2002 Volume 35 Issue 12 Pages 1282-1289
It is desirable to support operator activity in abnormal correction of chemical plants. Although fault diagnosis systems have very fertile grounds for theoretical and industrial development, there are few papers discussing countermeasure planning. In this paper, a method to select operating modes, in order to settle the abnormal situations down, is proposed. The operating modes are categorized into “maintained”, “compromised” and “shutdown”. In the maintained mode, all controlled variables can be maintained by using alternative actuators or sensors in abnormal situations. The compromised mode and shutdown mode are distinguished by the controlled variables to be abandoned in abnormal situations. Three fault trees, which are “safety”, “quality” and “quantity”, are prepared to classify the controlled variables. If the controlled variables, which are included in a safety tree, cannot be maintained, the shutdown mode is selected. In order to judge the capability to maintain the controlled variables, a controller configuration design method based on CE-matrices is applied. If all controlled variables for safety can be maintained, and if controlled variables for quantity or quality cannot be maintained, the plant can be operated in the compromised mode. In this paper, a countermeasure planning algorithm based on fault trees and CE-matrices is proposed. Even though this algorithm cannot propose the quantitative actions, it can suggest the situation, to which the abnormal plant will be settled down, to the operators. And it is also suggested to maintain a safe operation, which actuators should be manipulated and which sensors should be observed. This selection method of operating modes in abnormal situations is as useful as the first stage of countermeasure planning.
