a.
Final Routing of Pipe and Selection of Supports and Anchors. The
tentative routing of the piping systems selected for the preliminary flow
calculations must be examined to determine that all system requirements have
been adequately met. These requirements will include such items as operation
(are the controls properly located), maintenance (can the systems be repaired
and cleaned), and safety (are high pressure piping systems, particularly
O2 lines, adequately shielded to protect personnel and lines). Routing
modifications to meet such requirements can often increase system pressure
drops significantly.
With routing of the piping systems finally determined, supports and anchors
for the systems can be selected. The term "support" is used in a general
sense and includes such items as sliding supports, guides, spring hangers,
constant load hangers, braces, and shock absorbers. The term anchor refers
to any support or component (such as a pump or tank) which is considered to
be essentially immovable. Chapter 15 of 1970 Fluid Power Reference Issue
(Reference 17) will provide general background information. If the initial
system layout does not prove to be satisfactory when analyzed structurally
(Section 5, paragraph 5(a) (2)), changes in the layout will be required until
a satisfactory analysis is obtained.
b.
Final Fitting and Valve Selection. System detailing requires the
finalization of the locations and types of fittings and valves.
Consideration must also be given to the seals for separable joints between
fittings, valves, and piping.
(1) Fitting Selection. Pipe and tube fittings have become quite
standardized over the years. A number of standards acceptable for hyperbaric
facilities are listed in Reference 8 and MIL-STD-438, Schedule of Piping,
Valves, Fittings, and Associated Piping Components for Submarine Service
(Reference 18). These standards indicate fittings for various types of fluid
systems. Most fitting manufacturers will provide a list correlating their
fittings with military and industrial standards.
(2) Valve Selection. Although many types of valves have become
standardized over the years, a wide variety of nonstandard valves are
available for the different fluid systems. Valve types vary because of the
type of fluid control desired, the size of the pipe or tubing, the force
available to operate the valve, and other factors. Numerous articles in the
trade literature summarize valve types, factors involved in valve selection,
and qualitative suggestions concerning installation and maintenance. A
typical publication is contained in the 1970 Fluid Power Reference Issue
(Reference 17). Detailed information can be found in valve manufacturer's
catalogs.
An accurate measurement of the flow resistance of candidate valves is
required for the detailed calculations to determine system flow
characteristics. The piping designer must determine that the manufacturer's
measurements of flow resistance can be used in the formulas required by Flow
of Fluids Through Valves, Fittings, and Pipe (Reference 15) and that the
measurements were made with the valve mounted similar to that proposed for
the piping system.
Previous Page
