Fault localisation based on loop status monitoring

A problem loop in a process plant containing a number of interacting PI or PID control loops is identified by comparing the overall loop performance indices associated with each of the loops involved. These indices are derived from a number of loop performance statistics that include the qualitative loop status, which can be one of seven categories. The derivation of the index is described and its performance is tested on various data sets. The background is given in a companion paper