Marine Report 236, Independent investigation into the engine room ...

consistent with the manufacturer’s specifications for the hose to be fitted in that
position. Four distinct, significantly sized areas of damage were identified on the
hose. Examination of the damaged areas under a low power stereo microscope
indicated that abrasive wear was the principal process of primary wire braid failure
in each location (Figure 10). Further examination under a scanning electron
microscope confirmed that each wire in the braid had been worn to a thin flat
profile by a process of wear. No other failure mechanisms, such as overload from
excessive pressure or wire fatigue from cyclic oscillations, were evident.
Figure 10: Close-up of the filter hose’s wire braid wear
Analysis of the filter hose indicated that wear of the wire braid took place over a
considerable period of time while it was in hard contact with solid surfaces on the
engine. Vibration of the engine and fuel pressurisation cycles would have provided
the necessary conditions for the process. Burnt rubber foam covered an area of preexisting
wire braid damage and indicated that an attempt to isolate the hose from
further damage had been made some time before the fire.
The filter hose could have failed at any of the four areas of damage located on it. As
the fire had affected the entire length of the internal rubber hose, it was impossible
to say with certainty exactly where the hose may have failed before the fire.
However, it is likely that the hose’s failure provided the fuel to initiate the fire. It
operated at a higher pressure than the return hose even though both may have been
subject to much higher than normal pressures for very short periods of time due to
pressure pulses in the generator’s low pressure fuel system. The filter hose’s normal
working pressure was probably between two and five bar.
In two areas of damage on the filter hose, including the one shown in Figure 10, the
internal rubber hose had been entirely consumed. This indicates that the intensity of
the fire was much greater in these locations. Once the wire braid at either location
was worn, wear on the internal rubber hose would have weakened it. The evidence
therefore indicates that a failure at either of these locations was more likely to have
provided fuel to start the fire.
The return hose probably failed after the fire started. The hose extended from the
stop solenoid and overflow valve on top of the engine, across the exhaust manifold
casing and down to deck level. A temporary repair had been made to it by inserting
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