Diesel Generators’ Fuel Pumps Failed with Bad Quality Fuel.

Vessel Oil Tanker
Location At Sea
Bunker RMG 380

The Incident:

The vessel bunkered 1500 MT of RMG 380 at Vladivostok (Russia).  The vessel sailed out to Japan for discharging the cargo from Russia.  The regular full-spec ISO 8217:2005 analysis did not reveal any significant abnormality.  Thus, the fuel was put in use after consuming the old bunkers.  The vessel’s purifier feed pump filters started getting clogged and the engine room was kept manned as the filters required cleaning every 30 minutes.

The ship staff overlooked the filter choking issue since they have experienced similar problems after changing over to fresh bunkers.  The dirty sediments were assumed to get clogged at the filters as the tank contents got churned.

Approximately 30 hours after using the new bunkers, the diesel generators were unable to take up the sea-load.  Out of three generators, two shared the load at sea.  The third generator was taken on load and generator # 1 was stopped for investigation.  Fuel filters were found clogged, and the same were cleaned and the engine re-started.  However, diesel generator # 1 was unable to take up load more than 40%.  The same happened with diesel generator # 2.  The vessel changed over diesel generator # 3 to MDO to safeguard the potential dangerous situation.



Course of Action:

  1. Peak pressures which were taken on diesel generators, revealed that the pressures were low when compared with last performance report and sea-trial data.
  2. One of the fuel pumps on diesel generator # 1 was opened up for inspection.
  3. The fuel pump elements were completely worn out with scoring marks.
  4. The fuel pump was unable to pump because of excessive fuel leak past the plungers.
  5. The subsequent fuel pumps on diesel generators revealed the same. All six fuel pump elements were found damaged and hence replaced with new spare pumps.


Though the vessel was testing with some other lab, the Ship Management approached Viswa Lab to identify the root cause of the problem.  Viswa Lab requested the vessel to land representative fuel oil samples from the following points of the fuel system:

  1. Before purifier,
  2. After Purifier,
  3. Inlet to the diesel generator.

Upon receipt of the samples at the lab, full-spec analysis as per ISO 8217:2005 revealed high Al+ Si and Iron content in the fuel. Purifier efficiency determination (PED) revealed that the purifier was not operating efficiently.

Below are the Lab Test Results:

Sampling Point



Before Purifier

55 ppm

64 ppm

After Purifier

43 ppm

48 ppm

Inlet to Diesel Generator

39 ppm

41 ppm

It is to be noted that the Iron content is not part of the ISO 8217 specification.  The legal issues on one side of this case was supported by Viswa Lab, which is outside the scope of this case study *.

We seldom see iron content exceeding 25 ppm in a normal fuel oil.  This kind of iron content is a very rare case.  Further Al + Si (Cat-fines) were high noted at 64 ppm in the before purifier sample.  The Purifier was unable to remove the cat-fines, and 41 ppm was found at the inlet to the engine.  It seems that even the fine filters are not effective in removing these particles.

Viswa Lab – additionally examined the ashed fuel sample under the Microscope.  Below are the microscopic images with 10X magnification reveals the presence of Iron and cat-fines in fuel.




Recommended Actions/Lessons Learnt:

  1. Proper drip sample – representative sample should be sent for analysis.
  2. Purifier should be checked and maintained properly and it should not act like a pump.
  3. Clogging of filters to be attended properly and debris removed has to be inspected.
  4. Iron and cat-fines in the fuel can be removed by effective purification and filtration.
  5. Ensure purifier is operating at optimum performance, and the same is regularly verified by testing the samples at Viswa Lab.
  6. If you have not checked the efficiency of the purifier, you may consider testing before /after purifier samples to evaluate the purifier efficiency and confirm the removal of undesired particles.

We thank Viswa Lab for sharing this fuel problem case with us.  This study is intended to share and spread awareness in dealing with various machinery problems on board.

Please Feel Free to post your comments or share cases that you have come across.

*Certain essential/confidential details have been removed and this article has been shared to the benefit of all who suffer from daily shipboard problems and those who manage the ships facing daily challenges. 



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