12.1.1 Specifications. Use the appropriate NFGS electric generating plant
specification to specify all piping materials for diesel electric-generating
plants with temperature service below 750 deg. F (399 deg. C).
12.1.2 Metal Piping. Metal piping material should conform to the American
Society for Testing and Materials (ASTM) A53, Pipe Steel, Black and
Hot-Dipped, Zinc-Coated Welded and Seamless.
12.1.3 Plastic Piping. Pending issuance of technical requirements and
specifications by NAVFACENGCOM, addressing exterior distribution of salt
water piping systems, no plastic pipe shall be installed for this usage at
naval shore activities without prior approval of specified installations by
NAVFACENGCOM Headquarters. See NAVFAC DM-3.08, Exterior Distribution of a
Utility Steam, HTW, CHW, Fuel, Gas, and Compressed Air for design guidance
12.2 Pipe Thickness. Schedule numbers listed in the American National
Standards Institute (ANSI) B36.10, Welded and Seamless Wrought Steel Pipe,
correspond to certain wall thicknesses for nominal pipe diameters and are in
an approximate ratio of 1,000 times the internal pressure (pounds per square
inch gage) divided by the allowable stress (pounds per square inch).
Schedule numbers are superseding outmoded terms which indicated thickness,
such as "Standard," "extra strong," and "double extra-strong." For more
accurate formulas for pipe thicknesses, refer to ANSI B31.1, Power Piping.
12.3.1 General. Provide adequate flexibility in all piping systems
containing hot fluids under pressure. Refer to NAVFAC DM-3.08, Table 11-7
for expansion of metals with temperatures. Provision must also be made for
restraint and guiding of piping in seismic zone areas, as outlined in NAVFAC
P-355, Seismic Design for Buildings.
220.127.116.11 Thermal Expansion. Many methods of calculating stress reactions
and movements in piping due to thermal expansions have been developed.
Several piping equipment manufacturers supply calculation forms or graphs
for estimating such values.
18.104.22.168 Pipe Steam Flexibility. An inflexible piping system can
overstress the piping and destroy connected equipment and anchors. The
flexibility of a pipe arrangement can be determined on inspection by an
experienced designer. Where reasonable doubt of flexibility exists, make
formal piping stress calculations to verify that the stresses permitted by
Section 6 of ANSI B31.1 have not been exceeded and that piping reactions and
moments at the equipment connections of anchors are not excessive.
Flexibility of a piping system may be obtained by methods described below.