WÄRTSILÄ PAAE051728, Instruction Manual

Page: 312 / 394

The HT thermostatic valve is provided with four elements
(in-line engine) and six elements (V-engine). Since flow is diverted
either to by-pass or heat exchanger, failure of an element would
cause no change in pressure drop.
The contents of the elements has an almost infinite force when
heated and is positively sealed. When the elements are heated,
this force is transmitted to the piston thus moving the sliding
valve towards the seat (5) to the by-pass closed position. This force
is opposed by a high spring force, which moves the sliding valve
to the heat exchanger closed position when the elements are
cooled. The high force available on heating is the basis of the fail
safe feature in which failure of the element would cause the
engine to run cold.
Water flow in HT thermostatic valve
19.4.4 Maintenance
Normally, no service is required. Too low water temperature
depends on a defective thermostat, too high temperature may
depend on a defective thermostat, leaking O-rings, although, in
most cases, it depends on a dirty central cooler.
1 Drain the cooling water circuit.
2 Remove the cover (3) by opening the screws (1), see Fig
19-7.
3 Open the screws (2) and remove thermostat elements
(6) with element holders (5). Use extractor tools 800122 and
800029 for element holder if necessary.
COLD ENGINE WARM ENGINE
From engine
By-pass
From engine
To cooler
Fig 19-8
4019059601
19 Cooling Water System 32-200050
19 - 12 WÄRTSILÄ 32