Wartsila ?31DF Series, Product Manual, Page: 147 / 216

HT water temperature after cooler (38°C) T
in
=
9.2.9 Waste heat recovery
The waste heat in the HT cooling water can be used for fresh water production, central heating,
tank heating etc. The system should in such case be provided with a temperature control
valve to avoid unnecessary cooling, as shown in the example diagrams. With this arrangement
the HT water flow through the heat recovery can be increased.
The heat available from HT cooling water is affected by ambient conditions. It should also be
taken into account that the recoverable heat is reduced by circulation to the expansion tank,
radiation from piping and leakages in temperature control valves.
9.2.10 Air venting
Air may be entrained in the system after an overhaul, or a leak may continuously add air or
gas into the system. The engine is equipped with vent pipes to evacuate air from the cooling
water circuits. The vent pipes should be drawn separately to the expansion tank from each
connection on the engine, except for the vent pipes from the charge air cooler on V-engines,
which may be connected to the corresponding line on the opposite cylinder bank.
Venting pipes to the expansion tank are to be installed at all high points in the piping system,
where air or gas can accumulate.
The vent pipes must be continuously rising.
9.2.11 Expansion tank (4T05)
The expansion tank compensates for thermal expansion of the coolant, serves for venting of
the circuits and provides a sufficient static pressure for the circulating pumps.
Design data:
min. 10% of the total system volume Volume
NOTE
The maximum pressure at the engine must not be exceeded in case an electrically
driven pump is installed significantly higher than the engine.
Concerning the water volume in the engine, see chapter Technical data.
The expansion tank should be equipped with an inspection hatch, a level gauge, a low level
alarm and necessary means for dosing of cooling water additives.
The vent pipes should enter the tank below the water level. The vent pipes must be drawn
separately to the tank (see air venting) and the pipes should be provided with labels at the
expansion tank.
Small amounts of fuel gas may enter the DF-engine cooling water system. The gas (just like
air) is separated in the cooling water system and will finally be released in the cooling water
expansion tank. Therefore, the cooling water expansion tank has to be of closed-top type, to
prevent release of gas into open air.
The DF-engine cooling water expansion tank breathing has to be treated similarly to the gas
pipe ventilation. Openings into open air from the cooling water expansion tank other than the
breather pipe have to be normally either closed or of type that does not allow fuel gas to exit
the tank (e.g. overflow pipe arrangement with water lock). The cooling water expansion tank
breathing pipes of engines located in same engine room can be combined.
DBAE248994 9-9
9. Cooling Water System Wärtsilä 31DF Product Guide