Three-dimensional finite element simulation of the integral hydrobulge forming of a spherical LPG tank

A spherical LPG tank of 200 m3 in volume and 7·1 m in diameter was built by using the integral hydro-bulge forming technology in China in 1992. This tank is made of China alloy steel for pressure vessels—16 MnR—with thickness of 24 mm. Its design pressure is 1·77 MPa and its work pressure is 1·66 MPa. It is integrally hydroformed from a single-curvature shell with 25 lateral petals and two polar heads. The three-dimensional elastoplastic finite element method is used to analyse the hydro-bulging process of the tank; the deformation process and the deformation features are revealed, and the stress and strain distributions are analyzed. On the basis of the above analysis, reasonable suggestions are presented for improving the design, the fabrication and the welding of spherical LPG tank.