The designer decides to do both above, i.e., paint the inside and the outside
of the vessel. However, as a conservative measure he also decides to add a
corrosion allowance to all the vessel components that will be in direct
contact with seawater. Considering that the vessel will be empty during a
good part of its life and that normal inspection routines should ensure the
maintenance of the painted coating, the drawings are changed to show a
thickness increase of 0.050 inches on all sections of the vessel except the
support skirt.
e. Stress Documentation. The documentation submitted for the stress
analysis portion of the Design Review Report could very well resemble the
discussion as presented in this example. The basic design procedure need not
be discussed but the final design configuration must be shown to be adequate
from the viewpoints of good design practice and the stress intensity limita-
tions, both as presented in Section VIII, Division 2.
7. EXAMPLE OF DESIGN BY ANALYSIS AS APPLIED TO A CYLINDRICAL CHAMBER. The
design and analysis of a cylindrical chamber takes on greater complexity than
that for a spherical chamber due to the various geometric details that exist
in a cylindrical chamber which cause that structure to deviate from a body of
revolution. In the following example, those design and analysis procedures
which differ substantially from the previous example are discussed.
a.
Specification Data. Consider that the data presented in the
previous example (Paragraph 6.a) still apply, with the following changes.
(2)
The vessel shall be cylindrical in shape with an inside
radius of 60.0 inches and a straight length between heads
of 180.0 inches. It shall have torispherical end caps.
(3)
It shall be equipped with a nominal 5.0 inch diameter input
pipe.
(4)
It shall be equipped with a nominal 5.0 inch diameter output
pipe.
(5)
It shall have five (5) viewports. One in the center of one
of the torispherical end caps; the other four in the
cylinder wall.
(8)(f)
The chamber shall be supported by two saddles.
b.
Materials and Initial Calculations. As before, carbon steel, ASTM
Specification A-516, Grade 70 is chosen as the material from which to
fabricate both the chamber and the saddles. Thus our stress intensity limits
remain
Pm < / = 23,200 psi
PL < / = 34,800 psi
Pm (or PL) + Pb < / = 34,800 psi
PL + Pb + Q < / = 69,600 psi
PL + Pb + Q + F = 2 Sa < / = 74,000 psi.
(1)
Membrane Stress Intensity Limit. From Table AD-150.1, the
factor to apply to the Membrane Stress Intensity is 1.0.
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