Table 9-1 Minimum diameter of balance pipe
Max. number of vent
pipes with ø 5 mm ori-
fice
Max. flow velocity
(m/s)
Nominal pipe size
61.2DN 40
101.3DN 50
171.4DN 65
281.5DN 80
9.3.10 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.
9.3.11 Additive dosing tank (4T03)
It is also recommended to provide a separate additive dosing tank, especially when water
treatment products are added in solid form. The design must be such that the major part of
the water flow is circulating through the engine when treatment products are added.
The tank should be connected to the HT cooling water circuit as shown in the example system
diagrams.
9.3.12 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.
9.3.12.1 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.
The minimum required heating power is 12 kW/cyl, which makes it possible to warm up the
engine from 20 ºC to 60...70 ºC in 10-15 hours. The required heating power for shorter heating
time can be estimated with the formula below. About 6 kW/cyl is required to keep a hot engine
warm.
Design data:
min. 60°CPreheating temperature
Wärtsilä 46F Product Guide - a19 - 1 December 2017 9-17
9. Cooling Water SystemWärtsilä 46F Product Guide
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