Spot market differentials for IMO-compliant marine fuels have cracked to the lowest in seven months despite recent data showing firm demand for shipping fuel at the world's biggest bunkering port of Singapore. Cash differentials for Singapore Marine Fuel 0. April sales are also expected to remain broadly steady from March, according to market participants. Weakness in the marine fuel market may deal a further blow to Asian refiners already struggling with falling margins. While the COVID pandemic has caused massive demand destruction of land and air transportation fuels such as gasoline, gasoil and jet fuel, the marine fuel market had so far fared better given the relatively less stringent restriction on shipping.
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The mega marine engines of ships burn tonnes of fuel every day in order to propel massively loaded ships.
Fighting air pollution from ships has been the top agenda for the Marine Environmental Protection Committee, and hence several regulations have been enforced to curtail the harmful emissions from ships such as Sox and NOx. With the ever-changing technology on ships, the fuel that is used to run marine engines is also changing rapidly.
Due to the high aromatic nature, the density of a marine gas oil blended with LCGO will be higher than the gas oil from an atmospheric distillation refinery. The RM and DM are types of marine oils, which can be further divided into groups, depending upon the sulphur content in the marine fuel oil. Nowadays, the new age ULSFOs in the market typically have only 10 to 15 parts per million ppm sulphur or 0.
In general, the higher rpm engine requires high cetane index fuel. A low cloud point gas oil may only be stored onboard in drums because of its low flash point.
Microbial contamination, caused by bacteria and fungi, occurs in a fuel having water quantity. Due to bacterial presence, the fuel systems will generate problems such as chocked fuel filters and erratic engine operation. Possible microbiological contamination indicators are:. Fuel pumps of marine engines are designed for a minimum viscosity. The viscosity of Marine Gas Oil is very low as compared to the pump design factor which leads to inadequate hydrodynamic lubrication, causing wear and scuffing.
A decrease in fuel viscosity may cause an increase in fuel leakage between the pump plunger and barrel. The leakage can lead to hot start, and low fuel setting starts difficulties, especially in worn fuel pumps. Due to the low viscosity of the marine gas oil, the external and attached fuel pumps may not deliver the fuel at the required pressure, which will eventually hamper the designed power output of the engine.
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.
Most of the residual fuels are not compatible with sealing lubricating oil, hence the engineer must ensure to switch off the sealing oil to avoid compatibility issues, else it will lead to problems like fuel pump sticking etc. 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.
When using distillate fuel for a more extended run more than hours , it is always advisable to switch the lube oil with lower Total Base Number TBN with value as stated above. 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.
The contamination of fuel can happen at any part of the supply chain, i. The engineer must ensure correct fuel oil viscosity, and fuel pump pressure is maintained when the engine is running on marine gas oil. Most of the diesel fuel does not require pre-heating Distillate Marine fuel. Maintain correct temperature if Residual Marine fuel is used.
For the marine engine efficiency, it is essential to maintain the fuel viscosity when running on marine gas oil. 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.
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.
The article or images cannot be reproduced, copied, shared or used in any form without the permission of the author and Marine Insight. An ardent sailor and a techie, Anish Wankhede has voyaged on a number of ships as a marine engineer officer. He loves multitasking, networking, and troubleshooting. He is the one behind the unique creativity and aesthetics at Marine Insight. Running 2 purifier in parallel is known as batch purification system used for treating large quantity of fuel.
Thank you! Thanks for explaining that the diesel generators on machine ships use both residual and distillate fuels. Daphne: We are glad that the information in our portal came handy to you. I would like to know what MGO consists of in general.
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