This work applies a Safeness Index-based model predictive control to explore its benefits in two safety critical chemical processes. The first case study simulates a high-pressure flash drum in tandem with a pressure relief valve. In this simulation the Safeness Index-based MPC is used to maintain the system under safe conditions, avoiding the activation of the pressure relief valve. The second case study simulates 4 units in the Ammonia synthesis process. This work explores the ability of the MPC to mitigate large increases in temperature in the Methanation unit due to decreases in catalytic activity in the high temperature shift reactor. For both cases, a linear dynamic model is identified, and Safeness Index functions and threshold are established.