6. EXAMPLE OF DESIGN BY ANALYSIS AS APPLIED TO A SPHERICAL CHAMBER. The
following example, showing the steps taken and the application of Code
requirements for the design and analysis of a simple chamber may be of some
help to a designer of such vessels in fully understanding the concept of
design by analysis (See Figure 2-9).
a.
Specification Data. Assume that the following data has been
extracted from a User's Design Specification for a certain hyperbaric
facility pressure vessel.
(1) The vessel shall be designed for human occupancy.
(2) It shall be basically spherical in shape with an inside radius
of 90.00 inches.
(3) It shall be equipped with a nominal 4.0 inch diameter input
pipe.
(4) It shall be equipped with a nominal 4.0 inch diameter output
pipe.
(5) It shall be a combination (wet or dry) chamber.
(6) It shall have three view-ports.
(7) It shall have a 40.0 inch minimum inner diameter entrance way.
(8) The vessel shall be designed to meet the following operating
conditions.
(a)
Seawater shall be the primary pressurizing media.
(b)
1000 psig is the maximum design pressure.
(c) The pressurizing media shall, at different times, range
in temperature from 30 deg. F to 150 deg. F.
(d) The chamber must be capable of sustaining 10,000 cycles
of operation at 1000 psig and 150 deg. F.
(e)
The operational life of the chamber is to be at least 20
years.
(f) The chamber shall be supported by a cylinder
approximately 10 feet in diameter and 5 feet tall.
(g)
Neither wind loadings nor earthquake loadings need be
considered.
(h) The piping will be so designed that no moment loadings
shall occur on the spherical shell.
(i) Figure 2-9 shows a sketch of the centerline and mean
dimensions of the proposed chamber.
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