Section 3. DESIGN
1.
DESIGN. This section discusses the applicability of Section VIII,
Division 2, of the ASME Code to the design of pressure vessels to be used as
components of hyperbaric facilities. The design criteria contained in
Section VIII, Division 2 are explained in some detail, followed by paragraphs
dealing with the relation of these design criteria to the two classes of
pressure vessels described earlier. Examples are given of the design of two
simple pressure vessels using the stress analysis method based on the
mandatory Appendix 4 of Section VIII, Division 2.
2.
METHODS OF DETERMINING STRESSES. The basic intent of design by
analysis is to determine the stress conditions in a pressure vessel under
load for each load condition for the vessel's entire operational life. In
order to meet the intent and specifications of Section VIII, Division 2, the
designer must carry out a sufficiently detailed stress analysis of the vessel
to show compliance with the stress limitations imposed by the Code for the
material from which the vessel is to be fabricated. The designer may specify
any manner by which to determine the stresses in the vessel under load, so
long as use of the methodologies employed.
a.
Stress Analysis Methods.
In general there exist three basic
groups of stress analysis methods:
o
Classical
o
Experimental
o
Computer Programs
(1) Classical Methods. Classical methods are defined as those
works based on continuum mechanics and as particularly applied to shell and
plate theory, that are exemplified by the works of Timoshenko (see Reference
6, Theory of Plates and Shells, 1959), Flugge (see Reference 7, Stresses in
Shells, 1966), Novoshilov (see Reference 8, Thin Shell Theory, 1964), and
Kraus (see Reference 9, Thin Elastic Shells,1967). A "handbook" type
presentation titled, Shell Analysis Manual, by E.H. Baker, et al., (see
Reference 10, Shell Analysis Manual, 1968) may be quite useful to the
designer. Appendix 4 of Section VIII, Division 2 of the Code presents
classical design based on stress analysis in nine articles as follows:
Article 4-1 - Stress analysis
Article 4-2 - Analysis of cylindrical shells
Article 4-3 - Analysis of spherical shells
Article 4-4 - Design criteria and formula for torispherical and
ellipsoidal heads
Article 4-5 - Analysis of flat circular heads
Article 4-6 - Pressure stresses in openings for fatigue evaluation
Article 4-7 - Discontinuity stresses
Article 4-8 - Thermal stresses
Article 4-9 - Stresses in ligaments
Article 4-6, Pressure Stresses in Openings for Fatigue Evaluation, is
particularly valuable in presenting a means of carrying out a fatigue evalua-
tion of certain geometries of isolated nozzles. Article 4-7, Discontinuity
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