WÄRTSILÄ Vasa R22, Instruction Manual

Page: 231 / 297

19.1.2 HT circuit
The HT circuit cools the cylinders, cylinder heads and turbo-
charger(s).
A centrifugal pump (9), direct driven by the engine, pumps the
water through the HT circuit. From the pump the water flows to
the distributing duct, cast in the engine block (in V-engines the
water is distributed to the distributing ducts of each cylinder bank
through ducts cast into the pump cover at the free end of the
engine). From the distributing ducts the water flows to the
cylinder water jackets, further through connection pieces to the
cylinder heads where it is forced by the intermediate deck to flow
along the flame plate, around the valves to the exhaust valve
seats, efficiently cooling all these components. From the cylinder
head the water flows through a connection piece to the collecting
pipe.
Parallel to the flow to the cylinders, part of the water flows to the
turbocharger(s). The necessary cooling is gained from the central
cooler (14), Fig 19-1
19.1.3 LT circuit
The LT circuit consists of a charge air cooler (7) and a lube oil
cooler (15) through which a pump (8), identical to the HT pump,
pumps the water. The circuit temperature is controlled by a
temperature control valve (10) maintaining the LT circuit tem-
perature at a load dependent level. The necessary cooling is
gained from the central cooler (16), Fig 19-1.The system outside
the engine can vary from one installation to another.
19.1.4 Venting and pressure control
The collecting pipes from the cylinder and turbocharger cooling
system are connected to a box (2) for venting of the system. From
this box the vent pipe leads to the expansion tank (1) from which
the expansion pipe is connected to the inlet pipes of the pumps (8,
9). Static pressure of 0.7 - 1.5 bar is required before the pumps. If
the expansion tank cannot be located high enough to provide this
pressure, the system is to be pressurized.
19.1.5 Preheating
Before start, the HT and LT circuits are heated up to about 70 -
80°C. This is of utmost importance when starting and idling on
heavy fuel. As the lube oil is also heated (indirectly) by the LT
water, all fluids are close to working temperatures when the
engine is started. Thus the charge air is heated directly in the
charge air cooler when starting.
19 Cooling Water System 22-9601
19 - 2 VASA 22