This paper is an extension of the generalized parity vector (GPV) approach presented in Omana and Taylor (2005, 2006). In the present work, this fault detection and isolation (FDI) technique is implemented on a two-phase separator followed by a three-phase gravity separator model used in oil production facilities. This model simulates a larger scale process, which allows the technique to be tested in a higher dimensional space with more complex system dynamics. Also, the plant model availability issue is overcome by incorporating a system identification module before executing the FDI block. This shows that while the GPV is a model-based technique, it is still viable for FDI even for those plants where only input-output data are available.