9.3.1 Electrically driven HT and LT circulation pumps (4P03,
4P05, 4P14, 4P15)
Electrically driven pumps should be of centrifugal type. Required capacities and delivery
pressures for stand-by pumps are stated in Technical data.
In installations without engine driven LT pumps, several engines can share a common LT
circulating pump, also together with other equipment such as reduction gear, generator and
compressors. When such an arrangement is preferred and the number of engines in operation
varies, significant energy savings can be achieved with frequency control of the LT pumps.
Note
Some classification societies require that spare pumps are carried onboard even though the
ship has multiple engines. Stand-by pumps can in such case be worth considering also for
this type of application.
9.3.2 Sea water pump (4P11)
The sea water pumps are always separate from the engine and electrically driven.
The capacity of the pumps is determined by the type of coolers and the amount of heat to be
dissipated.
Significant energy savings can be achieved in most installations with frequency control of the
sea water pumps. Minimum flow velocity (fouling) and maximum sea water temperature (salt
deposits) are however issues to consider.
9.3.3 Temperature control valve for central cooler (4V08)
The temperature control valve is installed after the central cooler and it controls the temperature
of the LT water before the engine, by partly bypassing the cooler. The control valve can be
either self-actuated or electrically actuated. Normally there is one temperature control valve
per circuit.
The set-point of the control valve is 35 ºC, or lower if required by other equipment connected
to the same circuit.
9.3.4 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 recirculating
water flow (after the LO Cooler) through (to) the LT-stage of the charge air cooler in order to
reach and maintain the correct charge air receiver temperature.
9.3.5 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.
The set-point is usually somewhere close to 75 ºC.
The arrangement shown in the example system diagrams also results in a smaller flow through
the central cooler, compared to a system where the HT and LT circuits are connected in parallel
to the cooler.
9.3.6 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 charge air and lubricating oil cooler, for example a MDF cooler
or a generator cooler. Separate circulating pumps are required for larger flows.
Design guidelines for the MDF cooler are given in chapter Fuel system.
9-14 DBAD209883
Wärtsilä 46DF Product Guide9. Cooling Water System
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