A vigorous hazard assessment is almost mandatory for the safety and risk free operation of any chemical plant. A systematic approach has been developed in this study to construct a generic Petri-net (PN) model for analyzing the liquid ammonia loading process. A set of sub-PNs were first built for all components in the system. Failure mechanisms were then developed and incorporated into these component models. On the basis of predefined hazardous conditions, the critical fault propagation scenarios were identified accordingly with simulation studies. It is observed from the simulation results that the proposed model can be effectively used for hazard identification in the sequential operations.