A new alarm system design method is proposed, in which it is assumed that the sign
patterns and alarm sequences generated by the alarm system are invariant for each
possible plant malfunction in a plant. The proposed method gives the most sets yet
provided of plant malfunctions that operators can distinguish using the alarm system.
We applied the proposed method to select alarm variables for a simple chemical plant.
Results showed that the method provides more alarm variable combinations that can
identify possible malfunctions than a previously used method.