Wartsila ?31DF Series Product Manual page 146

9. Cooling Water System
9.2.4 Temperature control valve for central cooler (4V08)
When external equipment (e.g. a reduction gear, generator or MDO cooler) are installed in the
same cooling water circuit, there must be a common LT temperature control valve and separate
pump 4P15 in the external system. The common LT temperature control valve is installed after
the central cooler and controls the temperature of the water before the engine and the external
equipment, by partly bypassing the central cooler. The valve can be either direct acting or
electrically actuated.
The maximum inlet water temperature for those equipment is generally 38 ºC.
The set-point of the temperature control valve 4V08 can be up to 45 ºC for the engine.
9.2.5 Charge air temperature control valve (4V09)
The temperature of the charge air is maintained on desired level with an electrically actuated
temperature control valve in the external LT circuit. The control valve regulates the water flow
through the LT-stage of the charge air cooler according to the measured temperature in the
charge air receiver.
The charge air temperature is controlled according to engine load and fuel mode.
9.2.6 Temperature control valve for heat recovery (4V02)
The temperature control valve after the heat recovery controls the maximum temperature of
the water that is mixed with HT water from the engine outlet before the HT pump. The control
valve can be either self-actuated or electrically actuated.
Especially in installations with dynamic positioning (DP) feature, installation of valve 4V02 is
strongly recommended in order to avoid HT temperature fluctuations during low load operation.
The set-point is usually up to 75 ºC.
9.2.7 Coolers for other equipment and MDF coolers
The engine driven LT circulating pump can supply cooling water to one or two small coolers
installed in parallel to the engine, for example a MDF cooler or a reduction gear cooler. This
is only possible for engines operating on MDF, because the LT temperature control valve
cannot be built on the engine to control the temperature after the engine. Separate circulating
pumps are required for larger flows.
Design guidelines for the MDF cooler are given in chapter Fuel system.
9.2.8 Fresh water central cooler (4E08)
The flow to the fresh water cooler must be calculated case by case based on how the circuit
is designed.
In case the fresh water central cooler is used for combined LT and HT water flows in a parallel
system the total flow can be calculated with the following formula:
where:
T
9-8
q = total fresh water flow [m³/h]
q nominal LT pump capacity[m³/h]
LT =
Φ = heat dissipated to HT water [kW]
= HT water temperature after engine ( 96°C)
out
Wärtsilä 31DF Product Guide
DBAE248994