Thin-walled Pressure Vessels

Thin-walled Pressure Vessels

A pressure vessel can be described as thin walled when the ratio (about 10:1) of the inside radius to the wall thickness is sufficiently large so that the distribution of normal stress in the radial direction is essentially uniform across the vessel wall

The wall comprising a pressure vessel is sometimes termed the shell

Spherical Pressure Vessels

If the weights of the gas and vessel are negligible (a common situation), symmetry of loading and geometry requires that stresses must be equal on sections that pass through the center of the sphere.

Spherical Pressure Vessels

Typical sphere Free-body diagram

Spherical Pressure Vessels

There are no shear stresses on any of these planes, since there are no loads to induce them. The normal stress component in a sphere is referred to as axial stress and commonly denoted a .

Stress on spherical vessel

Cylindrical Pressure Vessels

Typical sphere

Cylindrical Pressure Vessels

Free-body diagram exposing long

PICTURE???

Spherical Pressure Vessels

Longitudinal Stress

Cylindrical Pressure Vessels

Free-body diagram exposing hoop

Spherical Pressure Vessels

Tangential or Circumferential Stress

Example 4.1

A standpipe with an inside diameter of 108 in. contains water, which has a weight density of 62.4 lb/ft3. The column of water stands 30 ft above an outlet pipe, which has an outside diameter of 6.625 in. and an inside diameter of 6.065 in.

Determine the longitudinal and hoop stresses in the outlet pipe at B.

If the maximum hoop stress in the standpipe at point must be limited to 2,500 psi, determine the minimum wall thickness that can be used for the standpipe.

Example 4.1