Abstract
When boilers are running normally, the ordinary process controllers which have been developed until now, act excellently, but they are almost useless in an abnormal condition. Usually simple automatic trip systems are so poor that the human operator is indispensable even in fully automated plants. On the other hand, if we equip the plant with many fault detectors, the plant may frequently make unnecessary halts due to noise or troubles in detectors.
The purpose of this paper is to develop a new type emergency control system which keeps the plant safe while making the down time minimum. The now system has two major actions. One is the automatic diagnosis finding the place of troubles, either in the plant side (including normal state) or in the detector side. The other action is the prediction whether the plant state is going into the dangerous state or not.
The basic idea of the diagnosis is the combination of “maximum likelihood” and “two out of three”. The prediction is done by “simulation”. After building the emergency control system, the authors tested it with a steam plant. This experiment gave fine results. The artifical troubles imposed by the authors were completely diagnosed.
