Pressure Vessel Stresses in Cylindrical Shells

Pressure vessels basically consist of a cylindrical or spherical body, with hemispherical, ellipsoidal, torispherical, conical, toriconical, or flat end-closures. The various shell components are usually welded together, forming a shell with a common rotational axis. Occasionally, components can be bolted together by utilizing flanges.

All structures with shapes resembling curved plates are referred to as shells. When shells are formed of plate where the thickness is small in comparison with other dimensions, they are called “membranes.” This condition is defined when the ratio between the radius of curvature “R” and the wall thickness “t” is greater than 10:1.

Stresses in thin shells, called membrane stresses, are average tension or compression stresses acting tangent to the surface of the shell and are assumed to be equally distributed through the wall thickness. Membrane stresses are calculated by neglecting bending. Bending stresses due to concentrated external loads are of high intensity only in close proximity to the area where the load is applied.

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