Piping system is the most efficient and common means of transporting fluids from one point to another. Every piping system has possibilities to become a critical pipe line. Critical pipeline is a pipe line that has the potential to exceed the maximum limit. High temperature, high pressure, and the size of diameter will cause the critical line. TN-S177RC pipe line become a critical pipeline because the temperature is 115oC, the pressure is 250 barg with 8 inch diameter of pipe. Therefore, stress analysis on critical piping system need to performed to reduce the effect of the exceed maximum limit. Pipe stress analysis was performed using software CAESAR II 2013, with static load and dynamic load as an input. The data was obtained from isometric drawing, and piping specification. Pipe stress analysis is carried out based on ASME B31.3. The results showed that pipe line TN-S177RC Tunu phase 11A was overstressed with the ratio of stress 143,3% and deflection was exceed the maximum limit with value 9,6052 mm. With adding the pipe support at nodal 150, it make the ratio of stress decrease become 89,7%, and the value of deflection become 3,1398 mm. On the other hand the piping system become safe.