Main engine drama

An essential premise for trouble free and economical engine operation is an optimized and well maintained fuel oil combustion system. The main aim is to burn the fuel as completely as possible and with smallest ignition delay.
Failure in maintaining your fuel treatment system in good operational condition can dramatically reduce cylinder-piston group lifespan.
As was reported, a purifier failure allowed in-fuel abrasives to enter engine combustion chamber. In result, piston rings on many cylinders were worn in no time. After the crew has stopped the engine, they failed to restart it again. Low fuel oil quality affected engine pistons and cylinder liners leaving by deposits of unburned fuel admixtures in the combustion chamber.
Investigation revealed – these damages showed different kinds of deposits on the top and also in the shaker chamber of the piston crown. These deposits led to local material overheating with disproportionately high material erosion which, in individual cases, even led to break through into the cooling oil chamber.

The reasons for this process were:

  • Fuels especially with high asphaltenes content;
  • Inadequate fuel treatment;
  • Improperly opening, leaking injection nozzles.
Ignition behavior and asphaltenes Use the CCAI (Calculated carbon aromaticity index) value as an indicator of the ignition behavior. Asphaltenes, especially in combination with a high content of aromatic compounds, are more likely to have a poor ignition quality. It is recommend to use only fuels with low asphaltenes content that have a CCAI value that is clearly within the permissible range.

Fuel treatment When fuels partly reach the limits particular attention should be paid to their treatment. Maintain fuel oil purifiers in proper condition – daily do manual discharge to observer correct operation. The testing of the alarms and shut downs is paramount. Sludge tank have to be sounded daily and any abnormal sludge level deviations investigated. Drain Settling and Day tanks twice a day.  Any abnormalities in the fuel treatment system have to be investigated immediately.

Nozzles A good combustion essentially requires a proper condition of the nozzles. As it is not always possible to recognize poorer fuel grades, it has to be expected that especially the injection nozzles will be subject to higher wear rates. Engine indicator cards will give you insight what is going on in the combustion chamber.

Turbocharger condition The operating data of the turbocharger should be checked and evaluated on a regular basis.
The values of charge air pressure, compression temperature of the air and turbocharger
speed directly depend on each other. If, in conjunction with the exhaust temperatures, bigger
deviations from normal condition should be ascertained, possible irregularities are to be
remedied as quickly as possible.

If you have an endoscope on board carry out a visual check of the combustion bowl each time a nozzle is exchanged.

 

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