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Maintenance: Raw water system
Raw water system
The raw water system is the engine's external cooling system and it is either a seawater system or a central
cooling system. It cools the internal cooling system in an engine mounted heat exchanger. The system is protec-
ted against galvanic corrosion by zinc anodes located in the heat exchanger and in the reverse gear oil cooler.
WARNING! The raw water system must be closed and drained before commencing work on the system.
This due to the risk of sea water or water from the central cooling system entering the vessel.
Z
Z
74
Draining the raw water system
1. Close the raw water in- and outlet cocks.
2. Connect a suitable hose to each drain point, refer
to section "Drain points". Open the drains and al-
low the raw water to drain off into a suitable ves-
sel.
IMPORTANT! Check that the raw water really
drains. Deposits may need to be removed from
inside the drain plugs/taps.
Zinc anodes. Check/change
WARNING! Risk of water entry. Close the raw-
water cock before doing any work on the rawwa-
Z
ter system.
NOTE! Valid only for engine mounted heat exchan-
ger.
1. Drain the external cooling water as described in
the section draining the raw water system.
2. Unscrew the zinc (Z) anodes from the heat ex-
changer (2 pcs.).
3. Replace the anode if less than 50% remains. If
not, clean the anode with emery cloth to remove
the layer of oxide.
IMPORTANT! Do not use a wire brush or other
metal tool for cleaning as this may decrease the
galvanic protection.
4. Fit the zinc anodes. Make sure there is good con-
tact between the anode and the metal goods.
5. Close drains and open the raw water cocks be-
fore starting the engine
6. Check the installation and make sure there are
no leaks.
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