We at Sai Engineering manufacture skirts which are supports for the pressure vessel. They do not take any load from the pressure of fluid inside the vessel, but only the weight of vessel + fluid inside and the environmental loads (e.g. wind). Skirts we manufacture serve as a cheap design for support of taller pressure vessels. Because they are basically cylinders with large diameter (usually close to pressure vessel diameter) the stress from induced loads will be low and moment of inertia will be high; two qualities desired. And their design calculation is similar to that for the pressure vessel.
