Operability study is a systematic technique for identifying hazards or operability problems throughout an entire facility. In this paper, we have proposed an approach using knowledge engineering techniques to the automated operability study. The computer-aided operability study system consists of the plant-specific knowledge-base, the generic knowledge-base and the inference engine. Causal relationships between input and output variable deviations for components are modeled using decision tables. Decision tables for components are developed by the user and stored in a generic knowledge-base in computers. The plant structure (piping and instrumentation diagram) and reaction types are inputted to the plant-specific knowledge-base in computers. Each process variable of equipment is examined in sequence by searching the generic knowledge-base, and operability study is generated resulting from the search. We demonstrate via the Solvey process how the computer-aided operability study can identify hazards, and substantiate the usefulness of the method.