Hot Oil Sprayed Over Hot Engine Surface Causes Fire

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The speakers at the IMarEST 6th Condition Based maintenance conference, Singapore, really made the attendees listen the ultrasound, see the infrared and sense the subtle vibrations. No doubt, when such technology and services are deployed to enhance the maintenance regime and safety of the ship, the number of incidents and loss of time will definitely drop.

Diesel-Generator-Thermal-Image-Hot-spots.JPG

One of the speakers at the conference presented about the infrared thermal imaging techniques.  The slides displayed a thermal image of a diesel generator engine and the speaker claimed that there is a potentially dangerous situation waiting to happen for the above engine as there are hot exposed surfaces contravening SOLAS requirements.

Upon questioning, he revealed that the temperatures of the exposed hot surface should not exceed 220 degree Celsius.  Still the question remains, what’s the interlink between exposed hot surfaces and  220 degrees?

Here is the slide which was used to explain about the exposed hot surfaces during the conference.

SOLAS-Violation-Exposed-Hot-Surfaces.JPG

(Source: Presentation by Mr Rajagopalan – CEO – SVL Singapore – Presentation at the 6th IMarEST Condition Based Maintenance Conference – CBM – A cost effective tool)

Surprisingly, MAIB UK has released a safety update that there was a fire on board a ship due to the incident as described below.

A fully loaded ro-ro passenger ferry was en route to its next port when the engineers in the control room acknowledged a low oil pressure alarm on one of the generators (Figure 1).

Fig-1-Diesel-Generator.JPG

On the CCTV, they observed that oil from this generator was spraying onto the adjacent generator.  While they were investigating the source of the leak, the oil that had been sprayed on the exhaust casing of the adjacent engine caught fire.  Fortunately, the crew were able to quickly identify and isolate the source of the leak and extinguish the fire before it was able to spread.  No one was hurt from the incident.

fig-2a-Loose-Oil-Plug-on-Lube-oil-pump.JPG

Subsequent investigation revealed that:

  1. The oil had come from a loose plug on the generator’s engine-mounted lubricating oil pump (Figure 2a).  This had vibrated loose as a result of it being insufficiently tightened by shore staff during a recent dry dock.
  2. A section of the adjacent generator’s exhaust piping had been left un-lagged following its overhaul during the recent dry dock (Figure 2b).  This was hidden from view by the exhaust casing.
  3. Fine oil spray ignited when it came into contact with the hot exhaust casing.

fig-2b-exhaust-piping-un-insulated.JPG

The Lessons Learnt:

  1. Unlagged sections of exhaust piping will radiate heat to the protective casing, causing it to attain temperatures sufficient to ignite an oil or fuel spray.
  2. These temperatures are not visible to the eye unless the surface is glowing.  However, a thermal image will immediately identify unlagged sections (Figure 3).
  3. All vessels are required to comply with SOLAS regulations regarding the maximum allowable temperature of an exposed surface (Chapter II/2):
    • All surfaces with temperatures above 220°C which may be impinged as a result of a fuel system failure shall be properly insulated.
  4. All fittings including nuts, bolts, screws and plugs can come loose if the vibration levels on the engines exceed acceptable limits. Overall vibration velocity can be measured with very simple instruments.  If excessive, frequency analysis of the vibration waveform can often identify the root cause of excessive vibration levels.

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Source: SVL Singapore Services, UK MAIB

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