UG27-e

Section VIII, Division 1 does not have either a screening method or a procedure for performing a fatigue analysis. However Section VIII, Division 2 has both. However it is still acceptable to build and stamp a vessel in cyclic service to Section VIII, Division 1 but to do the fatigue analysis per Section VIII, Division 2. There is no requirement for a vessel to be built to Section VIII, Division 2 simply because it is in cyclic service. On the other hand Section VIII. Division 1 vessels are not exempt from fatigue analysis because they are not built to Section VIII, Division 2.

from: "Pressure Vessel Design Manual, Dennis R. Moss, Michael M. Basic"

Condition for calculating as thin shell. Actually, in ASME UG-27 the condition is not ambiguous. There is a clear or in the conditions. Nevertheless, in general it is interpreted as ‚and‘.

You can always overwrite this value if you disagree.

Cylindrical shells

(c) Cylindrical Shells. The minimum thickness or maximum allowable working pressure of cylindrical shells shall be the greater thickness or lesser pressure as given by (1) or (2) below.

(1) Circumferential Stress (Longitudinal Joints). When the thickness does not exceed one‐half of the inside radius, or P does not exceed 0.385SE, the following formulas shall apply:

(2) Longitudinal Stress (Circumferential Joints).

When the thickness does not exceed one‐half of the inside radius, or P does not exceed 1.25SE, the following formulas shall apply:

Spherical shells

When the thickness of the shell of a wholly spherical vessel does not exceed 0.356R, or P does not exceed 0.665SE, the following formulas shall apply: