Sea Water Systems&nbs= p; Chapter
12
Sea water = is required for nearly all functions of the ship. The distribution of sea water is a system unto itself.
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early all systems in the ship require sea
water for cooling. The introd=
uction
of sea water requires that the hull be breeched both to introduce it into t=
he
hull as well as to remove it when complete. Challenges to introduce the sea wa=
ter
include the risk associated with holes in the hull as well as insuring an
adequate supply. The ship use=
s a
sea chest system to address this challenge. A sea chest is a single large open=
ing
that permits all of the required needs to be served from a common through
hull. In order to provide a b=
ack-up
if a sea chest inlet were to become clogged by some debris, a second sea ch=
est
also shares the ability to provide water into the ship.
Sea water enters the s=
hip
via both sea chests, located in the forward starboard side of the engine ro=
om
floor. Each sea chest has a an
output line which goes through a ball valve, a strainer, and a second ball =
valve
and then supplies the common manifold.&nbs=
p;
For each of these strainers, the two ball valves are used to disconn=
ect
sea water so the strainer can be removed and cleaned regularly. All these ball valves should norma=
lly be
open to permit sea water to be drawn through both sea chests.
Sea Chest Vents
Each sea chest also ha=
s a
connection with a ball valve which leads to a vent high on the forward
starboard wall of the engine room.
These lines permit air which would accumulate in the sea chest to ve=
nt
out of the chest. The ball va=
lve at
the vent should always be open. The
ball valve at the sea chest should be open whenever the sea chest is being =
used
to draw sea water for equipment.
Chiller Connection
The starboard-most sea=
chest
also has a connection with a ball valve that is dedicated to the Marin Air
chiller units. The specs for =
these
units require a dedicated connection to the sea chest. This line has its own strainer and=
needs
to be cleaned when the chillers have been in use and drawing sea water. A black low pressure water pump is
connected to this line toe feed water to the chiller. The pump is below the water line s=
o that
it will be self priming. The =
sea
water valve must be closed when doing any work on the pump, strainer, line =
or
chillers. The line to the chi=
llers
has a flow indicator. It is
important to verify flow periodically while the chillers are in operation.<=
span
style=3D'mso-spacerun:yes'> If flow stops or slows, check the =
valve
settings, pump operation, and strainer for constriction. If all of these are correct, the n=
ext
most likely occurrence is that the main filter on the hull for the entire s=
ea
chest has been clogged. See S=
ea
Chest Flow Restriction for information if this occurs.
![](3D"SeaWater_files/image002.gif")
Water Maker Source Water
The water mak= er removes the minerals and purifies water for use in the ship’s fresh water sys= tem. Sea water from the manifold is pum= ped by a white low pressure pump to the water maker. Check the flow indicator during operation for adequate flow. = The low pressure pump is located below the water line so that it is self priming. Be sure the ball val= ve on the line from the manifold is off when doing any work on this line, the pum= p, or the water maker. If flow s= tops or slows, check the valve settings and pump operation. If these are correct, the next most likely occurrence is that the main filter on the hull for the entire sea ch= est has been clogged. See Sea Che= st Flow Restriction for information if this occurs.
Engine Exhaust and Primary Hydraulic Cooling
Although the =
engine is
cooled with a closed loop keel cooler, the engine exhaust is sea water cool=
ed
in the muffler in the port aft corner of the engine room. Water for the muffler/cooler is pu=
mped
by the engine’s water pump on the port forward side of the engine.
If flow stops= or slows, immediately shut down the engine. Then check the valve settings and pump operation. If these are correct, the next most likely occurrence is that the main filter on the hull for the entire sea ch= est has been clogged. See Sea Che= st Flow Restriction for information if this occurs.
Generator Cooling
Each generato=
r has a
closed loop cooling system that is in-turn cooled by sea water in a heat
exchanger. After the heat
exchanger, the water is injected into the exhaust to cool and muffle the
exhaust. The generators are
equipped with an air/water separator for the exhaust after the muffler. This separates the air and water i=
n the
exhaust and the air is expelled below the water line and the air is expelled
above the water line. This no=
t only
effectively silences the generator noise, but also eliminates any “
If flow stops= or slows, immediately stop the generator. Then check the valve settings and pump operation. If these are correct, the next most likely occurrence is that the main filter on the hull for the entire sea ch= est has been clogged. See Sea Che= st Flow Restriction for information if this occurs.
Emergency Bilge Pump Prime
The emergency bilge pump is a 220 volt high volume centrifugal pump that can be used to remove large volumes of water from the bilge. Since it is a centrifu= gal pump, it must be primed to gain suction to pull water from the bilge. Priming and operating this pump is discussed in a separate section. The priming water source is the sea water manifold. This valve should always be open t= o be prepared to operate the emergency pump in a moment’s notice if it is = required. This pump can also be used to draw= large volumes of sea water through the sea chest if that is desired for testing s= ea water flow.
Sea Chest Flow Restriction
The sea chests must pr= ovide adequate flow for all of the machinery to cool properly. A quick test to isolate if a sea c= hest is clogged or restricted is to remove a filter and then open the ball valve= and time the duration required to fill a gallon into a bucket. Base line this time in normal cond= itions so a record is available of performance over time. The most likely cause of sudden restriction of the entire sea chest is if a plastic bag were trapped against it. This can be identified if= the sea water flow valves are not indicating proper flow. The only method to clear a sea che= st without diving is to shut off the chest and operate on the other chest and = let the flow of water across the opening wash away the restriction.