MIL-HDBK-1005/7A
b) Access. Provide blind flanges, hand holes,
removable sections, and other types of openings into the piping
for cleaning and inspection.
c) Protection Against Freezing. Perform a detailed
analysis to determine if insulation or other type of protection
is necessary. Allow for the lower freezing temperature of
seawater.
d) Protection Against Wind Damage. Pipes suspen ded
aboveground or on structural supports should be anchored to
withstand wind velocities specified for the design of structures
(refer to MIL-HDBK-1002 Series, Structural Engineering).
e) Protection Against Current/Tidal Action. Seawater
intake structures and piping exposed to current/tidal action
should be adequately protected.
f) Expansion/Contraction. Expansion/contraction
requires detailed analysis to determine if provisions for
expansion or contraction are necessary.
4.7.7
Corrosion and Fouling. Special criteria related to
corrosion and fouling are outlined below.
4.7.7.1
Cast Iron . Cast iron, which is normally used for
pumps and piping in potable water systems, is slowly attacked by
seawater which removes the iron, leaving a graphite residue
(graphitization). In quiescent water, this graphitized layer
remains intact and protects against the penetration of water
and further corrosion. This protective layer is soft, and high
velocity flow in pumps or piping will remove it and expose fresh
base metal to high-rate corrosion. Furthermore, the graphite
particles are cathodic and can accelerate the corrosion of new
cast iron brought into contact with them.
4.7.7.2
Cement Lined Steel and Cast Iron Pipe . Usually,
cement lining is good protection against corrosion. However,
the lining can be eroded by high velocity flow of
sediment-bearing water, fouling organisms can break the lining
away from the pipe wall, and impact and vibration at waterfront
structures can weaken the lining.
41
Previous Page
