CG, AND DD
locations along the seawater service main to
SEAWATER SYSTEMS
control the flow of seawater through the main.
To prevent marine growth and system
During normal operations, seawater is supplied
contamination, the system has simplex, duplex,
to the seawater service system through one of the
basket, and Y-type strainers located throughout
three seawater service pumps. When the
the system.
system demand increases, a second pump
can be started or seawater can be supplied through
FFG SEAWATER SYSTEMS
one of three fire main reducing stations. The seawater
main also provides backup cooling to the SS generators. If
The FFG-class ships have three separate
the generator cooling system fails, the seawater
systems within the seawater cooling system. These
main automatically cuts in.
systems are
The systems on the CG-, and DD-class
ships are basically the same. The basic system has
1. the main propulsion reduction gear cooling
three seawater service pumps that supply cooling
system,
water to a variety of equipment. These pumps are
2. the SSDG cooling system, and
centrifugal pumps that can be controlled locally
3. the auxiliary cooling system.
at their respective motor controllers or remotely
from the PACC. These pumps take suction
Main Propulsion Reduction
t h r o u g h a sea chest and then through a
Gear Cooling System
hydraulically operated valve. This valve is
controlled from the damage control deck. It is
Two propulsion seawater circulating pumps
used in case of damage to the system piping to
suction directly from the sea and discharge to the
prevent flooding from the sea. This valve can also
reduction gear LO cooler. Each pump can supply
be manually overridden at the valve location.
100 percent of system capacity and serves as a
From there flow is through a manual suction
standby for the other pump. Each pump has its
valve, a manual discharge valve, and a check valve
own sea suction line that suctions from the
that is used to prevent backflow to the pump.
sea through its own independent sea chest and
Relief valves protect the seawater system and
suction valve. Each pump discharges to a
associated equipment from overpressurization.
common header through its own strainer and
Pressure settings on the relief valves and
discharge valve. The common header is connected
reducing stations and system pressure itself vary
to the reduction gear LO cooler. Cooling water
between ships. Consult your ship's EOSS for the
discharged from the LO cooler is piped overboard
proper settings and alarm conditions.
through a common pipe and the LO cooler over-
Reducing stations are provided on the DD-
board discharge valve. Each seawater circulating
c l a s s ships to reduce pressure for use
pump can be started and stopped either locally
on the various equipment. However, design
or remotely.
modifications to the system pressure on the CG-
class ships have eliminated most of the reducing
stations. The ones remaining are for the firemain-
SSDG Cooling System
to-seawater system and the CRP cooler.
Temperature regulation of the reduction gear
Each SSDG has its own dedicated seawater
LO cooler, control of the waste heat boiler
cooling system and an emergency cooling water
condensers, and the condensate drain coolers is
supply from the firemain. Each SSDG cooling
done by pneumatically operated temperature
system has a seawater circulating pump, a duplex
regulators. These regulators control the flow of
strainer, and motor-operated suction and over-
seawater through the coolers to maintain the
board discharge valves. Each pump takes suction
temperature of the liquid being cooled within
from its own sea chest by way of its own suction
prescribed limits. The CG-class ships have a CRP
line and valve. The pump's discharge passes
cooler that is temperature regulated.
through a duplex strainer and then branches into
Nine manual/hydraulic operated butterfly
multiple paths to provide cooling water to the
valves are associated with the seawater service
various coolers of the SSDG. The outlet of the
system. Three of these valves control the flow of
coolers then joins into a single discharge line
seawater to the three seawater pumps, as mentioned
before going overboard through the motor-
previously. Six valves are installed at various
operated discharge valve. The seawater circulating
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