by Maryam Hussain When to operate a controller on MANUAL and AUTOMATIC control modes? To illustrate the need to operate a controller on MANUAL and AUTOMATIC control modes for controlling a process, let us consider an example of a shell and tube heat exchanger in which a process stream, on the tube side, is heated by condensing steam on the shell side. The objective of this heater is to supply the process fluid, at a specific temperature, to the downstream process otherwise the whole production will be upset . If this supply temperature deviates due to some reasons (there may be several causes/disturbing variables), then some action must be taken to correct the deviation. One way to achieve this objective is through the “monitor and control” job performed by the process plant operator. The operator observes the supply temperature of process stream Ta, compares it with the desired temperature Ts, and, on the basis of this comparison, decides whether to throttle or un-ch...
Process Constraints and Optimization, Mass and Energy balances of process, Converters development, Assignments writing.