AUTOMATING HAZOP ANALYSIS OF BATCH CHEMICAL-PLANTS - PART I - THE KNOWLEDGE REPRESENTATION FRAMEWORK

Hazard and operability (HAZOP) analysis is a systematic procedure for determining the abnormal causes of process deviations from normal beha vior and their adverse consequences in a chemical plant. This is a dif ficult, labor-intensive, time-consuming activity that would benefit fr om automation. While HAZOP analysis is generally applied only to conti nuous process plants, it can be generalized to include batch process s ystems as well, as shown in this paper. The main thrust of this paper, however, is to develop a general framework for automating the HAZOP a nalysis of batch plants. The proposed framework combines high-level Pe tri nets and digraphs with object-oriented knowledge representation fo r the development of a general, flexible, efficient, and user-friendly system, called Batch HAZOPExpert, implemented in G2. In this framewor k, the knowledge about tasks and sub-tasks in a batch process are mode led hierarchically using high-level Petri nets. Cause and effect relat ionships between process variables within a subtask are represented us ing subtask digraphs. Petri nets and subtask digraphs interact with ea ch other in a two-tier organization to model the behavior of batch pro cesses. One of the novel features of this framework is that both the c ontinuous and discrete nature of batch operation are represented expli citly. Another feature is the modeling of operator actions and errors, since they play a more crucial role in batch process systems than in continuous ones. The first part of this paper describes the details of the intelligent systems framework. The second part discusses the appl ication of the Batch HAZOPExpert system to an industrial case study. ( C) 1998 Elsevier Science Ltd. All rights reserved.