that will ensure a safe and efficient structure. If the stresses throughout
the chamber under the anticipated load conditions are accurately known, then
the chamber can be built and can be expected to operate successfully with a
very high probability that failure will not occur. This concept forms the
underlying philosophy for the ASME Code, Section VIII, Division 2. This
philosophy puts the burden of proof upon the designer, requiring the designer
of a pressure vessel to determine by use of mathematical and/or experimental
means the predicted stress conditions in the vessel under the anticipated
load conditions. He must show that the stresses to be developed in the
chamber will be equal to or less than a set of stress limits which are
imposed by the Code for the particular materials to be used. The Code itself
does not specify the manner by which these stresses shall be determined. In
a few instances, the Code allows a designer to by-pass detailed analysis if
he chooses to conform his design of specific penetrations and fittings to
those detailed in some of the Code's sections.
g.
When a pressure vessel is being designed in accordance with
Section VIII, Division 2, and a cyclic ,life in excess of 5,000 cycles is
desired, it may be necessary to consider the fatigue life of the vessel. The
procedure for determining whether a fatigue analysis is required is presented
in Section VIII, Division 2, Appendix 5, Mandatory Design Based on Fatigue
Analysis.
6.
MANUFACTURER'S DESIGN REPORT.
a.
Manufacturer's Design Report. The manufacturer, or his design
agent, furnishes a design report, including calculations and drawings, which
show that the design complies with the design specification.
b.
Design Report Format. There is no "specified" design report
format. However, it must be emphasized that the burden of proof of the
adequacy of a design lies with the designer. The design report should be
clear and concise, and justify the use of all design procedures and
materials. If design practices are followed that are not covered by the Code
or are in some other manner deviant from specified practices, then the
justification of such action must be documented.
7.
USER'S DESIGN SPECIFICATION. Before a designer can plan a facility,
the
user, usually with the assistance of the designer, must develop a complete
"User's Design Specification." In this specification, the user must spell out
in considerable detail the full range of performance required of the
facility. The information to be included in this Design Specification is
listed in the ASME Code, Division 1, Section U-2, and in Division 2, Article
G-3 of Part AG and Article D-1 of Part AD. In general, the "User's Design
Specification" will provide as a minimum the following information:
a.
Maximum internal working pressures, including static loads.
b.
Required sizes and dimensions.
c.
Maximum and minimum operating temperatures.
d.
Cyclic life.
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