REFERENCE: Riley, William F. (William Franklin), 1925 - Mechanics of materials / William F. Riley, Leroy D. Sturges, Don H. Morris. — 5th ed. Problems involving thin-walled vessels subjected to liquid (or gas) pressure p are readily solved with the aid of free-body diagrams of sections of the vessels together with the fluid contained therein. In the following subsections, spherical, cylindrical , and other thin shells of revolution are considered. * Spherical Pressure Vessels & * Cylindrical Pressure Vessels = used for gas storage * Thin Shells of Revolution = extended to include other shapes and other loading condition. Example Problem 5-16 A cylindrical pressure vessel with an inside diameter of 1.50 m is constructed by wrapping a 15-mm thick steel plate into a spiral and butt- welding the mating edges of the plate, as shown in Fig 5-36a. The butt- welded seams form an angle of 30 degree with a transverse plane through the cylinder. Determine the normal stress perpendicular to the weld and the shearing stress parallel to the weld when the internal pressure in the vessel is 1500 kPa.