A guide to marine gas oil and lsfo used on ships la gas prices now

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The diesel generator installed on ships these days operate on both residual and distillate fuel. The valve seat deposits (on the inlet valve) is significantly less when using distillate fuel as compared to using residual fuel oil. This is because the distillate fuels such as Marine Gas Oil produces fewer combustion deposits.

The 4 stroke marine engine efficiency on the ship is measured on the basis of residual oil, and the design of the engine is done focusing on the use of residual fuel. Most of the 4 stroke engines are installed with water-cooled injection nozzles to reduce the injector tip temperature (for avoiding coking of the fuel which would cause deposits known as trumpets on the nozzle tip).

When using distillate fuel, the nozzle cooling arrangement will further reduce the temperature of the distillate fuel, already having very low viscosity. The additional cooling with water may also cause overcooling of nozzle, leading to falling of temperature below the dew point of the sulphuric acid in the combustion gas and cause corrosion of the nozzle. To tackle this, the engineer must ensure to turn off nozzle cooling during distillate marine fuel oil operation.

Another problem associated with usage of marine gas oil is leakage. As the viscosity of the fuel is much lower than the regular fuel of the engine, it accelerates the fuel leakage from pumps and also contaminates the lubrication. To tackle this problem, most of the 4 stroke engines comes with lubricating sealing oil at the fuel pump. This oil seals the passage of distillate fuel to minimise the leakage.

During the burning of low sulphur fuel oil or LSFO, lacquering in liner may also be observed. Marine gas oil produces deposits which stick on the liner surface and disturbs the oil film lubrication in the liner. The engine design and use of aromatic fuels as the primary burning fuel are important factors that can contribute to increasing the lacquer formation.

The BN of the lube oil used in 4 stroke engines that operate majorly on distillate marine fuel oil is in the range of 10 to 16 mg KOH/g. When the engine is operated with residual fuels, the BN of the lubricating oil is kept between 30-55 mgKOH/g. When using distillate fuel for a more extended run (more than 1000 hours), it is always advisable to switch the lube oil with lower Total Base Number (TBN) with value as stated above. For shorter operation, it is not critical for the engine to keep using lubricating oil with BN of 30-55 mg KOH/g.

• During the switchover process, there is a mixing of heavy fuel oil with a low aromatic hydrocarbon distillate fuel. This increases the risk of two incompatible fuels burning inside the engine cylinder, causing the asphalt of the heavy fuel to precipitate as heavy sludge and leading to filter clogging

• As the names suggest, LSFO produces a negligible amount of sulphuric acid, and hence if the correct TBN lubricating oil is not used, the alkaline components produced in the cylinder will not be neutralised. This will potentially harm the liner and other parts of the combustion chamber. These alkaline deposits will lead to the removal of cylinder oil film causing contact of metal to metal parts between liner and piston rings and resulting in scuffing and seizure of the engine.

For new marine engines running on heavy fuel oil, the engineer officers have to evaluate the cylinder conditions and report to the engine maker after changing the fuel to LSFO to check the deposits and scuffing on combustion chamber parts such as piston, crown, liner, and ring. Responsibilities of ship staff While receiving Marine Gas Oil

• The company has to ensure all the technical requirements are in place when using LSFO or marine gas oil. If the ship is plying the first time into the ECA, the company should revise fuel oil management procedures to ensure the crew has prior knowledge of HFO to LSFO changeover and low TBN lube oil for the main engine etc.

Even with the advantage of low emission from ship’s engine, LSFO or ULSFO has few disadvantages i.e. not compatible with the current engines the ships are using. The problems arising due to marine gas oil may lead to severe catastrophes such as engine failure (due to fuel pump problem or seizure of combustion chamber parts), resulting in vessel collision, grounding and marine pollution. It is therefore important for the ship’s crew to know the pros and cons of these fuels and follow the correct procedure when handling such fuels on board ships.

Disclaimer: The views mentioned above are of the author only. Data and charts, if used, in the article have been sourced from available information and have not been authenticated by any statutory authority. The author and Marine Insight do not claim it to be accurate nor accept any responsibility for the same. The views constitute only the opinions and do not constitute any guidelines or recommendation on any course of action to be followed by the reader.