Abstract: A tube assembly is disposed between a cylinder head of an engine and a fuel supply valve housing. The tube assembly includes a tube member, a first fitting member coupled to each end of the tube member, a second fitting member coupled to the first fitting member proximate to the fuel supply valve housing and a third fitting member coupled to the first fitting member proximate to the cylinder head. The tube member includes an inner tube configured to receive fuel therein and an outer tube disposed around the inner tube. The outer tube is communicably coupled to a leakage detection system. The first fitting member, the second fitting member and the second fitting member include respective passages that fluidly communicate with the inner tube and the outer tube of the tube member. Each of the second and third fitting members also includes radially spaced grooves at both faces.