Posted by : sanjay swain Wednesday, August 7, 2013



1. THERE MIGHT BE A PROBLEM WITH LOW LUBRICITY OF LOW SULPHUR DIESEL FUELS. FOR FUEL DESTINED FOR AUTOMOTIVE APPLICATIONS, THE FUEL USUALLY HAS A MINIMUM LUBRICITY REQUIREMENT SPECIFIED, AND WILL USUALLY CONTAIN LUBRICITY ADDITIVES TO RAISE PERFORMANCE TO THE SPECIFIED LEVEL.

THE SAME DOES NOT APPLY TO MARINE DISTILLATES. FOR MARINE APPLICATIONS, A MINIMUM LUBRICITY IS NOT DEFINED IN FUEL SPECIFICATIONS. THERE IS LITTLE OR NO EXPERIENCE OF USING VERY LOW SULPHUR FUELS WITHOUT LUBRICITY ADDITIVES IN MARINE APPLICATIONS. WE BELIEVE FURTHER WORK IS REQUIRED TO ESTABLISH THAT SUCH LOW SULPHUR FUELS REQUIRED BY THE REGULATIONS HAVE A SUFFICIENT LUBRICITY.

2. DEEP-SEA SHIPPING ENTERING THE COASTAL WATERS HAVE TO SWITCH FROM HEAVY FUEL OIL  TO DIESEL FUEL. SUCH A SWITCHING IS POSSIBLE, BUT REQUIRES THAT DETAILED PROCEDURES BE FOLLOWED EXACTLY, IF PROBLEMS ARE TO BE AVOIDED. DURING OPERATION WITH HFO, THE FUEL PUMPS ARE HOT (ABOUT 150°C). DIESEL FUEL IS INTRODUCED INTO THE PUMPS AT AMBIENT (ENGINE ROOM) TEMPERATURE. IF THE CHANGING OF THE FUEL IS DONE TOO FAST, THE COMBINATION OF THERMAL CONTRACTION OF THE PUMP ELEMENTS, AND THE LOW LUBRICITY OF THE DIESEL FUEL (DUE TO ITS LOWERED VISCOSITY IN THE HOT PUMPS), COULD LEAD TO SUDDEN SEIZURE OF THE FUEL PUMPS, AND HENCE LOSS OF PROPULSIVE POWER OR   ELECTRICAL BLACKOUT ON THE VESSEL.

3. THE THIRD POTENTIAL PROBLEM, AND THE ONE THAT GIVES MOST CONCERN, IS COMPATIBILITY OF HFO WITH LOW-SULPHUR/LOW-AROMATICS DIESEL. WHEN SWITCHING FROM HFO TO DIESEL FUEL (OR VICE VERSA) THERE IS A MIXING OF THESE TWO DIFFERENT FUELS. (THIS CANNOT BE AVOIDED, BECAUSE OF THE GRADUAL CHANGEOVER PROCESS REQUIRED TO AVOID THE PROBLEMS DESCRIBED UNDER ITEM 2).

IF THE DIESEL FUEL IS NOT COMPATIBLE WITH THE HEAVY FUEL, THE ASPHALTENES OF THE HEAVY FUEL WILL BE PRECIPITATED OUT. THE RESULT WILL BE FILTER CLOGGING, OR FUEL PUMP STICKING, THAT AGAIN COULD LEAD TO LOSS OF PROPULSIVE POWER, OR ELECTRICAL BLACKOUT
ON THE VESSEL.

THE RISK OF AN INCOMPATIBILITY PROBLEM BETWEEN HFO AND LOW-SULPHUR / LOW AROMATICS DIESEL FUEL IS SIGNIFICANTLY HIGHER THAN FOR A “NORMAL” MARINE DIESEL FUEL (ISO-F-DMA OR ISO-F-DMB). THIS IS BECAUSE THE LOW CONTENT OF AROMATICS MEANS THERE IS LESS SOLVENCY IN THE HFO/DIESEL MIXTURE TO KEEP THE ASPHALTENES IN SOLUTION.

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