In this post, we shall see how the engine is started.
Engines are normally started by cranking the running masses of the engine by one of the following means
- Manual Starting
- Battery starting
- Compressed Air Startin
A) Manual Starting:
Manual starting is applied for cranking the engine on very small engines (of less than 10Hp)
B) Battery Starting:
Battery starting is applied on engines of power upto about 100KW.
C) Compressed Air starting
Engines of very high break power, the engines are started by using compressed air, because of the high moment of inertia of the rotating components of the engine.
The type of starting system provides, basically depends on the weight and running components of the engine.
The compressed air starting system provided on the large cargo vessels and other ocean-going vessels by the rules of the classification societies. As per the rules of the classification societies, the starting system provided shall be sufficient to give 1) 6 starts for a non-reversible engine 2) 12 starts for a reversible engine.
Accordingly, the capacity of air receivers is decided to give the required number of starts (without replenishing) as per classification societies rule.
The required storage capacity is delivered in between two air receivers so that when one receiver is under maintenance, the other receiver will be in operation.
As per rules, the compressors(one working + one standby) provided shall have the capacity to fill air bottles withing one hour. Normally, the engine manufacturers shall provide the guidelines for the capacity of air compressors (free air delivery and discharge pressure). On big cargo vessels, the compressors and receivers are designed for a pressure of 30 bar.
Starting System of Diesel Alternator Sets:
The compressor used in the starting system of main engines are electric motor driven and the power required to start these compressors is provided by diesel generating sets. For starting the diesel alternator sets a separate starting system is provided, which consists of a small auxiliary air compressor and aux air receiver.
Dead Ship Start Condition:
For a new vessel when there is no power on the ship there should be means to start the air compressors so that the D.A. set can be started to provide power to all the systems. Hence, initially, the auxiliary compressor is run by the power developed by emergency generator (which is battery started) and the D.A. sets are started.