Wartsila 31, Product Manual

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9.3.9 Drain tank (4T04)
It is recommended to collect the cooling water with additives in a drain tank, when the system
has to be drained for maintenance work. A pump should be provided so that the cooling water
can be pumped back into the system and reused.
Concerning the water volume in the engine, see chapter Technical data. The water volume in
the LT circuit of the engine is small.
9.3.10 Preheating
The cooling water circulating through the cylinders must be preheated to at least 60 ºC,
preferably 70 ºC. This is an absolute requirement for installations that are designed to operate
on heavy fuel, but strongly recommended also for engines that operate exclusively on marine
diesel fuel.
The energy required for preheating of the HT cooling water can be supplied by a separate
source or by a running engine, often a combination of both. In all cases a separate circulating
pump must be used. It is common to use the heat from running auxiliary engines for preheating
of main engines. In installations with several main engines the capacity of the separate heat
source can be dimensioned for preheating of two engines, provided that this is acceptable
for the operation of the ship. If the cooling water circuits are separated from each other, the
energy is transferred over a heat exchanger.
9.3.10.1 Heater (4E05)
The energy source of the heater can be electric power, steam or thermal oil.
It is recommended to heat the HT water to a temperature near the normal operating
temperature. The heating power determines the required time to heat up the engine from cold
condition.
Design data:
min. 60°C Preheating temperature
5 kW/cyl Required heating power
2 kW/cyl Heating power to keep hot engine warm
Required heating power to heat up the engine, see formula below:
where:
Preheater output [kW] P =
Preheating temperature = 60...70 °C T
1 =
Ambient temperature [°C] T
0 =
Engine weight [ton] m
eng
=
Lubricating oil volume [m 3 ] (wet sump engines only) V
LO
=
HT water volume [m 3 ] V
FW
=
Preheating time [h] t =
Number of cylinders n
cyl =
9.3.10.2 Circulation pump for preheater (4P04)
Design data:
80...100 kPa (0.8...1.0 bar) Delivery pressure
Wärtsilä 31 Product Guide - a1 - 18 October 2016 9-15
9. Cooling Water System Wärtsilä 31 Product Guide