Special Considerations. For wind and seismic loads, mechanical
piping and equipment and related systems shall be anchored, braced, or guyed
(as required) to satisfy seismic zone requirements and withstand minimum
expected wind velocity including gusts for the location of the installation.
Designs for construction, installation, and anchorage shall give special
attention to ensure minimum damage. Seismic design shall be in accordance
with NAVFAC P-355, Seismic Design for Buildings. In the computation
earthquake forces for a building, its components and all equipment, the
importance factor "I" shall be 1.5. Piping connections must be so made as to
preclude rupture under the most adverse conditions expected. Pipe supports
shall be close coupled to supporting structures when the more severe seismic
conditions are expected.
Protect against corrosion as a result of moisture and acids caused
by down wind drafts around cooling towers, evaporative condensers, and boiler
stacks. Avoid bare aluminum within two miles (3.2 km) of salt water.
Support ductwork, flue gas breeching, stacks, diesel engine
silencers, stacks, and other hot equipment so that contraction and expansion
will not impose detrimental loads and stresses on related structures.
Stacks shall be designed as follows:
a) Stack foundations shall totally support the stack and prevent
wind and seismic disturbances from collapsing or over turning the structure.
Take into consideration wind effects at various elevations.
c) Take into consideration vortexing effects and natural
d) Protect top of stack lining against water penetration between
stack shell plate and lining.
e) Seal all openings and connections on stacks, breechings, and
ducts to prevent air or flue gas leakage.
f) Stacks, breechings, and ducts, mounted on concrete shall be
designed to prevent temperatures in excess of 300 degrees F (149 degrees C)
Connections between stacks and flue gas ducts shall not be
Stacks with floors shall be provided with a minimum 2-inch size