984. 

As previously described, the use of computers and computerized systems in the pharmaceutical industry is growing at a rapid rate. Some of the systems used in the industry range in complexity from the use of personal computers for performing simple tasks (word processing, e-mail, Internet access) to the use of powerful computers in process-control applications. In addition, to help eliminate or reduce paper usage, the pharmaceutical industry has implemented a number of electronic batch record systems in drug substance and product manufacturing to keep track of process documentation. 

What are the basic and most important advantages offered by digital computers in process control Discuss the size, capabilities, and prices of the most recent digital microprocessors available in the market. Do you realize the inexpensive potential that they offer for process control ... 

Performance of Digi Control L(X)ps, presented at 4th Annual Conference on the Use of Digital Computers in Process Control, Baton Rouge, La., (Feb. 1969). 

The use of computers and microprocessors (also known as programmable electronic systems [PES]) in process control continues to grow. They have brought about many improvements but have also been responsible for some failures. If we can learn from these failures, we may be able to prevent them from happening again. A number of them are therefore described below. Although PES is the most precise descnption of the equipment used, I refer to it as a computer, as this is the term usually used by the nonexpert. 

West, B., Clark, J. A. (1974). Operator Interaction with a Computer-Controlled Distillation Column. In E. Edwards F. P. Lees (Eds.), The Human Operator in Process Control. London Taylor Francis. 

Gilmore, W. E., Gertman, D. I., Blackman, H. S. (1989), User-Computer Interface in Process Control—A Human Factors Engineering Handbook. New York Academic Press. 

A detailed discussion of the application of digital computers and microprocessors in process control is beyond the scope of this volume. The use of computers and microprocessor based distributed control systems for the control of chemical process is covered by Kalani (1988). 

The sensor, transmitter, and control valve are physically located on the process equipment ( in the field ). The controller is usually located on a panel or in a computer in a control room that is some distance from the process equipment. Wires connect the two locations, carrying current signals from transmitters to the controller and from the controller to the final control element. 

Digital computers are used in process control systems on a time-shared basis. A single digital computer (or microprocessor) services a number of control... 

Automation has been applied for a number of years in process control instrumentation, but the major impetus to introduce automatic devices into laboratories stems from three sources (1) the introduction of the continuous-flow principles as outlined by Skeggs [1] (2) the general demand for clinical chemical measurements, which represents a ready and sizeable market for instrument companies, and, more importantly, (3) the abihty to handle large volumes of data and package them in a form suitable for presentation to analysts and customers, through the use of mini- and micro computer systems hnked to a control computer. 

Robert W. Schrage, The Automatic Computer in the Control and Planning of Manufacturing Operations Ernest J. Henley and Nathaniel F. Barr, Ionizing Radiation Applied to Chemical Processes and to Food and Drug Processing... 

Often analytical solutions are permitted. Moreover, on today s high-speed computers they impose only minor CPU requirements, and therefore could find considerable use in process control, design and optimization. They also become very attractive models for solution on inexpensive personal computers which could be placed in a remote location or refinery. 

Kalman, R. E., Lapidus, L., and Shapiro, E. 1959. The optimal control of chemical and petroleum processes. Proceedings of the Joint Symposium on Instrumentation and Computation in Process Development and Plant Design, May 11-13, 1959. Institution of Chemical Engineers, London. 

Nowadays, for reasons of safety and performance, monitoring and supervision have an important role in process control. The complexity and the size of industrial systems induce an increasing number of process variables and make difficult the work of operators. In this context, a computer aided decision-making tool seems to be wise. Nevertheless the implementation of fault detection and diagnosis for stochastic system remains a challenging task. Various methods have been proposed in different industrial contexts (Venkatasubramanian et al., 2003). 

---