When the vessel was underway, vessel engineers drained
a deck hydraulic line to an engine room storage tank
by way of a reservoir/expansion tank.
During this evolution, the vessels was on a ballast passage
and trimmed three meters down by the stern.
As the large deck line was draining,
the vent to the expansion tank filled and overflowed
just above the main engine turbocharger.
The falling oil contacted hot surfaces, vaporized and ignited.
About 40 minutes passed until CO2 was released
which successfully extinguished the fire.
The ship's engineers were able to restore electrical power
but not propulsion and the vessel require a tow.
The hydraulic oil piping system was inadequately designed
in that its reservoir/expansion tank venting arrangements
failed to be suitable for all levels of trim.
In the condition of trim at the time of the casualty,
the tank's vent was lower than sections of the piping being drained.
Vessel operators and shipboard employees may be incorrect
to assume that an installed system is adequate
for all aspects of operation.
Shipboard engineering systems, their design and installation
although approved to various standards
may be in certain instances found inadequate
and lead to unintended and unfavorable circumstances.
The investigation revealed that the engine room escape
terminated near an area that shares access to the engine room doors.
Although the drain back process of overflowing
and emptying the reservoir/expansion tank
to the storage tank appeared innocuous,
the individual overseeing the process
should have recognized the potential risk
for problems occurring in the engine room.
Defenses could have been established by assigning an individual
to continually observe the levels in both the tanks.