A methodology to calculate process risk in combination with a data based fault detection method is proposed in this paper. The proposed approach aims to identify and screen the faults which are not safety concerns and also to dynamically update process risk at each sampling instant. The approach is built upon principal component analysis (PCA) combined with a quantitative operational risk assessment model. Through this approach, a warning system is activated only when the risk of operation exceeds the acceptable threshold. Combining PCA with the risk assessment model makes this approach more robust against false alarms. Application of this new risk based approach provides early warnings and early activation of safety systems prior to the fault impacting the system. This method has more power in discerning between operational deviations and abnormal conditions which potentially may cause an unwanted situation (an accident).