8. Compressed Air System
Compressed air is used to start engines and to provide actuating energy for safety and control
devices. The use of starting air for other purposes is limited by the classification regulations.
To ensure the functionality of the components in the compressed air system, the compressed
air has to be free from solid particles and oil.
8.1 Instrument air quality
The quality of instrument air, from the ships instrument air system, for safety and control
devices must fulfill the following requirements.
Instrument air specification:
1 MPa (10 bar)Design pressure
0.7 MPa (7 bar)Nominal pressure
+3°C (vapour pressure dewpoint)Max water in air
1 mg/m
3
Max. oil content
3 µmMax. particle size
8.2 Internal compressed air system
All engines are started by means of compressed air with a nominal pressure of 3 MPa, the
minimum recommended air pressure is 1.8 MPa. The start is performed by direct injection of
air into the cylinders through the starting air valves in the cylinder heads.
All engines have built-on non-return valves and flame arrestors. The engine can not be started
when the turning gear is engaged.
The main starting valve, built on the engine, can be operated both manually and electrically.
In addition to starting system, the compressed air system is also used for operating the
following systems:
● Electro-pneumatic overspeed trip device
● Starting fuel limiter
● Slow turning
● Fuel actuator booster
● Waste gate valve
● Turbocharger cleaning
● HT charge air cooler by-pass valve
● Charge air shut-off valve (optional)
● Fuel gas venting valve
● Oil mist detector
DBAD209883 8-1
8. Compressed Air SystemWärtsilä 46DF Product Guide
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