b.
Category III and IV Piping Systems.
(1) Design Information. In addition to the Design Pressure,
Design Temperature, and information from the System Layout, the piping system
designer must obtain:
(a)
The anticipated number of temperature cycles.
(b)
The magnitude of the displacements which will be
imposed on the piping system by the connected equipment and intermediate
attachments.
(c)
The magnitude of the loads from the piping system
acceptable by the connected equipment.
(2) Analysis Procedure for Category III and IV Piping Systems.
The structural analysis of Category III and IV piping systems shall conform
to the requirements of NAVFAC TS 15401 (Reference 13). The analysis
procedure discussed herein is generally analgous to that required for
commercial piping. However, neither cycles of pressure loading nor
temperature gradients need be considered.
(3) Analysis Procedure for Category III and IV System Valves. The
structural analysis of a Category III and IV system valve shall show that the
design of the valve fulfills the structural design requirements of ANSI B
31.1 (Reference 2).
While ANSI B 16.5 (Reference 20) is entitled Steel Pipe Flanges and Flanged
Fittings, it is nevertheless the primary standard for steel valves sold in
the United States. ANSI B 16.5 controls steel valve designs by prescribing:
(a)
Minimum wall thickness.
(b)
Dimensions of flanges and bolting, for flanged-end
valves.
(c)
Dimensions of welding ends, for welding end valves.
(d)
Face-to-face or end-to-end dimensions
(by reference to
ANSI B 16.10).
(e)
Pressure-temperature ratings.
(f)
Minimum hydrostatic test pressure (for the body, not
the seat).
(4) Stress Report. A Stress Report is not required for Category
III and IV piping systems. However, it is recommended that the Owner obtain
from the contractor a certification that the piping system meets the
requirements of NAVFAC TS 15401 (Reference 3).
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