TURBO GENERATOR FAILURE
05th Oct 2006
The vessel had picked up pilot at Rotterdam; she was coming to discharge crude oil loaded from Sture, Norway. Vessel had a practice of starting turbo-alternator (T/A) in order to have a load on boiler for inert gas.
Everything was going on smoothly, until when T/A was being synchronized to switch board and breaker engaged. Both running diesel generator breakers opened up resulting in blackout. Vessel's main steering was not connected to emergency power; only one auxiliary steering gear (Rudder Arrestor) was connected to emergency power.
Capacity of emergency generator was only 20KW and meant basically for lighting and few navigational aids and prime mover was also driving emergency fire pump. When the blackout occurred, the engineer tried closing the breakers of diesel generators. Unfortunately both the breakers would not close in. By now boiler steam pressure, going to vacuum condenser, via cargo turbines ruptured.
By the time the cause for diesel generator breakers not closing was ascertained, master had summoned third tug. It was found that diesel generator breakers could not be closed because turbo-alternator (now stopped/tripped) breaker was stuck in closed position. With express speed the turbo alternator breaker was forced out of the bus bar and before diesel generator could reach a trip stage, their breakers were closed.
But just as tugs were approaching power was restored, steering restored, and main engine started just in time before vessel would have hit a buoy.
Probable Cause Vessel believes that electronic control system of steam governor on T/G failed while synchronizing and went out of phase resulting in tripping of running generators and impact of high current welded the T/G breaker to the mains.