Marine Installation Manual
2021-08
4-13
4 Ancillary Systems
4.2 Cooling water system
X72DF
4.2.3
Pre-heating
To prevent corrosive liner wear when not in service or during short stays in port,
it is important that the ME is kept warm. Warming-through can be provided by
a dedicated heater, using boiler raised steam or hot water from the diesel auxilia
-
ries, or by direct circulation from the diesel auxiliaries.
Pre-heating from cooling water systems
If the requirement for warming-up is from the cooling water systems of the diesel
auxiliaries, it is essential that the amount of heat available at normal load is suf
-
ficient to warm the main engine.
If the main and auxiliary engines have a cooling water system which can be
cross-connected, it has to be ensured that, when the cross-connection is made,
any pressure drop across the main engine does not affect the cooling water pres
-
sure required by the auxiliaries.
If the cooling water systems are apart, then a dedicated heat exchanger is re
-
quired to transfer the heat to the main CCW system.
Pre-heating by direct water circulation
Use of main cylinder
cooling water pump
If the main CCW pump is used to circulate water through the engine during
pre-heating, then the heater is to be arranged parallel with the CCW system, and
on/off control is to be provided by a dedicated temperature sensor at the CCW
outlet of the engine. The flow through the heater is set by throttling discs, but not
by valves.
Use of separate
pre-heating pump
If the requirement is for a separate pre-heating pump, a small unit with 10 % of
the main pump capacity and an additional non-return valve between CCW pump
and heater are to be installed. In addition, the pumps are to be electrically inter
-
locked to prevent two pumps running at the same time.
Recommended
temperature
The recommended temperature to start and operate the engine is 60 °C at CCW
outlet. If the engine is started below the recommended temperature, engine
power must not exceed 80% of CMCR until the water temperature has reached
60°C.
The ambient engine room temperature and warm-up time are key parameters to
estimate the heater power capacity required to achieve the target temperature of
60°C. The shipyard or ship designer should determine the ambient engine room
temperature and the warm-up time (which may also be specified by the ship
owner) on the basis of their own experience.
Warm-up time
The graph in
shows the warm-up time needed in relation to
the ambient engine room temperature to arrive at the heat amount required per
cylinder. The graph covers the warming-up of engine components per cylinder,
taking also the radiation heat into account.
The readable figure is then multiplied by the number of cylinders to show the
heater capacity required for the engine.