A cylindrical tank with diameter d = 18 in. is subjected to internal gas pressure p = 450 psi. The tank is constructed of steel sections that are welded circumferentially (see figure). The heads of the tank are hemispherical. The allowable tensile and shear stresses are 8200 psi and 3000 psi, respectively. Also, the allowable tensile stress perpendicular to a weld is 6250 psi.
Determine the minimum required thickness tmin of (a) the cylindrical part of the tank and (b) the hemispherical heads?