e.
Thermal Insulation. Thermal insulation is not believed to be a
major consideration for piping for hyperbaric chambers.
f.
Possible Reclassification. During the selection of piping
materials described previously in Section 2, appropriate Category I, II, III,
or IV ratings were assigned to each fluid system. When the detailed system
layout has been completed each fluid system and subsystem is reexamined to
determine whether the proper classifications have been used and to determine
whether simple system changes might permit the reclassification of a Category
I and II system to a Category III and IV system. Considerably fewer
calculations are needed for the structural analysis of Category III and IV
systems and a wider choice of ASME-approved materials is available for
Category III and IV systems.
g.
Detailed Fluid Flow Calculations. As a last step before the struc-
tural analysis of the piping system described below, detailed calculations
are made to check the fluid flow, pressure drop, and power required for each
fluid system. In addition to checking previous approximations, these
calculations permit a final evaluation of the tentatively selected pipe size
and wall thickness. Where borderline situations are encountered, it may be
possible to reduce the pressure drop sufficiently to reduce wall thickness,
reduce inlet pressure, or select a smaller pump or compressor.
The detailed calculation of flow and pressure drop in a piping system
necessitates the understanding and use of many more quantities and
relationships than were described in the section on flow approximation.
There is no better overall approach to this problem for the designer of the
hyperbaric piping system than to obtain a copy of Flow of Fluids Through
Valves, Fittings, and Pipe (Reference 15), study it in detail, and use its
suggested approaches to accomplish the necessary calculations. The material
in this publication is greatly simplified for the design engineer. The
equation symbols are well-defined and used uniformly and a number of helpful
examples are given. For cryogenic piping systems, the designer should refer
additionally to the appropriate chapter in Piping Handbook, Crocker, S.,
(Reference 14). NAVSHIPS 0994-003-7010, U.S. Navy Diving-Gas Manual
(Reference 16) provides convenient values of gas densities for typical
hyperbaric chamber conditions.
5.
STRUCTURAL ANALYSIS. The degree of structural analysis necessary when
designing the various classes of piping systems is discussed in the following
paragraphs.
a.
Category I and II Piping Systems.
(1) Structural Design Specification. In order to conduct the
structural analysis required for Category I and II piping systems, it is
necessary to prepare a structural design specification which postulates all
significant loadings that will be imposed on the piping system during its
lifetime. Preparation of an appropriate structural design specification is
an exacting task. In general, inputs from both that engineer who is
cognizant of the overall function of the hyperbaric chamber complex and the
piping specialist are needed. Philosophically, the purpose of the structural
design specification is to force one or more competent engineers to carefully
list what the piping system is intended to do and what might happen to damage
the piping system. The analysis then makes a rigorous engineering evaluation
of the loadings and hazards to
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