WÄRTSILÄ 46F Series, Product Manual

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Fig 9-9 Sea water system DAAE020523
System components
Central cooler 4E08
Suction strainer (sea water) 4F01
Circulation pump (sea water) 4P11
Ships (with ice class) designed for cold sea-water should have provisions for recirculation
back to the sea chest from the central cooler:
●
For melting of ice and slush, to avoid clogging of the sea water strainer
●
To enhance the temperature control of the LT water, by increasing the seawater temperature
●
It is recommended to divide the engines into several circuits in multi-engine installations.
One reason is of course redundancy, but it is also easier to tune the individual flows in a
smaller system. Malfunction due to entrained gases, or loss of cooling water in case of
large leaks can also be limited. In some installations it can be desirable to separate the HT
circuit from the LT circuit with a heat exchanger.
The external system shall be designed so that flows, pressures and temperatures are close
to the nominal values in Technical data and the cooling water is properly de-aerated.
Pipes with galvanized inner surfaces are not allowed in the fresh water cooling system.
Some cooling water additives react with zinc, forming harmful sludge. Zinc also becomes
nobler than iron at elevated temperatures, which causes severe corrosion of engine
components.
9.3.1 Electrically driven HT and LT circulation pumps (4P03,
4P05, 4P14, 4P15)
Electrically driven pumps should be of centrifugal type. Required capacities and delivery
pressures for stand-by pumps are stated in Technical data.
In installations without engine driven LT pumps, several engines can share a common LT
circulating pump, also together with other equipment such as reduction gear, generator and
compressors. When such an arrangement is preferred and the number of engines in operation
varies, significant energy savings can be achieved with frequency control of the LT pumps.
Note
Some classification societies require that spare pumps are carried onboard even though the
ship has multiple engines. Stand-by pumps can in such case be worth considering also for
this type of application.
DAAB605814 9-13
9. Cooling Water System Wärtsilä 46F Product Guide