The analysis fo gas flowing inside the pipeline system for detecting leakage potentials. This paper presents of gas flowing inside the model of pipeline system in two dimensional geometries. The simulation has done using Computational Fluid Dynamics application. It is found that in general the potential of leakage in pipe will take place in the outer side of the connection of the pipeline or on the wall of pipe of which the gas flows with the length distance. For the expansion and contraction pipe the leakage potential will occur on the part of pipe with the change in diameter. particularly for contraction pipe the potential leakage only occurs in the inside part of the pipe connection while the diameter is decreasing.