Heat Exchanger is an equipment to transfer heat energy between two or more fluid with a different temperature when the thermal contact happens. In the research, Heat Exchanger HT-3120, which has the function to increase the temperature of Ortho-Xylene from 40 o C to 140 o C, is used. To make the process run safely, the control system has to be able to work and has sufficient protection system. So, a reliable control is needed to maintain the Ortho-Xylene temperature by manipulating flow rate of steam. An integrated simulation between control system and protection system is done. From the simulation result it is obtained that the temperature control system has Mp 31.01%, Settling time 1165 second and error steady state 0.1%. The total PFD of the system when Ti= 8760 hours is 0.8137, and when Ti=83712 hours is 6.3343. So, based on IEC 661508, heat exchanger HT-3120 is categorized as the system that has SIL of 1.